Passive Intermodulation in Printed Lines: Effects of Trace Dimensions and Substrate

A comprehensive experimental study was performed to identify and discriminate mechanisms contributing to passive intermodulation (PIM) in microstrip transmission lines. The effects of strip length and width, and substrate materials on PIM performance of printed lines were investigated in the GSM900, DCS1800 and UMTS frequency bands. The major features of the experiment design, sample preparation and test setup are discussed in detail. The measurement results have demonstrated that the PIM level cumulatively grows on the longer microstrip lines and decreases on wider strips and, thus, indicated that the distributed resistive nonlinearity of the printed traces represents the dominant mechanism of intermodulation generation in the printed lines on PTFE-based substrates. © 2009 The Institution of Engineering and Technology.

Passive Intermodulation Generation on Printed Lines: Near-Field Probing and Observations

The phenomenological mechanisms of passive intermodulation (PIM) in printed lines have been explored by mapping intermodulation products generated by the two-tone traveling waves in microstrip lines. Near-field probing based upon a commercial PIM analyzer has been employed for identification of the PIM sources in printed lines. The results of extensive near-field probing provide the direct experimental evidences of cumulative growth of the intermodulation products in the matched uniform microstrip lines and reveal the fundamental role of the nonlinear scattering by the lumped nonlinear inclusions in the intermodulation production. The distributed nature of the PIM generation in microstrip lines has been conclusively demonstrated and comprehensively described in terms of the four-wave mixing process that proved to be fully consistent with the results of experimental observations of third-order PIM products on the matched and mismatched microstrip lines. © 2006 IEEE.

Passive intermodulation in finite lengths of printed microstrip lines

This paper addresses the theoretical aspects of passive intermodulation (PIM) generation in printed transmission lines. In order to elucidate the mechanisms of PIM generation, a new model of the transmission line length with distributed nonlinearity is proposed. The developed model has been validated by the near-field measurements of PIM product distributions along the microstrip lines. The contributions of nonlinear mixing, power dissipation, and load matching to PIM products have been analyzed in detail. The obtained results reveal the fundamental properties of PIM generation in finite lengths of printed lines with distributed non-linearity and identify possible means for PIM mitigation. It was shown for the first time that the reverse PIM products in a matched transmission line with distributed nonlinearity are generated due to nonlinear scattering. © 2008 IEEE.

Observation of stable phase jump lines in convection of a twisted nematic liquid crystal

We report observations of stable, localized, linelike structures in the spatially periodic pattern formed by nematic electroconvection, along which the phase of the pattern jumps by pi. With increasing electric voltage, these lines form a gridlike structure that goes over into a structure indistinguishable from the well-known grid pattern. We present theoretical arguments that suggest that the twisted cell geometry we are using is indirectly stabilizing the phase jump lines, and that the phase jump lines lattice is caused by an interaction of phase jump lines and a zig-zag instability of the surrounding pattern.

Who We Are and Who Can Join Us: National Identity Content and Entry Criteria for New Immigrants

We argue that attitudes about immigration can be better understood by paying closer attention to the various ways in which national group boundaries are demarcated. We describe two related lines of work that address this. The first deals with national group definitions and, based on evidence from studies carried out in England and analyses of international survey data, argues that the relationship between national identification and prejudice toward immigrants is contingent on the extent to which ethnic or civic definitions of nationality are endorsed. The second, which uses European survey data, examines support for ascribed and acquired criteria that can be applied when determining who is permitted to migrate to one's country, and the various forms of national and individual threat that affect support for these criteria. We explain how the research benefits from a multilevel approach and also suggest how these findings relate to some current policy debates.

Effects of Interface Conditions and Long-Term Stability of Passive Intermodulation Response in Printed Lines

An experimental investigation of the effect of conductor-to-substrate interface on distributed passive intermodulation (PIM) generation in printed microstrip lines has been undertaken using the custom-designed microwave laminates with removed surface bonding layers and with the commercial adhesion promotion applied to the conductor underside. The study of long-term stability of PIM performance of the printed circuits is reported for the first time. The comprehensive measurement results, observations of the selfimprovement of the PIM performance and the effect of panel bending on PIM generation in printed boards with different finishing are presented. A consistent physical interpretation of the observed phenomena is proposed. The results of this study provide new important considerations for the design and characterisation of low-PIM printed circuits.

