Lifetime and polarization of the radiative decay of excitons, biexcitons and trions in CdSe nanocrystal quantum dots

Using the pseudopotential configuration-interaction method, we calculate the intrinsic lifetime and polarization of the radiative decay of single excitons (X), positive and negative trions (X+ and X−), and biexcitons (XX) in CdSe nanocrystal quantum dots. We investigate the effects of the inclusion of increasingly more complex many-body treatments, starting from the single-particle approach and culminating with the configuration-interaction scheme. Our configuration-interaction results for the size dependence of the single-exciton radiative lifetime at room temperature are in excellent agreement with recent experimental data. We also find the following. (i) Whereas the polarization of the bright exciton emission is always perpendicular to the hexagonal c axis, the polarization of the dark exciton switches from perpendicular to parallel to the hexagonal c axis in large dots, in agreement with experiment. (ii) The ratio of the radiative lifetimes of mono- and biexcitons (X):(XX) is ~1:1 in large dots (R=19.2 Å). This ratio increases with decreasing nanocrystal size, approaching 2 in small dots (R=10.3 Å). (iii) The calculated ratio (X+):(X−) between positive and negative trion lifetimes is close to 2 for all dot sizes considered

Model-independent determination of the carrier multiplication time constant in CdSe nanocrystals

The experimental determination of the carrier multiplication (CM) time constant is complicated by the fact that this process occurs within the initial few hundreds of femtoseconds after excitation and, in transient-absorption experiments, cannot be separated from the buildup time of the 1p-state population. This work provides an accurate theoretical determination of the electron relaxation lifetime during the last stage of the p-state buildup, in CdSe nanocrystals, in the presence of a single photogenerated hole (no CM) and of a hole plus an additional electron–hole pair (following CM). From the invariance of the 1p buildup time observed experimentally for excitations above and below the CM threshold producing hot carriers with the same average per-exciton excess energy, and the calculated corresponding variations in the electron decay time in the two cases, an estimate is obtained for the carrier multiplication time constant. Unlike previous estimates reported in the literature so far, this result is model-independent, i.e., is obtained without making any assumption on the nature of the mechanism governing carrier multiplication. It is then compared with the time constant calculated, as a function of the excitation energy, assuming an impact-ionization-like process for carrier multiplication (DCM). The two results are in good agreement and show that carrier multiplication can occur on timescales of the order of tens of femtoseconds at energies close to the observed onset. These findings, which are compatible with the fastest lifetime estimated experimentally, confirm the suitability of the impact-ionization model to explain carrier multiplication in CdSe nanocrystals

Advanced Temporal Control Structures for Business Process Modeling

Modeling time-constrained business processes is required in many domains but often challenging due to the difficulty of incorporating declarative temporal requirements in procedural process definitions. Here, we propose advanced temporal control structures based on highly expressive temporal conditions to give designers explicit control over the temporal behavior of a business process abstracting from low-level management of time aspects. These structures facilitate controlling executions to meet temporal requirements. We propose an approach for checking the temporal correctness of business processes featuring these structures in terms of dynamic controllability. The approach is based on the reduction to basic control structures and a further mapping to the CSTNUD, an expressive family of temporal constraint networks with established checking procedures

Negotiating Temporal Commitments in Cross-Organizational Business Processes

Cross-organizational business processes emerge from the cooperation of intra-organizational business processes through exchange of messages. The involved parties agree on communication protocols, which contain in particular temporal constraints: as obligations on one hand, and as guarantees on the other hand. These constraints form also requirements for the design of the hidden implementation of the processes and are the basis for control decisions for each party. We present a comprehensive methodology for modeling the temporal aspects of cross-organizational business processes, checking dynamic controllability of such processes, and supporting the negotiation of temporal commitments. We do so by computing the consequences of temporal constraints in choreographies, and by computing the weakest preconditions for the dynamic controllability of a participating process

