Relative Particle Number Research Articles

Progress of in-air microbeam system at the Wakasa Wan Energy Research Center

Modifications of an in-air microbeam system at the Wakasa Wan Energy Research Center designed to improve its performance are described. In the previous setup, a silicon nitride membrane (area: 1×1mm2; thickness: 100nm) was used for the beam exit window and the distance between the window and the sample was restricted to ⩾1.7mm. Due to this restriction, the beam spot size obtained using the previous setup was 13×13μm2. To reduce the beam spot size, the beam exit window was replaced by a silicon nitride membrane (area: 3 (horizontal)×2 (vertical)mm2; thickness: 200nm). In this setup, the sample can be moved as close as 0.7mm to the window, enabling a beam spot size of 7×6μm2 to be achieved. An additional Si-PIN X-ray detector was installed to estimate the relative number of beam particles. It detects X-rays from the beam exit window. The number of the X-rays from the beam exit window (which is proportional to the number of beam particles) is used for quantitative analysis and for online monitoring of the beam current. This system has the potential to be used for simultaneous particle-induced X-ray emission (PIXE) and particle-induced gamma-ray emission (PIGE) measurements and for studying dental medicine.

Constraining fundamental physics with future CMB experiments

The Planck experiment will soon provide a very accurate measurement of Cosmic Microwave Background anisotropies. This will let cosmologists determine most of the cosmological parameters with unprecedented accuracy. Future experiments will improve and complement the Planck data with better angular resolution and better polarization sensitivity. This unexplored region of the CMB power spectrum contains information on many parameters of interest, including neutrino mass, the number of relativistic particles at recombination, the primordial Helium abundance and the injection of additional ionizing photons by dark matter self-annihilation. We review the imprint of each parameter on the CMB and forecast the constraints achievable by future experiments by performing a Monte Carlo analysis on synthetic realizations of simulated data. We find that next generation satellite missions such as CMBPol could provide valuable constraints with a precision close to that expected in current and near future laboratory experiments. Finally, we discuss the implications of this intersection between cosmology and fundamental physics.

Modifying proton fluence spectra to generate spread-out Bragg peaks with laser accelerated proton beams

Currently, energy spectra of laser accelerated proton beams are far from being monoenergetic. For their application in radiation therapy, energy selection systems using magnetic fields have been proposed to single out particles with the desired energy. These systems allow the choice of protons between a lowest and a highest energy. In this work, we present a slight modification that allows us to influence the relative number of particles per energy bin. In fact, the transmitted spectrum can be shaped in such a way that it corresponds to a full spread out Bragg peak delivered simultaneously. This change of the spectrum can be achieved by inserting suitably formed scattering material at the central plane of the energy selection system where the particles are separated in space depending on their energy. With the help of Monte Carlo simulations we analysed both simple wedge geometries and various stacks of lead slices. We found that these configurations can provide energy spectra that naturally produce spread out Bragg peaks within one laser shot. This increases the particle efficiency of the whole system and makes laser accelerated protons more suitable for radiation therapy.

Influence of fractal surface dimension on the dissolution process of sparingly soluble CaCO3 microparticles

The dissolution process of sparingly soluble CaCO3 microparticles and how the fractal surface dimension of the particles changes during dissolution is analyzed. The particles and the dissolution process are studied using scanning electron microscopy, X-ray diffraction, nitrogen adsorption, laser diffraction and conductance measurements. Ball milling of the particles is shown to maintain the particle crystallinity, and to introduce an increased fractal surface dimension in the 1–10 μm size range. Dissolution is found to increase the surface dimension of initially smooth particles and to maintain the fractal surface roughness of milled particles. The dissolution process increases the relative number of small particles (50 nm–1 μm) whereas the larger ones decrease in size. The solubility of the milled fractal particles was ∼1.8 times higher than that for the initially smooth ones. The presented findings show that developing methods for increasing the fractal surface roughness of particles should be of interest for improving the solubility of poorly soluble drug candidates.

