The Extended Overlap Alternate Arm Converter:A Voltage Source Converter with DC Fault Ride-Through Capability and a Compact Design

The Alternate Arm Converter (AAC) was one of the first modular converter topologies to feature DC-side fault ride-through capability with only a small penalty in power efficiency. However, the simple alternation of its arm conduction periods (with an additional short overlap period) resulted in (i) substantial 6-pulse ripples in the DC current waveform, (ii) large DC-side filter requirements, and (iii) limited operating area close to an energy sweet-spot. This paper presents a new mode of operation called Extended Overlap (EO) based on the extension of the overlap period to 60 ◦ which facilitates a fundamental redefinition of the working principles of the AAC. The EO-AAC has its DC current path decoupled from the AC current paths, a fact allowing (i) smooth DC current waveforms, (ii) elimination of DC filters, and (iii) restriction lifting on the feasible operating point. Analysis of this new mode and EO- AAC design criteria are presented and subsequently verified with tests on an experimental prototype. Finally, a comparison with other modular converters demonstrates that the EO-AAC is at least as power efficient as a hybrid MMC (i.e. a DC fault ride-through capable MMC) while offering a smaller converter footprint because of a reduced requirement for energy storage in the submodules and a reduced inductor volume

Overview of Aerosolized Florida Red Tide Toxins: Exposures and Effects

Florida red tide is caused by Karenia brevis, a dinoflagellate that periodically blooms, releasing its potent neurotoxin, brevetoxin, into the surrounding waters and air along the coast of the Gulf of Mexico. Exposure to Florida red tide toxins has been associated with adverse human health effects and massive fish and marine mammal deaths. The articles in this mini-monograph describe the ongoing interdisciplinary and interagency research program that characterizes the exposures and health effects of aerosolized Florida red tide toxins (brevetoxins). The interdisciplinary research program uses animal models and laboratory studies to develop hypotheses and apply these findings to in situ human exposures. Our ultimate goal is to develop appropriate prevention measures and medical interventions to mitigate or prevent adverse health effects from exposure to complex mixtures of aerosolized red tide toxins

One-Dimensional Lateral Force Anisotropy at the Atomic Scale in Sliding Single Molecules on a Surface

Using a q+ atomic force microscopy at low temperature, a sexiphenyl molecule is slid across an atomically flat Ag(111) surface along the direction parallel to its molecular axis and sideways to the axis. Despite identical contact area and underlying surface geometry, the lateral force required to move the molecule in the direction parallel to its molecular axis is found to be about half of that required to move it sideways. The origin of the lateral force anisotropy observed here is traced to the one-dimensional shape of the molecule, which is further confirmed by molecular dynamics simulations. We also demonstrate that scanning tunneling microscopy can be used to determine the comparative lateral force qualitatively. The observed one-dimensional lateral force anisotropy may have important implications in atomic scale frictional phenomena on materials surfaces

Effectiveness of Metyrapone in Treating Cushing's Syndrome: A Retrospective Multicenter Study in 195 Patients

Background: Cushing's syndrome (CS) is a severe condition with excess mortality and significant morbidity necessitating control of hypercortisolemia. There are few data documenting use of the steroidogenesis inhibitor metyrapone for this purpose. Objective: The objective was to assess the effectiveness of metyrapone in controlling cortisol excess in a contemporary series of patients with CS. Design: This was designed as a retrospective, multicenter study. Setting: Thirteen University hospitals were studied. Patients: We studied a total of 195 patients with proven CS: 115 Cushing's disease, 37 ectopic ACTH syndrome, 43 ACTH-independent disease (adrenocortical carcinoma 10, adrenal adenoma 30, and ACTH-independent adrenal hyperplasia 3). Measurements: Measurements included biochemical parameters of activity of CS: mean serum cortisol “day-curve” (CDC) (target 150–300 nmol/L); 9 am serum cortisol; 24-hour urinary free cortisol (UFC). Results: A total of 164/195 received metyrapone monotherapy. Mean age was 49.6 ± 15.7 years; mean duration of therapy 8 months (median 3 mo, range 3 d to 11.6 y). There were significant improvements on metyrapone, first evaluation to last review: CDC (91 patients, 722.9 nmol/L [26.2 μg/dL] vs 348.6 nmol/L [12.6 μg/dL]; P < .0001); 9 am cortisol (123 patients, 882.9 nmol/L [32.0 μg/dL] vs 491.1 nmol/L [17.8 μg/dL]; P < .0001); and UFC (37 patients, 1483 nmol/24 h [537 μg/24 h] vs 452.6 nmol/24 h [164 μg/24 h]; P = .003). Overall, control at last review: 55%, 43%, 46%, and 76% of patients who had CDCs, UFCs, 9 am cortisol less than 331 nmol/L (12.0 μg/dL), and 9 am cortisol less than upper limit of normal/600 nmol/L (21.7 μg/dL). Median final dose: Cushing's disease 1375 mg; ectopic ACTH syndrome 1500 mg; benign adrenal disease 750 mg; and adrenocortical carcinoma 1250 mg. Adverse events occurred in 25% of patients, mostly mild gastrointestinal upset and dizziness, usually within 2 weeks of initiation or dose increase, all reversible. Conclusions: Metyrapone is effective therapy for short- and long-term control of hypercortisolemia in CS

