Large Mass Density Research Articles

Light competition drives species replacement during secondary tropical forest succession

Light competition is thought to drive successional shifts in species dominance in closed vegetations, but few studies have assessed this for species-rich and vertically structured tropical forests. We analyzed how light competition drives species replacement during succession, and how cross-species variation in light competition strategies is determined by underlying species traits. To do so, we used chronosequence approach in which we compared 14 Mexican tropical secondary rainforest stands that differ in age (8–32 year-old). For each tree, height and stem diameter were monitored for 2 years to calculate relative biomass growth rate (RGR, the aboveground biomass gain per unit aboveground tree biomass per year). For each stand, 3D light profiles were measured to estimate individuals’ light interception to calculate light interception efficiency (LIE, intercepted light per unit biomass per year) and light use efficiency (LUE, biomass growth per intercepted light). Throughout succession, species with higher RGR attained higher changes in species dominance and thus increased their dominance over time. Both light competition strategies (LIE and LUE) increased RGR. In early succession, a high LIE and its associated traits (large crown leaf mass and low wood density) are more important for RGR. During succession, forest structure builds up, leading to lower understory light levels. In later succession, a high LUE and its associated traits (high wood density and leaf mass per area) become more important for RGR. Therefore, successional changes in relative importance of light competition strategies drive shifts in species dominance during tropical rainforest succession.

Elastic fields generated by multiple small inclusions with high mass density at nearly resonant frequencies

We derive the elastic field generated by multiple small-scaled inclusions distributed in a bounded set of R3. These inclusions are modelled with moderate values of the Lamé coefficients while they have a large relative mass density. These properties allow them to enjoy sequences of resonant frequencies that can be computed via the eigenvalues of the volume integral operator having the Navier fundamental matrix as a kernel, i.e., the Navier volume operator. The dominant field, i.e., the Foldy-Lax field, models the multiple interactions between the inclusions with scattering coefficients that are inversely proportional to the difference between the used incident frequency and the already mentioned resonances. We show, in particular, that to reconstruct remotely the scattered field generated after N interactions between the inclusions, one needs to use an incident frequency appropriately close to the proper resonance of the inclusions. We provide an explicit link between the order N of interactions and the distance from the incident frequency to the resonance. Finally, if the cluster of the inclusions is densely distributed in a given bounded domain, then the expression of the induced dominant field suggests that the equivalent homogenized mass density can change sign depending if the used incident frequencies is smaller or larger than a certain threshold (which is explicitly given in terms of the resonant frequencies of the inclusions).

Application of a linear interpolation algorithm in radiation therapy dosimetry for 3D dose point acquisition

Air-vented ion chambers are generally used in radiation therapy dosimetry to determine the absorbed radiation dose with superior precision. However, in ion chamber detector arrays, the number of array elements and their spacing do not provide sufficient spatial sampling, which can be overcome by interpolating measured data. Herein, we investigated the potential principle of the linear interpolation algorithm in volumetric dose reconstruction based on computed tomography images in the volumetric modulated arc therapy (VMAT) technique and evaluated how the ion chamber spacing and anatomical mass density affect the accuracy of interpolating new data points. Plane measurement doses on 83 VMAT treatment plans at different anatomical sites were acquired using Octavius 729, Octavius1500, and MatriXX ion chamber detector arrays, followed by the linear interpolation to reconstruct volumetric doses. Dosimetric differences in planning target volumes (PTVs) and organs at risk (OARs) between treatment planning system and reconstruction were evaluated by dose volume histogram metrics. The average percentage dose deviations in the mean dose (Dmean) of PTVs reconstructed by 729 and 1500 arrays ranged from 4.7 to 7.3% and from 1.5 to 2.3%, while the maximum dose (Dmax) counterparts ranged from 2.3 to 5.5% and from 1.6 to 7.6%, respectively. The average percentage dose/volume deviations of mixed PTVs and OARs in the abdomen/gastric and pelvic sites were 7.6%, 3.5%, and 7.2%, while mediastinum and lung plans showed slightly larger values of 8.7%, 5.1%, and 8.9% for 729, 1500, and MatriXX detector arrays, respectively. Our findings indicated that the smaller the spacing between neighbouring detectors and the more ion chambers present, the smaller the error in interpolating new data points. Anatomical regions with small local mass density inhomogeneity were associated with superior dose reconstruction. Given a large mass density difference in the various human anatomical structures and the characteristics of the linear interpolation algorithm, we suggest that an alternative data interpolation method should be used in radiotherapy dosimetry.

