bluuebunny/crossref_metadata_2025 huggingface dataset:
Nonthermal ion acceleration by the kink instability in nonrelativistic jets
Authors: Alves E. P. , Zrake J. , Fiuza F.
Published: July 2019

We investigate the self-consistent particle acceleration physics associated with the development of the kink instability (KI) in nonrelativistic, electron-ion plasma jets. Using 3D fully kinetic particle-in-cell simulations, we show that the KI efficiently converts the initial toroidal magnetic field energy into energetic ions. The accelerated ions form a nonthermal power-law tail in the energy spectrum, containing ≃10% of the initial magnetic field energy, with the maximum ion energy extending to the confinement energy of the jet. We find that the ions are efficiently accelerated by the concerted action of the motional electric field and the highly tangled magnetic field that develop in the nonlinear phase of the KI: fast curvature drift motions of ions across magnetic field lines enable their acceleration along the electric field. We further investigate the role of Coulomb collisions in the ion acceleration efficiency and identify the collisional threshold above which nonthermal ion acceleration is suppressed. Our results reveal how energetic ions may result from unstable nonrelativistic plasma jets in space and astrophysics and provide constraints on the plasma conditions required to reproduce this acceleration mechanism in laboratory experiments.
Low field mobility in electrostatically evolved AlGaN/GaN one-dimensional channel from a two-dimensional electron gas system
Authors: Kumar Akhil S. , Garigapati Navya S. , Saha D.
Published: July 2019

Here, we have investigated size dependent electron mobility in an electrostatically evolved AlGaN/GaN one-dimensional channel from a two-dimensional heterostructure. An architecture with lateral gates, which allows partial depletion of channel widths, has been used. The low field mobility is found to manifest multiple peaks and valleys for progressively changing quantum confinement. The number of sub-bands increases with the increasing dimension. However, electron and phonon confinement decrease, which leads to less wave-function overlap. Although an increase in the number of sub-bands decreases the mobility due to the larger number of density of states, the overlap decreases monotonically which increases the mobility. The two competing effects lead to a unique signature on the mobility. The depletion region voltage exponent is found to differ from the traditional value of 0.5 in this case. The exponent is found to be close to unity for a one-dimensional system.
Linear-scaling ab initio simulations of spin diffusion in rotating solids
Authors: Perras Frédéric A. , Pruski Marek
Published: July 2019

We investigated the utility of locally restricting the basis sets involved in low-order correlations in Liouville space (LCL) calculations of spin diffusion. Using well-known classical models of spin diffusion, we describe a rationale for selecting the optimal basis set for such calculations. We then show that the use of these locally restricted basis sets provides the same computational accuracy as the full LCL set while reducing the computational time by several orders of magnitude. Speeding up the calculations also enables us to use higher maximum spin orders and increase the computational accuracy. Furthermore, unlike exact and full LCL calculations, locally restricted LCL calculations scale linearly with the system size and should thus enable the ab initio study of spin diffusion in spin systems containing several thousand spins.
Tin-based donors in SiSn alloys
Authors: Scheffler L. , Roesgaard S. , L. Hansen J. , Nylandsted Larsen A. , Julsgaard B.
Published: July 2019

Tin-containing Group IV alloys show great promise for a number of next-generation CMOS-compatible devices. Not least of those are optoelectronic devices such as lasers and light-emitting diodes. To obtain reliable operation, a high control over the doping in such materials is needed at all stages of device processing. In this paper, we report tin-based donors in silicon, which appear after heat treatment of a silicon-tin alloy at temperatures between 650°C and 900°C. Two stages of the donor are observed, called SD I and SD II, which are formed subsequently. A broad long-lifetime infrared photoluminescence is also observed during the first stages of donor formation. We discuss evolving tin clusters as the origin of both the observed donors and the photoluminescence, in analogy to the oxygen-based thermal donors in silicon and germanium.
Effects of metal silicide inclusion interface and shape on thermal transport in silicon nanocomposites
Authors: Ferrer-Argemi Laia , Yu Ziqi , Lee Jaeho
Published: July 2019

While various silicon nanocomposites with their low thermal conductivity have received much attention for thermoelectric applications, the effects of inclusion interface and shape on thermal transport remain unclear. Here, we investigate thermal transport properties of silicon nanocomposites, in which metal silicide inclusions are periodically arranged within silicon. Using the known phonon dispersion relations and the diffuse mismatch model, we explore the effects of different silicide-silicon interfaces, and using Monte Carlo ray tracing simulations, we explore the effects of silicide inclusion shapes. Our investigations show that the thermal conductivity of silicon nanocomposites can be reduced to the range of nanoporous silicon of the same geometry, depending on the interface density, crystal orientation, and acoustic mismatch. For instance, CoSi2 inclusions of [111] orientation can reduce the nanocomposite thermal conductivity more effectively than inclusion materials with lower intrinsic thermal conductivity, such as NiSi2, when the inclusion density is up to 12.5% with an interface density of 7.5 μm−1. Among the silicide inclusion materials investigated in this work, Mn4Si7 leads to the lowest nanocomposite thermal conductivity due to a combination of low intrinsic thermal conductivity and high acoustic mismatch. Compared to widely spaced and symmetric inclusions such as a circular shape, narrowly spaced and asymmetric inclusions such as a triangular shape are more effective in limiting the phonon mean free path and reducing the nanocomposite thermal conductivity. These findings regarding thermal transport in silicon nanocomposites with respect to inclusion interface and shape will guide optimal material designs for thermoelectric cooling and power generation.
Microstrip-line resonator with broadband, circularly polarized, uniform microwave field for nitrogen vacancy center ensembles in diamond
Authors: Yang Xiaoying , Zhang Ning , Yuan Heng , Bian Guodong , Fan Pengcheng , Li Mingxin
Published: July 2019

