We performed a preliminary study of neutron resonance absorption imaging to investigate the spatial distribution of constituent elements in borosilicate glasses containing simulated high-level ...radioactive waste, in which elemental inhomogeneities affect the physical and chemical stabilities of the glass. Dips generated by the resonance absorptions of Rh, Pd, Na, Gd, Cs, and Sm were observed in the neutron transmission spectra of the glass samples. The spatial distributions of these elements were obtained from the neutron transmission images at the resonance energies. The distributions of Rh and Pd visualized the sedimentation of these platinum group elements. In contrast, the lanthanides (Gd and Sm) and Cs were uniformly dispersed. These results show that neutron resonance absorption imaging is a promising tool for characterizing borosilicate glasses and investigating the vitrification mechanism of high-level radioactive waste.
This investigation focused on the self-assembly of poly(N-isopropylacrylamide)-block-poly(ethylene glycol) (PNIPA-block-PEG) in water. A quasi-living radical polymerization technique including a ...Ce(IV) ion redox system enabled us to prepare block copolymers with relatively narrow molecular weight distributions. We distinguish five regions in the phase diagram: a transparent sol, opaque sol, transparent gel, opaque gel, and syneresis. By examining the extent of changes in the spectroscopic properties of a fluorescence probe, pyrene, as a function of block polymer concentration and/or temperature, we determined the critical association concentration as well as the partition coefficient K v for pyrene. The spectroscopic properties indicate that the hydrophobicity around the probe starts to increase far below the demixing line of the PNIPA-block-PEG, a remarkable finding which suggests that even in the temperature region below the LCST temperature of a PNIPA block (∼32 °C), this block copolymer provides more space for a preferential transfer of pyrene molecules than a bulk water medium at a higher temperature. This result may be attributed to the action of water, which starts to behave as a selective solvent for PEG blocks; the PEG chains are more swollen with water than are the PNIPA chains. Dynamic light scattering measurements also indicate that contraction of the PNIPA block starts to occur around 18 °C, which is consistent with results obtained by fluorescence measurements. By employing small-angle neutron scattering, it is also confirmed that microphase separation occurs above 17 °C to form disordered micelles, which includes a range of states from (i) asymmetric swelling to (ii) micelle formation with only short-range liquidlike order. Above 30 °C, network domains are formed as a result of macrophase separation due to dehydration of PNIPA blocks. As the temperature increased up to 40 °C, the network domain is collapsed along a direction parallel to PNIPA-block-PEG interface, leading to increase in interfacial thickness and to macroscopic syneresis.
This investigation focused on the self-assembly of poly(
N-isopropylacrylamide)-
block-poly(ethylene glycol) (PNIPA-
b-PEG) in water. We distinguish four regions in the phase diagram: a transparent ...sol, opaque sol, opaque gel, and syneresis. Small-angle neutron scattering measurements revealed that microphase separation occurs above
17
∘
C
to form disordered micelles, which includes a range of states from (i) asymmetric swelling to (ii) micelle formation with only short-range liquid-like order. This result may be attributed to the action of water, which starts to behave as a selective solvent for PEG blocks; the PEG chains are more swollen with water than are the PNIPA chains.
To synthesize an amphiphilic block copolymer of poly(
N-isopropylacrylamide)-
block-poly(ethylene glycol) (NE), an aqueous soap-free emulsion polymerization system was employed where poly(
...N-isopropylacrylamide) (PNIPA), polymerized from the radically activated chain ends of poly(ethylene glycol) (PEG), forms micelle cores stabilized by PEG brush chains emanating there from. When this polymerization was carried out at temperatures equal to or higher than 34
°C, narrowly-dispersed NE, which cannot be obtained by solution polymerization, was successfully obtained. To elucidate the living nature of the soap-free emulsion polymerization, time-dependent monomer conversion and molecular weight of NE was investigated by time-resolved gel permeation chromatography (GPC). The results indicate that the compartmentalization of end radicals into micelles cores leads to the quasi-living behavior of the polymerization.