I.S.Mu.L.T - Rotator cuff tears guidelines

Despite the high level achieved in the field of shoulder surgery, a global consensus on rotator cuff tears management is lacking. This work is divided into two main sessions: in the first, we set questions about hot topics involved in the rotator cuff tears, from the etiopathogenesis to the surgical treatment. In the second, we answered these questions by mentioning Evidence Based Medicine. The aim of the present work is to provide easily accessible guidelines: they could be considered as recommendations for a good clinical practice developed through a process of systematic review of the literature and expert opinion, in order to improve the quality of care and rationalize the use of resources

Some results and challenges Extending Dynamic Controllability to Agile Controllability in Simple Temporal Networks with Uncertainties

Simple Temporal Networks with Uncertainty (STNU) are an expressive means to represent temporal constraints, requirements, or obligations. They feature contingent timepoints, which are set by the environment with a specified interval. Dynamic controllability is the current most relaxed notion for checking that the constraints are not in conflict. It requires that a timepoint may only depend on earlier timepoints. Agile controllability extends dynamic controllability by taking into account that a later timepoint might already be known earlier and allowing a timepoint to depend on all timepoints whose value is known before. In this report, we formally introduce the notion of an STNU with oracle timepoints, formally define the notion of agile controllability, and discuss approaches for checking agile controllability

Introducing Agile Controllability in Temporal Business Processes

Dynamic controllability is currently regarded as the most adequate notion for checking the temporal correctness of business processes with temporal constraints when a process model includes uncontrollable activities whose duration is revealed at the time of activity completion. However, dynamic controllability cannot take advantage when an actual duration is revealed earlier, leading to unnecessary strict checks for temporal correctness. We propose a novel notion of agile controllability, which takes into account that uncontrollable durations are revealed earlier and that in a viable execution strategy, a time point may depend on time points whose value is known earlier. We formalize the notion of agile controllability and present an effective checking procedure evaluated by a software implementation within a publicly available modeling and checking software tool

GEN-O-MA project: an Italian network studying clinical course and pathogenic pathways of moyamoya disease—study protocol and preliminary results

Background: GENetics of mOyaMoyA (GEN-O-MA) project is a multicenter observational study implemented in Italy aimed at creating a network of centers involved in moyamoya angiopathy (MA) care and research and at collecting a large series and bio-repository of MA patients, finally aimed at describing the disease phenotype and clinical course as well as at identifying biological or cellular markers for disease progression. The present paper resumes the most important study methodological issues and preliminary results. Methods: Nineteen centers are participating to the study. Patients with both bilateral and unilateral radiologically defined MA are included in the study. For each patient, detailed demographic and clinical as well as neuroimaging data are being collected. When available, biological samples (blood, DNA, CSF, middle cerebral artery samples) are being also collected for biological and cellular studies. Results: Ninety-eight patients (age of onset mean ± SD 35.5 ± 19.6 years; 68.4% females) have been collected so far. 65.3% of patients presented ischemic (50%) and haemorrhagic (15.3%) stroke. A higher female predominance concomitantly with a similar age of onset and clinical features to what was reported in previous studies on Western patients has been confirmed. Conclusion: An accurate and detailed clinical and neuroimaging classification represents the best strategy to provide the characterization of the disease phenotype and clinical course. The collection of a large number of biological samples will permit the identification of biological markers and genetic factors associated with the disease susceptibility in Italy

Dynamic Controllability of Parameterized CSTNUs

A Conditional Simple Temporal Network with Uncertainty (CSTNU) models temporal constraint satisfaction problems in which the environment sets uncontrollable timepoints and conditions. The executor observes and reacts to such uncontrollable assignments as time advances with the CSTNU execution. However, there exist scenarios in which the occurrence of some future timepoints must be fixed as soon as the execution starts. We call these timepoints \textit{parameters}. For a correct execution, parameters must assume values that guarantee the possibility of satisfying all temporal constraints, whatever the environment decides the execution time for uncontrollable timepoints and the truth value of conditions, i.e., dynamic controllability (DC). Here, we formalize the extension of the CSTNU with parameters. Furthermore, we define a set of rules to check the DC of such extended CSTNU. These rules additionally solve the problem inverse to checking DC: computing restrictions on parameter values that yield DC guarantees. The proposed rules can be composed into a sound and complete procedure