Transmutation of MAs and LLFPs with a lead-cooled fast reactor.

The management of nuclear wastes has long been a problem that hinders the sustainable and clean utilization of nuclear energy since the advent of nuclear power. These nuclear wastes include minor actinides (MAs: 237Np, 241Am, 243Am, 244Cm and 245Cm) and long-lived fission products (LLFPs: 79Se, 93Zr, 99Tc, 107Pd, 129I and 135Cs), and yet are hard to be handled. In this work, we propose a scheme that can transmute almost all the MAs and LLFPs with a lead-cooled fast reactor (LFR). In this scheme, the MAs and the LLFPs are loaded to the fuel assembly and the blanket assembly for transmutation, respectively. In order to study the effect of MAs loading on the operation of the core, the neutron flux distribution, spectra, and the keff are further compared with and without MAs loading. Then the LLFPs composition is optimized and the support ratio is obtained to be 1.22 for 237Np, 1.63 for 241Am, 1.27 for 243Am, 1.32 for 79Se, 1.53 for 99Tc, 1.02 for 107Pd, and 1.12 for 129I, respectively, indicating that a self-sustained transmutation can be achieved. Accordingly, the transmutation rate of these nuclides was 13.07%/y for 237Np, 15.18%/y for 241Am, 13.34%/y for 243Am, 0.58%/y for 79Se, 0.92%/y for 99Tc, 1.17%/y for 107Pd, 0.56%/y for 129I. Our results show that a lead-cooled fast reactor can be potentially used to manage nuclear wastes with high levels of long-lived radioactivity.

Quantum thermodynamics from the nonequilibrium dynamics of open systems: Energy, heat capacity, and the third law.

In a series of papers, we intend to take the perspective of open quantum systems and examine from their nonequilibrium dynamics the conditions when the physical quantities, their relations, and the laws of thermodynamics become well defined and viable for quantum many-body systems. We first describe how an open-system nonequilibrium dynamics (ONEq) approach is different from the closed combined system +  environment in a global thermal state (CGTs) setup. Only after the open system equilibrates will it be amenable to conventional thermodynamics descriptions, thus quantum thermodynamics (QTD) comes at the end rather than assumed in the beginning. The linkage between the two comes from the reduced density matrix of ONEq in that stage having the same form as that of the system in the CGTs. We see the open-system approach having the advantage of dealing with nonequilibrium processes as many experiments in the near future will call for. Because it spells out the conditions of QTD's existence, it can also aid us in addressing the basic issues in quantum thermodynamics from first principles in a systematic way. We then study one broad class of open quantum systems where the full nonequilibrium dynamics can be solved exactly, that of the quantum Brownian motion of N strongly coupled harmonic oscillators, interacting strongly with a scalar-field environment. In this paper, we focus on the internal energy, heat capacity, and the third law. We show for this class of physical models, amongst other findings, the extensive property of the internal energy, the positivity of the heat capacity, and the validity of the third law from the perspective of the behavior of the heat capacity toward zero temperature. These conclusions obtained from exact solutions and quantitative analysis clearly disprove claims of negative specific heat in such systems and dispel allegations that in such systems the validity of the third law of thermodynamics relies on quantum entanglement. They are conceptually and factually unrelated issues. Entropy and entanglement will be the main theme of our second paper on this subject matter.

Nonequilibrium fluctuation-dissipation inequality and nonequilibrium uncertainty principle.

The fluctuation-dissipation relation is usually formulated for a system interacting with a heat bath at finite temperature, and often in the context of linear response theory, where only small deviations from the mean are considered. We show that for an open quantum system interacting with a nonequilibrium environment, where temperature is no longer a valid notion, a fluctuation-dissipation inequality exists. Instead of being proportional, quantum fluctuations are bounded below by quantum dissipation, whereas classically the fluctuations vanish at zero temperature. The lower bound of this inequality is exactly satisfied by (zero-temperature) quantum noise and is in accord with the Heisenberg uncertainty principle, in both its microscopic origins and its influence upon systems. Moreover, it is shown that there is a coupling-dependent nonequilibrium fluctuation-dissipation relation that determines the nonequilibrium uncertainty relation of linear systems in the weak-damping limit.