We proposed an annular microstrip-line resonator (AMLR) to provide a broadband, circularly polarized and uniform microwave field for state manipulation of negatively charged nitrogen-vacancy (NV–) center ensembles in order to achieve wide magnetic field detection range and large area microwave synchronous manipulation in miniaturized magnetic sensing devices. The bandwidth of the designed AMLR was 410 MHz when the input return losses was -10dB. With the designed bandwidth, a magnetic field detection range of 292 G was achieved based on the NV– center ensembles. The relationship between the direction of the magnetic field and the phase of the source signal indicated that the generated microwave field of AMLR was circularly polarized. Furthermore, the magnetic field magnitude homogeneity is higher than the parallel-microstrip-lines resonator (PMLR) and the intersected-microstrip-lines resonator (IMLR), and the magnetic field magnitude of AMLR had a difference of 0.012 G in the center of a 1×1 mm2 area. The AMLR has a great potential in magnetic field detection, temperature and pressure detection, which is useful for quantum applications with NV– center ensembles in diamond.
Relative density and isobaric expansivity of cold and supercooled heavy water from 254 to 298 K and up to 100 MPa
Authors: Blahut A. , Hykl J. , Peukert P. , Vinš V. , Hrubý J.
Published: July 2019

A dual-capillary apparatus was developed for highly accurate measurements of density of liquids, including the supercooled liquid region. The device was used to determine the density of supercooled heavy water in the temperature range from 254 K to 298 K at pressures ranging from atmospheric to 100 MPa, relative to density at reference isotherm 298.15 K. The measurements of relative density were reproducible within 10 ppm, and their expanded (k = 2) uncertainty was within 50 ppm. To obtain absolute values of density, thermodynamic integration was performed using recent accurate speed of sound measurements in the stable liquid region. An empirical equation of state (EoS) was developed, giving specific volume as a rational function of pressure and temperature. The new experimental data are represented by EoS within their experimental uncertainty. Gibbs energy was obtained by EoS integration allowing computation of all thermodynamic properties of heavy water using Gibbs energy derivatives. Although based on data in relatively narrow temperature and pressure ranges, the developed EoS shows an excellent agreement with literature data for densities, isothermal compressibilities, and isobaric expansivities of deeply supercooled heavy water. The curvature of the thermodynamic surface steeply increases toward low temperatures and low pressures, thus supporting the existence of the hypothesized liquid-liquid coexistence boundary in a close vicinity of existing experimental data.
Application of single-electron effects to fingerprints of chips using image recognition algorithms
Authors: Tanamoto T. , Nishi Y. , Ono K.
Published: July 2019

Single-electron effects have been widely investigated as a typical physical phenomenon in nanoelectronics. The single-electron effect caused by trap sites has been observed in many devices. In general, traps are randomly distributed and not controllable; therefore, different current–voltage characteristics are observed through traps even in silicon transistors having the same device parameters (e.g., gate length). This allows us to use single-electron effects as fingerprints of chips. In this study, we analyze the single-electron effect of traps in conventional silicon transistors. At sufficiently low temperatures at which single-electron effects can be observed (in this case, 1.54 K), we show that current–voltage characteristics can be used as fingerprints of chips through image recognition algorithms. Resonant tunneling parts in the Coulomb diagram can also be used supportively to characterize each device in a low-temperature region. These results show that single-electron effects can provide a quantum version of a physically unclonable function.
Bounding the stationary distributions of the chemical master equation via mathematical programming
Authors: Kuntz Juan , Thomas Philipp , Stan Guy-Bart , Barahona Mauricio
Published: July 2019

The stochastic dynamics of biochemical networks are usually modeled with the chemical master equation (CME). The stationary distributions of CMEs are seldom solvable analytically, and numerical methods typically produce estimates with uncontrolled errors. Here, we introduce mathematical programming approaches that yield approximations of these distributions with computable error bounds which enable the verification of their accuracy. First, we use semidefinite programming to compute increasingly tighter upper and lower bounds on the moments of the stationary distributions for networks with rational propensities. Second, we use these moment bounds to formulate linear programs that yield convergent upper and lower bounds on the stationary distributions themselves, their marginals, and stationary averages. The bounds obtained also provide a computational test for the uniqueness of the distribution. In the unique case, the bounds form an approximation of the stationary distribution with a computable bound on its error. In the nonunique case, our approach yields converging approximations of the ergodic distributions. We illustrate our methodology through several biochemical examples taken from the literature: Schlögl’s model for a chemical bifurcation, a two-dimensional toggle switch, a model for bursty gene expression, and a dimerization model with multiple stationary distributions.
Tunnel junction I(V) characteristics: Review and a new model for p-n homojunctions
Authors: Moulin N. , Amara M. , Mandorlo F. , Lemiti M.
Published: July 2019