Space probe of the gravitational constant G

The empirical Gravitational constant G is of fundamental interest in metrology, Newtonian physics, and the field equations in General Relativity, particle physics, geophysics, and astrophysics. The precise value of G has yet to be known with the desired level of accuracy. In the 233 years since Cavendish, hundreds of experiments sought more accurate results but produced inconsistent results. Although they have had much more advanced supporting technology, past experiments have mostly stayed the same from the Cavendish approach. This paper shows that a different method is feasible to enhance the accuracy of G. A sphere made of metal with a large uniform mass density having a channel through the center with a bead oscillating back and forth in a simple-harmonic fashion. Monitoring the positions of the bead experimentally and comparing the predictions of the channel model will allow refining the value of G. The study develops a gravitational force function for the bead in a channeled sphere to provide more accuracy in the prediction of the bead's motion. This study determines that the best place to perform future gravitation constant experiments is in space far away from interfering effects. A near-perfect place is likely to be in outer space at the Sun-Earth Lagrange point L1, located about 1.5 million kilometers from the Earth on a line toward the Sun where other probes reside. It is estimated that three to six significant figures may be added to the current value of G.

Vertical integration of multi-electrodes inside a single sheet of paper and the control of the equivalent circuit for high-density flexible supercapacitors

Paper is an excellent substrate for flexible devices due to its various advantages such as flexibility, porosity, lightness, and thinness. Its inherent characteristics can be also exploited to overcome the limitations of conventional substrates, such as weak adhesion and large mass densities. Here, we propose a method for fabricating vertically integrated multi-electrodes within only a single sheet of paper. Despite the randomly distributed fibrous networks in a paper, the multi-layered electrodes were uniformly formed and completely separated by applying a removable hydrophobic wax barrier confinement inside a single sheet of paper. The integrated multi-layer electrodes inside a single sheet of paper mean that conventional two-dimensional planes can be used as three-dimensional scaffolds. The highly integrated electrodes and circuit systems are located within only a sheet of paper, making a new possibility to design maximizing the energy storage performance, integrated circuit systems, and significantly decreasing the thickness of the system without external complex structure. In consequence, this unique platform can circumvent most of the fabrication challenges related to two-dimensional energy storage sheets.

R2-gravity quark stars from perturbative QCD

We investigate the structure of quark stars in the framework of f(R)= R + αR 2 gravity using an equation of state for cold quark matter obtained from perturbative QCD, parametrized only by the renormalization scale. We show that a considerably large range of the free parameter α, within and even beyond the constraints previously reported in the literature, yield non-negligible modifications in the mass and radius of stars with large central mass densities. Their stability against baryon evaporation is analyzed through the behavior of the associated total binding energies which are slightly affected by the modified gravity term in the regime of high proper (baryon) masses.

Suspension printing of liquid metal in yield-stress fluid for resilient 3D constructs with electromagnetic functions

Liquid metal is an ideal conductive material for soft electronics because of its high conductivity and fluidity at room temperature. However, the large surface tension and high mass density of liquid metal make forming three-dimensional (3D) dangling structures a challenging task. Reported here is a suspension printing strategy for direct deposition of galinstan-based liquid metal into 3D dangling structures with high shape fidelity and spatial resolution (~150 μm). Acrylamide/nanoclay suspension served as a yield-stress fluid support bath, with selected hydrogen peroxide to immediately oxidize the gallium skin and strengthen the extruded liquid metal, thus continuous liquid metal filaments were deposited successfully. The subsequent photo-curing of acrylamide/nanoclay works as a resilient outer packaging, giving rise to a ~500% tensile deformation for liquid metal-hydrogel composite. This suspension printing strategy should broaden the opportunity of using 3D and functional liquid metal constructs for soft yet resilient electromagnetic devices.

