Supply modulator for linear wideband RF power amplifiers

Este artículo trata de las técnicas de diseño de reguladores de potencia conmutados de alta eficiencia destinados a alimentar amplificadores de potencia (PAs) lineales, empleando técnicas de seguimiento para estándares inalámbricos de banda ancha. Los cuellos de botella presentados implican un compromiso entre tensión, slew rate y ancho de banda. De hecho, la limitación de slew rate es identificada como el principal desafío. Por tanto, se propone una técnica de mejora del slew rate denominada “bang-bang”. Este enfoque permite el uso de moduladores de alimentación eficientes para la alimentación de los mencionado amplificadores de potencia de banda ancha. El esquema propuesto no degrada significativamente la eficiencia del PA y preserva, e incluso mejora, la estabilidad del regulador conmutado. El prototipo ha sido implementada utilizando la tecnología de TSMC 0,18 μm. Resultados de simulación post-layout en Cadence® son presentados para demostrar la viabilidad del diseño llevado a cabo.This paper deals with the design techniques of power efficient switching regulators intended for linear power amplifiers (PAs) employing envelope tracking techniques in wideband wireless standards. The bottlenecks involve a tradeoff between ripple voltage, slew rate and bandwidth. The slew rate limitation is identified as the main challenge; thus a ‘bang-bang’ slew-enhancement technique is proposed. This approach enables the use of efficient supply modulators in wideband power amplifiers. The proposed scheme does not significantly degrade PA efficiency and preserves, and even improves, the stability of the switching regulator. The prototype has been implemented using the TSMC 0.18 μm technology; schematic simulation results in Cadence® are presented to prove the concept.Peer Reviewe

An Efficient Supply Modulator for Linear Wideband RF Power Amplifiers

Radio Frequency (RF) Power Amplifiers are responsible for a considerable amount of the power consumption in the entire transmitter-receiver (transceiver) of modern communication systems. The stringent linearity requirements of multi-standard transceivers to minimize cross-talking effects makes Linear Power Amplifiers, particularly class A, the preferred choice in broadband transceivers. This linearity requirement coupled with the fact that the Power Amplifier operates at low transmit power during most of its operation makes the efficiency of the entire transceiver poor. The limited transceiver efficiency leads to a reduction in the battery life of battery operated portable devices like mobile phones; hence drastically limiting talk time. To alleviate this issue, several research groups propose solutions to improve PA power efficiency. However, these solutions usually have a low efficiency at low power and are mostly limited to narrow bandwidth applications. In this thesis, the efficiency of a class A Power amplifier in wideband wireless standards like WiMax is improved by dynamically controlling the bias current and supply voltage of the PA. An efficient supply modulator based on a switching regulator architecture is proposed for controlling the supply voltage. The switching regulator is found to be slew-limited by the bulky inductor and capacitor used to regulate the supply voltage. The proposed solution alleviates the slew rate limitation by adding a bang-bang controlled current source. The proposed supply modulator has an average power efficiency of 81.6 percent and is suitable for wireless standards with bandwidths up to 20MHz compared to the relatively lower efficiencies and bandwidths of state of the art modulators. A class-A PA is shown to promise an average power efficiency of 21.3 percent when the bias current is controlled dynamically and the supply voltage is varied using the proposed supply modulator. This is a significant improvement over the poor average efficiency of 1.06 percent for a fixed bias conventional linear class A PA. The project has been simulated using the TSMC 0.18 micrometer technology

STAT3 inhibitor having anti-cancer activity and methods (US)

A small-molecule Stat3 dimerization inhibitor, S3I-M2001, is described and the dynamics of intracellular processing of activated Stat3 within the context of the biochemical and biological effects of the Stat3 chemical probe inhibitor are elucidated. S3I-M2001 is a newly-identified oxazole-based peptidomimetic of the Stat3 Src Homology (SH) 2 domain-binding phosphotyrosine peptide that selectively disrupts active Stat3:Stat3 dimers. Stat3-dependent malignant transformation, survival, and migration and invasion of mouse and human cancer cells harboring persistently-activated Stat3 were inhibited by S3I-M2001. S3I-M2001 inhibited Stat3-dependent transcriptional regulation of tumor survival genes, such as Bcl-xL. The disclosed compound is useful as a new potential treatment for certain cancers

