Inequivalence of pure state ensembles for open quantum systems: the preferred ensembles are those that are physically realizable

An open quantum system in steady state $\hat\rho_{ss}$ can be represented by a weighted ensemble of pure states $\hat\rho_{ss}=\sum_{k}\wp_{k}\ket{\psi_k} \bra{\psi_k}$ in infinitely many ways. A physically realizable (PR) ensemble is one for which some continuous measurement of the environment will collapse the system into a pure state $\ket{\psi(t)}$, stochastically evolving such that the proportion of time for which $\ket{\psi(t)} = \ket{\psi_{k}}$ equals $\wp_{k}$. Some, but not all, ensembles are PR. This constitutes the preferred ensemble fact, with the PR ensembles being the preferred ensembles. We present the necessary and sufficient conditions for a given ensemble to be PR, and illustrate the method by showing that the coherent state ensemble is not PR for an atom laser.Comment: 5 pages, no figure

Non-Markovian dynamics of a qubit

In this paper we investigate the non-Markovian dynamics of a qubit by comparing two generalized master equations with memory. In the case of a thermal bath, we derive the solution of the post-Markovian master equation recently proposed in Ref. [A. Shabani and D.A. Lidar, Phys. Rev. A {\bf 71}, 020101(R) (2005)] and we study the dynamics for an exponentially decaying memory kernel. We compare the solution of the post-Markovian master equation with the solution of the typical memory kernel master equation. Our results lead to a new physical interpretation of the reservoir correlation function and bring to light the limits of usability of master equations with memory for the system under consideration.Comment: Replaced with published version (minor changes

The role of attention and consistency with schema expectation in memory for objects in place

The role of attention and consistency with schema expectation in memory for objects in place were examined in one experiment. Forty participants were asked to study a picture of either the graduate student office or the preschool classroom, and either under full attention condition or under divided attention condition. Sixteen stimulus items, half consistent and half inconsistent with schema expectation about the room settings were placed throughout the room. Participants were later given a free recall test, followed by a same-changed recognition memory test immediately after that. The results show that participants remembered better under full attention condition than under divided attention condition. Items inconsistent with schema expectation were better recalled and recognized than items consistent with schema expectation both under full attention and divided attention conditions. These results support the findings on the consistency effect in some previous studies. More importantly, the present study reveals the influence of manipulation of attention on the consistency effect. The results show that consistency effect occurs in both conditions, with a greater effect reported under divided attention condition than under full attention condition. Reducing the participants’ attention increases the consistency effect

Effect of water-to-feed ratio on feed disappearance, growth rate, feed efficiency, and carcass traits in growing-finishing pigs

peer-reviewedThe optimum proportion of water for preparing liquid feed to maximize growth and optimize feed efficiency (FE) in growing-finishing pigs is not known. The aim of the current study was, using an automatic short-trough sensor liquid feeding system, to identify the water-to-feed ratio at which growth was maximized and feed was most efficiently converted to live-weight. Two experiments were conducted in which four commercially used water-to-feed ratios were fed: 2.4:1, 3.0:1, 3.5:1, and 4.1:1 on a dry matter (DM) basis (the equivalent of 2:1, 2.5:1, 3.0:1, and 3.5:1 on a fresh matter basis). Each experiment comprised 216 pigs, penned in groups of 6 same sex (entire male and female) pigs/pen with a total of 9 pen replicates per treatment. The first experiment lasted 62 days (from 40.6 to 102.2 kg at slaughter) and the second experiment was for 76 days (from 31.8 to 119.6 kg at slaughter). Overall, in Exp. 1, FE was 0.421, 0.420, 0.453, and 0.448 (s.e. 0.0081 g/g; P < 0.01) for pigs fed at 2.4:1, 3.0:1, 3.5:1, and 4.1:1, respectively. Overall, in Exp. 2, average daily gain was 1,233, 1,206, 1,211, and 1,177 (s.e. 12.7 g/day; P < 0.05) for pigs fed at 2.4:1, 3.0:1, 3.5:1, and 4.1:1, respectively. At slaughter, in Exp. 1, dressing percentage was 76.7, 76.6, 76.7, and 75.8 (s.e. 0.17%; P < 0.01) for 2.4:1, 3.0:1, 3.5:1, and 4.1:1, respectively. There were no differences between treatment groups for DM, organic matter, nitrogen, gross energy, or ash digestibilities. These findings indicate that liquid feeding a diet prepared at a water-to-feed ratio of 3.5:1 maximizes FE of growing-finishing pigs without negatively affecting dressing percentage. Therefore, preparing liquid feed for growing-finishing pigs at a water-to-feed ratio of 3.5:1 DM is our recommendation for a short-trough liquid feeding system

Evaluation of routes to chiral core dendrimers

Dendrimers are macromolecules with a highly branched three-dimensional shape, produced in an iterative sequence of reaction steps, in which each reaction results in a new generation. Dendrimers have stimulated wide interest in the field of chemistry and biology, particularly with respect to applications to drug delivery and more recently imaging. They have also been of growing interest as macromolecular hosts, potential catalysts and have been attached to surfaces and polymeric materials, and have significant potential in new materials development. Dendrimers can have comparable molecular dimensions to some proteins and could potentially have internal microenvironments akin to the active site of an enzyme. Encapsulation within dendrimers has significant potential biomedical applications, whilst dendrimer surface behavior is of interest to evaluate interactions of dendrimer surface functionality (its most accessible region) with biological molecules. Exploiting many of these areas are dependent on generating chirality in dendrimers

