Ion beam plume and efflux characterization flight experiment study

A flight experiment and flight experiment package for a shuttle-borne flight test of an 8-cm mercury ion thruster was designed to obtain charged particle and neutral particle material transport data that cannot be obtained in conventional ground based laboratory testing facilities. By the use of both ground and space testing of ion thrusters, the flight worthiness of these ion thrusters, for other spacecraft applications, may be demonstrated. The flight experiment definition for the ion thruster initially defined a broadly ranging series of flight experiments and flight test sensors. From this larger test series and sensor list, an initial flight test configuration was selected with measurements in charged particle material transport, condensible neutral material transport, thruster internal erosion, ion beam neutralization, and ion thrust beam/space plasma electrical equilibration. These measurement areas may all be examined for a seven day shuttle sortie mission and for available test time in the 50 - 100 hour period

Nano- and Microgels of Poly(Vinyl Methyl Ether) Obtained by Radiation Techniques

Hydroxyl radicals were generated radiolytically in N2O-saturated aqueous solutions in the presence of poly(vinyl methyl ether) (PVME, 6×104 Da, 10-3-10-2 mol⋅dm-3 in monomer units). As measured by pulse radiolysis, they react (k = 2.2×108 dm3⋅mol-1⋅s-1) with PVME by giving mainly rise to α-alkoxyalkyl radicals (~72%) that reduce (k ≈ 2×109 dm3⋅mol-1⋅s-1) Fe(CN)6 3-, IrCl6 2- or tetranitromethane. Based on the formaldehyde yield in the presence of the latter two oxidants (∼40% of •OH), it is concluded that OH radicals undergo H-abstraction at ROCH2–H, R3C–H and R2HC–H with probabilities of ∼40%, ∼32% and ∼28%, respectively. The momentary rate constant of the decay of the PVME radicals depends on the number of radicals per polymer chain and drops as they decay. The yield of intermolecular crosslinks, as measured by an increase of the molecular weight, strongly increases with decreasing dose rate, and it is concluded that the majority of crosslinks occur intramolecularly, even at the lowest dose rate used (0.0015 Gy⋅s-1, G (intermolecular crosslinks) = 0.62×10-7 mol⋅J-1). At low temperatures and low polymer concentrations the intramolecular crosslinking reaction is favored. A large number of radicals are formed in a short period of time during each pulse of accelerated electrons. The  combination of the formed polymeric radicals is in the intramolecular way and nanogels formation occurs. Without changes in the molecular weight the dimension (radius of gyration and hydrodynamic radius), as well as the intrinsic viscosity of the nanogels decreases with increasing radiation dose. At temperatures above the LCST PVME molecules collapse to globular particles. Electron beam irradiation of these stable phase-separated structures leads to the formation of temperature-sensitive microgel particles. The additive-free method of crosslinking of polymers in aqueous solutions by high-energy radiation offers the application of these microgels in the field of medicine because of no remaining toxic substances (monomers, initiators, crosslinkers, etc.). The variation of the crosslinking density and the particle diameter can be performed by varying the polymer concentration and the radiation dose. Applying the closed-loop system reduces the amount of un-crosslinked molecules (sol content)

Comments on the High Pressure Preservation of Human Milk

The current state of studies on the high pressure preservation of the human milk is briefly presented. It is indicated that reaching (i) the antimicrobial safety, (ii) antiviral safety, and (iii) high nutritional, metabolic and immunological quality, may be difficult for a “classical” single pressure pulse High Pressure Preservation (HPP) treatment. It is shown that the sudden decompression leads to additional physical processes, which can be important for supporting the HPP technology. Additional advantages were reached due to the two-pulse compression, with subsequent values: P = 200 MPa and 400 MPa. Tests included the microbiological insight for the two-weeks storage. It is also shown that the decay of the number of microorganisms under the high pressure follows the relation n(t) = n0exp(At)exp(Bt2). Finally, issues regarding containers for the high pressure preservation of human milk are discussed

Poly(vinyl methyl ether) hydrogels at temperatures below the freezing point of water - molecular interactions and states of water

Water interacting with a polymer reveals a number of properties very different to bulk water. These interactions lead to the redistribution of hydrogen bonds in water. It results in modification of thermodynamic properties of water and the molecular dynamics of water. That kind of water is particularly well observable at temperatures below the freezing point of water, when the bulk water crystallizes. In this work, we determine the amount of water bound to the polymer and of the so-called pre-melting water in poly(vinyl methyl ether) hydrogels with the use of Raman spectroscopy, dielectric spectroscopy, and calorimetry. This analysis allows us to compare various physical properties of the bulk and the premelting water. We also postulate the molecular mechanism responsible for the pre-melting of part of water in poly(vinyl methyl ether) hydrogels. We suggest that above −60 °C, the first segmental motions of the polymer chain are activated, which trigger the process of the pre-melting

Poly(vinyl methyl ether) hydrogels at temperatures below the freezing point of water - molecular interactions and states of water

Water interacting with a polymer reveals a number of properties very different to bulk water. These interactions lead to the redistribution of hydrogen bonds in water. It results in modification of thermodynamic properties of water and the molecular dynamics of water. That kind of water is particularly well observable at temperatures below the freezing point of water, when the bulk water crystallizes. In this work, we determine the amount of water bound to the polymer and of the so-called pre-melting water in poly(vinyl methyl ether) hydrogels with the use of Raman spectroscopy, dielectric spectroscopy, and calorimetry. This analysis allows us to compare various physical properties of the bulk and the premelting water. We also postulate the molecular mechanism responsible for the pre-melting of part of water in poly(vinyl methyl ether) hydrogels. We suggest that above −60 °C, the first segmental motions of the polymer chain are activated, which trigger the process of the pre-melting

The observation of vibrating pear-shapes in radon nuclei (vol 10, 2473, 2019)

An amendment to this paper has been published and can be accessed via a link at the top of the paper

Restoring the valence-shell stabilization in Nd-140

A projectile Coulomb-excitation experiment was performed at the radioactive-ion beam facility HIE-ISOLDE at CERN to obtain E2 and M1 transition matrix elements of Nd-140 using the multistep Coulomb-excitation code GOSIA. The absolute M1 strengths, B(M1; 2(2)(-) -> 2(1)(+)) = 0.033(8)mu(2)(N), B(M1 ; 2(3)(+) -> 2(1)(+)) = 0.26(-0.10)(+0.11)mu(2)(N), and B(M1; 2(4)+ -> 2(1)(+)) <0.04 mu(2)(N) identify the 2(3)(+) state as the main fragment of the one-quadrupole-phonon proton-neutron mixed-symmetry state of Nd-140. The degree of F-spin mixing in Nd-140 was quantified with the determination of the mixing matrix element VF-mix <7(-7)(-13) keV.Peer reviewe