‘Bang-Bang’ technique in supply modulation for linear wideband RF power amplifiers

This paper deals with the design techniques of power efficient switching regulators intended for linear power amplifiers employing envelope tracking techniques in wideband wireless standards. The bottlenecks involve a tradeoff between ripple voltage, slew rate and bandwidth. The slew rate limitation is identified as the main challenge, then a ‘bang-bang’ slew enhancement technique is proposed. This approach enables the use of efficient supply modulators in wideband power amplifiers. The proposed scheme does not significantly degrade PA efficiency and preserves the stability of the switching regulator. The prototype has been implemented using the TSMC 0.18 µm technology; schematic simulation results in Cadence® are presented to prove the concept.Postprint (published version

Driver Preference for Automatic or Manual Transmission Systems for Vehicles: A Case Study in Ghana

Systems in vehicles are being modified due to current technological trends. One of the commonest modified systems in vehicles was the transmission system. This study presented    views of drivers on preference for automatic or manual transmission vehicles in Ghana.   In all, data was collected from 1260 drivers selected randomly through survey, in-depth interviews and six focus group discussions. The study indicated that manual transmission vehicles were more in Ghana with the automatic now gaining relative patronage. However, automatic transmission vehicles were preferred by females than males. The first three factors that determined preference for automatic transmission were shifting quality, easy to use and power (engine) performance. However, for manual transmission vehicles repairability (easily reparable), reliability and better fuel economy were the first three factors that determined driver’s choice for such vehicles. The results further showed that most respondents believed that manual transmission vehicles had strong advantages over the automatic ones. The study concludes that more people prefer manual transmission vehicles than the automatic ones although the automatic ones are now gaining popularity. Key words:Automatic transmission, Manual Transmission, Vehicles, Preference, Ghan

Selective chemical probe inhibitor of Stat3, identified through structure-based virtual screening, induces antitumor activity

S31-201 (NSC 74859) is a chemical probe inhibitor of Stat3 activity, which was identified from the National Cancer Institute chemical libraries by using structure-based virtual screening with a computer model of the Stat3 SH2 domain bound to its Stat3 phosphotyrosine peptide derived from the x-ray crystal structure of the Stat3 beta homodimer. S31-201 inhibits Stat3-Stat3 complex formation and Stat3 DNA-binding and transcriptional activities. Furthermore, S31-201 inhibits growth and induces apoptosis preferentially in tumor cells that contain persistently activated Stat3. Constitutively climerized and active Stat3C and Stat3 SH2 domain rescue tumor cells from S31-201-induced apoptosis. Finally, S31-201 inhibits the expression of the Stat3-regulated genes encoding cyclin D1, BcI-xL, and survivin and inhibits the growth of human breast tumors in vivo. These findings strongly suggest that the antitumor activity of S31-201 is mediated in part through inhibition of aberrant Stat3 activation and provide the proof-of-concept for the potential clinical use of Stat3 inhibitors such as S31-201 in tumors harboring aberrant Stat3

Necdin, a Negative Growth Regulator, Is a Novel STAT3 Target Gene Down-Regulated in Human Cancer