Despite the widespread use of tunnel junctions in high-efficiency devices (e.g., multijunction solar cells, tunnel field effect transistors, and resonant tunneling diodes), simulating their behavior still remains a challenge. This paper presents a new model to complete that of Karlovsky and simulate an I(V) characteristic of an Esaki tunnel junction. A review of different analytical models of band-to-band tunneling models is first presented. As a complement to previous work on tunnel junction simulation, the transmission coefficient is precisely determined and incorporated, the valley current between the tunneling and drift regimes is included, and calculations of physical parameters are updated. It is found that the model works for a broad range of values of the forward bias.
Thermal stability of CsPbBr3 perovskite as revealed by in situ transmission electron microscopy
Authors: Zhang Chao , Fernando Joseph F. S. , Firestein Konstantin L. , von Treifeldt Joel E. , Siriwardena Dumindu , Fang Xiaosheng , Golberg Dmitri
Published: July 2019

The thermal stability of all-inorganic halide perovskites is their key advantage over organic/hybrid halide perovskites. Here, in situ high-resolution transmission electron microscopy (HRTEM) was used to directly investigate crystallography dynamics of a CsPbBr3 perovskite at high temperature (up to 690 K). In high vacuum TEM conditions (∼10−5 Pa), CsPbBr3 nanocrystals possessed superb stability at temperatures below 690 K. By sealing the crystals in amorphous carbon, their melting and solidification processes were directly observed at temperatures of 840 K and 838 K, respectively. This study should be valuable for future perovskite-containing solar cells, lasers, light-emitting diodes, and photodetectors working at high temperatures.
Small ion effects on self-coacervation phenomena in block polyampholytes
Authors: Danielsen Scott P. O. , McCarty James , Shea Joan-Emma , Delaney Kris T. , Fredrickson Glenn H.
Published: July 2019

Self-coacervation is a phenomenon in which a solution of polyampholytes spontaneously phase separates into a dense liquid coacervate phase, rich in the polyampholyte, coexisting with a dilute supernatant phase. Such coacervation results in the formation of membraneless organelles in vivo and has further been applied industrially as synthetic encapsulants and coatings. It has been suggested that coacervation is primarily driven by the entropy gain from releasing counter-ions upon complexation. Using fully fluctuating field-theoretic simulations employing complex Langevin sampling and complementary molecular dynamics simulations, we have determined that the small ions contribute only weakly to the self-coacervation behavior of charge-symmetric block polyampholytes in solution. Salt partitioning between the supernatant and coacervate is also found to be negligible in the weak-binding regime at low electrostatic strengths. Asymmetries in charge distribution along the polyampholytes can cause net-charges that lead to “tadpole” configurations in dilute solution and the suppression of phase separation at low salt content. The field and particle-based simulation results are compared with analytical predictions from the random phase approximation (RPA) and postulated scaling relationships. The qualitative trends are mostly captured by the RPA, but the approximation fails at low concentration.
Phase-dependence of sorption-induced mass streaming in an acoustic field
Authors: Blayer Yuval , Elkayam Nimrod , Ramon Guy Z.
Published: July 2019

A nonzero time-averaged mass flux is generated in oscillating flows due to phase-lags between the fluctuating velocity field and the diffusive transport. Herein, we demonstrate how, in addition, the acoustic phasing of a sound wave—the phase difference between pressure and velocity oscillations—interacts with material properties and geometry to affect the preferential transport of a “reactive” species undergoing reversible sorption. Experimental results illustrate how phasing affects the induced mass flux, its dependence on the diffusive and oscillation time-scales, and how they compare well with model calculations. The model is used to reveal the underlying mechanisms that generate the concentration gradient, vs those that dissipate it. This insight can assist the future development and design of acoustic gas separation processes.
A measurement method for responsivity of microwave kinetic inductance detector by changing power of readout microwaves
Authors: Kutsuma H. , Hattori M. , Koyano R. , Mima S. , Oguri S. , Otani C. , Taino T. , Tajima O.
Published: July 2019

Superconducting detectors are a modern technology applied in various fields. The microwave kinetic inductance detector (MKID) is one of the cutting-edge superconducting detectors. It is based on the principle of a superconducting resonator circuit. A radiation entering the MKID breaks the Cooper pairs in the superconducting resonator, and the intensity of the radiation is detected as a variation of the resonant condition. Therefore, calibration of the detector responsivity, i.e., the variation of the resonant phase with respect to the number of Cooper-pair breaks (quasiparticles), is important. We propose a method for responsivity calibration. Microwaves used for the detector readout locally raise the temperature in each resonator, which increases the number of quasiparticles. Since the magnitude of the temperature rise depends on the power of readout microwaves, the number of quasiparticles also depends on the power of microwaves. By changing the power of the readout microwaves, we simultaneously measure the phase difference and lifetime of quasiparticles. We calculate the number of quasiparticles from the measured lifetime and by using a theoretical formula. This measurement yields a relation between the phase responses as a function of the number of quasiparticles. We demonstrate this responsivity calibration using the MKID maintained at 285 mK. We also confirm the consistency between the results obtained using this method and conventional calibration methods in terms of the accuracy.
Reactor Monte Carlo (RMC) model validation and verification in compare with MCNP for plate-type reactor
Authors: Alrwashdeh Mohammad , Alameri Saeed A.
Published: July 2019

