Bilinear Quantum Monte Carlo: Expectations and Energy Differences

We propose a bilinear sampling algorithm in Green's function Monte Carlo for expectation values of operators that do not commute with the Hamiltonian and for differences between eigenvalues of different Hamiltonians. The integral representations of the Schroedinger equations are transformed into two equations whose solution has the form $\psi_a(x) t(x,y) \psi_b(y)$, where $\psi_a$ and $\psi_b$ are the wavefunctions for the two related systems and $t(x,y)$ is a kernel chosen to couple $x$ and $y$. The Monte Carlo process, with random walkers on the enlarged configuration space $x \otimes y$, solves these equations by generating densities whose asymptotic form is the above bilinear distribution. With such a distribution, exact Monte Carlo estimators can be obtained for the expectation values of quantum operators and for energy differences. We present results of these methods applied to several test problems, including a model integral equation, and the hydrogen atom.Comment: 27 page

An Exact Monte Carlo Method for Continuum Fermion Systems

We offer a new proposal for the Monte Carlo treatment of many-fermion systems in continuous space. It is based upon Diffusion Monte Carlo with significant modifications: correlated pairs of random walkers that carry opposite signs; different functions ``guide'' walkers of different signs; the Gaussians used for members of a pair are correlated; walkers can cancel so as to conserve their expected future contributions. We report results for free-fermion systems and a fermion fluid with 14 $^3$He atoms, where it proves stable and correct. Its computational complexity grows with particle number, but slowly enough to make interesting physics within reach of contemporary computers.Comment: latex source, 3 separated figures (2 in jpg format, 1 in eps format

Decisions, Decisions: Noise and its Effects on Integral Monte Carlo Algorithms

In the present paper we examine the effects of noise on Monte Carlo algorithms, a problem raised previously by Kennedy and Kuti (Phys. Rev. Lett. {\bf 54}, 2473 (1985)). We show that the effects of introducing unbiased noise into the acceptance/rejection phase of the conventional Metropolis approach are surprisingly modest, and, to a significant degree, largely controllable. We present model condensed phase numerical applications to support these conclusions.Comment: Chemical Physics Letters, 12 pages text, 5 figure

DESIGNING A WIRELESS COUNTER FOR BALE PRODUCTION

The immerge rise of crop production force engineers to design efficient ways for checking and inspecting the agricultural machines. Smart sensors that can monitor the temperature, operating time or even count the amount of the produced bales can fulfill these requirements. This can be realized by installing a monitoring device for the driver in the cabinet of the tractor that communicates over a wireless channel with the smart sensors mounted on the agricultural machine. The target of this thesis was to develop the software and hardware of a device that is able to monitor the bale production process with the help of wireless sensor nodes to enable an easy installation process and low installation costs. The device should also be able to log and save the amount of the produced bales in a database which can be accessed from a certain website. This leads to the advantage that the crop bale production can be observed from almost every place in the world. The thesis describes the implementation of the hardware and software for a bale monitoring device and shows the results of the power consumption of a wireless node. Furthermore the reliability of the wireless channel between two nodes has been investigated.fi=Opinnäytetyö kokotekstinä PDF-muodossa.|en=Thesis fulltext in PDF format.|sv=Lärdomsprov tillgängligt som fulltext i PDF-format

The effect of azithromycin on the non-surgical treatment of peri-implantitis. A prospective double blind placebo controlled randomised clinical trial. A pilot study