Photodetection and scintillation characterizations of novel lead-bismuth double perovskite halides

Double perovskite materials with large effective atomic numbers and high mass densities generate short absorption length for radiation detection. Bromide and iodide variants were characterized for their scintillation and photodetection properties.

Synthesis of a Three-Dimensional Interconnected Oxygen-, Boron-, Nitrogen-, and Phosphorus Tetratomic-Doped Porous Carbon Network as Electrode Material for the Construction of a Superior Flexible Supercapacitor.

To construct a high-performance next-generation carbon-based flexible supercapacitor, high porosity, large mass density, and high flexibility are three significant challenging goals. However, one side always affects another. Herein, high-density tetratomic-doped porous composite carbon derived from sustainable biomaterials is achieved via two-step processes of carbonization and acid-washing treatment. The assembled carbon-based electrodes are highly doped with various heteroatoms (B, O, N, and P) for 33.59 atom %, resulting in abundant porosity, high densities, high pseudocapacitive contribution for 84.5%, and superior volumetric capacitive performance. The fabricated flexible electrode exhibits high flexibility, high mass loading (316 mg cm-3), and remarkable tensile strength (44.6 MPa). Generally, the volumetric performance is key and a significant parameter to appraise the electrochemical characteristics of flexible supercapacitors within a limited space. The aqueous symmetric supercapacitor demonstrates a high volumetric energy density and an excellent power density of 2.08 mWh cm-3 and 498.4 mW cm-3, respectively, along with 99.6% capacitance retention after 20 000 cycles, making it competitive to even some pseudocapacitors.

MOF derived multi-metal oxides anchored N, P-doped carbon matrix as efficient and durable electrocatalyst for oxygen evolution reaction

Because the oxygen evolution reaction (OER) process is a rate-determining step for water splitting, it is extremely significant to rationally design and explore highly efficient and durable as well as the low-cost OER electrocatalyst to promote electrocatalytic water splitting. Based on this consideration, herein, for the first time, multi-metal oxides MoO2/Co2Mo3O8/Fe2Mo3O8 (MCF) compactly anchored N, P-doped carbon matrix (CNT and amorphous carbon derived from cobalt hexacyanoferrate) (MCF/NPCCNT) is fabricated by simply pyrolyzing composite precursor consisted of phosphomolybdic acid, cobalt hexacyanoferrate and CNT under the nitrogen atmospheres. The as-prepared MCF/NPCCNT-40 hybrid catalyst delivers a high OER electrochemical activity with a smaller overpotential of 292 mV at the current density of 10 mA cm−2 and a lower Tafel slope of 45.9 mV dec-1, as well as favorable cycle stability in 1.0 M KOH solution, markedly improving the charge transfer efficiency in catalytic processes and preventing the corrosion of the metallic compounds. In addition, the MCF/NPCCNT-40 hybrid catalyst exhibits large mass density of 323.2 A g−1 at a fixed potential of 1.7 V, which is the highest mass activity towards OER process compared to the other reference samples. The design idea and synthetic strategy of this work can be expanded to design and fabricate other novel, highly effective and low-cost multi-metal oxide anchored N, P-doped carbon matrix based electrocatalysts with greatly improved OER performance.

The Mass–Metallicity Relation at z ∼ 0.8: Redshift Evolution and Parameter Dependency

Abstract The spectra of emission-line galaxies from the extended Baryon Oscillation Spectroscopic Survey of the Sloan Digit Sky Survey (SDSS) are used to study the mass–metallicity relation (MZR) at z ∼ 0.8. The selected sample contains about 180,000 massive star-forming galaxies with 0.6 < z < 1.05 and . The spectra are stacked in bins of different parameters including redshift, stellar mass, star formation rate (SFR), specific star formation rate (sSFR), half-light radius, mass density, and optical color. The average MZR at z ∼ 0.83 has a downward evolution in the MZR from the local to high-redshift universe, which is consistent with previous works. At a specified stellar mass, galaxies with higher SFR/sSFR and larger half-light radius have systematically lower metallicity. This behavior is reversed for galaxies with larger mass density and optical color. Among the above physical parameters, the MZR has the most significant dependency on SFR. Our galaxy sample at 0.6 < z < 1.05 approximately follows the fundamental metallicity relation (FMR) in the local universe, although the sample inhomogeneity and incompleteness might have an effect on our MZR and FMR.