Bloch Equations and Completely Positive Maps

The phenomenological dissipation of the Bloch equations is reexamined in the context of completely positive maps. Such maps occur if the dissipation arises from a reduction of a unitary evolution of a system coupled to a reservoir. In such a case the reduced dynamics for the system alone will always yield completely positive maps of the density operator. We show that, for Markovian Bloch maps, the requirement of complete positivity imposes some Bloch inequalities on the phenomenological damping constants. For non-Markovian Bloch maps some kind of Bloch inequalities involving eigenvalues of the damping basis can be established as well. As an illustration of these general properties we use the depolarizing channel with white and colored stochastic noise.Comment: Talk given at the Conference "Quantum Challenges", Falenty, Poland, September 4-7, 2003. 21 pages, 3 figure

Roton immiscibility in a two-component dipolar Bose gas

We characterize the immiscibility-miscibility transition (IMT) of a two-component Bose-Einstein condensate (BEC) with dipole-dipole interactions. In particular, we consider the quasi-two dimensional geometry, where a strong trapping potential admits only zero-point motion in the trap direction, while the atoms are more free to move in the transverse directions. We employ the Bogoliubov treatment of the two-component system to identify both the well-known long-wavelength IMT in addition to a roton-like IMT, where the transition occurs at finite-wave number and is reminiscent of the roton softening in the single component dipolar BEC. Additionally, we verify the existence of the roton IMT in the fully trapped, finite systems by direct numerical simulation of the two-component coupled non-local Gross-Pitaevskii equations.Comment: 13 pages, 2 columns, 9 figure

Early activation of wheat polyamine biosynthesis during Fusarium head blight implicates putrescine as an inducer of trichothecene mycotoxin production

<p>Abstract</p> <p>Background</p> <p>The fungal pathogen <it>Fusarium graminearum </it>causes Fusarium Head Blight (FHB) disease on wheat which can lead to trichothecene mycotoxin (<it>e.g</it>. deoxynivalenol, DON) contamination of grain, harmful to mammalian health. DON is produced at low levels under standard culture conditions when compared to plant infection but specific polyamines (<it>e.g</it>. putrescine and agmatine) and amino acids (<it>e.g</it>. arginine and ornithine) are potent inducers of DON by <it>F. graminearum </it>in axenic culture. Currently, host factors that promote mycotoxin synthesis during FHB are unknown, but plant derived polyamines could contribute to DON induction in infected heads. However, the temporal and spatial accumulation of polyamines and amino acids in relation to that of DON has not been studied.</p> <p>Results</p> <p>Following inoculation of susceptible wheat heads by <it>F. graminearum</it>, DON accumulation was detected at two days after inoculation. The accumulation of putrescine was detected as early as one day following inoculation while arginine and cadaverine were also produced at three and four days post-inoculation. Transcripts of ornithine decarboxylase (ODC) and arginine decarboxylase (ADC), two key biosynthetic enzymes for putrescine biosynthesis, were also strongly induced in heads at two days after inoculation. These results indicated that elicitation of the polyamine biosynthetic pathway is an early response to FHB. Transcripts for genes encoding enzymes acting upstream in the polyamine biosynthetic pathway as well as those of ODC and ADC, and putrescine levels were also induced in the rachis, a flower organ supporting DON production and an important route for pathogen colonisation during FHB. A survey of 24 wheat genotypes with varying responses to FHB showed putrescine induction is a general response to inoculation and no correlation was observed between the accumulation of putrescine and infection or DON accumulation.</p> <p>Conclusions</p> <p>The activation of the polyamine biosynthetic pathway and putrescine in infected heads prior to detectable DON accumulation is consistent with a model where the pathogen exploits the generic host stress response of polyamine synthesis as a cue for production of trichothecene mycotoxins during FHB disease. However, it is likely that this mechanism is complicated by other factors contributing to resistance and susceptibility in diverse wheat genetic backgrounds.</p

Restoration of Southern Ecosystems

Restoration of the myriad communities of bottomland hardwood and wetland forests and of the diverse communities of fire-dominated pine forests is the subject of intense interest in the Southern United States. Restoration practice is relatively advanced for bottomland hardwoods and longleaf pine (Pinus palustris Mill.), and less so for swamps and shortleaf pine (P. echinata Mill.). Most bottomland hardwood restoration is taking place on private land, while restoration of swamps and shortleaf pine occurs mostly on public land. Both public and private landowners are involved in the restoration of longleaf pine. Proper matching of species to site is critical to successful restoration of bottomland hardwoods. Techniques for longleaf pine restoration include the reintroduction of growing-season fire and the planting of longleaf pine seedlings and understory species. Safely reintroducing growing-season fire, however, may require initial manipulation of other vegetation by mechanical or chemical means to reduce built-up fuels