Diagnostic value of magnetic resonance cholangiopancreatography for biliary complications in orthotopic liver transplantation: a meta-analysis.

BACKGROUND AND OBJECTIVE: Magnetic resonance cholangiopancreatography (MRCP) is a noninvasive procedure to diagnose biliary complications. The aim of the present meta-analysis was to establish the overall diagnostic accuracy of MRCP to diagnose biliary complications post-orthotopic liver transplantation (OLT). METHODS: A systematic review was performed by searching electronic bibliographic databases prior to May 2012. Sensitivity, specificity, and other measures of the accuracy of MRCP for diagnosis of post-OLT were summarized using a random-effects or a fixed-effects model. Receiver operating characteristic curves were used to summarize overall test performance. RESULTS: Fourteen studies, which involved 892 subjects were eligible for the analysis. The summary estimates of sensitivity, specificity, positive likelihood ratio, negative likelihood ratio, diagnostic odds ratio, and area under cure of MRCP for diagnosis of biliary complications were as follows: 0.95, 0.92, 10.23, 0.08, 206.59, and 0.979, respectively. The results for biliary strictures in four studies involving 177 subjects were 0.94, 0.95, 0.96, 0.09, 178.33, and 0.973 respectively. CONCLUSIONS: MRCP is a sensitive and specific technique to diagnose biliary complications.

Diagnostic accuracy of multidetector computed tomography in the detection of left atrial/left atrial appendage thrombus: a meta-analysis.

BACKGROUND AND OBJECTIVE: The current results on the diagnostic accuracy of multidetector computed tomography (MDCT) in the detection of left atrial/left atrial appendage (LA/LAA) thrombus are conflicting. AIM: The aim of the present study was to determine the diagnostic accuracy of MDCT in LA/LAA thrombus with meta-analysis. METHODS: We searched for studies in PubMed, Embase and Cochrane library prior to May 2012 evaluating the accuracy of MDCT in detecting LA/LAA thrombus. Primary results were summarised using a random-effects model or a fixed-effects model. Receiver operating characteristic curves were used to summarise overall diagnosis accuracy. Metaregression and subgroup analysis were used to explore the potential sources of heterogeneity. RESULTS: A total of 10 studies with 1313 subjects was included in this meta-analysis. The summary estimates of sensitivity, specificity, positive likelihood ratio, negative likelihood ratio, diagnostic odds ratio and the area under cure of overall analysis were 0.84, 0.93, 9.32, 0.21, 50.84 and 0.951, respectively, but all with significant heterogeneity (P < 0.01). Meta-regression and subgroup analysis showed that using electrocardiogram (ECG)-gating technique was a source of heterogeneity (P = 0.022); studies using ECG-gating technique had a higher summary sensitivity than studies with non-gating technique (0.97 vs 0.33). CONCLUSION: Our results suggest that MDCT is a potentially useful technique in the diagnosis of LA/LAA thrombus, especially when ECG gating is applied.

Quantum and classical fluctuation theorems from a decoherent histories, open-system analysis.