Traditional neutronics calculations and simulation behavior of plate type research reactors pose a challenge comparing with the conventional pressurized water reactors. This is due to its complex geometry, characteristics, heterogeneity, and neutron leakage that lead to modeling difficulties. The Reactor Monte Carlo code (RMC) is employed in stochastic approach for the neutronic analysis in the plate type research reactor. The goal of this report is to examine the capability and validity of the model built using RMC and compare the results with a well-known Monte Carlo code such as MCNP. The results between RMC and MCNP are in a good agreement for effective multiplications factor (keff), radial power peaking factor, total power peaking factor, and integral and differential control rods worth.
Pressure drop reduction of power-law fluids in hydrophobic microgrooved channels
Authors: Javaherchian Javane , Moosavi Ali
Published: July 2019

Using hydrophobic surfaces is one of the efficient methods to preserve energy in fluid transfer systems. However, the studies have been concentrated on Newtonian fluids despite the wide applications of non-Newtonian fluids in daily life and many industries such as the biological, foodstuff, chemical, petroleum, cosmetic, and lab on a chip fields. In this study, we consider power-law fluids as a typical example of non-Newtonian fluids and investigate the effect of hydrophobic microgrooves on the pressure drop in channels by utilizing the phase field method. We demonstrate that the optimum size of the rectangular microgrooves in which the maximum pressure drop reduction (PDR) happens for both the considered Newtonian and non-Newtonian fluids is identical, but the PDR is different for the Newtonian and non-Newtonian fluids. For shear-thickening fluids, the PDR is more than shear-thinning fluids, which means that using the hydrophobic surfaces in dilatant fluids provides the best performance. It is seen that pressure drop reduces more at lower Reynolds numbers. We also investigate the efficiency of the microgrooved surfaces in convergent and divergent channels for both the Newtonian and non-Newtonian fluids and find the critical slope angles for a specific length of the channels in which the hydrophobic microgrooves have a sufficient performance in the PDR and stability.
Conformational switching of chiral colloidal rafts regulates raft–raft attractions and repulsions
Authors: Miller Joia M. , Joshi Chaitanya , Sharma Prerna , Baskaran Arvind , Baskaran Aparna , Grason Gregory M. , Hagan Michael F. , Dogic Zvonimir
Published: July 2019

Significance

We describe hierarchical assemblages of colloidal rods that mimic some of the complexity and reconfigurability of biological structures. We show that chiral rod-like inclusions dissolved in an achiral colloidal membrane assemble into rafts, which are adaptable finite-sized liquid droplets that exhibit 2 distinct chiral states of opposite handedness. Interconverting between these 2 states switches the membrane-mediated raft interactions between long-ranged repulsions and attractions. Rafts with switchable interactions assemble into analogs of electrostatic complexation observed in charged particulate matter. Our results demonstrate a robust pathway for self-assembly of reconfigurable colloidal superstructures that does not depend on tuning the shape and interactions of the elemental units, but rather on the complexity of the emergent membrane-mediated interactions.
Mutagenesis of odorant coreceptor
Orco
fully disrupts foraging but not oviposition behaviors in the hawkmoth
Manduca sexta
Authors: Fandino Richard A. , Haverkamp Alexander , Bisch-Knaden Sonja , Zhang Jin , Bucks Sascha , Nguyen Tu Anh Thi , Schröder Katrin , Werckenthin Achim , Rybak Jürgen , Stengl Monika , Knaden Markus , Hansson Bill S. , Große-Wilde Ewald
Published: July 2019

The hawkmoth
Manduca sexta
and one of its preferred hosts in the North American Southwest,
Datura wrightii
, share a model insect–plant relationship based on mutualistic and antagonistic life-history traits.
D. wrightii
is the innately preferred nectar source and oviposition host for
M. sexta
. Hence, the hawkmoth is an important pollinator while the
M. sexta
larvae are specialized herbivores of the plant. Olfactory detection of plant volatiles plays a crucial role in the behavior of the hawkmoth. In vivo, the odorant receptor coreceptor (Orco) is an obligatory component for the function of odorant receptors (ORs), a major receptor family involved in insect olfaction. We used CRISPR-Cas9 targeted mutagenesis to knock out (KO) the
MsexOrco
gene to test the consequences of a loss of OR-mediated olfaction in an insect–plant relationship. Neurophysiological characterization revealed severely reduced antennal and antennal lobe responses to representative odorants emitted by
D. wrightii
. In a wind-tunnel setting with a flowering plant, Orco KO hawkmoths showed disrupted flight orientation and an ablated proboscis extension response to the natural stimulus. The Orco KO gravid female displayed reduced attraction toward a nonflowering plant. However, more than half of hawkmoths were able to use characteristic odor-directed flight orientation and oviposit on the host plant. Overall, OR-mediated olfaction is essential for foraging and pollination behaviors, but plant-seeking and oviposition behaviors are sustained through additional OR-independent sensory cues.
An essential bifunctional enzyme in
Mycobacterium tuberculosis
for itaconate dissimilation and leucine catabolism
Authors: Wang Hua , Fedorov Alexander A. , Fedorov Elena V. , Hunt Debbie M. , Rodgers Angela , Douglas Holly L. , Garza-Garcia Acely , Bonanno Jeffrey B. , Almo Steven C. , de Carvalho Luiz Pedro Sório
Published: July 2019

