Exploration of jet energy loss via direct γ\gamma-charged particle azimuthal correlation measurements

The multiplicities of charged particles azimuthally associated with direct photons and $\pi^{0}$ have been measured for Au+Au, p+p, and d+Au collisions at $\sqrt{s_{NN}}$ = 200 GeV in the STAR experiment. Charged particles with transverse momentum 0.5 $<$ $p_T^{h^{\pm}}$ $<$ 16 GeV/c for p+p and d+Au, and 3 $<$ $p_T^{h^{\pm}}$ $<$ 16 GeV/c for Au+Au and pseudorapidity $\mid\eta\mid$ $\leq$ 1.5 in coincidence with direct photons and $\pi^{0}$ of high transverse momentum 8 $<$ $p_T^{\gamma,\pi^{0}}$ $<$ 16 GeV/c at $\mid\eta\mid$ $\leq$ 0.9 have been used for this analysis. Within the considered range of kinematics, the observed suppressions of the associated yields per direct $\gamma$ in central Au+Au relative to p+p and d+Au are similar and constant with direct photon fractional energy $z_{T}$ ($z_{T}=p_{T}^{h^{\pm}}/p_{T}^{\gamma}$). The measured suppressions of the associated yields with direct $\gamma$ are comparable to those with $\pi^{0}$. The data are compared to theoretical predictions.Comment: 4 pages, 5 figures, Quark Matter 2009, March 30 - April 4, Knoxville, Tennesse

Generalized Kinetic Theory of Electrons and Phonons: Models, Equilibrium, Stability

In the present paper our aim is to introduce some models for the generalization of the kinetic theory of electrons and phonons (KTEP), as well as to study equilibrium solutions and their stability for the generalized KTEP (GKTEP) equations. We consider a couple of models, relevant to non standard quantum statistics, which give rise to inverse power law decays of the distribution function with respect to energy. In the case of electrons in a phonon background, equilibrium and stability are investigated by means of Lyapounov theory. Connections with thermodynamics are pointed out.Comment: 10 pages, 2 figures, (RevTeX4), to appear in Physica B (2003

Bubble dissolution in horizontal turbulent bubbly flow in domestic central heating system

In a domestic central heating system, the phenomenon of microbubble nucleation and detachment on the surface of a boiler heat exchanger finds its origins in the high surface temperature of the wall and consequential localised super saturation conditions. If the surrounding bulk fluid is at under-saturated conditions, then after exiting the boiler, the occurrence is followed by bubbly flow and bubble dissolution. A comprehensive understanding of the fundamentals of bubble dissolution in such a domestic wet central heating system is essential for an enhanced deaeration technique that would consequently improve system performance. In this paper, the bubble dissolution rate along a horizontal pipe was investigated experimentally at different operating conditions in a purpose built test rig of a standard domestic central heating system. A high speed camera was used to measure the bubble size at different depths of focal plane using two square sectioned sight glasses at two stations, spaced 2.2 m apart. A dynamic model for bubble dissolution in horizontal bubbly flow has been developed and compared with experimental data. The effects of several important operating and structural parameters such as saturation ratio, velocity, temperature, pressure of the bulk liquid flow, initial bubble size and pipe inside diameter on the bubble dissolution were thus examined using the model. This model provides a useful tool for understanding bubble behaviours in central heating systems and optimising the system efficiency

Superoscillations and tunneling times

It is proposed that superoscillations play an important role in the interferences which give rise to superluminal effects. To exemplify that, we consider a toy model which allows for a wave packet to travel, in zero time and negligible distortion a distance arbitrarily larger than the width of the wave packet. The peak is shown to result from a superoscillatory superposition at the tail. Similar reasoning applies to the dwell time.Comment: 12 page

