High Nd3+→Yb3+ energy transfer efficiency in tungsten‐tellurite glass: A promising converter for solar cells

This work reports on the energy transfer efficiency for Nd³⁺/Yb³⁺ co‐doped tellurite glasses (80TO₂‐20WO₃, in mol%,). The correlation between Yb³⁺ ion concentration and the downconversion mechanism was investigated using optical and thermal lens spectroscopies, which enabled investigation of the radiative and nonradiative processes, respectively, involved in energy transfer from neodymium to ytterbium. The Nd³⁺ near‐infrared fluorescence disappeared almost entirely when the maximum concentration of Yb³⁺ ions (4 mol%) was doped into the host. In contrast, there was a corresponding increase in the ytterbium emission at around 980 nm. When ytterbium was added, there was also a simultaneous reduction in the amount of heat generated by the sample due to a reduction in the nonradiative decay rate, corroborating the suspected high energy transfer efficiency of Nd³⁺→Yb³⁺. The results indicate that tungsten‐tellurite glasses may be of potential use in solar cells for matching the solar emission spectrum to the semiconductor cell.     

Symbolic execution of concurrent systems using Petri nets

Techniques for analyzing sequential programs in order to improve their reliability have been widely studied in the past. Among the most interesting analysis techniques, we consider symbolic execution. However, analysis techniques for concurrent programs, and in particular symbolic execution, are still an open research area. In this paper, we define a method for symbolic execution of concurrent systems, based on an extension of the Petri net formalism, called EF nets. EF nets are a powerful, highly expressive and general formalism. Depending on the level of abstraction of actions and predicates that one associates to the transitions of the net, EF nets can be used as a high-level specification formalism for concurrent systems, or as a lower level internal representation of concurrent programs. Thus, the model is not dependent on a particular concurrent programming language, but it is flexible enough to be the kernel model for the representation of a wide set of systems and programming languages. In the paper, in order to support the analysis of a concurrent system or program, at first a general algorithm for symbolically executing an EF net is defined. Then, a more efficient algorithm is given for the particular, though important, subclass of EF nets, defined as safe EF nets. Such algorithm is proved to significantly help in reducing the amount of information needed to characterize a symbolic execution. Both the modelling power of the EF nets and the usefulness of the concurrent symbolic execution algorithms defined are illustrated by means of a case study.     

Nutritional Characterization and Phenolic Profiling of Moringa oleifera Leaves Grown in Chad,Sahrawi Refugee Camps,and Haiti

Moringa oleifera is a plant that grows in tropical and subtropical areas of the world. Its leaves are rich of nutrients and bioactive compounds. However, several differences are reported in the literature. In this article we performed a nutritional characterization and a phenolic profiling of M. oleifera leaves grown in Chad, Sahrawi refugee camps, and Haiti. In addition, we investigated the presence of salicylic and ferulic acids, two phenolic acids with pharmacological activity, whose presence in M. oleifera leaves has been scarcely investigated so far. Several differences were observed among the samples. Nevertheless, the leaves were rich in protein, minerals, and β-carotene. Quercetin and kaempferol glycosides were the main phenolic compounds identified in the methanolic extracts. Finally, salicylic and ferulic acids were found in a concentration range of 0.14–0.33 and 6.61–9.69 mg/100 g, respectively. In conclusion, we observed some differences in terms of nutrients and phenolic compounds in M. oleifera leaves grown in different countries. Nevertheless, these leaves are a good and economical source of nutrients for tropical and sub-tropical countries. Furthermore, M. oleifera leaves are a source of flavonoids and phenolic acids, among which salicylic and ferulic acids, and therefore they could be used as nutraceutical and functional ingredients.     

Evaluation of partial pressure CO2 change in the dialyzer blood inlet during hemodialysis as a measure of vascular access recirculation

Introduction

Vascular access recirculation during hemodialysis is associated with reduced effectiveness and worse survival outcomes. To evaluate recirculation, an increase in pCO₂ in the blood of the arterial line during hemodialysis (threshold of 4.5 mmHg) was proposed. The blood returning from the dialyzer in the venous line has significantly higher pCO₂, so in the presence of recirculation, pCO2 in the arterial blood line may increase (ΔpCO₂) during hemodialysis sessions. The aim of our study was to evaluate ΔpCO₂ as a diagnostic tool for vascular access recirculation in chronic hemodialysis patients.

Methods

We evaluated vascular access recirculation with ΔpCO₂ and compared it with the results of a urea recirculation test, which is the gold standard. ΔpCO₂ was obtained from the difference in pCO₂ in the arterial line at baseline (pCO₂T1) and after 5 min of hemodialysis (pCO₂T2). ∆pCO₂ = pCO₂T2–pCO₂T1.