Nuclear microbomb propulsion for manned deep space exploration with return travel

For manned deep space exploration with return travel a novel nuclear microbomb propulsion concept is proposed. It assumes the presence of easily mineable natural uranium and lithium deposits on Solar System planets. The concept makes use of large negative mass densities in a rapidly rotating reference system predicted by Hund as a consequence of Einstein's general theory of relativity. It permits the ignition of the deuterium thermonuclear reaction by the implosion of Li6D salt inside a rapidly rotating natural uranium shell by an intense relativistic electron beam of over 100 MJ. This concept avoids the drawbacks of carrying along liquid deuterium-tritium and Plutonium 239 or Uranium 235 for fission spark plugs on a deep space mission.The generation of the pulsed high-energy relativistic beams can be done by solar collectors charging the high-voltage Marx generators, or by a small natural uranium reactor, requiring not much more than a small chemical factory, not a large isotope separating facility. A small chemical plant is also needed to make the high explosives used to achieve the large rotational target velocity.

Inverse elastic surface scattering with far-field data

A rigorous mathematical model and an efficient computational method are proposed to solving the inverse elastic surface scattering problem which arises from the near-field imaging of periodic structures. We demonstrate how an enhanced resolution can be achieved by using more easily measurable far-field data. The surface is assumed to be a small and smooth perturbation of an elastically rigid plane. By placing a rectangular slab of a homogeneous and isotropic elastic medium with larger mass density above the surface, more propagating wave modes can be utilized from the far-field data which contributes to the reconstruction resolution. Requiring only a single illumination, the method begins with the far-to-near (FtN) field data conversion and utilizes the transformed field expansion to derive an analytic solution for the direct problem, which leads to an explicit inversion formula for the inverse problem. Moreover, a nonlinear correction scheme is developed to improve the accuracy of the reconstruction. Results show that the proposed method is capable of stably reconstructing surfaces with resolution controlled by the slab's density.

Brzine čestica praha u plazmi na niskom pritisku

Low pressure of inert gas in the vacuum chamber significantly affects the transfer of plasma particle velocity onto powder particles, residence time of powder particles in plasma and the kinetic energy of molten particles before the collision with the substrate. In addition to low pressure of inert gas in the vacuum chamber, the size and mass density of powder particles, together with plasma arc power, have the biggest impact on the average velocity of powder particles. To measure the velocity of powder particles in the vacuum chamber at low pressure, a laser speedometer is applied.The average velocity of molten powder particles V=s/t is calculated when the length of the path of powder particles that pass between two focus distances of the laser beam is divided by the time of particle passage between the two focuses. Measurements are done for vacuum chamber pressure, the values of which are usually from 6.7 to 80 kPa. The paper describes the relationship between the average velocity of Al2O3 and W powder particles and the vacuum chamber pressure, granulate distribution, mass density and plasma arc power. It was found that, for powder of lower mass density, the average velocity of particles can increase for 200 m/s with a decrease in chamber pressure.The effect of pressure on W particles of larger mass density is lower but still important, because a decrease in pressure increases the average velocity of particles up to 50%. Reducing plasma arc power reduces the maximum velocity of both types of powder particles. .