Role for Interactive Tradespace Exploration in Multi-Stakeholder Negotiations

The significant time, effort, and resource expenditures needed to design and develop aerospace systems motivate on-going research into developing methods for generating, evaluating, and selecting candidate system solutions that can deliver more benefit for a given cost. Compounding the problem is the multiplicity of perspectives of the many stakeholders for such systems, altering the meaning of “benefit” and “cost” depending on the stakeholder considered. Tradespace exploration techniques have been used in the past to generate large datasets in order to gain insights into design-value, cost-benefit tradeoffs for complex aerospace systems. Using interactive tradespace exploration to support multi-stakeholder negotiations can reveal these tradeoffs not only for individuals, but also across a group. A method is introduced and applied to two aerospace cases in order to explore the potential for interactive tradespace exploration to support stakeholder negotiations. Preliminary results indicate the method to be a rapid and beneficial technique, which generated compromise alternatives, guided the elicitation of previously unarticulated information, and resulted in increased confidence and solution buy-in of participating stakeholders.Massachusetts Institute of Technology. Systems Engineering Advancement Research Initiativ

Flat histogram simulation of lattice polymer systems

We demonstrate the use of a new algorithm called the Flat Histogram sampling algorithm for the simulation of lattice polymer systems. Thermodynamics properties, such as average energy or entropy and other physical quantities such as end-to-end distance or radius of gyration can be easily calculated using this method. Ground-state energy can also be determined. We also explore the accuracy and limitations of this method. Key words: Monte Carlo algorithms, flat histogram sampling, HP model, lattice polymer systemsComment: 7 RevTeX two-column page

Intensive variables in the framework of the non-extensive thermostatistics

By assuming an appropriate energy composition law between two systems governed by the same non-extensive entropy, we revisit the definitions of temperature and pressure, arising from the zeroth principle of thermodynamics, in a manner consistent with the thermostatistics structure of the theory. We show that the definitions of these quantities are sensitive to the composition law of entropy and internal energy governing the system. In this way, we can clarify some questions raised about the possible introduction of intensive variables in the context of non-extensive statistical mechanics.Comment: 14 pages, elsart style, version accepted on Physics Letters

Self-Averaging, Distribution of Pseudo-Critical Temperatures and Finite Size Scaling in Critical Disordered Systems

The distributions $P(X)$ of singular thermodynamic quantities in an ensemble of quenched random samples of linear size $l$ at the critical point $T_c$ are studied by Monte Carlo in two models. Our results confirm predictions of Aharony and Harris based on Renormalization group considerations. For an Ashkin-Teller model with strong but irrelevant bond randomness we find that the relative squared width, $R_X$, of $P(X)$ is weakly self averaging. $R_X\sim l^{\alpha/\nu}$, where $\alpha$ is the specific heat exponent and $\nu$ is the correlation length exponent of the pure model fixed point governing the transition. For the site dilute Ising model on a cubic lattice, known to be governed by a random fixed point, we find that $R_X$ tends to a universal constant independent of the amount of dilution (no self averaging). However this constant is different for canonical and grand canonical disorder. We study the distribution of the pseudo-critical temperatures $T_c(i,l)$ of the ensemble defined as the temperatures of the maximum susceptibility of each sample. We find that its variance scales as $(\delta T_c(l))^2 \sim l^{-2/\nu}$ and NOT as $\sim l^{-d}. We find that$R_\chi$is reduced by a factor of$\sim 70$with respect to$R_\chi (T_c)$by measuring$\chi$of each sample at$T_c(i,l)$. We analyze correlations between the magnetization at criticality$m_i(T_c,l)$and the pseudo-critical temperature$T_c(i,l)$in terms of a sample independent finite size scaling function of a sample dependent reduced temperature$(T-T_c(i,l))/T_c$. This function is found to be universal and to behave similarly to pure systems.Comment: 31 pages, 17 figures, submitted to Phys. Rev.

