Relevance of electron spin dissipative processes to dynamic nuclear polarization via thermal mixing

The available theoretical approaches aiming at describing Dynamic Nuclear spin Polarization (DNP) in solutions containing molecules of biomedical interest and paramagnetic centers are not able to model the behaviour observed upon varying the concentration of trityl radicals or the polarization enhancement caused by moderate addition of gadolinium complexes. In this manuscript, we first show experimentally that the nuclear steady state polarization reached in solutions of pyruvic acid with 15 mM trityl radicals is substantially independent from the average internuclear distance. This evidences a leading role of electron (over nuclear) spin relaxation processes in determining the ultimate performances of DNP. Accordingly, we have devised a variant of the Thermal Mixing model for inhomogenously broadened electron resonance lines which includes a relaxation term describing the exchange of magnetic anisotropy energy of the electron spin system with the lattice. Thanks to this additional term, the dependence of the nuclear polarization on the electron concentration can be properly accounted for. Moreover, the model predicts a strong increase of the final polarization on shortening the electron spin-lattice relaxation time, providing a possible explanation for the effect of gadolinium doping.Comment: 13 pages, 12 figure

Role of the glassy dynamics and thermal mixing in the dynamic nuclear polarization and relaxation mechanisms of pyruvic acid

The temperature dependence of $^1$H and $^{13}$C nuclear spin-lattice relaxation rate $1/T_1$ has been studied in the 1.6 K - 4.2 K temperature range in pure pyruvic acid and in pyruvic acid containing trityl radicals at a concentration of 15 mM. The temperature dependence of $1/T_1$ is found to follow a quadratic power law for both nuclei in the two samples. Remarkably the same temperature dependence is displayed also by the electron spin-lattice relaxation rate $1/T_{1e}$ in the sample containing radicals. These results are explained by considering the effect of the structural dynamics on the relaxation rates in pyruvic acid. Dynamic nuclear polarization experiments show that below 4 K the $^{13}$C build up rate scales with $1/T_{\text{1e}}$, in analogy to $^{13}$C $1/T_1$ and consistently with a thermal mixing scenario where all the electrons are collectively involved in the dynamic nuclear polarization process and the nuclear spin reservoir is in good thermal contact with the electron spin system.Comment: 14 pages, 13 figure

An Architecture for Declarative Real-Time Scheduling on Linux

This paper proposes a novel framework and programming model for real-time applications supporting a declarative access to real-time CPU scheduling features that are available on an operating system. The core idea is to let applications declare their temporal characteristics and/or requirements on the CPU allocation, where, for example, some of them may require real-time POSIX priorities, whilst others might need resource reservations through SCHED_DEADLINE. The framework can properly handle such a set of heterogeneous requirements configuring an underlying multi-core platform so to exploit the various scheduling disciplines that are available in the kernel, matching applications requirements. The framework is realized as a modular architecture in which different plugins handle independently certain real-time scheduling features within the underlying kernel, easing the customization of its behavior to support other schedulers or operating systems by adding further plugins

Scheduling Replica Voting in Fixed-Priority Real-Time Systems

Reliability and safety are mandatory requirements for safety-critical embedded systems. The design of a fault-tolerant system is required in many fields (e.g., railway, automotive, avionics) and redundancy helps in achieving this goal. Redundant systems typically leverage voting techniques applied to the outputs produced by tasks to detect and even tolerate failures. This paper studies the integration of distributed voting protocols in fixed-priority real-time systems from a scheduling perspective. It analyzes two scheduling strategies for implementing voting. One is attractive and friendly for software developers and based on suspending the task execution until the replica provides the data to be voted. The other one is inspired by the Logical Execution Time (LET) paradigm and requires introducing additional tasks in the system to accomplish voting-related activities. Queuing and delays introduced by inter-replica communication interfaces are also analyzed. Experimental results are finally presented to compare the two strategies, showing that LET-inspired voting is much more predictable and hence more suitable than the other strategy for fixed-priority real-time systems

Environmental Pollution and Peripheral Artery Disease

Peripheral artery disease (PAD) of the lower limbs represents one of the most important clinical conditions among vascular disease and can negatively impact quality of life of affected patients, representing also an important socioeconomic burden. Several risk factors predispose to PAD and its complications. Nevertheless, the role of pollution in this context has not been fully evaluated and this article explored the most updated information on epidemiology and environmental pollution in order to hypothesize the possible contribution of air pollution in the onset of PAD. Pollution is an important problem for the global community and has harmful effects on human health and cardiovascular system, and, specifically, particulate matter 10 (PM10) was found significantly associated with PAD

Equivalent modelling of reciprocating engines generators for microgrid frequency response analysis

Typical microgrid configurations include small-scale generation units that belong to the class of reciprocating engines (gas, diesel, heavy fuel oil). A simplified equivalent model for representing the frequency response of a given set of this kind of generators is proposed in this paper. The model parameters are tuned to obtain frequency responses compliant with the performance classes stated by the ISO 8528-5 standard. The result is a set of equivalent and simple models that can be used to simulate the frequency response within a given microgrid configuration that includes a set of reciprocating engines generators. Finally, a suitable validation of the proposed models is carried out using two highly detailed models of real diesel and heavy fuel oil generators

Papillary thyroid carcinoma presented as a hypercaptant nodule: a case report

Hot thyroid nodules are mostly benign and rarely show a malignant nature. Here we present the case of a 45- year-old man with a hypercaptant but ultrasound suspicious nodule; he underwent fine needle aspiration (FNA) and subsequent thyroidectomy. Pathology revealed a papillary thyroid carcinoma (PTC) with focal tall cell features, positivity to BRAF V600E and focal hyperspression of p53. A multidisciplinary clinicopathological approach is crucial for the correct diagnosis

Propeller geometry optimization for pressure pulses reduction: an analysis of the influence of the rake distribution

The evaluation of pressure pulses is a current issue for any high-performance propeller design. It has been addressed experimentally, by means of model tests, and numerically but in most cases the analysis has been limited to the verification of a given geometry (or, at least of few configurations) identified at the end of a traditional design loop. A more direct inclusion of pressure pulses evaluation in the design procedure, for instance by very attractive multi-objective optimization approaches, could be beneficial, especially if more accurate codes may be exploited. Among the others, BEM represent an acceptable compromise between computational costs and accuracy with the further advantage, with respect to lower fidelity approaches, to account for effects of geometrical haracteristics (such as rake distribution) which are often defined only according to designer experience and special needs. However, if the ability of the BEM methods to predict propeller performance and cavitation extension is well documented, the direct computation of pressure pulses may be less reliable, especially in correspondence to heavy cavitating conditions, requiring further validations in particular when the influence of characteristics such as rake distribution, hardly addressed in literature also from the experimental point of view, are considered. Cavitation tunnel test, BEM and RANS calculations have been consequently carried out for two propellers, designed for the same functioning conditions with different rake distributions, in order to stress the capabilities and the limitations of the numerical approaches in dealing with cavitation, pressure pulses predictions and the capability to discriminate between slightly different geometries in the light of their possible application in a design by optimization procedure