Performance of a low-power subsonic-arc-attachment arcjet thruster

A subsonic-arc-attachment thruster design was scaled from a 30 kW 1960's vintage thruster to operate at nominally 3 kW. Performance measurements were obtained over a 1-4 kW power range using hydrogen as the propellant. Several modes of operation were identified and were characterized by varying degrees of voltage instability. A stability map was developed showing that the voltage oscillations were brought upon by elevated current or propellant levels. At a given specific energy level the specific impulse increased asymptotically with increased flow rates. Comparisons of performance were made between radial and tangential propellant injection. When the vortex flow was eliminated using radial injection, the operating voltages were lower at a given current, and the specific impulse and efficiency decreased. Tests were also conducted to determine the effects of background pressure on operation, and performance data were obtained at pressures of 0.047 Pa and 18 Pa. For a given specific energy level, the performance increased with a decrease in facility background pressure. Lowering the background pressure also caused a dramatic change in the voltage-current characteristic and the voltage stability, a phenomenon not previously reported with conventional supersonic-arc-attachment thrusters

The Technology Bias in Entrepreneur-Investor Negotiations

Entrepreneur-investor negotiations are pivotal for ventures in need of funding. Yet, to date, little is known about the dynamics of these negotiations. We investigate a critical feature of this phenomenon by examining the role of technology, via cognitive heuristics, in shaping entrepreneur and investor perceptions as well as subsequent negotiation outcomes. In a controlled laboratory setting, we simulated 103 negotiations between entrepreneurs and investors. We hypothesize and find that there is a pervasive technology bias that influences the perceptions of both parties of the negotiation, and consequently negotiation outcomes. Our findings offer unique insights into the relationships of technology, cognitive heuristics, and negotiations. We discuss the implications for both practitioners and theoreticians in the areas of technology, decision making, negotiations, and entrepreneurial financing

The clinical significance of epidermal growth factor receptor (egf-r) in human breast cancer: A review on 5232 patients

Epidermal growth factor (EGF) is a 53-aminoacid polypeptide (mol wt 6.045 K) that can influence proliferation and differentiation of a wide variety of cells (1–6). EGF as well as transforming growth factor-α (TGF-α), both of which can activate EGF receptor (EGF-R), are probably produced locally in many tissues as local growth factors rather than as systemic hormones. There is evidence that EGF plays a role in carcinogenesis and that the EGF-stimulated growth regulatory system (apart from that of benign cells) is also involved in proliferation of malignant cells (3). Cellular events are induced by EGF via its cell membrane receptor (EGF-R). The EGF-R is a 170 K glycoprotein that can be divided into an extracellular domain binding EGF or TGF-α, a short transmembrane domain, and an intracellular domain carrying tyrosine kinase activity (7). This intracellular domain shows close sequence homology with the c-erbB-2 and with neu (8), the rat homolog of c-erbB-2 oncogene. Increased expression of the EGF-R gene has been found in a variety of tumors, generally indicating a more aggressive behavior of cancers compared to those with low or normal expression (9–10) although this association is not invariant (11). EGF-R has been identified by several methods including radioligand binding assays, autoradiography, immunocytohistochemistry, immunoenzymatic assays, and measurement of EGF-R transcripts

Influencing investors : an examination of angel investor perceptions of entrepreneurial investment opportunities

This dissertation examines the factors which influence angel investor perceptions and their eventual investment decision. I propose a model which has perceived risk and expected return at its core. Visually, this model can be translated into a malleable hurdle rate which entrepreneurs must exceed to receive financing. In this model, influential factors can exert influence in two ways - by moving the investment relative to the hurdle rate and/or moving the hurdle rate relative to the investment. Using a survey data from 203 investment opportunities analyzed by 106 angel investors, this model is empirically tested. The direct effect of leadership quality and business quality had no effect on perceived risk, but leadership quality did have a direct effect on expected return (business quality could not be tested). Experience (as an investor, in industry, and as an entrepreneur), an angel characteristic, had no moderating effect on these relationships. Further analyses suggest that angel investors rely only on return expectations and seem not to consider risk when making investment decisions. Entrepreneur enthusiasm and having a social tie moderated the risk-investment relationship while personal relevance and risk aversion moderated the return-investment relationship. Finally, the nuances of social ties are examined with findings suggesting that entrepreneurs with stronger relationships with the investor benefited by securing investment to a greater extent than entrepreneurs with weaker ties or no ties. Other tie nuances did not seem to have an effect. Through examining not only which factors exert influence, but also how these factors exert their influence, these findings offer valuable insights about the distinctions between risk and return, theoretical boundary conditions, and a better understanding of angel investment decision making