Runx2, p53, and pRB Status as Diagnostic Parameters for Deregulation of Osteoblast Growth and Differentiation in a New Pre-Chemotherapeutic Osteosarcoma Cell Line (OS1)

Osteosarcomas are the most prevalent primary bone tumors found in pediatric patients. To understand their molecular etiology, cell culture models are used to define disease mechanisms under controlled conditions. Many osteosarcoma cell lines (e.g., SAOS-2, U2OS, MG63) are derived from Caucasian patients. However, patients exhibit individual and ethnic differences in their responsiveness to irradiation and chemotherapy. This motivated the establishment of osteosarcoma cell lines (OS1, OS2, OS3) from three ethnically Chinese patients. OS1 cells, derived from a pre-chemotherapeutic tumor in the femur of a 6-year-old female, were examined for molecular markers characteristic for osteoblasts, stem cells, and cell cycle control by immunohistochemistry, reverse transcriptase-PCR, Western blotting and flow cytometry. OS I have aberrant G-banded karyotypes, possibly reflecting chromosomal abnormalities related to p53 deficiency. OS I had ossification profiles similar to human fetal osteoblasts rather than SAOS-2 which ossifies ab initio, (P

Establishing Clonal Cell Lines with Endothelial-Like Potential from CD9(hi), SSEA-1(-) Cells in Embryonic Stem Cell-Derived Embryoid Bodies

Background. Differentiation of embryonic stem cells (ESCs) into specific cell types with minimal risk of teratoma formation could be efficiently directed by first reducing the differentiation potential of ESCs through the generation of clonal, self-renewing lineage-restricted stem cell lines. Efforts to isolate these stem cells are, however, mired in an impasse where the lack of purified lineage-restricted stem cells has hindered the identification of defining markers for these rare stem cells and, in turn, their isolation. Methodology/Principal Findings. We describe here a method for the isolation of clonal lineage-restricted cell lines with endothelial potential from ESCs through a combination of empirical and rational evidence-based methods. Using an empirical protocol that we have previously developed to generate embryo-derived RoSH lines with endothelial potential, we first generated E-RoSH lines from mouse ESC-derived embryoid bodies (EBs). Despite originating from different mouse strains, RoSH and E-RoSH lines have similar gene expression profiles (r(2) = 0.93) while that between E-RoSH and ESCs was 0.83. In silico gene expression analysis predicted that like RoSH cells, E-RoSH cells have an increased propensity to differentiate into vasculature. Unlike their parental ESCs, E-RoSH cells did not form teratomas and differentiate efficiently into endothelial-like cells in vivo and in vitro. Gene expression and FACS analysis revealed that RoSH and E-RoSH cells are CD9(hi), SSEA-1(-) while ESCs are CD9(lo), SSEA-1(+). Isolation of CD9(hi), SSEA-1(-) cells that constituted 1%-10% of EB-derived cultures generated an E-RoSH-like culture with an identical E-RoSH-like gene expression profile (r(2) = 0.95) and a propensity to differentiate into endothelial-like cells. Conclusions. By combining empirical and rational evidence-based methods, we identified definitive selectable surface antigens for the isolation and propagation of lineage-restricted stem cells with endothelial-like potential from mouse ESCs.

Mutational hotspot in Exon 20 of PIK3CA in breast cancer among Singapore Chinese

The recent identification of somatic mutations in the catalytic region of PIK3 (PIK3CA) in breast cancer and demonstration of their oncogenic function has implicated PIK3CA in mammary carcinogenesis. To investigate possible ethnic differences in patterns of PIK3CA mutations in Singaporean Chinese breast cancer and to characterize these in a panel of cell lines, we sequenced exons 9 and 20 in 80 primary tumors, 19 breast cancer cell lines and 7 normal human mammary epithelial cells (HMECs). Searching for novel hotspots of mutation, we sequenced additional exons ( 1, 2, 6, 7, 14 and 18) in 20 primary tumors and 6 breast cancer cell lines. We detected 33 point mutations in 31 of 80 (39%) breast cancers, and 11 mutations in 10 of 19 (53%) breast cancer cell lines. No mutations were detected in normal breast tissue adjacent to the tumor, or in the 6 normal HMECs. The exon 20 A3140G (H1047R) substitution was identified most frequently (22/31, 71%) and showed a significant association with patient age ( p = 0.043) and stage of the disease ( p = 0.025), but not with ER/PR status or histological grade of the tumor. The incidence of point mutations in PIK3CA, the A3140G substitution in particular, in Singapore breast cancers are among the most frequent reported to date for any gene in breast cancer. The results suggest that mutation of PIK3CA might contribute to development of early stage breast cancer and could provide a potent target for early diagnosis and therapy.