Mycobacterium tuberculosis
(Mtb) is the etiological agent of tuberculosis. One-fourth of the global population is estimated to be infected with Mtb, accounting for ∼1.3 million deaths in 2017. As part of the immune response to Mtb infection, macrophages produce metabolites with the purpose of inhibiting or killing the bacterial cell. Itaconate is an abundant host metabolite thought to be both an antimicrobial agent and a modulator of the host inflammatory response. However, the exact mode of action of itaconate remains unclear. Here, we show that Mtb has an itaconate dissimilation pathway and that the last enzyme in this pathway, Rv2498c, also participates in
l
-leucine catabolism. Our results from phylogenetic analysis, in vitro enzymatic assays, X-ray crystallography, and in vivo Mtb experiments, identified Mtb Rv2498c as a bifunctional β-hydroxyacyl-CoA lyase and that deletion of the
rv2498c
gene from the Mtb genome resulted in attenuation in a mouse infection model. Altogether, this report describes an itaconate resistance mechanism in Mtb and an
l
-leucine catabolic pathway that proceeds via an unprecedented (
R
)-3-hydroxy-3-methylglutaryl-CoA (HMG-CoA) stereospecific route in nature.
Random coefficient autoregressive processes describe Brownian yet non-Gaussian diffusion in heterogeneous systems
Authors: Ślęzak Jakub , Burnecki Krzysztof , Metzler Ralf
Published: July 2019

Many studies on biological and soft matter systems report the joint presence of a linear mean-squared displacement and a non-Gaussian probability density exhibiting, for instance, exponential or stretched-Gaussian tails. This phenomenon is ascribed to the heterogeneity of the medium and is captured by random parameter models such as ‘superstatistics’ or ‘diffusing diffusivity’. Independently, scientists working in the area of time series analysis and statistics have studied a class of discrete-time processes with similar properties, namely, random coefficient autoregressive models. In this work we try to reconcile these two approaches and thus provide a bridge between physical stochastic processes and autoregressive models. We start from the basic Langevin equation of motion with time-varying damping or diffusion coefficients and establish the link to random coefficient autoregressive processes. By exploring that link we gain access to efficient statistical methods which can help to identify data exhibiting Brownian yet non-Gaussian diffusion.
Handling leakage with subsystem codes
Authors: Brown Natalie C , Newman Michael , Brown Kenneth R
Published: July 2019

Leakage is a particularly damaging error that occurs when a qubit state falls out of its two-level computational subspace. Compared to independent depolarizing noise, leaked qubits may produce many more configurations of harmful correlated errors during error-correction. In this work, we investigate different local codes in the low-error regime of a leakage gate error model. When restricting to bare-ancilla extraction, we observe that subsystem codes are good candidates for handling leakage, as their locality can limit damaging correlated errors. As a case study, we compare subspace surface codes to the subsystem surface codes introduced by Bravyi et al. In contrast to depolarizing noise, subsystem surface codes outperform same-distance subspace surface codes below error rates as high as ⪅ 7.5 × 10−4 while offering better per-qubit distance protection. Furthermore, we show that at low to intermediate distances, Bacon–Shor codes offer better per-qubit error protection against leakage in an ion-trap motivated error model below error rates as high as ⪅ 1.2 × 10−3. For restricted leakage models, this advantage can be extended to higher distances by relaxing to unverified two-qubit cat state extraction in the surface code. These results highlight an intrinsic benefit of subsystem code locality to error-corrective performance.
Stable continuous-wave single-frequency intracavity frequency-doubled laser with intensity noise suppressed in audio frequency region*
Authors: Gao Ying-Hao , Li Yuan-Ji , Feng Jin-Xia , Zhang Kuan-Shou
Published: July 2019

We demonstrated a continuous wave (cw) single-frequency intracavity frequency-doubled Nd:YVO4/LBO laser with 532 nm output of 7.5 W and

1.06

μ
m

output of 3.1 W, and low intensity noise in audio frequency region. To suppress the intensity noise of the high power 532 nm laser, a laser frequency locking system and a feedback loop based on a Mach–Zehnder interferometer were designed and used. The influences of the frequency stabilization and the crucial parameters of the MZI, such as the power splitting ratio of the beam splitters and the locking state of the MZI, on the intensity noise of the 532 nm laser were investigated in detail. After the experimental optimizations, the laser intensity noise in the frequency region from 0.4 kHz to 10 kHz was significantly suppressed.
Shades of dark uncertainty and consensus value for the Newtonian constant of gravitation
Authors: Merkatas Christos , Toman Blaza , Possolo Antonio , Schlamminger Stephan
Published: July 2019

The Newtonian constant of gravitation, G, stands out in the landscape of the most common fundamental constants owing to its surprisingly large relative uncertainty, which is attributable mostly to the dispersion of the values measured for it by different methods and in different experiments, each of which may have rather small relative uncertainty.

