[en] An equation was derived to determine the required thickness of concrete for protection against scattered radiation encountered in Cobalt-60 teletherapy. This single step approach was possible since empirical data for intensity and half value layer for scattered radiation were found to be simple functions of the scattering angle (for Cobalt-60). A family of curves was plotted for quick determination of the required thickness of concrete as a function of appropriate shielding factors and scattering angle. The maximum barrier thickness was found to not occur at a scattering angle of 90 deg as is typically assumed. Application of this technique is more accurate and far simpler than the procedure outlined by the NCRP in Report Number 49. (author)

[en] This paper establishes a strategy for chemical deposition of functionalized nanoparticles onto solid substrates in a layer-by-layer process based on self-limiting surface chemical reactions leading to complete monolayer formation within the multilayer system without any additional intermediate layers — nanoparticle layer deposition (NPLD). This approach is fundamentally different from previously established traditional layer-by-layer deposition techniques and is conceptually more similar to well-known atomic and molecular layer deposition processes. The NPLD approach uses efficient chemical functionalization of the solid substrate material and complementary functionalization of nanoparticles to produce a nearly 100% coverage of these nanoparticles with the use of “click chemistry”. Following this initial deposition, a second complete monolayer of nanoparticles is deposited using a copper-catalyzed “click reaction” with the azide-terminated silica nanoparticles of a different size. This layer-by-layer growth is demonstrated to produce stable covalently-bound multilayers of nearly perfect structure over macroscopic solid substrates. The formation of stable covalent bonds is confirmed spectroscopically and the stability of the multilayers produced is tested by sonication in a variety of common solvents. The 1-, 2- and 3-layer structures are interrogated by electron microscopy and atomic force microscopy and the thickness of the multilayers formed is fully consistent with that expected for highly efficient monolayer formation with each cycle of growth. This approach can be extended to include a variety of materials deposited in a predesigned sequence on different substrates with a highly conformal filling. - Highlights: • We investigate the formation of high-coverage monolayers of nanoparticles. • We use “click chemistry” to form these monolayers. • We form multiple layers based on the same strategy. • We confirm the formation of covalent bonds spectroscopically for up to 3 layers. • We confirm that chemical attachment, not self-assembly, drives the process.

[en] Highlights: • Parametric study of a solid state Ericsson heat engine was performed. • Good recuperator design was the greatest contributor to cycle efficiency. • Power was most impacted by ratio of device surface area to ion exchange thickness. The Johnson Thermoelectric Converter (JTEC) operates as an approximation of an Ericsson cycle thermodynamic heat engine with no moving parts. During operation, hydrogen flows from a high-temperature high-pressure region to a low-pressure region by way of a membrane-electrode assembly. In passing through the assembly, the hydrogen is stripped of its electrons which flow through the circuit and reform with protons to the recover hydrogen on the low-pressure side. Some of the electrical power extracted is used to electrochemically “pump” the hydrogen back to the low-temperature high-pressure side and sustain the pressure differential. The objective of the work presented here was to mathematically characterize a JTEC system and to develop the coupled relationships between design goals like efficiency, net power production, and power density; and design parameters like high versus low operating temperatures and pressures, device geometry, and thermophysical properties of the device materials and working fluid. Power production is related to the operating pressure ratio, the ratio of high to low device operating temperatures, the high operating temperature, and the effective heat transfer area of the hot end. The efficiency is related to several non-dimensional and dimensional number groups (especially the recuperator effectiveness). The power density or volume of the device is related to a different recuperator parameter, the high temperature of the heat addition source, the cold temperature of the thermal rejection source, and the internal device geometry. Even with reasonable simplifications and assumptions, the design space contains a large number of variable parameters. The model equations were exercised over the large parametric trade space.

