Seed contamination with polyketide mycotoxins such as sterigmatocystin (ST) produced by Aspergilli is a worldwide issue. The ST biosynthetic pathway is well-characterized in A. nidulans, but regulatory aspects related to the carbon source are still enigmatic. This is particularly true for lactose, inasmuch as some ST production mutant strains still synthesize ST on lactose but not on other carbon substrates. Here, kinetic data revealed that on d-glucose, ST forms only after the sugar is depleted from the medium, while on lactose, ST appears when most of the carbon source is still available. Biomass-specified ST production on lactose was significantly higher than on d-glucose, suggesting that ST formation may either be mediated by a carbon catabolite regulatory mechanism, or induced by low specific growth rates attainable on lactose. These hypotheses were tested by d-glucose limited chemostat-type continuous fermentations. No ST formed at a high growth rate, while a low growth rate led to the formation of 0.4 mg·L⁻¹ ST. Similar results were obtained with a CreA mutant strain. We concluded that low specific growth rates may be the primary cause of mid-growth ST formation on lactose in A. nidulans, and that carbon utilization rates likely play a general regulatory role during biosynthesis.

In this study, we report the findings of a morphological analysis of a resorcinol–formaldehyde (RF)-based carbon aerogel (CA) and its graphene oxide (GO)-doped version (CA-GO), prepared for possible applications as an electrode material. Beyond some electron microscopic and N₂ sorption investigations, we mostly used NMR cryoporometry and relaxometry to characterize the gels in a wet state, as they are usually applied. The precursor RF polymer aerogel was prepared both with and without GO and was subsequently carbonized into carbon aerogel. Modifying the polymer aerogel using GO resulted in a larger variety of C-O bonds in both polymer aerogels. However, the most important changes occurred in the morphology of the carbon aerogels. NMR relaxometry revealed the highly hydrophilic nature of the pore wall of the RF polymer aerogels, as demonstrated by their uniform wetting behavior. The carbonization resulted in a mostly hydrophobic pore wall decorated by some oxygen-containing spots and a macroporous system. Doping with GO after pyrolysis resulted in spherical pores in the CA and cylindrical pores in the CA-GO, which is potentially a more promising material for electrochemical use than CA.

Thermal convection is always present when the temperature of an NMR experiment is different from the ambient one. Most often, it falsifies the value of the diffusion coefficient determined by NMR diffusiometry using a PGSE NMR experiment. In spite of common belief, it acts not only at higher temperatures but also at temperatures lower than in the laboratory. Sodium alkyl-sulfate monomers and micelles in D₂O solvent were used as model molecules measured at T = 319 K in order to show that thermal convection sometimes remains hidden in experiments. In this paper, we demonstrate that the increase in apparent diffusion coefficient with increasing diffusion time is a definite indicator of thermal convection. Extrapolation to zero diffusion time can also be used to obtain the real diffusion coefficient, likewise applying the less sensitive pulse sequences designed for flow compensation or the expensive hardware, e.g., sapphire or Shigemi NMR tubes, to decrease the temperature gradient. Further, we show experiments illustrating the effect of a long diffusion time in which the periodic changes of the echo intensity with gradient strength appear as predicted by theories.

A sebgyógyulást elősegítő anyagoknak számos kémiai, biológiai, mechanikai feltételnek kell megfelelniük, mint például a biokompatibilitás, biodegradábilitás; eközben adott ideig meg kell tartaniuk a kialakított szerkezetet, és szelektíven kell kölcsönhatásba lépniük pl. a csontképződésben részt vevő sejtekkel is. Munkánk célja stabil szerkezetet biztosító, hőkezeléssel iniciált, citromsavval keresztkötött polivinil-alkohol vázak elektrosztatikus szálképzéssel történő előállítása volt. A szálak stabilitását a keresztkötőanyag mennyiségének optimalizálásával és a szövetek hőkezelésével kívántuk elérni. A kiindulási polimer oldatok viszkozitását folyásgörbe mérésekből határoztuk meg. Az ebből készített szövetek felületi morfológiáját alacsony vákuumú pásztázó elektronmikroszkópia és nedvesítési peremszög mérésekkel meghatározott paraméterek változásait detektálva tanulmányoztuk. A keresztkötőanyag-tartalom növelése a szálátmérő növekedését, (224 ± 52 nm-ről, 269 ± 109 nm-re) az eloszlás kiszélesedését és a hidrofilicitás csökkenését eredményezte, amely hatásokat a hőkezelés még kifejezettebbé tett. Az ekképpen előállított minták hőkezelés után a desztillált vizes 24–120 órányi áztatásnak is ellenálltak. Az eredmények alapján meghatározható egy felhasználás szempontjából optimális polimer oldat összetétel.