This study focuses on a set of measurements of G comprising results published very recently as well as older results, some of which have been corrected since the original publication. This set is inconsistent, in the sense that the dispersion of the measured values is significantly larger than what their reported uncertainties suggest that it should be. Furthermore, there is a loosely defined group of measured values that lie fairly close to a consensus value that may reasonably be derived from all the measurement results, and then there are one or more groups with measured values farther away from the consensus value, some appreciably higher, others lower.

This same general pattern is often observed in many other interlaboratory studies and meta-analyses. In the conventional treatments of such data, the mutual inconsistency is addressed by inflating the reported uncertainties, either multiplicatively, or by the addition of ‘random effects’, both reflecting the presence of dark uncertainty. The former approach is often used by CODATA and by the Particle Data Group, and the latter is common in medical meta-analysis and in metrology. However, both achieve consistency ignoring how the measured values are arranged relative to the consensus value, and measured values close to the consensus value often tend to be penalized excessively, by such ‘extra’ uncertainty.

We propose a new procedure for consensus building that models the results using latent clusters with different shades of dark uncertainty, which assigns a customized amount of dark uncertainty to each measured value, as a mixture of those shades, and does so taking into account both the placement of the measured values relative to the consensus value, and the reported uncertainties. We demonstrate this procedure by deriving a new estimate for G, as a consensus value

m3 kg−1 s−2, with

m3 kg−1 s−2.
Criticality safety analysis of spent fuel pool for TRIGA Puspati Reactor using MCNP5
Authors: Bahri Nurlaila Syamsul , Zainal Jasman , Hamzah Khaidzir , Mohammad Saleh Muneer Aziz , Rabir Mohamad Hairie
Published: July 2019

Spent fuel pool uses water to temporarily cool spent nuclear fuels before final disposal. The Malaysian Nuclear Agency is recently working on its spent fuel pool facility to store irradiated TRIGA fuel rods. These irradiated fuels still contain significant amount of fissile material which are capable to induce criticality in the fuel storage facility. This study is therefore performed to investigate the safety criticality analysis for the proposed fuel storage rack design of 5x5 arrays. MCNP5 code was used to model the 5x5 array of fuel storage rack in order to determine the optimal fuel pitch distance. The analysis was based on the standard UZrH1.6 TRIGA fuel cladded with stainless steel used in PUSPATI TRIGA Reactor, which is 19.9% enriched 235U and 20% weight of Uranium. By varying the pitch distance between 4 cm to 14 cm with no neutron absorber included, the optimum fuel rack design was determined where sub-criticality condition can be maintained.
An overview of the development of a multigroup Monte Carlo code for TRIGA reactors
Authors: Omar M R , Karim J A , Yoon T L
Published: July 2019

This paper discusses the overview of the development of TRIMON, a next-generation core management code for TRIGA reactors. The newly developed code employs Monte Carlo method which uses diffusion theory type homogenized neutron cross section data, thus, speeding up the stochastic simulation via simplification of a complex core geometry. It has the capability of running three-dimensional core simulation up to 16 neutron energy groups. In general, the group neutron cross sections are pre-processed and homogenized via the Effective Diffusion Homogenization (EDH) method. The important features of TRIMON include core eigenvalue calculation, fuel burnup management, three-dimensional power and neutron flux distribution prediction. In this paper, the numerical results obtained using TRIMON were compared with the actual measured operational data. The performance comparison was also made between TRIMON and MCNP.
A review on multilayer radiation shielding
Authors: Arif Sazali Muhammad , Alang Md Rashid Nahrul Khair , Hamzah Khaidzir
Published: July 2019

Radiation shielding is a body of material that is placed between a radiation source and an object to be protected with the aim of reducing the intensity of radiation at the object’s location. It can be made from various materials. These materials can be stacked into a multilayer shield or they can be mixed into a composite shield. The main objective of the present study is to review the list of multilayer shield combinations that have been studied and to highlight the findings on material arrangement and consequent buildup factor. The scope of the study is limited to the results of the performed studies. It was observed that there was no clear method on arranging the layer. Buildup factor was also found to be complicated in multilayer shields. Future studies may focus on new multilayer shielding design with unlisted materials, complementary buildup calculations, and applications of metaheuristics in shielding optimization.
Study on natural rubber absorption of selected actinides
Authors: Nahhar Alkhaledi , Kok Siong Khoo
Published: July 2019

This paper contains the research done concerning natural rubber. This included its origin, economic importance, and how the functional groups in the natural rubber reacted with selected actinides. The selected actinides discussed were Thorium, Uranium and Plutonium. The information was retrieved from different sources including information from laboratory experiments. The results obtained were gathered when conducted under different conditions. The conditions varied based on the temperatures and the pH. The functional groups exhibited different outcomes when reacted with different actinides under different conditions. The functional groups namely amine carboxyl and hydroxyl groups have different efficiency and capacity of adsorption. Besides economic importance, the environmental significance of rubber also has been discussed.
The design of a Hot Cell with interlocking concrete wall
Authors: Bahrin Muhammad Hannan , Hasan Hasni , Rahman Anwar Abdul , Hamzah Mohd Arif , Hassan Mohd Zaid , Mamat@Ibrahim Mohd Rizal , Rabir Mohamad Hairie , Karim Julia Abdul
Published: July 2019

