595 research outputs found
Fluid flow through porous media using distinct element based numerical method
Many analytical and numerical methods have been developed to describe and analyse fluid flow through the reservoir’s porous media. The medium considered by most of these models is continuum based homogeneous media. But if the formation is not homogenous or if there is some discontinuity in the formation, most of these models become very complex and their solutions lose their accuracy, especially when the shape or reservoir geometry and boundary conditions are complex. In this paper, distinct element method (DEM) is used to simulate fluid flow in porous media. The DEM method is independent of the initial and boundary conditions, as well as reservoir geometry and discontinuity. The DEM based model proposed in this study is appeared to be unique in nature with capability to be used for any reservoir with higher degrees of complexity associated with the shape and geometry of its porous media, conditions of fluid flow, as well as initial and boundary conditions. This model has first been developed by Itasca Consulting Company and is further improved in this paper. Since the release of the model by Itasca, it has not been validated for fluid flow application in porous media, especially in case of petroleum reservoir. In this paper, two scenarios of linear and radial fluid flow in a finite reservoir are considered. Analytical models for these two cases are developed to set a benchmark for the comparison of simulation data. It is demonstrated that the simulation results are in good agreement with analytical results. Another major improvement in the model is using the servo controlled walls instead of particles to introduce tectonic stresses on the formation to simulate more realistic situations. The proposed model is then used to analyse fluid flow and pressure behaviour for hydraulically induced fractured and naturally fractured reservoir to justify the potential application of the model
Local Thermometry of Neutral Modes on the Quantum Hall Edge
A system of electrons in two dimensions and strong magnetic fields can be
tuned to create a gapped 2D system with one dimensional channels along the
edge. Interactions among these edge modes can lead to independent transport of
charge and heat, even in opposite directions. Measuring the chirality and
transport properties of these charge and heat modes can reveal otherwise hidden
structure in the edge. Here, we heat the outer edge of such a quantum Hall
system using a quantum point contact. By placing quantum dots upstream and
downstream along the edge of the heater, we can measure both the chemical
potential and temperature of that edge to study charge and heat transport,
respectively. We find that charge is transported exclusively downstream, but
heat can be transported upstream when the edge has additional structure related
to fractional quantum Hall physics.Comment: 24 pages, 18 figure
Immunotherapy for neuroblastoma using syngeneic fibroblasts transfected with IL-2 and IL-12
Cytokine-modified tumour cells have been used in clinical trials for immunotherapy of neuroblastoma, but primary tumour cells from surgical biopsies are difficult to culture. Autologous fibroblasts, however, are straightforward to manipulate in culture and easy to transfect using nonviral or viral vectors. Here we have compared the antitumour effect of fibroblasts and tumour cells transfected ex vivo to coexpress interleukin-2 (IL-2) and IL-12 in a syngeneic mouse model of neuroblastoma. Coinjection of cytokine-modified fibroblasts with Neuro-2A tumour cells abolished their in vivo tumorigenicity. Treatment of established tumours with three intratumoral doses of transfected fibroblasts showed a significant therapeutic effect with reduced growth or complete eradication of tumours in 90% of mice, associated with extensive leukocyte infiltration. Splenocytes recovered from vaccinated mice showed enhanced IL-2 production following Neuro-2A coculture, and increased cytotoxicity against Neuro-2A targets compared with controls. Furthermore, 100% of the tumour-free mice exhibited immune memory against tumour cells when rechallenged three months later. The potency of transfected fibroblasts was equivalent to that of tumour cells in all experiments. We conclude that syngeneic fibroblasts cotransfected with IL-2 and IL-12 mediate therapeutic effects against established disease, and are capable of generating immunological memory. Furthermore, as they are easier to recover and manipulate than autologous tumour cells, fibroblasts provide an attractive alternative immunotherapeutic strategy for the treatment of neuroblastoma
Differentiation and Glucocorticoid Regulated Apopto-Phagocytic Gene Expression Patterns in Human Macrophages. Role of Mertk in Enhanced Phagocytosis
The daily clearance of physiologically dying cells is performed safely mainly by cells in the mononuclear phagocyte system. They can recognize and engulf dying cells utilizing several cooperative mechanisms. In our study we show that the expression of a broad range of apopto-phagocytic genes is strongly up-regulated during differentiation of human monocytes to macrophages with different donor variability. The glucocorticoid dexamethasone has a profound effect on this process by selectively up-regulating six genes and down-regulating several others. The key role of the up-regulated mer tyrosine kinase (Mertk) in dexamethasone induced enhancement of phagocytosis could be demonstrated in human monocyte derived macrophages by gene silencing as well as blocking antibodies, and also in a monocyte-macrophage like cell line. However, the additional role of other glucocorticoid induced elements must be also considered since the presence of autologous serum during phagocytosis could almost completely compensate for the blocked function of Mertk
Microwave studies of the fractional Josephson effect in HgTe-based Josephson junctions
The rise of topological phases of matter is strongly connected to their
potential to host Majorana bound states, a powerful ingredient in the search
for a robust, topologically protected, quantum information processing. In order
to produce such states, a method of choice is to induce superconductivity in
topological insulators. The engineering of the interplay between
superconductivity and the electronic properties of a topological insulator is a
challenging task and it is consequently very important to understand the
physics of simple superconducting devices such as Josephson junctions, in which
new topological properties are expected to emerge. In this article, we review
recent experiments investigating topological superconductivity in topological
insulators, using microwave excitation and detection techniques. More
precisely, we have fabricated and studied topological Josephson junctions made
of HgTe weak links in contact with two Al or Nb contacts. In such devices, we
have observed two signatures of the fractional Josephson effect, which is
expected to emerge from topologically-protected gapless Andreev bound states.