A prospective longitudinal study of Pasireotide in Nelson's syndrome

PURPOSE: Nelson's syndrome is a challenging condition that can develop following bilateral adrenalectomy for Cushing's disease, with high circulating ACTH levels, pigmentation and an invasive pituitary tumor. There is no established medical therapy. The aim of the study was to assess the effects of pasireotide on plasma ACTH and tumor volume in Nelson's syndrome. METHODS: Open labeled multicenter longitudinal trial in three steps: (1) a placebo-controlled acute response test; (2) 1 month pasireotide 300-600 μg s.c. twice-daily; (3) 6 months pasireotide long-acting-release (LAR) 40-60 mg monthly. RESULTS: Seven patients had s.c. treatment and 5 proceeded to LAR treatment. There was a significant reduction in morning plasma ACTH during treatment (mean ± SD; 1823 ± 1286 ng/l vs. 888.0 ± 812.8 ng/l during the s.c. phase vs. 829.0 ± 1171 ng/l during the LAR phase, p < 0.0001). Analysis of ACTH levels using a random intercept linear mixed-random effects longitudinal model showed that ACTH (before the morning dose of glucocorticoids) declined significantly by 26.1 ng/l per week during the 28-week of treatment (95% CI - 45.2 to - 7.1, p < 0.01). An acute response to a test dose predicted outcome in 4/5 patients. Overall, there was no significant change in tumor volumes (1.4 ± 0.9 vs. 1.3 ± 1.0, p = 0.86). Four patients withdrew during the study. Hyperglycemia occurred in 6 patients. CONCLUSIONS: Pasireotide lowers plasma ACTH levels in patients with Nelson's syndrome. A longer period of treatment may be needed to assess the effects of pasireotide on tumor volume. TRIAL REGISTRATION: Clinical Trials.gov ID, NCT01617733

The state of the Martian climate

60°N was +2.0°C, relative to the 1981–2010 average value (Fig. 5.1). This marks a new high for the record. The average annual surface air temperature (SAT) anomaly for 2016 for land stations north of starting in 1900, and is a significant increase over the previous highest value of +1.2°C, which was observed in 2007, 2011, and 2015. Average global annual temperatures also showed record values in 2015 and 2016. Currently, the Arctic is warming at more than twice the rate of lower latitudes

Oxychlorine Species in Gale Crater and Broader Implications for Mars

Of 15 samples analyzed to date, the Sample Analysis at Mars (SAM) instrument on the Mars Science Laboratory (MSL) has detected oxychlorine compounds (perchlorate or chlorate) in 12 samples. The presence of oxychlorine species is inferred from the release of oxygen at temperatures less than 600degC and HCl between 350-850degC when a sample is heated to 850degC. The O2 release temperature varies with sample, likely caused by different cations, grain size differences, or catalytic effects of other minerals. In the oxychlorine-containing samples, perchlorate abundances range from 0.06 +/- 0.03 to 1.15 +/- 0.5 wt% Cl2O7 equivalent. Comparing these results to the elemental Cl concentration measured by the Alpha Particle X-ray Spectrometer (APXS) instrument, oxychlorine species account for 5-40% of the total Cl present. The variation in oxychlorine abundance has implications for their production and preservation over time. For example, the John Klein (JK) and Cumberland (CB) samples were acquired within a few meters of each other and CB contained approximately1.2 wt% Cl2O7 equivalent while JK had approximately 0.1 wt%. One difference between the two samples is that JK has a large number of veins visible in the drill hole wall, indicating more post-deposition alteration and removal. Finally, despite Cl concentrations similar to previous samples, the last three Murray formation samples (Oudam, Marimba, and Quela) had no detectable oxygen released during pyrolysis. This could be a result of oxygen reacting with other species in the sample during pyrolysis. Lab work has shown this is likely to have occurred in SAM but it is unlikely to have consumed all the O2 released. Another explanation is that the Cl is present as chlorides, which is consistent with data from the ChemCam (Chemical Camera) and CheMin (Chemistry and Mineralogy) instruments on MSL. For example, the Quela sample has approximately1 wt% elemental Cl detected by APXS, had no detectable O2 released, and halite (NaCl) has been tentatively identified in CheMin X-ray diffraction data. These data show that oxychlorines are likely globally distributed on Mars but the distribution is heterogenous depending on the perchlorate formation mechanism (production rate), burial, and subsequent diagenesi

Oxychlorine Detection in Gale Crater, Mars and Implications for past Environmental Conditions

The Sample Analysis at Mars (SAM) instrument on the Mars Science Laboratory (MSL) rover has detected oxychlorine compounds such as perchlorate or chlorate in Gale Crater samples. Two potential pathways for oxychlorine formation on Mars are UV-induced interaction between chlorine and metal oxides or atmospheric oxygen and radiolysis of Cl-containing surface materials by galactic cosmic rays, with the chlorine being volcanically derived in both cases. Oxychlorine compounds are identified by a diagnostic release of O2 at temperatures <600 C and an HCl release from ~350-850 C during sample pyrolysis. Of the 16 samples analyzed by SAM as of July 2018, 12 have contained oxychlorine compounds, including all four scooped samples and 8 of the 12 drilled samples