Formation of Fibrils by the Periplasmic Molecular Chaperone HdeB from Escherichia coli

The molecular chaperones HdeA and HdeB of the Escherichia coli (E. coli) periplasm protect client proteins from acid denaturation through a unique mechanism that utilizes their acid denatured states to bind clients. We previously demonstrated that the active, acid-denatured form of HdeA is also prone to forming inactive, amyloid fibril-like aggregates in a pH-dependent, reversible manner. In this study, we report that HdeB also displays a similar tendency to form fibrils at low pH. HdeB fibrils were observed at pH < 3 in the presence of NaCl. Similar to HdeA, HdeB fibrils could be resolubilized by a simple shift to neutral pH. In the case of HdeB, however, we found that after extended incubation at low pH, HdeB fibrils were converted into a form that could not resolubilize at pH 7. Fresh fibrils seeded from these “transformed” fibrils were also incapable of resolubilizing at pH 7, suggesting that the transition from reversible to irreversible fibrils involved a specific conformational change that was transmissible through fibril seeds. Analyses of fibril secondary structure indicated that HdeB fibrils retained significant alpha helical content regardless of the conditions under which fibrils were formed. Fibrils that were formed from HdeB that had been treated to remove its intrinsic disulfide bond also were incapable of resolubilizing at pH 7, suggesting that certain residual structures that are retained in acid-denatured HdeB are important for this protein to recover its soluble state from the fibril form.     

Modeling response granularity with mixture models: A case of severity ratings in child maltreatment

Behaviormetrika - Heaping, where responses are concentrated in round numbers, such as 5 or 10, is one of the response behaviors observed in surveys. The heaping phenomenon in subjective quantities...     

Densities of liquid lanthanoid sesquioxides measured with the electrostatic levitation furnace in the ISS

The densities of several liquid lanthanoid sesquioxides (Ln₂O₃, Ln = Er, Ho, Tb, Gd) were measured over the temperature range from 2700 K (the approximate melting point of these materials) to 3200 K. These measurements were performed using the Electrostatic Levitation Furnace onboard the International Space Station (ISS-ELF). Based on the Coulomb force between the charged samples and surrounding electrodes and employing a rapid feedback control process, specimens were stably levitated and subsequently melted by high power lasers. The molten oxides exhibited spherical morphologies and their volumes were readily calculated from magnified images. Subsequent weighing of the samples on Earth allowed the densities of the oxides to be determined. The densities of Er₂O₃, Ho₂O₃, Tb₂O₃, and Gd₂O₃ at their melting temperatures (T_m) were found to be 8170, 8035, 7451, and 7268 kg/m³, respectively, and these density values were shown to exhibit a linear correlation with temperature. The molar volumes of these oxides at their T_m values were calculated and compared with those of other sesquioxides (Al₂O₃, Ga₂O₃, and B₂O₃). The molar volumes of the nonglass-forming sesquioxides (Er₂O₃, Ho₂O₃, Tb₂O₃, Gd₂O₃, Al₂O₃, and Ga₂O₃) showed linear correlations with the cubes of their cation radii, whereas those of the glass-forming oxide (B₂O₃, As₂O₃, and Sb₂O₃) showed different correlations.     

Photoinduced electron transfer between the anionic porphyrins and viologens in titania nanosheets and monodisperse mesoporous silica hybrid films

Photoinduced electron transfer between an anionic porphyrin derivative (tetrakis(p-carboxyphenyl)porphyrin; H(2)TCPP(4-)) and an electron accepting methyl viologen (MV(2+)) was investigated in two different nanoscale configurations, i.e., layered titania nanosheet (TNS) photocatalysts and ammonium-functionalized monodisperse mesoporous silica (AMMSS) particles. Cationic MV(2+) intercalated within the TNS interlayers while anionic H(2)TCPP(4-) was accommodated within AMMSS nanocavities to form (MV(2+)-TNS)/(H(2)TCPP(4-)-AMMSS) hybrid films. Upon irradiation with UV light and excitation of the TNS in the (MV(2+)-TNS)/(H(2)TCPP(4-)-AMMSS) hybrid films, the consumption of H(2)TCPP(4-) and the formation of a one-electron reduced MV(2+) (MV(+·)) were simultaneously observed. No consumption of H(2)TCPP(4-) was observed when an electrically insulating poly(styrene) (PS) was also introduced at the interface. These results suggest that photoinduced electron transfer occurred at the interface between the TNS and the AMMSS.     

Detection of chatter vibration in end milling applying disturbance observer

Suppression of chatter vibration is required to improve the machined surface quality and enhance tool life. For monitoring the chatter vibrations, additional sensors such as acceleration sensors are generally used, which results in high costs and low reliability of the machine tools. In this study, a novel in-process method to detect chatter vibrations in end milling is developed on the basis of a disturbance observer theory. The developed system does not require any external sensors because it uses only the servo information of the spindle control system. Self-excited and forced chatter vibrations are successfully detected.     

Combinatorial catalyst approach for high-density growth of horizontally aligned single-walled carbon nanotubes on sapphire

We studied effects of metal catalyst and gas composition on the chemical vapor deposition (CVD) growth of horizontally aligned single-walled carbon nanotubes (SWCNTs) on r-plane sapphire substrates. The SWCNTs are sitting on the substrate and aligned along [10] direction of the sapphire surface. A combinatorial metal deposition method was applied for single and binary metal catalysts to systematically investigate the thickness and the composition dependence. The horizontally-aligned SWCNTs grown from stripe-patterned catalysts enable the direct comparison of the catalytic activity based on nanotube density. We found that the SWCNT density strongly depends on the metal catalyst in the order Fe > Co ? Ni ≈ Cu, while no nanotubes were grown over Mo. In addition, the methane concentration during CVD strongly influenced the nanotube density, and the optimal concentration varied depending on the metal species and its thickness. The study on the binary metal catalysts revealed that Fe–Co combination increases the SWCNT density (7–9 tubes/μm) about twice of the original metal film. The Co–Cu binary catalyst also showed the high density (8–10 tubes/μm) under a limited methane concentration. Different catalytic activity of each metal is discussed.     

粉煤灰桩模型试验和工程实例

本文通过室内模型试验对粉煤灰桩复合地基进行了研究,同时通过实例说明了粉煤灰桩在工程中的可行性和经济性,并对其设计等方面提出了一些建议.