Survival of Patients with Multiple Myeloma in Western Australia, a Large State of 2.5 Million Square Kilometers: A Population Based Study

BackgroundThere has been concern that patients with malignant disease from remote and regional country areas may have adverse outcomes compared with those from cities. Western Australia (WA) with an area of 2,526,786 square kilometers, is one third the size of Australia. It has a population of 2.6 million of which 92% live in the capital city Perth and the southwest corner. In WA, multiple myeloma is managed in tertiary public hospitals and private physician practice located in Perth. While oral based immunomodulators and alkylators are readily delivered in the regional areas, patients travel to Perth for parenteral chemotherapy and stem cell transplantation. The WA state government subsidizes transport and accommodation for patients from regional areas to travel to Perth for treatment and clinical review via the Patient Assisted Travel Scheme (PATS). Telehealth through video conferencing is also used for review of patients on oral-based anti-myeloma treatment or during surveillance periods to avoid expensive and time-consuming travel to Perth. The Royal Flying Doctor Service (RFDS), a non-profit medical organization, provides prompt transfer of unwell patients from regional and remote areas of WA to Perth. Pathology services in remote regions are provided by the publicly funded PathWest organization.MethodWe retrospectively reviewed the survival outcomes of patients with multiple myeloma in the WA public healthcare system. Patients diagnosed between 2008 to 2017 were included (n=569). Staging information was extracted from the laboratory information system and the cytogenetic database in PathWest. Patient demographics, complications requiring admission, mortality and follow-up data were extracted from the public hospital patient management systems. Patients were segregated into regional or metropolitan by their residential address postcodes. Patients diagnosed and/or followed-up in the private sector were excluded. Survival was analyzed by Kaplan-Meier curves, Log-rank test and Cox proportional hazards model.ResultMedian age at diagnosis was 67 years old (range 29 to 98), with 56% above 65 years. 56% were males, 44% were females. Overall median survival was 46 months (95%CI:41,52). 1-year, 3-years and 5-years survival rates were 80%, 56% and 30% respectively. 25% (n=143) of patients resided in regional areas. No statistically significant difference in overall survival time between patients from metropolitan and regional areas was identified (p=0.2): 47 months (95% CI:43,54) and 42 months (95% CI: 33,54) respectively. Subgroup analysis also did not find any significant difference in overall survival of each R-ISS staging between metropolitan and regional areas.DiscussionThis retrospective study provides real-life survival data of of an Australian-based population in a state with a large land mass and low population density outside the capital city. The overall survival of patients living in regional areas was not significantly different from those living in the capital city. This gives credence to the benefit of the WA government supported regional network of travel, accommodation and Telehealth conferencing overcoming the distance barrier in the provision of comprehensive medical care in the management of a hematological malignancy. [Display omitted] DisclosuresNo relevant conflicts of interest to declare.

A Numerical Study to Investigate the Effect of Inlet Reynolds Number on the Thermal–Fluid Phenomena in the Supercritical Carbon Dioxide-Cooled Pebble Bed Reactor

This paper presents a numerical investigation into thermal–fluid phenomena in a supercritical carbon dioxide-cooled pebble bed reactor (SCPBR) core under steady state using computational fluid dynamic. In this study, a three-dimensional model with the capability to simulate the fluid flow and heat transfer in the SCPBR core has been developed. The developed model was implemented on a personal computer using ANSYS Fluent 14.5. Several important fluid flow and heat transfer parameters have been examined, including the pressure drop over the reactor core, the heat transfer coefficient, the temperature distribution, the coolant density and the coolant velocity. Results obtained from the simulation show that with increasing the inlet Reynolds number, the pressure drop, the coolant density and the heat transfer coefficient increase. However, the coolant temperature and the temperature difference between pebble and coolant decrease with increasing the inlet Reynolds number. The conclusion of the analysis is that supercritical carbon dioxide (S-CO\(_{2})\), compared to other coolants such as helium, could be a suitable coolant for use in a pebble bed reactor due to its large mass density and heat transfer characteristics, which could lead to obtain a higher temperature rise and a lower pressure gradient.