The Prototype and Plant Development Center (PDC) of Malaysian Nuclear Agency is developing a hot cell facility which is meant for research activities such as spent fuel inspection, fuel fabrication and post irradiation material examination/inspection. The hot cell is of alpha-gamma shielding hot cell type. The size of the hot cell is 4.4 x 3.9 x 3.825 meter. The 1-meter thickness hot cell wall consists of 89 pieces of interlocking curve design concrete. The 1-meter hot cell roof consists of 41 pieces of square shape concrete. The density of all concrete blocks is 2350kg/m3. The hot cell is designed to handle up to 227.5 Ci 60Co activity. This paper will discuss the detailed design of the shielding wall, as well as the shielding evaluation/analysis against gamma and fission products of 50% burnup RTP 20wt% fuel type using MCNP.
A study on surface contact effect using ground penetrating radar
Authors: Mohd Amin Mohamad Syafiq , Hanim Alias Fatasya Izreen , Tengku Amran Tengku Sarah , Ahmad Mohamad Ridzuan , Mansor Ishak , Sayuti Shaharudin
Published: July 2019

In this paper, the effect of contact and non-contact antenna system of ground penetrating radar (GPR) for buried pipes are presented. The frequency for GPR antenna used in this project is 400MHz which is suitable for GPR system to detect buried pipes for the tested surfaces, since the soil involved is sand which has low electrical conductivity. The results of the radargram obtained from this experiment and the limitations occurred are discussed.
Preliminary analysis of gamma and neutron irradiation on sand and activated carbon by using SEM, XRD and SAXS
Authors: Abu Bakar Asyraf Arif , Pauzi Anas Muhamad , Mohamed Abdul Aziz , Idris Faridah Mohamad , Yazid Hafizal
Published: July 2019

Gamma and neutron irradiation effect on sand and activated carbon were studied in this paper intensively and, were found from various studies to have strong correlation between neutron fluence or gamma energy on physical and mechanical damage of materials. Sand and activated carbon were irradiated with neutron at Reactor TRIGA PUSPATI (RTP) and gamma at Sinagamma Malaysia Nuclear Agency (Nuklear Malaysia). Morphological analysis was carried out on the irradiated elements using the SEM, XRD and SAXS which showed changes on the microstructure of irradiated samples. Irradiation of activated carbon showed increase in the numbers of pores while change of textural profile of the surface take place at gamma irradiated sand. XRD pattern graph did not indicate any changes, however the specific surface area for both irradiation materials decreased.
Evaluation of image quality and recovery coefficient of corn starch-bonded Rhizophora spp. particleboards as phantom for SPECT/CT imaging
Authors: Abd Hamid P N K , Mohd Yusof M F , Tajuddin A A , Hashim R , Zainon R
Published: July 2019

The aim of this study was to evaluate the performance of corn starch-bonded Rhizophora spp. particleboards as phantom for SPECT/CT including the image contrast, source dimension ratio and recovery coefficient values. Phantom set made of the Rhizophora spp. particleboards was constructed according to the Jaszczak phantom commonly used in SPECT/CT with external dimension of 22 and 18 cm diameter and length respectively. Cylindrical vials with different diameter sizes filled with 99mTc unsealed source were inserted in drilled holes of the constructed particleboards phantom. The particleboards phantom was scanned by using SPECT/CT scanning mode and the SPECT images were reconstructed using clinical protocol. The results showed that the contrast value, source dimension ratio and recovery coefficient of Rhizophora spp. particleboards in good agreement with Jaszczak phantom. The overall results showed an excellent agreement of performance between corn starch-bonded Rhizophora spp. particleboards to the Jaszczak (water) as standard phantom material. The overall results indicated that the corn starch-bonded Rhizophora spp. can be highly recommended to be used as tissue-equivalent phantom material for Quality Assurance and dosimetry works in SPECT/CT imaging.
Key within-membrane residues and precursor dosage impact the allotopic expression of yeast subunit II of cytochromecoxidase
Authors: Rubalcava-Gracia Diana , García-Rincón Juan , Pérez-Montfort Ruy , Hamel Patrice Paul , González-Halphen Diego
Published: July 2019

Experimentally relocating mitochondrial genes to the nucleus for functional expression (allotopic expression) is a challenging process. The high hydrophobicity of mitochondria-encoded proteins seems to be one of the main factors preventing this allotopic expression. We focused on subunit II of cytochrome c oxidase (Cox2) to study which modifications may enable or improve its allotopic expression in yeast. Cox2 can be imported from the cytosol into mitochondria in the presence of the W56R substitution, which decreases the protein hydrophobicity and allows partial respiratory rescue of a cox2-null strain. We show that the inclusion of a positive charge is more favorable than substitutions that only decrease the hydrophobicity. We also searched for other determinants enabling allotopic expression in yeast by examining the COX2 gene in organisms where it was transferred to the nucleus during evolution. We found that naturally occurring variations at within-membrane residues in the legume Glycine max Cox2 could enable yeast COX2 allotopic expression. We also evidence that directing high doses of allotopically synthesized Cox2 to mitochondria seems to be counterproductive because the subunit aggregates at the mitochondrial surface. Our findings are relevant to the design of allotopic expression strategies and contribute to the understanding of gene retention in organellar genomes.
The role of nonmuscle myosin 2A and 2B in the regulation of mesenchymal cell contact guidance
Authors: Zhovmer Alexander S. , Tabdanov Erdem D. , Miao Houxun , Wen Han , Chen Jinqiu , Luo Xiaoling , Ma Xuefei , Provenzano Paolo P. , Adelstein Robert S.
Published: July 2019

