Ludwigite-group minerals and szaibélyite: rare borate minerals from Vysoká – Zlatno skarn, Štiavnica stratovolcano, Slovakia

Beside of sedimentary evaporitic rocks, borate minerals occur also in some high temperature contact-metamorphic rocks, especially in skarns, locally in association with Fe and Sn ore minerals (e.g., Anovitz and Grew, 1996). The borate minerals are generally associated to the post-magmatic processes which occur in the contact aureolas of intrusive, acid to intermediary, calc-alkaline rocks (Pertsev, 1991). Borate minerals of the ludwigite group and szaibélyite were identificated from the Mg-skarn in the R-20 drilling core during geological exploration for Cu-Au porphyry-skarn ores in the Vysoká – Zlatno area near Banská Štiavnica, in the Štiavnica Neogene stratovolcano, centralSlovakia(Koděra et al., 2010).            Ludwigite-group minerals (LGM) form massive black aggregates (>5 cmlarge) of numerous acicular, euhedral to subhedral prismatic crystals (usually 0.2 to 3 mmlong). Ludwigite associates with clinohumite, szaibelyite, clinochlore, serpentine-group mineral, magnesite, dolomite, hematite, rarely valeriite, chalcopyrite, and sphalerite. Under transmitted light, LGM crystals are mostly opaque; locally they are translucent with strong pleochroism in sections parallel to z-axis (deep green - dark reddish brown). In BSE, LGM crystals show regular concentric, rarely oscillatory or irregular zoning caused by distinct element variations during their growth or partial alteration: the dark zones show enrichment in Mg, Al and Ti, in contrast to the pale zones which reveal larger amounts of Fe. The electron-microprobe analyses reveal growth evolution of LGM crystals from Al-rich azoproite [with £79 mol.% of Mg2(Mg0.5Ti0.5)(BO3)O2 end-member] to Al±Ti-rich ludwigite and Al-dominant LGM phase [“aluminoludwigite” with £53 mol.% of Mg2Al(BO3)O2 end-member] in central zones, whereas rim zones of the crystals and secondary veinlets attain nearly pure ludwigite composition [87–99 mol.% of Mg2Fe3+(BO3)O2 end-member]. Consequently, LGM from the Vysoká – Zlatno skarn show the largest compositional variations ever known from one occurrence and they reach the highest contents of Ti (£17.4 wt.% TiO2, 0.39 apfu) and Al (£14.4 wt.% Al2O3,0.53 apfu) ever reported in LGM (Schaller and Vlisidis, 1961; Marincea, 2000; Pertsev et al., 2004; Aleksandrov and Troneva, 2008, 2011).            The compositional variations indicate the following substitution mechanisms in the studied LGM: Mg2+ = Fe2+ for the all compositions, Fe3+ = Al3+  for samples without higher amount of Ti, and 2Al = Mg2++Ti4+ or 2Fe3+ = Mg2++Ti4+ for analyses including high Ti content.            Szaibélyite MgBO2(OH) occurs as aggregates of fibrous crystals, up to 0.5 mm in size, replacing LGM. Zoning in szaibélyite was not observed. The amounts of Mg are uniform (0.98 to 0.99 apfu), content of Fe2+ oscillates from 0.2 to 1.2 wt.% FeO (0.002–0.014 apfu) and indicates the Mg2+ = Fe2+ substitution. Szaibélyite also contains small admixtures of Mn (0.1–0.4 wt.% MnO), Al and Cr (£0.3 wt.% Al2O3 or Cr2O3).            The skarn mineralization originated as a result of contact thermal metamorphism of  Miocene calc-alkaline granodiorite intrusion on host Middle to Upper Triassic limestones, dolomites, shales and evaporitic anhydrite beds (the Veľký Bok Group). The evaporites were most likely the primary source of boron, whereas Ti was probably derived from the granodiorite. Clinohumite and LGM (azoproite to Al±Ti-rich ludwigite and “aluminoludwigite”) precipitated during the high-temperature contact metamorphic event at ~700 °C and £100 MPa, whereas the youngest Al,Ti-poor ludwigite veinlets, szaibéllyite, serpentine-group mineral, clinochlore, magnesite, dolomite, hematite and probably also sulfide minerals were formed during younger, lower-temperature hydrothermal-metasomatic event. 

Vývoj křidélka pro AERO L-39NG

Příspěvek prezentuje vývoj kompozitního křidélka letounu L-39NG. V první části je popsán samotný díl, jeho funkce a specifický způsob zatížení, který byl zohledněn při konstrukci. Dále je představen způsob návrhu kompozitního řešení zahrnujícího statickou a modální konečně prvkovou analýzu a aplikaci pevnostních kritérií. Křidélko je vyráběno technologií vláknového navíjení s osovým kladením vláken, která je zde také představena. Pro účely ověření výpočtů a certifikaci křidélka byly zákazníkem realizovány statické a únavové zkoušky a zkoušky odolnosti proti impaktu

Individualized versus conventional ovarian stimulation for in vitro fertilization: a multicenter, randomized, controlled, assessor-blinded, phase 3 noninferiority trial

Objective To compare the efficacy and safety of follitropin delta, a new human recombinant FSH with individualized dosing based on serum antimüllerian hormone (AMH) and body weight, with conventional follitropin alfa dosing for ovarian stimulation in women undergoing IVF. Design Randomized, multicenter, assessor-blinded, noninferiority trial (ESTHER-1). Setting Reproductive medicine clinics. Patient(s) A total of 1,329 women (aged 18â40 years). Intervention(s) Follitropin delta (AMH <15 pmol/L: 12 μg/d; AMH â¥15 pmol/L: 0.10â0.19 μg/kg/d; maximum 12 μg/d), or follitropin alfa (150 IU/d for 5 days, potential subsequent dose adjustments; maximum 450 IU/d). Main Outcomes Measure(s) Ongoing pregnancy and ongoing implantation rates; noninferiority margins â8.0%. Result(s) Ongoing pregnancy (30.7% vs. 31.6%; difference â0.9% [95% confidence interval (CI) â5.9% to 4.1%]), ongoing implantation (35.2% vs. 35.8%; â0.6% [95% CI â6.1% to 4.8%]), and live birth (29.8% vs. 30.7%; â0.9% [95% CI â5.8% to 4.0%]) rates were similar for individualized follitropin delta and conventional follitropin alfa. Individualized follitropin delta resulted in more women with target response (8â14 oocytes) (43.3% vs. 38.4%), fewer poor responses (fewer than four oocytes in patients with AMH <15 pmol/L) (11.8% vs. 17.9%), fewer excessive responses (â¥15 or â¥20 oocytes in patients with AMH â¥15 pmol/L) (27.9% vs. 35.1% and 10.1% vs. 15.6%, respectively), and fewer measures taken to prevent ovarian hyperstimulation syndrome (2.3% vs. 4.5%), despite similar oocyte yield (10.0 ± 5.6 vs. 10.4 ± 6.5) and similar blastocyst numbers (3.3 ± 2.8 vs. 3.5 ± 3.2), and less gonadotropin use (90.0 ± 25.3 vs. 103.7 ± 33.6 μg). Conclusion(s) Optimizing ovarian response in IVF by individualized dosing according to pretreatment patient characteristics results in similar efficacy and improved safety compared with conventional ovarian stimulation. Clinical Trial Registration Number NCT01956110