[en] In this paper, we introduce the Solion ion source for high-throughput solar cell doping. As the source power is increased to enable higher throughput, negative effects degrade the lifetime of the plasma chamber and the extraction electrodes. In order to improve efficiency, we have explored a wide range of electron energies and determined the conditions which best suit production. To extend the lifetime of the source we have developed an in situ cleaning method using only existing hardware. With these combinations, source life-times of >200 h for phosphorous and >100 h for boron ion beams have been achieved while maintaining 1100 cell-per-hour production

[en] The high-resolution mid-infrared spectrometer (HIRMES) is a high resolving power (R ~ 100,000) instrument operating in the 25–122 μm spectral range and will fly on board the Stratospheric Observatory for Far-Infrared Astronomy in 2019. Central to HIRMES are its two transition edge sensor (TES) bolometric cameras, an 8 × 16 detector high-resolution array and a 64 × 16 detector low-resolution array. Both types of detectors consist of Mo/Au TES fabricated on leg-isolated Si membranes. Whereas the high-resolution detectors, with a noise equivalent power (NEP) ~ 1.5 × 10⁻¹⁸ W/rt (Hz), are fabricated on 0.45 μm Si substrates, the low-resolution detectors, with NEP ~ 1.0 × 10⁻¹⁷ W/rt (Hz), are fabricated on 1.40 μm Si. Here, we discuss the similarities and differences in the fabrication methodologies used to realize the two types of detectors.

[en] We present a study of the BAL outflows seen in quasar SDSS J1042+1646 (z = 0.978) in the rest-frame 500–1050 Å (EUV500) region. The results are based on the analysis of recent Hubble Space Telescope/Cosmic Origins Spectrograph observations. Five outflow systems are identified, where, in total, they include ∼70 outflow troughs from ionic transitions. These include the first non-solar detections from transitions of O v*, Ne v*, Ar vi, Ca vi, Ca vii, and Ca viii. The appearance of very high-ionization species (e.g., Ne viii, Na ix, and Mg x) in all outflows necessitates at least two ionization phases for the observed outflows. We develop an interactive Synthetic Spectral Simulation method to fit the multitude of observed troughs. Detections of density sensitive troughs (e.g., S iv* λ661.40 Å and the O v* multiplet) allow us to determine the distance of the outflows (R) as well as their energetics. Two of the outflows are at R ≃ 800 pc and one is at R ≃ 15 pc. One of the outflows has the highest kinetic luminosity on record ($\stackrel{\dot{}<!--\; ??\; -->}{E_k}$ $=5\times <!--\; ??\; -->{10}^{46}$ erg s⁻¹), which is 20% of its Eddington luminosity. Such a large ratio suggests that this outflow can provide the energy needed for active galactic nucleus feedback mechanisms.

[en] We present the analysis of two outflows (S1 at −5500 km s⁻¹ and S2 at −9700 km s⁻¹) seen in recent Hubble Space Telescope/Cosmic Origins Spectrograph observations of quasar SDSS J0755+2306 (z = 0.854). The outflows are detected as absorption troughs from both high-ionization species, including N iii, O iii, and S iv, and very high-ionization species, including Ar viii, Ne viii, and Na ix. The derived photoionization solutions show that each outflow requires a two ionization-phase solution. For S1, troughs from S iv* and S iv allow us to derive an electron number density, $n_{\mathrm{e}}$ = 1.8 × 10⁴ cm⁻³, and its distance from the central source of R = 270 pc. For S2, troughs from O iii* and O iii yield $n_{\mathrm{e}}$ = 1.2 × 10³ cm⁻³ and R = 1600 pc. The kinetic luminosity of S2 is >12% of the Eddington luminosity for the quasar and, therefore, can provide strong AGN feedback effects. Comparison of absorption troughs from O iii and O vi in both outflow systems supports the idea that for a given element, higher-ionization ions have larger covering fractions than lower-ionization ones.