We first recall the theoretical background on topological Josephson junctions,
then move to the experimental observations. Then, we assess the topological
origin of the observed features and conclude with an outlook towards more
advanced microwave spectroscopy experiments, currently under development.Comment: Lectures given at the San Sebastian Topological Matter School 2017,
published in "Topological Matter. Springer Series in Solid-State Sciences,
vol 190. Springer
How Do Police Respond to Stalking? An Examination of the Risk Management Strategies and Tactics Used in a Specialized Anti-Stalking Law Enforcement Unit
How do police respond to and manage complaints of stalking? To answer this question, we conducted a 3-phase study. First, we reviewed the literature to identify risk management tactics used to combat stalking. Second, we asked a group of police officers to review those tactics for completeness and group them into categories reflecting more general risk management strategies. The result was 22 categories of strategies. Finally, we used qualitative methods to evaluate the files of 32 cases referred to the specialized anti-stalking unit of a metropolitan police department. We coded specific risk management tactics and strategies used by police. Results indicated that a median number of 19 specific tactics from 7 general strategies were used to manage risk. Also, the implementation of strategies and tactics reflected specific characteristics of the cases (e.g., perpetrator risk factors, victim vulnerability factors), suggesting that the risk management decisions made by police were indeed strategic in nature. Qualitative analyses indicated that some of the strategies and tactics were more effective than others. We discuss how these findings can be used to understand and use stalking risk management more generally, as well as improve research on the efficacy of risk assessment and management for stalking
Measurement of the Relative Branching Fraction of to Charged and Neutral B-Meson Pairs
We analyze 9.7 x 10^6 B\bar{B}$ pairs recorded with the CLEO detector to
determine the production ratio of charged to neutral B-meson pairs produced at
the Y(4S) resonance. We measure the rates for B^0 -> J/psi K^{(*)0} and B^+ ->
J/psi K^{(*)+} decays and use the world-average B-meson lifetime ratio to
extract the relative widths f+-/f00 = Gamma(Y(4S) -> B+B-)/Gamma(Y(4S) ->
B0\bar{B0}) = = 1.04 +/- 0.07(stat) +/- 0.04(syst). With the assumption that
f+- + f00 = 1, we obtain f00 = 0.49 +/- 0.02(stat) +/- 0.01(syst) and f+- =
0.51 +/- 0.02(stat) +/- 0.01(syst). This production ratio and its uncertainty
apply to all exclusive B-meson branching fractions measured at the Y(4S)
resonance.Comment: 11 pages postscript, also available through
http://w4.lns.cornell.edu/public/CLN
First Observation of the Decays and B^{0}\to D^{*-}p\bar{n}$
We report the first observation of exclusive decays of the type B to D^* N
anti-N X, where N is a nucleon. Using a sample of 9.7 times 10^{6} B-Bbar pairs
collected with the CLEO detector operating at the Cornell Electron Storage
Ring, we measure the branching fractions B(B^0 \to D^{*-} proton antiproton
\pi^+) = ({6.5}^{+1.3}_{-1.2} +- 1.0) \times 10^{-4} and B(B^0 \to D^{*-}
proton antineutron) = ({14.5}^{+3.4}_{-3.0} +- 2.7) times 10^{-4}. Antineutrons
are identified by their annihilation in the CsI electromagnetic calorimeter.Comment: 9 pages postscript, also available through
http://w4.lns.cornell.edu/public/CLN
Study of the Decays B0 --> D(*)+D(*)-
The decays B0 --> D*+D*-, B0 --> D*+D- and B0 --> D+D- are studied in 9.7
million Y(4S) --> BBbar decays accumulated with the CLEO detector. We determine
Br(B0 --> D*+D*-) = (9.9+4.2-3.3+-1.2)e-4 and limit Br(B0 --> D*+D-) < 6.3e-4
and Br(B0 --> D+D-) < 9.4e-4 at 90% confidence level (CL). We also perform the
first angular analysis of the B0 --> D*+D*- decay and determine that the
CP-even fraction of the final state is greater than 0.11 at 90% CL. Future
measurements of the time dependence of these decays may be useful for the
investigation of CP violation in neutral B meson decays.Comment: 21 pages, 5 figures, submitted to Phys. Rev.
A Search for
We report results of a search for in a sample of 9.7 million
charged meson decays. The search uses both and
decay modes of the , and demands exclusive reconstruction of the
companion decay to suppress background. We set an upper limit on the
branching fraction at 90%
confidence level. With slight modification to the analysis we also establish
at 90% confidence
level.Comment: 10 ages postscript, also available through
http://w4.lns.cornell.edu/public/CLN
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