In this paper we present a first-principles analysis of the nonequilibrium work distribution and the free energy difference of a quantum system interacting with a general environment (with arbitrary spectral density and for all temperatures) based on a well-understood microphysics (quantum Brownian motion) model under the conditions stipulated by the Jarzynski equality [Jarzynski, Phys. Rev. Lett. 78, 2690 (1997)] and Crooks' fluctuation theorem [Crooks, Phys. Rev. E 60, 2721 (1999)] (in short, fluctuation theorems, FTs). We use the decoherent histories conceptual framework to explain how the notion of trajectories in a quantum system can be made viable and use the environment-induced decoherence scheme to assess the strength of noise that could provide sufficient decoherence to warrant the use of trajectories to define work in open quantum systems. From the solutions to the Langevin equation governing the stochastic dynamics of such systems we were able to produce formal expressions for these quantities entering in the FTs and from them prove explicitly the validity of the FTs at the high temperature limit. At low temperatures our general results would enable one to identify the range of parameters where FTs may not hold or need be expressed differently. We explain the relation between classical and quantum FTs and the advantage of this microphysics open-system approach over the phenomenological modeling and energy-level calculations for substitute closed quantum systems.

Equilibrium states of open quantum systems in the strong coupling regime.

In this work we investigate the late-time steady states of open quantum systems coupled to a thermal reservoir in the strong coupling regime. In general such systems do not necessarily relax to a Boltzmann distribution if the coupling to the thermal reservoir is nonvanishing or equivalently if the relaxation time scales are finite. Using a variety of nonequilibrium formalisms valid for non-Markovian processes, we show that starting from a product state of the closed system = system+environment, with the environment in its thermal state, the open system which results from coarse graining the environment will evolve towards an equilibrium state at late times. This state can be expressed as the reduced state of the closed system thermal state at the temperature of the environment. For a linear (harmonic) system and environment, which is exactly solvable, we are able to show in a rigorous way that all multitime correlations of the open system evolve towards those of the closed system thermal state. Multitime correlations are especially relevant in the non-Markovian regime, since they cannot be generated by the dynamics of the single-time correlations. For more general systems, which cannot be exactly solved, we are able to provide a general proof that all single-time correlations of the open system evolve to those of the closed system thermal state, to first order in the relaxation rates. For the special case of a zero-temperature reservoir, we are able to explicitly construct the reduced closed system thermal state in terms of the environmental correlations.

Initial-state preparation with dynamically generated system-environment correlations.

The dependence of the dynamics of open quantum systems upon initial correlations between the system and environment is an utterly important yet poorly understood subject. For technical convenience most prior studies assume factorizable initial states where the system and its environments are uncorrelated, but these conditions are not very realistic and give rise to peculiar behaviors. One distinct feature is the rapid buildup or a sudden jolt of physical quantities immediately after the system is brought in contact with its environments. The ultimate cause of this is an initial imbalance between system-environment correlations and coupling. In this paper we demonstrate explicitly how to avoid these unphysical behaviors by proper adjustments of correlations and/or the coupling, for setups of both theoretical and experimental interest. We provide simple analytical results in terms of quantities that appear in linear (as opposed to affine) master equations derived for factorized initial states.

Dendritic cell-directed lentivector vaccine induces antigen-specific immune responses against murine melanoma.

Lentivectors are potential vaccine delivery vehicles because they can efficiently transduce a variety of non-dividing cells, including antigen-presenting cells, and do not cause expression of extra viral proteins. To improve safety while retaining efficiency, a dendritic cell (DC)-specific lentivector was constructed by pseudotyping the vector with an engineered viral glycoprotein derived from Sindbis virus. We assessed the level of anti-tumor immunity conferred by this engineered lentivector encoding the melanoma antigen gp100 in a mouse model. Footpad injection of the engineered lentivectors results in the best antigen-specific immune response as compared with subcutaneous and intraperitoneal injections. A single prime vaccination of the engineered lentivectors can elicit a high frequency (up to 10%) of gp100-specific CD8(+) T cells in peripheral blood 3 weeks after the vaccination and this response will be maintained at around 5% for up to 8 weeks. We found that these engineered lentivectors elicited relatively low levels of anti-vector neutralizing antibody responses. Importantly, direct injection of this engineered lentivector inhibited the growth of aggressive B16 murine melanoma. These data suggest that DC-specific lentivectors can be a novel and alternative vaccine carrier with the potential to deliver effective anti-tumor immunity for cancer immunotherapy.