Biomass accumulation and nutrient uptake of cereals at different growth stages in the parkland region of Saskatchewan

Non-Peer ReviewedField experiments were conducted with spring wheat (cv. AC Barrie - CWRS and cv. AC Taber - CPS), barley (cv. AC Oxbow - malt and cv. AC Lacombe - feed) and oats (cv. CDC Boyer or CDC Pacer) in 1998 and 1999 at Melfort, Saskatchewan, Canada, to determine biomass accumulation and nutrient uptake in cereal crops at different growth stages, and their relationship. All cereal crops followed a similar pattern of biomass and nutrient accumulation, which increased at early growth stages, reached at maximum and then decreased at late growth stages. Cereal crops usually reached their maximum biomass at late milk to full ripening stages (72-90 days after emergence), although some cultivars had a several days difference between the two years. Maximum biomass accumulation rate was 164-204 kg ha-1d-1 for wheat, 211-308 kg ha-1d-1 for barley and 185-217g ha-1d-1 for oats. Maximum uptake of nutrients usually occurred at beginning of flower to late milk (63-82 days after emergence) in both years. Maximum accumulation rate of N, P, K and S was 2.0-4.7, 0.3-0.4, 2.4-5.1 and 0.3-0.5 kg ha-1d-1 for wheat, 2.4-5.2, 0.3-0.5, 3.1-7.6 and 0.4-0.8 kg ha-1d-1 for barley, and 2.7-3.6, 0.3, 4.2-4.7 and 0.4-0.5 kg ha-1d-1 for oats, respectively. Both seed yield and nutrient uptake were lower in 1999 than in 1998, due to differences in weather conditions in the growing season in the two years. In summary, maximum nutrient accumulation rate occurred earlier than maximum biomass accumulation rate, and maximum nutrient uptake occurred earlier than maximum biomass. This indicates that in order to get high seed yields, there should be sufficient supply of nutrients to ensure higher nutrient uptake rate at tillering to stem elongation growth stage first, then a higher biomass accumulation rate at early to late boot growth stage, a greater nutrient uptake at beginning of flower to late milk growth stage, and a greater biomass at late milk to full ripening growth stage. This also suggests that sufficient supply of nutrients from soil/fertilizers at early growth stages is of great importance for high-yield crop production systems

Biomass accumulation and nutrient uptake of oilseeds at different growth stages in the parkland region of Saskatchewan

Non-Peer ReviewedField experiments were conducted with canola (Brassica napus and B. rapa, cv. Quantum and Tobin), mustard (cv. AC Vulcan) and flax (cv. Norlin) in 1998 and 1999 at Melfort, Saskatchewan, Canada, to determine biomass and nutrient accumulation in oilseeds at different growth stages and their relationship to seed yield. In general, all oilseed crops followed a similar pattern in biomass accumulation and nutrient uptake, which increased at early growth stages, reached maximum and then decreased at late growth stages. Oilseed crops usually reached their maximum biomass at medium to end of pod forming growth stages (74-80 days after emergence), although Quest canola cultivar had a several day delay at early ripening stage (84 days after emergence) in 1998. Maximum biomass accumulation rate was 146-190 kg ha-1d-1 for canola, 158-182 kg ha-1d-1 for mustard and 174-189 kg ha-1d-1 for flax. Maximum nutrient uptake usually occurred at flowering to seed filling stage (59-85 days after emergence. Maximum nutrient uptake rate for N, P, K, S and B, respectively, was 2.3-4.5, 0.3-0.5, 2.5-5.7, 0.7-1.1 and 0.005-0.008 kg ha-1d-1 for canola, 2.3-3.9, 0.4-0.5, 2.6-4.9, 1.2-1.4 and 0.006-0.008 kg ha-1d-1 for mustard and 3.2-4.0, 0.3-0.4, 2.9-4.1, 0.3-0.5 and 0.004-0.009 kg ha-1d-1 for flax. Both seed yield and nutrient uptake in seed were lower in 1999 than in 1998, due to differences in weather conditions in the growing season in the two years. In summary, maximum nutrient accumulation rate occurred earlier than maximum biomass accumulation rate, and maximum nutrient uptake was earlier than maximum biomass. This indicates that in order to get high seed yields, there should be sufficient supply of nutrients to plants to ensure higher nutrient uptake rate at side shooting to bud forming stage, and then a greater biomass accumulation rate at early to late bud forming stage. This further suggests that adequate supply of nutrients from soil/fertilizers at early growth stages is of great importance for high-yield crop production systems