Abrasive jet micromachining of acrylic and polycarbonate polymers at oblique angles of attack

Masked and unmasked micro-channels were machined in polymethylmethacrylate (PMMA) using an abrasive jet of 25 μm Al 2O 3 particles at a variety of impact angles. The erosion rate was found to depend on the jet scanning direction when the nozzle was inclined with respect to the target surface at 55°. This effect was explained in terms of the relative number of particles embedded in the target surface when scanning in the forwards, as opposed to backwards, directions. A simple, fast and relatively accurate analytical technique was introduced to predict the profiles of masked and unmasked micro-channels machined at oblique impact angles, and masked micro-holes machined at normal impact. Comparison of the predicted and measured profiles of micro-channels and micro-holes machined in PMMA showed good agreement in both shape and depth. Masked holes at normal incidence were also micromachined in LUCITE™ (an acrylic) and LEXAN™ (a polycarbonate), and revealed a similar shape to that found for PMMA (flat bottom and very steep side walls), implying that the present analytical technique may also be used for the prediction of the profile of abrasive jet micromachined features in a variety of polymers.

Behaviour of the energy gap in a model of Josephson coupled Bose–Einstein condensates

In this work we investigate the energy gap between the ground state and the first excited state in a model of two single-mode Bose-Einstein condensates coupled via Josephson tunneling. The energy gap is never zero when the tunneling interaction is non-zero. The gap exhibits no local minimum below a threshold coupling which separates a delocalised phase from a self-trapping phase which occurs in the absence of the external potential. Above this threshold point one minimum occurs close to the Josephson regime, and a set of minima and maxima appear in the Fock regime. Analytic expressions for the position of these minima and maxima are obtained. The connection between these minima and maxima and the dynamics for the expectation value of the relative number of particles is analysed in detail. We find that the dynamics of the system changes as the coupling crosses these points.

Matter-wave amplification and phase conjugation via stimulated dissociation of a molecular Bose-Einstein condensate

We propose a scheme for parametric amplification and phase conjugation of an atomic Bose-Einstein condensate (BEC) via stimulated dissociation of a BEC of molecular dimers consisting of bosonic atoms. This can potentially be realized via coherent Raman transitions or using a magnetic Feshbach resonance. We show that the interaction of a small incoming atomic BEC with a (stationary) molecular BEC can produce two counterpropagating atomic beams -- an amplified atomic BEC and its phase-conjugate or time-reversed replica. The two beams can possess strong quantum correlation in the relative particle number, with squeezed number-difference fluctuations.

Diagnostics of macroscopic quantum states of Bose–Einstein condensate in double-well potential by nonstationary Josephson effect

We propose a method of diagnostics of a degenerate ground state of Bose condensate in a double-well potential. The method is based on the study of the one-particle coherent tunneling under switching of the time-dependent weak Josephson coupling between the wells. We obtain a simple expression that allows one to determine the phase of the condensate and the total number of the particles in the condensate from the relative number of particles in the two wells Δn=n1−n2 measured before the Josephson coupling is switched on and after it is switched off. The specifics of the application of the method in the cases of the external and the internal Josephson effect are discussed.

Quantum dynamics of a model for two Josephson-coupled Bose–Einstein condensates

In this work we investigate the quantum dynamics of a model for two single-mode Bose--Einstein condensates which are coupled via Josephson tunneling. Using direct numerical diagonalisation of the Hamiltonian, we compute the time evolution of the expectation value for the relative particle number across a wide range of couplings. Our analysis shows that the system exhibits rich and complex behaviours varying between harmonic and non-harmonic oscillations, particularly around the threshold coupling between the delocalised and self-trapping phases. We show that these behaviours are dependent on both the initial state of the system as well as regime of the coupling. In addition, a study of the dynamics for the variance of the relative particle number expectation and the entanglement for different initial states is presented in detail.

New fast method for determination of number of UHMWPE wear particles

Ultra-high molecular weight polyethylene (UHMWPE) wear particles are the major cause of total joint replacement (TJR) failures because the wear particles, released from TJR's, cause bone loosening. To simplify the study of the relationship between numbers of particles at various locations around TJR's and extent of bone loosening at these locations, the authors of this work tried to develop a new method for easy and fast determination of number of wear particles. The method, called LSC (Light Scattering with Calibration spheres), is based on light scattering of a suspension of wear particles and calibration spheres, and yields relative numbers of particles. A modified LSC method, called LSCm, requires one additional experiment, a gravimetric analysis of a mixture of all studied samples, to determine absolute numbers of wear particles. LSC and LSCm methods are easy and fast, which make them suitable for processing and comparing high number of samples.