3.0 Abstract 3.1 Aim The aim of this study is to determine in a randomized control trial the microbiological and immunological effect of azithromycin (AZM) in cases of peri-implantitis versus a placebo at the peri-implant tissue level in a sample of patients diagnosed with peri-implantitis. 3.2 Methodology 17 patients referred to periodontics department at the Westmead Centre for Oral Health for the treatment of peri-implantitis were invited to participate in the study. Five subjects with healthy implants were also recruited for the immuno-regulatory part of the study to act as healthy controls. After clinical assessment, subjects received non-surgical debridement of implant/abutment surfaces and oral hygiene instruction. The subjects were then randomly assigned to receive AZM (1 x 500mg capsule per day for 3 days) and the controls received placebo tablets. Submucosal plaque and peri-implant crevicular fluid samples were collected from selected implants at the following time points: day 0, 3, 7, 21, 90 and 180 for microbiological and immunological analysis. The primary outcome variables were mean counts and mean changes from baseline levels in the anaerobic and aerobic microbiological counts (CFU/ml) and the proinflammatory cytokine Il-1β levels (pg/ml) over time. Analysis of the species associated with peri-implantitis and the cytokine levels of healthy control implants was also determined. 7 3.3 Results The placebo group showed a trend for aerobic bacteria to steadily rebound after day 7. This rebound appeared to be delayed until day 90 in the azithromycin group. Both treatment groups showed a trend for the mean anaerobic bacteria count to decrease from day 1 to 7 after which a gradual increase in counts was observed for the remainder of the study. The magnitude of this rebound in anaerobic bacteria levels was greater in the placebo group. There were no statistical significant differences observed between the two groups at any times points (p>0.05). The placebo group showed a mean change from baseline resulting in reduction in anaerobic bacteria counts up to day 7, after which a rebound in bacteria levels were observed above baseline levels and sustained throughout the remainder of the study. The azithromycin group showed mean changes from baseline levels resulting in a sustained decrease in mean anaerobic bacteria levels below baseline observed up 180 days. No statistical significant differences observed between the two groups at any times points (p>0.05). Orange complex species were found in the highest frequency (94.1%) whilst the red complex bacteria were found at the lowest frequency (17.6%) with no statistical significant differences between treatment groups observed at baseline. Both groups demonstrated a trend for mean reduction in IL-1β levels after treatment over time which was sustained throughout the study. The magnitude of changes from baseline levels appeared greater in the azithromycin group. No statistical significance was observed between treatment groups (p>0.05). It was observed that the percentage frequency of subjects who were “positive responders” was higher in the azithromycin group at all time points. 8 3.4 Conclusion The reductions and subsequent recolonization observed in the immunological data closely correlated with that of the microbiological data. Despite reductions in levels of IL-1β initially after treatment, the levels gradually rebounded throughout the course of the study. Throughout all time points, IL-1β did not return to baseline levels, which were likely a result of the treatment effect. Similarly, a reduction in microbiological parameters was seen initially post therapy with a trend for a gradual rebound in counts seen over time. No statistical significant effect was observed between treatment groups despite a trend for a greater magnitude change in outcome measures for subjects’ allocated azithromycin. We demonstrated that the response to non-surgical treatment, with or without adjunctive azithromycin is highly variable and unpredictable with gradual rebound in immunological and microbiological parameters seen after 6 months. Because of the limited number of patients recruited, no definitive conclusions can be made. There is clear indication that further longitudinal research into the effects of azithromycin at peri-implant-host interface is warranted.Australian Periodontal Research Foundatio

The Fermion Monte Carlo revisited

In this work we present a detailed study of the Fermion Monte Carlo algorithm (FMC), a recently proposed stochastic method for calculating fermionic ground-state energies [M.H. Kalos and F. Pederiva, Phys. Rev. Lett. vol. 85, 3547 (2000)]. A proof that the FMC method is an exact method is given. In this work the stability of the method is related to the difference between the lowest (bosonic-type) eigenvalue of the FMC diffusion operator and the exact fermi energy. It is shown that within a FMC framework the lowest eigenvalue of the new diffusion operator is no longer the bosonic ground-state eigenvalue as in standard exact Diffusion Monte Carlo (DMC) schemes but a modified value which is strictly greater. Accordingly, FMC can be viewed as an exact DMC method built from a correlated diffusion process having a reduced Bose-Fermi gap. As a consequence, the FMC method is more stable than any transient method (or nodal release-type approaches). We illustrate the various ideas presented in this work with calculations performed on a very simple model having only nine states but a full sign problem. Already for this toy model it is clearly seen that FMC calculations are inherently uncontrolled.Comment: 49 pages with 4 postscript figure