Findings

In 70 hemodialysis patients (mean age: 70.52 ± 13.97 years; hemodialysis vintage of 41.36 ± 34.54, KT/V 1.4 ± 0.3), ∆pCO₂ was 4 ± 4 mmHg, and urea recirculation was 7% ± 9%. Vascular access recirculation was identified using both methods in 17 of 70 patients, who showed a ∆pCO₂ of 10 ± 5 mmHg and urea recirculation of 20% ± 9%; time in months of hemodialysis was the only difference between vascular access recirculation and non-vascular access recirculation patients (22 ± 19 vs. 46 ± 36, p: 0.05). In the non-vascular access recirculation group, the average ΔpCO₂ was 1.9 ± 2 (p: 0.001), and the urea recirculation % was 2.8 ± 3 (p: 0.001). The ΔpCO₂ correlated with the urea recirculation % (R: 0.728; p < 0.001).

Discussion

ΔpCO₂ in the arterial blood line during hemodialysis is an effective and reliable diagnostic tool for identifying recirculation of the vascular access but not its magnitude. The ΔpCO₂ test application is simple and economical and does not require special equipment.     

Selecting services in the cloud: a decision support methodology focused on infrastructure-as-a-service context

Growing demand for reduced local hardware infrastructure is driving the adoption of Cloud Computing. In the Infrastructure-as-a-Service model, service providers offer virtualized computational resources in the form of virtual machine instances. The existence of a large variety of providers and instances makes the decision-making process a difficult task for users, especially as factors such as the datacenter location - where the virtual machine is hosted - have a direct influence on the price of instances. The same instance may present price differences when hosted in different geographically distributed datacenters and, because of that, the datacenter location needs to be taken into account through the decision-making process. Given this problem, we propose the D-AHP, a methodology to aid decision-making based on Pareto Dominance and Analytic Hierarchy Process (AHP). In the D-AHP, the dominance concept is applied to reduce the number of instances to be compared; the instances selection is based on a set of objectives, while AHP ranks the selected ones from a set of criteria and sub-criteria, among them the datacenter location. The results from case studies show that differences may arise in the results, regarding which instance is more suitable for the user, when considering the datacenter location as a criterion to choose an instance. This fact highlights the need to consider this factor during the process of migrating applications to the Cloud. In addition, Pareto Dominance applied early over the set of total instances has proved to be efficient, once it significantly reduces the number of instances to be compared and ordered by the AHP by excluding instances with less computational resources and higher cost in the decision-making process, mainly for larger application workloads.

     

Correlation between microstructure and corrosion behavior in an AISI 316L steel pipeline exposed for 100,700 h at 640°C in a petrochemical plant

The microstructure and electrochemical properties of 316L stainless steel were investigated after two conditions: aged at 640°C for 100,700 h and solution annealed at 1050°C for 2 h. While the aged samples were obtained from a pipe of a petrochemical reactor plant that was in service, the solution annealing was carried out in a conventional laboratory furnace. After aging, the precipitates present in decreasing order of quantity were sigma, Laves phase, and M₂₃C₆. After solution annealing, the microstructure was full austenitic. These results were in agreement with equilibria phase simulation with Thermo-Calc software. Intergranular corrosion susceptibility, evaluated by means of the single loop electrochemical potentiokinetic reactivation technique and Practice A of ASTM 262, indicated a preponderant role for the sigma precipitate. The pitting potential (E_pit) was evaluated through potentiodynamic polarization curves in 0.6 M NaCl and electrochemical impedance spectroscopy was performed at the corrosion potential to complement the information about the corrosion resistance.     

Seminal Plasma Proteomic Biomarkers of Oxidative Stress

The prevalence of idiopathic male infertility is high, up to 75% of patients with abnormal sperm parameters. Hence, the research of its causes is mandatory. Oxidative stress (OS) can be responsible for male infertility in 30–80% of cases. In recent years, seminal plasma (SP) proteomics has developed as a useful tool to provide biomarkers of specific diseases. This systematic review aims to collect the available evidence on the changes of SP proteome in patients exposed to OS to provide possible SP biomarkers of sperm OS. To accomplish this, the following keyterms “seminal fluid proteome”, “seminal plasma proteome”, “oxidative stress”, and “sperm oxidative stress” were used and 137 records were found. Among these, 17 were finally included. Nine proteins involved with OS were found overexpressed in patients with OS. Twenty-three proteins were found differentially expressed in patients with clinical conditions associated with OS, such as varicocele, male accessory gland infection/inflammation, cigarette smoke, and obesity. These proteins do not seem to overlap among the clinical conditions taken into account. We speculate that specific SP proteins may mediate OS in different clinical conditions. Altogether, these results suggest that proteomics could help to better understand some of the molecular mechanisms involved in the pathogenesis of infertility. However, further studies are needed to identify potential biomarkers of male infertility with valuable clinical significance.