Phase separation and vortex states in binary mixture of Bose-Einstein condensates in trapping potentials with displaced centers

The system of two simultaneously trapped codensates consisting of $^{87}Rb$ atoms in two different hyperfine states is investigated theoretically in the case when the minima of the trapping potentials are displaced with respect to each other. It is shown that the small shift of the minima of the trapping potentials leads to the considerable displacement of the centers of mass of the condensates, in agreement with the experiment. It is also shown that the critical angular velocities of the vortex states of the system drastically depend on the shift and the relative number of particles in the condensates, and there is a possibility to exchange the vortex states between condensates by shifting the centers of the trapping potentials.

A possible radiative model for microniccarbonaceous particle sizing based on time-resolved laser-induced incandescence

A numerical model of time-resolved laser-induced incandescence(TIRE-LII) for different kinds of large carbonaceous particleis developed in this paper. Theoretical temporal LII signalswere computed for the following classes of particles: soot,the well known hollow particles called cenospheres (tens ofmicrons) and full carbonaceous particles called by analogypleospheres (a few microns), pleo- from the Greek pleos(solid). The large carbonaceous particles have a characteristictime for internal gradient dissipation much longer than soot,thus a temperature profile establishes inside them. On thebasis of these observations, a spatial time-dependent model forcenospheres and pleospheres was considered, i.e. a system ofpartial differential equations based on mass and energybalances.The computed LII signals pointed out the sensitivity of themodel to the different kinds of particle considered in thispaper. The two classes of large carbonaceous particles showeddifferent thermal behaviours. Furthermore, the analysis of thecombined effects on the total theoretical LII signal of thedifferent particles highlighted the sensitivity of the time decayof the LII profiles to the mean particle size distributionsand to the relative particle number ratios inside thecontrol volume. These results may constitute a basis of astrategy for a comprehensive discrimination between soot andlarge particles, and for their identification, as in heavy-oilcombustion.

Exact form factors for the Josephson tunneling current and relative particle number fluctuations in a model of two coupled Bose-Einstein condensates

Form factors are derived for a model describing the coherent Josephson tunneling between two coupled Bose-Einstein condensates. This is achieved by studying the exact solution of the model within the framework of the algebraic Bethe ansatz. In this approach the form factors are expressed through determinant representations which are functions of the roots of the Bethe ansatz equations.

Geochemistry of suspended particles in a mine-affected mountain stream

The particles in a mine drainage and the creek into which it drains were examined using microbeam and filtration methods. The composition of the particles in the drainage and creek were distinctly different, though both carried a chemical signal from the mine. High concentrations of particles made up of Fe and S were seen in the drainage, especially during low flow. The molar Fe:S ratio of these suspended particles was 3.5:1. The influx of the mine drainage into the creek increased the relative number of aggregates and particles with associated Fe. However, few discrete Fe–S particles were seen in the creek, where solid-phase Fe and S were consistently associated with aluminosilicate minerals. Instream precipitation is predicted and appears to be an important additional source of Fe and Al oxyhydroxides to the particles. Some of the Fe and Al associated with particles in the creek was acid-soluble, but most of the acid-soluble Zn, Mn, Cu, Ca, Mg and Si were transported in the <0.45 μm fraction at a site downstream of the mine drainage. One third of the suspended particles had associated P. These suspended particles take part in the complex geochemistry of this system, and represent an important pool as a potential sink and source of metals and other elements.

Dissolution Effects on Specific Surface Area, Particle Size, and Porosity of Pentelic Marble

Dissolution of natural stone such as marble is not limited to its surface. The porous structure, known to play an important role in stone decay, is also affected by the conditions of dissolution. In the present work, the changes in pore size distribution of Pentelic marble particles accompanying chemical dissolution in undersaturated solutions and at alkaline pH 8.25 were investigated. The specific surface area and the mesopore distribution of the Pentelic marble tested showed a pronounced decrease to very low values. On the other hand, the sizes of macropores exhibited a tendency to increase with the extent of dissolution due either to dissolution in the interior of the pores or to fusion of small pores into larger. Furthermore, the number of small particles decreased significantly, reaching complete disappearance, depending on the extent of dissolution. At the same time, the relative number of particles of intermediate size increased.