Investigation of a subsonic-arc-attachment thruster using segmented anodes

To investigate high frequency arc instabilities observed in subsonic-arc-attachment thrusters, a 3 kW, segmented-anode arc jet was designed and tested using hydrogen as the propellant. The thruster nozzle geometry was scaled from a 30 kW design previously tested in the 1960's. By observing the current to each segment and the arc voltage, it was determined that the 75-200 kHz instabilities were results of axial movements of the arc anode attachment point. The arc attachment point was fully contained in the subsonic portion of the nozzle for nearly all flow rates. The effects of isolating selected segments were investigated. In some cases, forcing the arc downstream caused the restrike to cease. Finally, decreasing the background pressure from 18 to 0.05 Pa affected the pressure distribution in the nozzle including the pressure in the subsonic arc chamber

Induction of small cell lung cancer by somatic inactivation of both Trp53 and Rb1 in a conditional mouse model

AbstractSmall cell lung cancer (SCLC) is a highly aggressive human tumor with a more than 95% mortality rate. Its ontogeny and molecular pathogenesis remains poorly understood. We established a mouse model for neuroendocrine (NE) lung tumors by conditional inactivation of Rb1 and Trp53 in mouse lung epithelial cells. Mice carrying conditional alleles for both Rb1 and Trp53 developed with high incidence aggressive lung tumors with striking morphologic and immunophenotypic similarities to SCLC. Most of these tumors, which we designate MSCLC (murine small cell lung carcinoma), diffusely spread through the lung and gave rise to extrapulmonary metastases. In our model, inactivation of both Rb1 and p53 was a prerequisite for the pathogenesis of SCLC

Pleiotropic actions of suramin on the proliferation of human breast-cancer cells in vitro

Suramin, a non‐specific growth factor antagonist, is currently under investigation for treatment of cancer patients. We studied its action on 6 different human breast‐cancer cell lines in vitro. In complete growth medium, pleiotropic effects were observed with respect to cell proliferation, i.e. suramin is stimulatory at low concentrations and inhibitory at higher concentrations, for 4 of the 6 cell lines studied. The various cell lines showed marked differences with respect to the antiproliferative action of suramin, the Evsa‐T cells being by far the most sensitive ones. A suramin concentration of 100 μg/ml brought about a 100% stimulation of the proliferation of ZR/HERc cells, ZR 75.1 cells ectopically expressing a human epidermal growth factor receptor (EGF‐R) cDNA. Although less pronounced (10 to 60% stimulation), a similar response was observed for the parent ZR 75.1 cells, as well as for T‐47D and MDA‐MB‐231 cells. The non‐specificity of the action of suramin was established by the observation that suramin‐induced inhibition of cell proliferation could be abolished by insulin‐like growth factor‐1 (IGF‐I) or basic fibroblast growth factor (bFGF), and even by estradiol, both in complete growth medium and under defined serum‐free conditions. Our data indicate that suramin exerts pleiotropic effects on the proliferation of human breast cancer cells in vitro, and confirm the non‐specific nature of its action. The stimulatory effect of low concentrations of suramin on the proliferation of breast cancer cells may have important consequences for breast cancer patients treated with suramin. Copyrigh

Increased MAPK1/3 Phosphorylation in Luminal Breast Cancer Related with PIK3CA Hotspot Mutations and Prognosis

INTRODUCTION: While mutations in PIK3CA are most frequently (45%) detected in luminal breast cancer, downstream PI3K/AKT/mTOR pathway activation is predominantly observed in the basal subtype. The aim was to identify proteins activated in PIK3CA mutated luminal breast cancer and the clinical relevance of such a protein in breast cancer patients. MATERIALS AND METHODS: Expression levels of 171 signaling pathway (phospho-)proteins established by The Cancer Genome Atlas (TCGA) using reverse phase protein arrays (RPPA) were in silico examined in 361 breast cancers for their relation with PIK3CA status. MAPK1/3 phosphorylation was evaluated with immunohistochemistry on tissue microarrays (TMA) containing 721 primary breast cancer core biopsies to explore the relationship with metastasis-free survival. RESULTS: In silico analyses revealed increased phosphorylation of MAPK1/3, p38 and YAP, and decreased expression of p70S6K and 4E–BP1 in PIK3CA mutated compared to wild-type luminal breast cancer. Augmented MAPK1/3 phosphorylation was most significant, i.e. in luminal A for both PIK3CA exon 9 and 20 mutations and in luminal B for exon 9 mutations. In 290 adjuvant systemic therapy naïve lymph node negative (LNN) breast cancer patients with luminal cancer, high MAPK phosphorylation in nuclei (HR = 0.49; 95% CI, 0.25–0.95; P =.036) and in tumor cells (HR = 0.37; 95% CI, 0.18–0.79; P =.010) was related with favorable metastasis-free survival in multivariate analyses including traditional prognostic factors. CONCLUSION: Enhanced MAPK1/3 phosphorylation in luminal breast cancer is related to PIK3CA exon-specific mutations and correlated with favorable prognosis especially when located in the nuclei of tumor cells