Time-dependent density-functional and reduced density-matrix methods for few electrons: Exact versus adiabatic approximations

To address the impact of electron correlations in the linear and non-linear response regimes of interacting many-electron systems exposed to time-dependent external fields, we study one-dimensional (1D) systems where the interacting problem is solved exactly by exploiting the mapping of the 1D $N$-electron problem onto an $N$-dimensional single electron problem. We analyze the performance of the recently derived 1D local density approximation as well as the exact-exchange orbital functional for those systems. We show that the interaction with an external resonant laser field shows Rabi oscillations which are detuned due to the lack of memory in adiabatic approximations. To investigate situations where static correlations play a role, we consider the time-evolution of the natural occupation numbers associated to the reduced one-body density matrix. Those studies shed light on the non-locality and time-dependence of the exchange and correlation functionals in time-dependent density and density-matrix functional theories.Comment: 19 pages, 13 figures, version as published apart from layou

Plasma concentrations of anserine, carnosine and pi-methylhistidine as biomarkers of habitual meat consumption.

Background/Objectives Dietary intake of red and processed meat has been associated with disease risk. Since dietary intake assessment methods are prone to measurement errors, identifying biomarkers of meat intake in bio-samples could provide more valid intake estimates. We examined associations of habitual red and processed meat, poultry, fish, and dairy products consumption with plasma concentrations of anserine, carnosine, pi-methylhistidine (Pi-MH), tau-methylhistidine (T-MH), and the ratio of T-MH to Pi-MH in a cross-sectional study.Subjects/Methods Plasma anserine, carnosine, Pi-MH, and T-MH concentrations were measured using ion-pair LC-MS/MS in 294 participants in the second Bavarian Food Consumption Survey (BVS II). Habitual food consumption was assessed using three 24-h dietary recalls. Associations between plasma metabolites concentrations and meat, fish, eggs, and dairy products consumption were assessed by fitting generalized linear model, adjusted for age, sex, and BMI.Results Total meat intake was associated with plasma concentrations of anserine, carnosine, Pi-MH and, the ratio of T-MH to Pi-MH. Red meat intake was related to carnosine (p-trend = 0.0028) and Pi-MH plasma levels (p-trend = 0.0493). Poultry (p-trend = 0.0006) and chicken (p-trend = 0.0003) intake were associated with Pi-MH. The highest anserine concentrations were observed in individuals consuming processed meat or turkey. For T-MH we did not observe any association with meat intake.Conclusions Our results indicate an association between habitual meat consumption and plasma concentrations of anserine, carnosine, Pi-MH and the ratio of T-MH to Pi-MH. Intervention studies should clarify whether the analyzed plasma metabolites are indicative for a specific type of meat before proposing them as biomarkers of habitual meat intake in epidemiologic studies

Excitation energies with time-dependent density matrix functional theory: Singlet two-electron systems

Time-dependent density functional theory in its current adiabatic implementations exhibits three striking failures: (a) Totally wrong behavior of the excited state surface along a bond-breaking coordinate, (b) lack of doubly excited configurations, affecting again excited state surfaces, and (c) much too low charge transfer excitation energies. We address these problems with time-dependent density matrix functional theory (TDDMFT). For two-electron systems the exact exchange-correlation functional is known in DMFT, hence exact response equations can be formulated. This affords a study of the performance of TDDMFT in the TDDFT failure cases mentioned (which are all strikingly exhibited by prototype two-electron systems such as dissociating H2 and He