Contact guidance refers to the ability of cells to sense the geometrical features of the microenvironment and respond by changing their shape and adopting the appropriate orientation. Inhibition and ablation of nonmuscle myosin 2 (NM2) paralogues have demonstrated their importance for contact guidance. However, the specific roles of the NM2 paralogues have not been systematically studied. In this work we use micropatterned substrates to examine the roles of NM2A and NM2B and to elucidate the relationship of the microenvironment, actomyosin, and microtubules in contact guidance. We show that contact guidance is preserved following loss of NM2B and that expression of NM2A alone is sufficient to establish an appropriate orientation of the cells. Loss of NM2B and overexpression of NM2A result in a prominent cell polarization that is found to be linked to the increased alignment of microtubules with the actomyosin scaffold. Suppression of actomyosin with blebbistatin reduces cell polarity on a flat surface, but not on a surface with contact guidance cues. This indicates that the lost microtubule–actomyosin interactions are compensated for by microtubule–microenvironment interactions, which are sufficient to establish cell polarity through contact guidance.
Mechanical stability of αT-catenin and its activation by force for vinculin binding
Authors: Pang Si Ming , Le Shimin , Kwiatkowski Adam V. , Yan Jie
Published: July 2019

αT (Testes)-catenin, a critical factor regulating cell–cell adhesion in the heart, directly couples the cadherin-catenin complex to the actin cytoskeleton at the intercalated disk (ICD), a unique cell–cell junction that couples cardiomyocytes. Loss of αT-catenin in mice reduces plakophilin2 and connexin 43 recruitment to the ICD. Since αT-catenin is subjected to mechanical stretch during actomyosin contraction in cardiomyocytes, its activity could be regulated by mechanical force. To provide insight in how force regulates αT-catenin function, we investigated the mechanical stability of the putative, force-sensing middle (M) domain of αT-catenin and determined how force impacts vinculin binding to αT-catenin. We show that 1) physiological levels of force, <15 pN, are sufficient to unfold the three M domains; 2) the M1 domain that harbors the vinculin-binding site is unfolded at ∼6 pN; and 3) unfolding of the M1 domain is necessary for high-affinity vinculin binding. In addition, we quantified the binding kinetics and affinity of vinculin to the mechanically exposed binding site in M1 and observed that αT-catenin binds vinculin with low nanomolar affinity. These results provide important new insights into the mechanosensing properties of αT-catenin and how αT-catenin regulates cell–cell adhesion at the cardiomyocyte ICD.
A Dictionary of Mechanical Engineering
Authors: Escudier Marcel , Atkins Tony
Published: July 2019

Over 8,000 entries

This Dictionary provides definitions and explanations for mechanical engineering terms in clear and concise A to Z entries, many illustrated. This new edition greatly expands the coverage of materials engineering terms, with a complete revision of the existing entries and the addition of more than 200 new ones in this area. Other new entries include atomic force microscope, epitrochoid, fundamental physical constant, light-emitting diode, motor generator unit, Ohm’s law, and turbomachine. Also touched upon are related subject areas such as acoustics, bioengineering, chemical engineering, civil engineering, aeronautical engineering, and environmental engineering.

It is the most comprehensive and authoritative dictionary of its kind, and an essential reference for students of mechanical engineering and for anyone with an interest in the subject.
Association Between Transient Opioid Use and Short-Term Respiratory Exacerbation Among Adults With Chronic Obstructive Pulmonary Disease: A Case-Crossover Study
Authors: Rong Yiran , Bentley John P , McGwin Gerald , Yang Yi , Banahan Benjamin F , Noble Sara L , Kirby Terri , Ramachandran Sujith
Published: July 2019

The association of historical opioid use with health care use and death among patients with chronic obstructive pulmonary disease (COPD) has been tested. Using Mississippi Medicaid data, we examined the association of transient or short-term opioid use and acute respiratory exacerbations among adults with COPD. We used a case-crossover design and 2013–2017 Mississippi Medicaid administrative claims data. A total of 1,972 qualifying exacerbation events occurred in 1,354 beneficiaries. The frequency and dose of opioid exposure in the 7 days before the exacerbation were examined and compared with the opioid exposure in 10 control windows, each 7 days long, before the exacerbation. Adjusted odds ratios were estimated using conditional logistic regression models to estimate the risk of opioid use on exacerbations after accounting for use of bronchodilators, corticosteroids, benzodiazepines, and β-blockers. Overall, opioid exposure in the 7 days before an exacerbation was significantly associated with acute respiratory exacerbation (odds ratio = 1.81; 95% confidence interval: 1.60, 2.05). Each 25-mg increase in morphine equivalent daily dose was associated with an 11.2% increase in the odds of an acute respiratory exacerbation (odds ratio = 1.11; 95% confidence interval: 1.04, 1.20). Transient use of opioids was significantly associated with acute respiratory exacerbation of COPD.