By employing small-angle neutron scattering (SANS), we investigated the microstructures of, poly(
N-isopropylacrylamide) (PNIPA)-
block-poly(ethylene glycol) (PEG) (NE) in deuterated water D
2O, as ...related to macroscopic behaviors of fluidity, turbidity and synerisis. SANS revealed following results: (i) microphase separation occurs at around above 17
°C in a temperature range of transparent sol below 30
°C. In the microdomain appeared in the transparent sol state, both block chains of PNIPA and PEG are swollen by water; (ii) for the NE solution of polymer concentration
W
p > 3.5% (w/v), corresponding to opaque gel above 30
°C, a percolated structure, i.e., network-like domain is formed by NE as a result of macrophase separation due to dehydration of the PNIPA chains. As the temperature increases toward 40
°C, the network domain is squeezed along a direction parallel to the NE interface, which leads to increase of the interfacial thickness given by swollen PEG chains and to the macroscopic synerisis behavior.
Multiple phase behavior was found in copolymer gels consisting of dimethylacrylamide and methacrylic acid. They are characterized by distinct degrees of swelling; the gel can take one of a set of ...swelling values, but none of the intermediate values. Three different phases, denoted as phase051 (as-prepared), phase376 (swollen at high pH), phase440 (swollen after treatment by pH 12) were clearly resolved, where the three digits denote their linear swelling ratios in percentage with respect to the size at preparation. Each phase was stable and did not change its swelling ratio with pH or temperature as long as the values of pH or temperature were within limited ranges. Transitions among different phases were discrete with hysteresis loops. The microenvironment of these three phases was observed by steady-state and transient fluorescence spectroscopy, which indicated the multiple phase behavior appeared as the result of the coexistence of hydrophilic and less-hydrophilic (hydrophobic) domains in the gel and their fraction varied depending on pH.
BACKGROUND: Nonenveloped and thermostable viruses such as parvovirus B19 (B19) can be transmitted to patients who are receiving plasma‐derived coagulation factor concentrates treated by the S/D ...method for inactivating enveloped viruses. Therefore, it is important to develop and validate new methods for the inactivation of nonenveloped viruses.
STUDY DESIGN AND METHODS: Suspensions of B19 in coagulation factor concentrates (FVIII) were irradiated with UVC light. B19 infectivity was determined by an indirect immunofluorescence assay using CFU–E, as a host cell, derived from peripheral blood CD34+ cells. The effects of catechins on B19 infectivity and on FVIII activity after UVC illumination were also examined.
RESULTS: The indirect immunofluorescence assay estimated the B19 infectivity of samples containing virus copies of 105 to 1011 per 10 μL to be a median tissue culture‐infectious dose of 100.3 to 105.4 per 10 μL. B19 was inactivated by 3 log at 750 J per m2 of UVC radiation and was undetectable after 1000 or 2000 J per m2 of irradiation. However, FVIII activity decreased to 55 to 60 percent of pretreatment activity after 2000 J per m2 of UVC radiation. This was inhibited in the presence of rutin or catechins. Epigallocatechin gallate could maintain FVIII activity at almost 100 percent of pretreatment activity after 2000 J per m2 of UVC radiation, while B19 infectivity was decreased to undetectable levels, which resulted in >3.9 log inactivation.
CONCLUSION: UVC radiation in the presence of catechins, especially epigallocatechin gallate, appears to be an effective method of increasing the viral safety of FVIII concentrates without the loss of coagulation activity.
Mesoscopic structures of a dehydrated N-isopropylacrylamide/sodium acrylate (NIPA/SA) gel and the re-moistened one are investigated with complementary use of the small-angle X-ray scattering (SAXS) ...and small-angle neutron scattering (SANS) methods. The SAXS profile of the dehydrated NIPA/SA gel shows a clear peak at
q=0.026
Å
−1 but that of the re-moistened one does not. On the other hand, only the SANS profile of the re-moistened NIPA/SA gel shows a peak at
q=0.022
Å
−1. Taking into account that SAXS is sensitive to the fluctuation of the distribution of the SA bases and SANS is sensitive to that of the water in the NIPA/SA gel, these results indicate that inhomogeneous evaporation of water in the NIPA/SA gel occurs on the dehydration and that the SA clusters are finally generated.