Cytokine and growth factor signaling pathways involving STAT3 are frequently constitutively activated in many human primary tumors, and are known for the transcriptional role they play in controlling cell growth and cell cycle progression. However, the extent of STAT3's reach on transcriptional control of the genome as a whole remains an important question. We predicted that this persistent STAT3 signaling affects a wide variety of cellular functions, many of which still remain to be characterized. We took a broad approach to identify novel STAT3 regulated genes by examining changes in the genome-wide gene expression profile by microarray, using cells expressing constitutively-activated STAT3. Using computational analysis, we were able to define the gene expression profiles of cells containing activated STAT3 and identify candidate target genes with a wide range of biological functions. Among these genes we identified Necdin, a negative growth regulator, as a novel STAT3 target gene, whose expression is down-regulated at the mRNA and protein levels when STAT3 is constitutively active. This repression is STAT3 dependent, since inhibition of STAT3 using siRNA restores Necdin expression. A STAT3 DNA-binding site was identified in the Necdin promoter and both EMSA and chromatin immunoprecipitation confirm binding of STAT3 to this region. Necdin expression has previously been shown to be down-regulated in a melanoma and a drug-resistant ovarian cancer cell line. Further analysis of Necdin expression demonstrated repression in a STAT3-dependent manner in human melanoma, prostate and breast cancer cell lines. These results suggest that STAT3 coordinates expression of genes involved in multiple metabolic and biosynthetic pathways, integrating signals that lead to global transcriptional changes and oncogenesis. STAT3 may exert its oncogenic effect by up-regulating transcription of genes involved in promoting growth and proliferation, but also by down-regulating expression of negative regulators of the same cellular processes, such as Necdin

Cytoplasmic transport of Stat3 by receptor-mediated endocytosis

Signal transducer and activator of transcription (STAT) proteins are cytoplasmic transcription factors that translocate to the nucleus and regulate gene expression upon activation of cytokine or growth factor receptors. While this translocation event is essential for gene regulation by STATs, their mechanism of transport through the cytoplasm to the nucleus has remained elusive. We now report that cytoplasmic transport of Stat3 is an active process that requires receptor-mediated endocytosis. Stat3 co-localizes with endocytic vesicles in transit from the cell membrane to the perinuclear region in response to growth factor stimulation. Consistent with a role for receptor endocytosis in growth factor signaling, disruption of endocytosis with specific inhibitors blocks Stat3 nuclear translocation and Stat3-dependent gene regulation. These results indicate that receptor-mediated endocytosis may be a general mechanism of transport through the cytoplasm for a subset of cytoplasmic signaling proteins destined for the nucleus

Platinum IV complex inhibitor

The invention disclosed herein provides methods for diagnosing and treating diseases and/or conditions associated with dysregulated Stat3-mediated activity

A Bibliometric Survey of Research Output on Wireless Charging for Electric Vehicles

Wireless charging modules for electric vehicles are being increasingly studied. Previous research has focused on developing more effective wireless-charging modules for electric vehicles in order to pave the way for a more sustainable urban transportation. The objectives of the study were to identify the social structure of the field by mapping of research collaborations among authors and countries, measure the influence of authors and sources, identify the interactions between different researchers and the most influential authors, sources, documents and organizations. To achieve these objectives, a bibliometric search in the SCOPUS database was conducted using a combination of keywords and Boolean operators. The initial keyword search returned 2163 documents. The documents retrieved were manually filtered for further analysis. A scientometric analysis was carried out on the remaining 1367 documents using co-authorship, co-citation, and citation analyses for a number of measurement units. The results showed that “object detection” and “shielding effectiveness” were the most current research topics. Authors who were widely cited did not generally produce a large number of papers or collaborate with other authors. Authors from China, the United States, and the United Kingdom have all co-authored published works on the topic, indicating that they have all contributed considerably to the field’s achievements. This strongly highlighted the amount of funding localized in developed countries towards such technologies. The number of international co-authored studies conducted was low. This is most significant with no research conducted in this field in the less developed world. The most cited and influential scholars were G. A. Covic, J. T. Boys, and C. C. Mi. The most influential sources were IEEE Trans. on Power Electronics and IEEE Trans. on Induction Electronics, while the most productive sources were Energies and IEEE Access. The most influential documents were those by Covic G.A. (2013a) and Covic G.A. (2013b). Finally, emerging trends in charging and energy storage in electric vehicles were also discussed