Exact master equation and quantum decoherence of two coupled harmonic oscillators in a general environment.

In this paper we derive an exact master equation for two coupled quantum harmonic oscillators interacting via bilinear coupling with a common environment at arbitrary temperature made up of many harmonic oscillators with a general spectral density function. We first show a simple derivation based on the observation that the two harmonic oscillator model can be effectively mapped into that of a single harmonic oscillator in a general environment plus a free harmonic oscillator. Since the exact one harmonic oscillator master equation is available [B. L. Hu, J. P. Paz, and Y. Zhang, Phys. Rev. D 45, 2843 (1992)], the exact master equation with all its coefficients for this two harmonic oscillator model can be easily deduced from the known results of the single harmonic oscillator case. In the second part we give an influence functional treatment of this model and provide explicit expressions for the evolutionary operator of the reduced density matrix which are useful for the study of decoherence and disentanglement issues. We show three applications of this master equation: on the decoherence and disentanglement of two harmonic oscillators due to their interaction with a common environment under Markovian approximation, and a derivation of the uncertainty principle at finite temperature for a composite object, modeled by two interacting harmonic oscillators. The exact master equation for two, and its generalization to N, harmonic oscillators interacting with a general environment are expected to be useful for the analysis of quantum coherence, entanglement, fluctuations, and dissipation of mesoscopic objects toward the construction of a theoretical framework for macroscopic quantum phenomena.

[Kinetics of anaerobic ammonia oxidation].

The kinetic characteristics of anaerobic ammonia oxidation was studied. The cell yield was 1.573 mgVS (mmolNH4+)-1 and the cell decay coefficient was 0.052 mgVS(gVS.d)-1. The maximal rate of anaerobic ammonia oxidation and nitrite conversion rate by the mixed culture were 1.320-2.761 mmol(gVS.d)-1 and 14.497 mmol(gVS.d)-1, respectively. Km for ammonia and for nitrite were 1.801-4.215 and 0.468 mmol.L-1. Ki for ammonia was 38.018-98.465 mmol.L-1, the optimal ammonia concentration was 16.656 mmol.L-1. Ki for nitrite was 5.401-11.995 mmol.L-1. The optimal pH was around 7.5 and the theoretical value was 7.605. The optimal temperature was about 30 degrees C. The activation energy for Vmaxa, Kma, Kia and Kin was 37.316, 30.239, 33.695 and 30.473 kJ.mol-1.

Hemodynamic evaluation of bovine pericardial xenograft valves in the mitral position by stress Doppler echocardiography.

The function of a bovine pericardial xenograft valve in the mitral position was studied in 18 patients by using stress Doppler echocardiography after submaximal supine exercise. In 10 patients with normally functioning tissue valve, peak and mean gradients increased from 9.3 +/- 1.3 and 2.7 +/- 0.7 mmHg, respectively at rest, to 14.7 +/- 0.9 and 4.1 +/- 1.0 mmHg at peak exercise. The tissue valve area assessed by the Doppler pressure half-time method increased from 2.69 +/- 0.38 cm2 at rest, to 3.15 +/- 0.38 cm2 at peak exercise (P < 0.05). In 6 patients with mitral regurgitation, peak and mean gradients increased from 17.3 +/- 5.3 and 7.0 +/- 1.8 mmHg, respectively at rest, to 24.3 +/- 5.0 and 9.0 +/- 2.6 mmHg at peak exercise, but there was no significant change in valve area at peak exercise. Patients with severe isolated mitral regurgitation had a Vmax of more than 2 m/s and elevated pressure gradients at peak exercise. But the pressure half-time was relatively unaffected, allowing their differentiation from patients with tissue valvular stenosis. Stress Doppler echocardiography is a simple, noninvasive and reliable method for the evaluation of the mitral tissue valve function which is recommendable for patients with suspected mitral tissue valve dysfunction.