Modal Resonant Frequencies and Radiation Quality Factors of Microstrip Antennas

The chosen rectangular and fractal microstrip patch antennas above an infinite ground plane are analyzed by the theory of characteristic modes. The resonant frequencies and radiation Q are evaluated. A novel method by Vandenbosch for rigorous evaluation of the radiation Q is employed for modal currents on a Rao-Wilton-Glisson (RWG) mesh. It is found that the resonant frequency of a rectangular patch antenna with a dominant mode presents quite complicated behaviour including having a minimum at a specific height. Similarly, as predicted from the simple wire model, the radiation Q exhibits a minimum too. It is observed that the presence of out-of-phase currents flowing along the patch antenna leads to a significant increase of the Q factor

Obrazovanje na području antena, rasprostiranja valova i mikrovalova

The paper is focused on teaching of »applied microwaves«. Attention is turned to antennas, but the same structure of education process is possible to apply for e.g. radio-wave propagation, microwaves, EMC, and other »electromagnetic topics« in their whole. The structure of the education is based on the appropriate amount of the theory followed by the computer simulations, the theoretical and engineering design and development, the measurement and final evaluation, which acts as the feedback between the initial goals and the final results. Important role of laboratory experiments based on flexible experimental set-ups is introduced and the possibility of distant (internet) laboratory excess is mentioned.Rad je usredotočen na učenje »primijenjenih mikrovalova«. Pozornost je okrenuta antenama, ali se ista struktura obrazovnog procesa može primijeniti na rasprostiranje radijskih valova, mikrovalove, elektromagnetsku kompatibilnost i druge elektromagnetske sadržaje. Struktura obrazovanja osniva se na odgovarajućoj teoriji popraćenoj simulacijama na računalu, teorijskom i inženjerskim proračunima i razvoju, mjerenjima i konačnoj provjeri, koja djeluje kao povratna veza između početnih ciljeva i konačnih rezultata. Utvrđena je važna uloga laboratorijskih eksperimenata temeljenih na fleksibilnim eksperimentalnim modelima i spomenuta mogućnost učenja na daljinu

Future paradigms for precision oncology

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Mutations in PIK3CA are infrequent in neuroblastoma

BACKGROUND: Neuroblastoma is a frequently lethal pediatric cancer in which MYCN genomic amplification is highly correlated with aggressive disease. Deregulated MYC genes require co-operative lesions to foster tumourigenesis and both direct and indirect evidence support activated Ras signaling for this purpose in many cancers. Yet Ras genes and Braf, while often activated in cancer cells, are infrequent targets for activation in neuroblastoma. Recently, the Ras effector PIK3CA was shown to be activated in diverse human cancers. We therefore assessed PIK3CA for mutation in human neuroblastomas, as well as in neuroblastomas arising in transgenic mice with MYCN overexpressed in neural-crest tissues. In this murine model we additionally surveyed for Ras family and Braf mutations as these have not been previously reported. METHODS: Sixty-nine human neuroblastomas (42 primary tumors and 27 cell lines) were sequenced for PIK3CA activating mutations within the C2, helical and kinase domain "hot spots" where 80% of mutations cluster. Constitutional DNA was sequenced in cases with confirmed alterations to assess for germline or somatic acquisition. Additionally, Ras family members (Hras1, Kras2 and Nras) and the downstream effectors Pik3ca and Braf, were sequenced from twenty-five neuroblastomas arising in neuroblastoma-prone transgenic mice. RESULTS: We identified mutations in the PIK3CA gene in 2 of 69 human neuroblastomas (2.9%). Neither mutation (R524M and E982D) has been studied to date for effects on lipid kinase activity. Though both occurred in tumors with MYCN amplification the overall rate of PIK3CA mutations in MYCN amplified and single-copy tumors did not differ appreciably (2 of 31 versus 0 of 38, respectively). Further, no activating mutations were identified in a survey of Ras signal transduction genes (including Hras1, Kras2, Nras, Pik3ca, or Braf genes) in twenty-five neuroblastic tumors arising in the MYCN-initiated transgenic mouse model. CONCLUSION: These data suggest that activating mutations in the Ras/Raf-MAPK/PI3K signaling cascades occur infrequently in neuroblastoma. Further, despite compelling evidence for MYC and RAS cooperation in vitro and in vivo to promote tumourigenesis, activation of RAS signal transduction does not constitute a preferred secondary pathway in neuroblastomas with MYCN deregulation in either human tumors or murine models

Compact Circular/Linear Polarization Dual-Band Prime-Focus Feed for Space Communication

We propose a novel, compact, prime-focus antenna feed for space communication. The feed requires full-wave simulator optimization for a given parabolic reflector and is designed to operate simultaneously on two bands, offering LHC/RHC polarizations for the 13 cm band and V/H polarizations for the 70 cm band. With performance results confirmed by measurement, it has been verified in practice that this compact feed is suitable for use in a low-noise Earth-Moon-Earth communication link

Electromagnetic Field in Anechoic and EMC Chambers - Part I - Modelling

Anechoic and EMC chamber at the CTU in Prague was designed and used for a variety of antenna measurements and EMI testing. Due to different measurement methods (near field, far field, compact range, and EMI measurement) applied in the laboratory, different simulations were performed during the design process

Wireless Mobile and Personal Communications.

Available from STL Prague, CZ / NTK - National Technical LibrarySIGLECZCzech Republi

Traffic lights for retinoids in oncology: molecular markers of retinoid resistance and sensitivity and their use in the management of cancer differentiation therapy

Abstract For decades, retinoids and their synthetic derivatives have been well established anticancer treatments due to their ability to regulate cell growth and induce cell differentiation and apoptosis. Many studies have reported the promising role of retinoids in attaining better outcomes for adult or pediatric patients suffering from several types of cancer, especially acute myeloid leukemia and neuroblastoma. However, even this promising differentiation therapy has some limitations: retinoid toxicity and intrinsic or acquired resistance have been observed in many patients. Therefore, the identification of molecular markers that predict the therapeutic response to retinoid treatment is undoubtedly important for retinoid use in clinical practice. The purpose of this review is to summarize the current knowledge on candidate markers, including both genetic alterations and protein markers, for retinoid resistance and sensitivity in human malignancies

Metronomic therapy has low toxicity and is as effective as current standard treatment for recurrent high-risk neuroblastoma

The metronomic therapy concept uses low doses of continuously applied chemotherapeutic, anti-angiogenetic, and immunomodulating drugs. Twenty patients with recurrent and 3 with refractory high-risk neuroblastoma were treated by the metronomic concept using celecoxib, cyclophosphamide, vinblastine, and etoposide for up to 24months. The outcome was compared to 274 matched patients with a first recurrence from stage 4 neuroblastoma using the variables time from diagnosis to first recurrence, number of organs involved, and MYCN amplification. All were treated with dose-intensive conventional chemotherapy. The study patients experienced 1-3 recurrences and had 1-3 sites involved (osteomedullary, primary tumor, central nervous system, lymph nodes, liver, lungs) before the metronomic therapy started. Two patients in complete remission and three with active refractory disease following recurrence treatment were excluded from the outcome analysis. The curves for secondary event-free and overall survival demonstrated no significant differences. The toxicity was minimal except for 3 grade thrombocytopenia and leukopenia (all heavily pretreated). The treatment was realized in an outpatient setting. The metronomic approach is similarly effective as standard treatment in recurrent high-risk neuroblastoma, has low toxicity, and is applicable in an outpatient setting. A prospective study including propranolol as a fifth drug is underway