[en] The Hubble Space Telescope/Cosmic Origins Spectrograph (COS) has opened a new discovery space for studying quasar absorption outflows and their contribution to active galactic nucleus (AGN) feedback. Specifically, COS provides high-quality far-ultraviolet (FUV) spectra covering the diagnostic-rich 500–1050 Å rest frame (hereafter, EUV500) of medium redshift objects. The quality and quantity of EUV500 diagnostic troughs allow us to probe the very high-ionization phase, which carries 90% or more of the outflowing material, as well as to determine the distance of most outflows from the central source (R). The first objective is impossible to achieve with ground-based spectra, and R can be measured in only ∼1% of them. Here, we summarize the main results of the first dedicated survey of such outflows, including the following.

1. Measurements of the three most energetic outflows to date, which can be the main agents for AGN feedback processes in the environments of the host galaxies.

2. All the outflows have a very high-ionization component, similar to the one found in warm absorbers, which carries most of the outflow’s kinetic luminosity. This finding suggests that all the high-ionization outflows observed from the ground also have a similar undetected very high-ionization component.

3. Of the 13 studied EUV500 outflows, 9 have 100 < R < 2000 parsecs, 2 have 5 < R < 20 parsecs, 1 has 0.05 < R < 50 parsecs, and in 1 case, R cannot be determined.

4. One of the outflows has the largest velocity shift (1550 km s⁻¹) and acceleration (1.5 cm s⁻²) measured to date. This outflow is physically similar to the fast X-ray outflow detected in quasar PG 1211+143.

[en] From Hubble Space Telescope/Cosmic Origins Spectrograph spectra of five quasars, 16 outflows are detected. For 11 outflows, we are able to constrain their distances to the central source (R) and their energetics. In instances of multiple electron number density determinations (used in the calculation of R) for the same outflow, the values are consistent within errors. For the 11 outflows, eight have measurements for R (between 10 and 1000 pc), one has a lower limit, another has an upper limit, and the last has a range in R. There are two outflows that have enough kinetic luminosity to be major contributors to active galactic nucleus feedback. The outflowing mass is found primarily in a very high-ionization phase, which is probed using troughs from, e.g., Ne viii, Na ix, Mg x, and Si xii. Such ions connect the physical conditions of these ultraviolet outflows to the X-ray warm absorber outflows seen in nearby Seyfert galaxies. The ion Cl vii and several new transitions from Ne v have been detected for the first time.

[en] We present an analysis of the broad absorption line (BAL) velocity shift that appeared in one of the outflow systems in quasar SDSS J1042+1646. Observations were taken by the Hubble Space Telescope/Cosmic Origins Spectrograph in 2011 and 2017 in the 500–1050 Å rest frame. The outflow’s velocity centroid shifted by ∼−1550 km s⁻¹ from −19,500 km s⁻¹ to −21,050 km s⁻¹ over a rest-frame time of 3.2 yr. The velocity shift signatures are most apparent in the absorption features from the Ne viii λλ770.41 and 780.32 doublet and are supported by the absorption troughs from O v λ629.73 and the Mg x λλ609.79 and 624.94 doublet. This is the first time where a quasar outflow velocity shift is observed in troughs from more than one ion and in distinct troughs from a doublet transition (Ne viii). We attribute the velocity shift to an acceleration of an existing outflow as we are able to exclude photoionization changes and motion of material into and out of the line of sight as alternate explanations. This leads to an average acceleration of 480 km s⁻¹ yr⁻¹ (1.52 cm s⁻²) in the quasar rest frame. Both the acceleration and the absolute velocity shift are the largest reported for a quasar outflow to date. Based on the absorption troughs of the O v* multiplet, we derive a range for the distance of the outflow (R) from the central source, 0.05 pc < R < 54.3 pc. This outflow shows similarities with the fast X-ray outflow detected in quasar PG 1211+143. We use the acceleration and velocity shift to constrain radiatively accelerated active galactic nucleus disk–wind models and use them to make predictions for future observations.