Phase-resolution limit in the macroscopic interference between Bose-Einstein condensates

We study the competition between phase definition and quantum phase fluctuations in interference experiments between independently formed Bose condensates. While phase-sensitive detection of atoms makes the phase progressively better defined, interactions tend to randomize it faster as the uncertainty in the relative particle number grows. A steady state is reached when the two effects cancel each other. Then the phase resolution saturates to a value that grows with the ratio between the interaction strength and the atom detection rate, and the average phase and number begin to fluctuate classically. We discuss how our study applies to both recently performed and possible future experiments.

Settling statistics of hard sphere particles.

Direct imaging of settling, non-Brownian, hard sphere, particles allows measurement of particle occupancy statistics as a function of time and sampling volume dimension. Initially random relative particle number fluctuations, <N2-<N>(2)>/<N> = 1, become suppressed, anisotropic, and <N> dependent. Fitting to a simple Gaussian pair correlation model suggests a minute long ranged correlation leads to strong if not complete suppression of number fluctuations. Calflisch and Luke predict a divergence in velocity fluctuations with increasing sample volume size based on random (Poisson) statistics. Our results suggest this is not a valid assumption for settling particles.

The influence of hypoxia on the myocardium of experimentally diabetic rats with and without protection by Ginkgo biloba extract: III: Ultrastructural investigations on mitochondria

Completing our preceding ultrastructural studies on diabetes and additional acute hypoxia of rat myocardium and the protective effect of Ginkgo extract (EGb) we investigated specific ultrastructural-morphometric parameters of corresponding mitochondria. Aim of the study was to answer the question whether mitochondria of diabetic myocardium are more sensitive to hypoxia than in normal condition, and whether antioxidative protection by EGb is effective. Further we compared the ultrastructural reactions of mitochondria of different intracellular locations. Voluminal parameters of mitochondria indicated a moderate swelling after diabetes and a further slight swelling after additional hypoxia, which was slightly reduced after EGb pretreatment. Decrease of volume density of mitochondrial cristae was less expressed after diabetes and much stronger after additional hypoxia; slight protection by EGb was only visible after diabetes. Degenerative intramitochondrial areas increased significantly after diabetes and after hypoxia; EGb was protective only after additional hypoxia. The relative number of ATPase particles (F1-coupling factors) at the inner mitochondrial membranes was slightly but significantly reduced after diabetes and stronger reduced after additional hypoxia; only in the latter condition Ginkgo extract was slightly protective. The product of volume density of mitochondria x volume density of cristae x relative number of ATPase particles at the inner mitochondrial membrane (as structural equivalent of the myocardial capacity for ATP production) indicated better than single parameters the increasing mitochondrial damage after diabetes of 4 months duration and subsequent acute hypoxia of 20 min duration. After hypoxia this capacity amounted only to 46% of the normal and was improved by EGb to 53%.

The possibility of achieving an interactive mixture with high dose homogeneity containing an extremely low proportion of a micronised drug

The homogeneity of binary mixtures containing coarse particulate mannitol and three different size fractions of sodium salicylate particles was investigated. The proportion of sodium salicylate (0.15% w/w and 0.015% w/w) and the sample size of the mixture were also varied. The homogeneity of these experimental mixtures was compared with the theoretical values that would be expected from ordered, adhesive interactive (pseudo-random) and random model mixtures. The results indicated that adhesive interactive forces were created between the drug and the carrier particles in most of the experimental mixtures, since their homogeneity tended to be higher than that of a theoretical randomised mixture. In fact, there was some resemblance to an ideal ordered state in mixtures containing the highest drug proportion (0.15%) and the smallest particles. However, the effect of sample size was not negligible and it was concluded that the number of drug particles interacting with individual carrier particles was not constant but was in fact related to a process of randomisation. The homogeneity of the mixture was predicted using two approaches: the ratio of the number of drug to carrier particles in the mixture and the absolute number of drug particles, estimated by weight, in the sample. It is suggested that calculating the relative numbers of particles by weight in the mixture could aid in predicting the feasibility of achieving an interactive powder mixture with a high dose-homogeneity.

Spin-mixing dynamics of a spinor Bose-Einstein condensate

We study the spin-mixing dynamics of an $f=1$ spinor condensate. We show that the dynamics is sensitive to the relative phase and particle number distribution among the individual components of the condensate, and find that complex structures can develop in the density profiles during the time evolution. We investigate the different time scales of the spin-mixing process and their dependence on the total particle number.