The effect of azithromycin on the non-surgical treatment of peri-implantitis. A prospective double blind placebo controlled randomised clinical trial. A pilot study

3.0 Abstract 3.1 Aim The aim of this study is to determine in a randomized control trial the microbiological and immunological effect of azithromycin (AZM) in cases of peri-implantitis versus a placebo at the peri-implant tissue level in a sample of patients diagnosed with peri-implantitis. 3.2 Methodology 17 patients referred to periodontics department at the Westmead Centre for Oral Health for the treatment of peri-implantitis were invited to participate in the study. Five subjects with healthy implants were also recruited for the immuno-regulatory part of the study to act as healthy controls. After clinical assessment, subjects received non-surgical debridement of implant/abutment surfaces and oral hygiene instruction. The subjects were then randomly assigned to receive AZM (1 x 500mg capsule per day for 3 days) and the controls received placebo tablets. Submucosal plaque and peri-implant crevicular fluid samples were collected from selected implants at the following time points: day 0, 3, 7, 21, 90 and 180 for microbiological and immunological analysis. The primary outcome variables were mean counts and mean changes from baseline levels in the anaerobic and aerobic microbiological counts (CFU/ml) and the proinflammatory cytokine Il-1β levels (pg/ml) over time. Analysis of the species associated with peri-implantitis and the cytokine levels of healthy control implants was also determined. 7 3.3 Results The placebo group showed a trend for aerobic bacteria to steadily rebound after day 7. This rebound appeared to be delayed until day 90 in the azithromycin group. Both treatment groups showed a trend for the mean anaerobic bacteria count to decrease from day 1 to 7 after which a gradual increase in counts was observed for the remainder of the study. The magnitude of this rebound in anaerobic bacteria levels was greater in the placebo group. There were no statistical significant differences observed between the two groups at any times points (p>0.05). The placebo group showed a mean change from baseline resulting in reduction in anaerobic bacteria counts up to day 7, after which a rebound in bacteria levels were observed above baseline levels and sustained throughout the remainder of the study. The azithromycin group showed mean changes from baseline levels resulting in a sustained decrease in mean anaerobic bacteria levels below baseline observed up 180 days. No statistical significant differences observed between the two groups at any times points (p>0.05). Orange complex species were found in the highest frequency (94.1%) whilst the red complex bacteria were found at the lowest frequency (17.6%) with no statistical significant differences between treatment groups observed at baseline. Both groups demonstrated a trend for mean reduction in IL-1β levels after treatment over time which was sustained throughout the study. The magnitude of changes from baseline levels appeared greater in the azithromycin group. No statistical significance was observed between treatment groups (p>0.05). It was observed that the percentage frequency of subjects who were “positive responders” was higher in the azithromycin group at all time points. 8 3.4 Conclusion The reductions and subsequent recolonization observed in the immunological data closely correlated with that of the microbiological data. Despite reductions in levels of IL-1β initially after treatment, the levels gradually rebounded throughout the course of the study. Throughout all time points, IL-1β did not return to baseline levels, which were likely a result of the treatment effect. Similarly, a reduction in microbiological parameters was seen initially post therapy with a trend for a gradual rebound in counts seen over time. No statistical significant effect was observed between treatment groups despite a trend for a greater magnitude change in outcome measures for subjects’ allocated azithromycin. We demonstrated that the response to non-surgical treatment, with or without adjunctive azithromycin is highly variable and unpredictable with gradual rebound in immunological and microbiological parameters seen after 6 months. Because of the limited number of patients recruited, no definitive conclusions can be made. There is clear indication that further longitudinal research into the effects of azithromycin at peri-implant-host interface is warranted.Australian Periodontal Research Foundatio