Comparison of heat- and pressure-induced gelation of β-lactoglobulin aqueous solutions studied by small-angle neutron and dynamic light scattering

The gelation mechanism of β-lactoglobulin (bLG) aqueous solutions was investigated by dynamic light scattering (DLS) and small-angle neutron scattering (SANS). Temperature- and pressure-jump experiments, respectively, abbreviated as T-jump (from 20 to 75 °C; T-jump) and P-jump (from 0.1 to 315 MPa) were carried out and the time evolution of gel structure was monitored by DLS and SANS as a function of time. The gelation threshold was determined by DLS as the point when nonergodicity appeared. In the case of T-jump, a rapid increase of the time-average scattered intensity, 〈I〉_T, and a steep decrease of the initial amplitude of the intensity-intensity time correlation function, , were observed at the gelation threshold. On the other hand, P-jump showed a gradual increase of the 〈I〉_T and a continuous decrease of the . It was revealed by SANS that bLG underwent thermal denaturation, resulting in a formation of gels consisting of densely aggregated unfolded bLG oligomers. On the other hand, the pressure-induced gels were found to be a fractal aggregates consisting of primary particles of bLG monomers. The difference in the gel structure as well as gelation mechanism between bLGs treated by T-jump and P-jump is discussed in comparison with T-induced and P-induced microphase separation of amphiphilic block copolymers in water [Osaka N, Shibayama M. Phys Rev Lett 2006;96:048303].     

Structural aspects of the LCST phase behavior of poly(benzyl methacrylate) in room-temperature ionic liquid

The structure and lower critical solution temperature (LCST) phase behavior of well-defined poly(benzyl methacrylate) (PBnMA) solution using 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)amide, [C₂mim][NTf₂] ionic liquid (IL) as a solvent have been studied by dynamic light scattering (DLS) and small-angle neutron scattering (SANS) at various temperatures. The SANS profiles observed for fully deuterated IL ([C₂mim]-d₁₁[NTf₂]) containing PBnMA were kept practically unchanged in the temperature range between 298 and 363 K, while they suddenly changed at 363 K. This indicates that the LCST behavior of PBnMA-IL solution is a first-order phase transition, which is consistent with the DLS results. The SANS profiles below 363 K were well represented by the theoretical Debye scattering function with inter-molecular interaction and the radius of gyration, R_g was estimated to be almost constant, i.e., ∼45 Å. The SANS result obtained here was compared with those in aqueous PNIPAm solutions as a typical LCST system, and some differences between IL and aqueous solution systems are pointed out. It is found that thermodynamic quantities (ΔH_demix, ΔS_demix and ΔG_demix) from the homogeneous solution to the phase separation states strongly depend on the solvation of the PBnMA polymer by the IL ([C₂mim] cation and [NTf₂] anion). We propose an LCST phase separation mechanism in the polymer-IL solution.     

Neural network adaptive output feedback control for intensive care unit sedation and intraoperative anesthesia.

The potential applications of neural adaptive control for pharmacology, in general, and anesthesia and critical care unit medicine, in particular, are clearly apparent. Specifically, monitoring and controlling the depth of anesthesia in surgery is of particular importance. Nonnegative and compartmental models provide a broad framework for biological and physiological systems, including clinical pharmacology, and are well suited for developing models for closed-loop control of drug administration. In this paper, we develop a neural adaptive output feedback control framework for nonlinear uncertain nonnegative and compartmental systems with nonnegative control inputs. The proposed framework is Lyapunov-based and guarantees ultimate boundedness of the error signals. In addition, the neural adaptive controller guarantees that the physical system states remain in the nonnegative orthant of the state space. Finally, the proposed approach is used to control the infusion of the anesthetic drug propofol for maintaining a desired constant level of depth of anesthesia for noncardiac surgery.     

