Design, Analysis, and Construction of an Equal Split Wilkinson Power Divider

The Wilkinson power divider is a well known device in the RF/microwave community used for splitting or combining signals. It is composed of simple transmission lines and a resistor, and takes advantage of the properties of quarter-wavelength transmission line sections to provide ideal power divider characteristics. Three different equal split Wilkinson power dividers are designed to operate near 1800 MHz and constructed using typical microstrip fabrication techniques. The three power dividers each feature a unique design to help determine how the microstrip layout can impact isolation and return loss. A circuit analysis of the general Wilkinson power divider schematic is performed to provide insight into the device characteristics as well as present a clear derivation of the correlating scattering matrix. A thorough comparison between the performances of each of the three different designs is conducted and the results are provided and discussed. The conclusions drawn from this investigation are that multiple Wilkinson power divider microstrip layouts can meet specific design criteria with similar results, indicating the robustness of the Wilkinson design. In particular and contrary to what is typically claimed within the RF/microwave community, a power divider featuring straight, parallel quarter-wavelength sections showed no degradation in isolation (or negligible effects of coupling) when compared to a power divider with curved quarter-wavelength sections

A statistical model for application of maneuver flight loads data to structural design criteria

Statistical model for application of maneuver flight loads data to structural design dat

Fatigue life estimates for helicopter loading spectra

Helicopter loading histories applied to notch metal samples are used as examples, and their fatigue lives are calculated by using a simplified version of the local strain approach. This simplified method has the advantage that it requires knowing the loading history in only the reduced form of ranges and means and number of cycles from the rain-flow cycle counting method. The calculated lives compare favorably with test data

The CSR-Quality Trade-off: When Can Corporate Social Responsibility and Corporate Ability Compensate Each Other?

This paper investigates under what conditions a good corporate social responsibility (CSR) can compensate for a relatively poor corporate ability (CA) (quality), and vice versa. The authors conducted an experiment among business administration students, in which information about a financial services company’s CA and CSR was provided. Participants indicated their preferences for the company’s products, stocks, and jobs. The results show that for stock and job preferences, a poor CA can be compensated by a good CSR. For product preferences, a poor CA could not be compensated by a good CSR, at least when people thought that CA is personally relevant to them. Furthermore, a poor CSR could be compensated by a good CA for product, stocks, and job preferences

The genomic health of ancient hominins

The genomes of ancient humans, Neandertals, and Denisovans contain many alleles that influence disease risks. Using genotypes at 3180 disease-associated loci, we estimated the disease burden of 147 ancient genomes. After correcting for missing data, genetic risk scores were generated for nine disease categories and the set of all combined diseases. These genetic risk scores were used to examine the effects of different types of subsistence, geography, and sample age on the number of risk alleles in each ancient genome. On a broad scale, hereditary disease risks are similar for ancient hominins and modern-day humans, and the GRS percentiles of ancient individuals span the full range of what is observed in present day individuals. In addition, there is evidence that ancient pastoralists may have had healthier genomes than hunter-gatherers and agriculturalists. We also observed a temporal trend whereby genomes from the recent past are more likely to be healthier than genomes from the deep past. This calls into question the idea that modern lifestyles have caused genetic load to increase over time. Focusing on individual genomes, we find that the overall genomic health of the Altai Neandertal is worse than 97% of present day humans and that Ötzi the Tyrolean Iceman had a genetic predisposition to gastrointestinal and cardiovascular diseases. As demonstrated by this work, ancient genomes afford us new opportunities to diagnose past human health, which has previously been limited by the quality and completeness of remain

Origin of trap assisted tunnelling in ammonia annealed SiC trench MOSFETs

The interface between silicon carbide (SiC) and silicon dioxide (SiO2) is of considerable importance for the performance and reliability of 4H-SiC (trench) metal oxide semiconductor field effect transistors (MOSFETs) and various different post oxidation anneals (POAs) have been used to optimize its quality. Whereas nitric oxide (NO) POA leads to very reliable and well performing MOSFETs, ammonia (NH3) can further improve the device performance, however, at the cost of the gate oxide (GOX) reliability, e.g. leading to trap assisted tunneling (TAT). We investigate the origin of TAT and GOX leakage in differently annealed gate oxides experimentally, using 4H-SiC trench MOSFETs, and theoretically, using Density Functional Theory (DFT) simulations. Our findings reinforce the view that the NO anneal for SiC devices results in the best overall quality as devices annealed in NH3 and nitrogen N2 show higher oxide charge density and leakage currents. DFT simulations demonstrate that, contrary to what has often been assumed so far, NH3 annealing leads to the formation of additional hydrogen related defects, which open leakage paths in the oxide otherwise not present in NO treated oxides

Drug-tolerant persister cancer cells are vulnerable to GPX4 inhibition.

Acquired drug resistance prevents cancer therapies from achieving stable and complete responses. Emerging evidence implicates a key role for non-mutational drug resistance mechanisms underlying the survival of residual cancer 'persister' cells. The persister cell pool constitutes a reservoir from which drug-resistant tumours may emerge. Targeting persister cells therefore presents a therapeutic opportunity to impede tumour relapse. We previously found that cancer cells in a high mesenchymal therapy-resistant cell state are dependent on the lipid hydroperoxidase GPX4 for survival. Here we show that a similar therapy-resistant cell state underlies the behaviour of persister cells derived from a wide range of cancers and drug treatments. Consequently, we demonstrate that persister cells acquire a dependency on GPX4. Loss of GPX4 function results in selective persister cell ferroptotic death in vitro and prevents tumour relapse in mice. These findings suggest that targeting of GPX4 may represent a therapeutic strategy to prevent acquired drug resistance

Notes

Notes by Robert J. Affeldt, Andrew V. Giorgi, Mark Harry Berens, Robert C. Enburg, James J. Haranzo, F. Richard Kramer, George J. Murphy, Jr., James F. O\u27Rieley, and Edward J. VanTassel