Occurrence Locations, Dipole Tilt Angle Effects, and Plasma Cloud Drift Paths of Polar Cap Neutral Density Anomalies

AbstractPolar cap neutral density anomaly (PCNDA) with large mass density enhancements over the background has been frequently observed in the polar cap during magnetic storms. By tracing field lines to the magnetosphere from the polar ionosphere, we divide the polar cap into two regions, an open field line (OFL) region with field lines connecting to the magnetopause boundary and a distant tail field line (TFL) region threaded with magnetotail lobe field lines. A statistical study of neutral density observed by the Challenging Minisatellite Payload satellite during major magnetic storms with Dst < −100 from July 2001 to 2006 indicates that over 85% of density anomalies were detected in the TFL region, at about 18° to 25° equatorward the center of the OFL region. PCNDAs were frequently accompanied by plasma clouds with peak density greater than 105 #/cm3. Modeling of plasma cloud drift paths suggests that plasma clouds originating in the dayside ionosphere could convect through the OFL region following the zero‐potential line and reach the PCNDA locations. Plasma clouds could become stagnate in the TFL region, allowing a long duration of collisions with the neutral gas and possibly contributing to heating of PCNDAs. The PCNDA observations are interpreted as evidence that traveling atmospheric disturbance could be generated in the nightside polar cap. From the PCNDA size and speed of sound at 400 km, we derive an initial energy deposition duration for producing traveling atmospheric disturbance in the range from 0.5 to 2.5 hr.

Non-diffraction propagation of acoustic waves in a rapidly modulated stratified medium

A rapidly modulated stratified medium with a large mass density modulation depth (LMMD) is proposed to achieve non-diffraction propagation (NDP) of acoustic waves. It is found that the NDP in LMMD medium is independent of the incident angle and can be operated in a broad-band manner. Such an NDP is robust and is unhampered by medium losses. An effective medium theory (EMT) is developed for acoustic waves propagating in the LMMD medium based on the first-principles method. The LMMD EMT is verified by using the transfer-matrix method (TMM) for both propagating and evanescent waves. Furthermore, we discuss the influence of the geometry on NDP, and finite element simulations are conducted to verify the NDP in the LMMD medium.

Performance study of Lagrangian methods: reconstruction of large scale peculiar velocities and baryonic acoustic oscillations

NoAM for "No Action Method" is a framework for reconstructing the past orbits of observed tracers of the large scale mass density field. It seeks exact solutions of the equations of motion (EoM), satisfying initial homogeneity and the final observed particle (tracer) positions. The solutions are found iteratively reaching a specified tolerance defined as the RMS of the distance between reconstructed and observed positions. Starting from a guess for the initial conditions, NoAM advances particles using standard N-body techniques for solving the EoM. Alternatively, the EoM can be replaced by any approximation such as Zel'dovich and second order perturbation theory (2LPT). NoAM is suitable for billions of particles and can easily handle non-regular volumes, redshift space, and other constraints. We implement NoAM to systematically compare Zel'dovich, 2LPT, and N-body dynamics over diverse configurations ranging from idealized high-res periodic simulation box to realistic galaxy mocks. Our findings are (i) Non-linear reconstructions with Zel'dovich, 2LPT, and full dynamics perform better than linear theory only for idealized catalogs in real space. For realistic catalogs, linear theory is the optimal choice for reconstructing velocity fields smoothed on scales > 5 Mpc/h. (ii) all non-linear back-in-time reconstructions tested here, produce comparable enhancement of the baryonic oscillation signal in the correlation function.

Researches on the structure and electrochemical properties of MoxV2-xO5+y nanosheets

Vanadium pentoxide (V2O5) with various nanostructures has been investigated during the past decades. Notably, two-dimensional V2O5 nanosheets had attracted most attentions due to the large mass density. Here, the V2O5 nanosheets doped by MoO3 (MoxV2-xO5+y) have been synthesized by sol-gel method combined with freezing–drying process. The structures and morphology of MoxV2-xO5+y were characterized by XRD, FTIR, TEM, and FESEM analysis. The MoxV2-xO5+y show a two-dimensional layered structure and the XRD can be indexed to an orthorhombic V2O5 phase. Meanwhile, the doping of MoO3 was confirmed by the XPS and TEM analysis. The electrochemical behaviors of the nanocomposites were investigated by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and galvanostatic charge-discharge test. As a result, the interlayer spacing of the Mox V2-x O5+y nanosheets were inlarged by V2MoO8. The improvment of electrochemical properties was due to defects and the layer structure.