Incidence and influence of GB virus C and hepatitis C virus infection in patients undergoing bone marrow transplantation

Markers of GB virus C (GBV-C) and hepatitis C virus (HCV) were sought in 80 patients before and after they underwent BMT in a metropolitan hospital in Tokyo between 1990 and 1996. RNA of GBV-C was detected in 14 (18%) patients before BMT. Of the 55 patients who had been transfused, 14 (25%) possessed GBV-C RNA at a frequency significantly higher than in the 25 untransfused patients who were all negative (P < 0.01). HCV RNA was detected in three of the 55 (5%) transfused patients, but in none of the 25 untransfused patients. Sera at 3 months after BMT were available for 57 patients. GBV-C RNA persisted in all 10 patients who were infected before BMT, while it was detected in five of the remaining 47 (11%) patients who were not. However, persistent and/or ongoing GBV-C infection had no appreciable influence on patient morbidity or mortality. Two of the 57 patients were positive for HCV RNA before BMT and this persisted after BMT in both. HCV RNA became positive in eight of the remaining 55 (15%) patients who were negative before BMT. Of the 14 patients who received transfusions screened by the first-generation test at BMT, seven (50%) became positive for HCV RNA, a rate significantly higher than the one of 41 (2%) patients who received transfusions screened by the second-generation test (P < 0.001). These results indicate that BMT patients are at increased risk of GBV-C infection transmitted by transfusions received before and at the time of BMT, and that the risk of HCV infection has decreased after the implementation of the second-generation anti-HCV test.     

Characteristics of ammonia permeation through porous silica membranes

A sol–gel method was applied for the preparation of silica membranes with different average pore sizes. Ammonia (NH₃) permeation/separation characteristics of the silica membranes were examined in a wide temperature range (50–400°C) by measurement of both single and binary component separation. The order of gas permeance through the silica membranes, which was independent of membrane average pore size, was as follows: He > H₂ > NH₃ > N₂. These results suggest that, for permeation through silica membranes, the molecular size of NH₃ is larger than that of H₂, despite previous reports that the kinetic diameter of NH₃ is smaller than that of H₂. At high temperatures, there was no effect of NH₃ adsorption on H₂ permeation characteristics, and silica membranes were highly stable in NH₃ at 400°C (i.e., gas permeance remained unchanged). On the other hand, at 50°C NH₃ molecules adsorbed on the silica improved NH₃‐permselectivity by blocking permeation of H₂ molecules without decreasing NH₃ permeance. The maximal NH₃/H₂ permeance ratio obtained during binary component separation was ～30 with an NH₃ permeance of ～10^?7 mol m^?2 s^?1 Pa^?1 at an H₂ permeation activation energy of ～6 kJ mol^?1. © 2009 American Institute of Chemical Engineers AIChE J, 2010     

Effect of metal ion location in reaction medium on formation process and structure of PtCu–CuO nanoparticles supported on carbon and γ-Fe2O3

The process of nanoparticle formation by radiochemical synthesis in a heterogeneous system has been investigated considering the effects of the metal ion location in the reaction medium. PtCu nanoparticles supported on carbon and γ-Fe₂O₃ were synthesized using a high-energy electron beam. The metal ions in the precursor were categorized as those dissolved in solution, adsorbed on support, and precipitated. The ratio of metal ions in the solution was varied prior to the electron beam irradiation and its effects on the synthesized particle structures were examined. The nanoparticles were characterized by inductively coupled plasma-atomic emission spectrometry, transmission electron microscopy, X-ray diffraction, and X-ray absorption spectroscopy. A PtCu alloy and CuO were immobilized on the support in all the samples. The PtCu alloy nanoparticle composition depended on the Cu ion content in the solution. The nanoparticle formation mechanism could be explained using the obtained results. Metal ions present in the solution resulted in formation of the alloy. The adsorbed ions also contributed to the alloy formation by desorbing from the support when irradiated. On the other hand, alloy formation with Pt from the precipitated Cu ions was found to be difficult.