The Role of Education in Nanomedicine as a Current Need for Academic Programs Related to the Healthcare Field: A Scoping Review.

Introduction: Clinical research has recently focused on developing diagnostic and therapeutic alternatives through nanomedicine, and it has become essential for both current and coming healthcare professionals, especially medical residents, to know about it to face actual challenges in the setup of their professional practice. Approach: This scoping review was conducted to show the relevance of nanomedicine in the formation of medical residents and to determine the educational strategies proposed worldwide for their teaching. Results: 12 records met the inclusion and exclusion criteria, including information related to the importance of teaching nanotechnology, possible educational approaches, or the best action strategies for incorporating said teaching. Discussion: Multiple studies showed the need for students in health-related programs to be trained and instructed in topics related to nanotechnology. Still, the students' perceptions highlight how inadequate or non-existent such education in this field is. Although a few studies have proposed strategies and approaches for incorporating nanotechnology in academic programs in different areas, it is still necessary to establish educational standards so that the training of future professionals will be uniform and of high quality. The concerned educational institutions' directives must try to ensure that their in-training staff receives an updated, full, and excellency education.

Competency-Based Cultural Safety Training in Medical Education at La Sabana University, Colombia: A Roadmap of Curricular Modernization.

Issue: Cultural safety enhances equitable communication between health care providers and cultural groups. Most documented cultural safety training initiatives focus on Indigenous populations from high-income countries, and nursing students, with little research activity reported from low- and middle-income countries. Several cultural safety training initiatives have been described, but a modern competency-based cultural safety curriculum is needed. Evidence: In this article, we present the Competency-Based Education and Entrustable Professional Activities frameworks of the Faculty of Medicine at La Sabana University in Colombia, and illustrate how this informed modernization of medical education. We describe our co-designed cultural safety training learning objectives and summarize how we explored its impact on medical education through mixed-methods research. Finally, we propose five cultural safety intended learning outcomes adapted to the updated curriculum, which is based on the Competency-Based Education model. Implications: This article presents five cultural safety intended learning outcomes for undergraduate medical education. These learning outcomes are based on Competency-Based Education and the Entrustable Professional Activities framework and can be used by faculties of medicine interested in including the cultural safety approach in their curriculum.

Implementing Vancomycin Population Pharmacokinetic Models: An App for Individualized Antibiotic Therapy in Critically Ill Patients.

In individualized therapy, the Bayesian approach integrated with population pharmacokinetic models (PopPK) for predictions together with therapeutic drug monitoring (TDM) to maintain adequate objectives is useful to maximize the efficacy and minimize the probability of toxicity of vancomycin in critically ill patients. Although there are limitations to implementation, model-informed precision dosing (MIPD) is an approach to integrate these elements, which has the potential to optimize the TDM process and maximize the success of antibacterial therapy. The objective of this work was to present an app for individualized therapy and perform a validation of the implemented vancomycin PopPK models. A pragmatic approach was used for selecting the models of Llopis, Goti and Revilla for developing a Shiny app with R. Through ordinary differential equation (ODE)-based mixed effects models from the mlxR package, the app simulates the concentrations' behavior, estimates whether the model was simulated without variability and predicts whether the model was simulated with variability. Moreover, we evaluated the predictive performance with retrospective trough concentration data from patients admitted to the adult critical care unit. Although there were no significant differences in the performance of the estimates, the Llopis model showed better accuracy (mean 80.88%; SD 46.5%); however, it had greater bias (mean -34.47%, SD 63.38%) compared to the Revilla et al. (mean 10.61%, SD 66.37%) and Goti et al. (mean of 13.54%, SD 64.93%) models. With respect to the RMSE (root mean square error), the Llopis (mean of 10.69 mg/L, SD 12.23 mg/L) and Revilla models (mean of 10.65 mg/L, SD 12.81 mg/L) were comparable, and the lowest RMSE was found in the Goti model (mean 9.06 mg/L, SD 9 mg/L). Regarding the predictions, this behavior did not change, and the results varied relatively little. Although our results are satisfactory, the predictive performance in recent studies with vancomycin is heterogeneous, and although these three models have proven to be useful for clinical application, further research and adaptation of PopPK models is required, as well as implementation in the clinical practice of MIPD and TDM in real time.

Validation of the National Early Warning Score (NEWS)-2 for adults in the emergency department in a tertiary-level clinic in Colombia: Cohort study.

ABSTRACT: The National Early Warning Score (NEWS)-2 is an early warning scale that is used in emergency departments to identify patients at risk of clinical deterioration and to help establish rapid and timely management. The objective of this study was to determine the validity and prediction of mortality using the NEWS2 scale for adults in the emergency department of a tertiary clinic in Colombia.A prospective observational study was conducted between August 2018 and June 2019 at the Universidad de La Sabana Clinic.The nursing staff in the triage classified the patients admitted to the emergency room according to Emergency Severity Index and NEWS2. Demographic data, physiological variables, admission diagnosis, mortality outcome, and comorbidities were extracted.Three thousand nine hundred eighty-six patients were included in the study. Ninety-two (2%) patients required intensive care unit management, with a mean NEWS2 score of 7. A total of 158 patients died in hospital, of which 63 were women (40%). Of these 65 patients required intensive care unit management. The receiver operating characteristic curve for NEWS2 had an area of 0.90 (CI 95%: 0.87-0.92). A classification and score equivalency analysis was performed between triage and the NEWS2 scale in terms of mortality. Of the patients classified as triage I, 32.3% died, and those who obtained a NEWS2 score greater than or equal to 10 had a mortality of 38.6%.Among our population, NEWS2 was not inferior in its area under the receiver operating characteristic curve when predicting mortality than triage, and the cutoff point for NEWS2 to predict in-hospital mortality was higher.

Estimation of the Difference in Colistin Plasma Levels in Critically Ill Patients with Favorable or Unfavorable Clinical Outcomes.

In recent decades, antimicrobial resistance (AMR) has led to an increased use of therapeutic alternatives. Among these options, colistin continues to be an option for the treatment of multi-resistant (MDR) Gram-negative bacterial infections. However, due to its high toxicity (nephrotoxicity and neurotoxicity) and narrow therapeutic window, colistin treatment must be utilized carefully. Colistin-treated patients have been observed to have higher mortality due to inadequate therapeutic levels. The objective of this study was to estimate the difference in colistin plasma levels in critically ill patients, and its relationship to favorable or unfavorable clinical outcomes. This prospective observational study was conducted between September 2017 and June 2020 at the Universidad de La Sabana Clinic, in patients who had been treated with colistimethate sodium (CMS) for at least 72 h until day 7 of drug treatment in the critical care unit of a university hospital. There were no statistically significant differences in colistin levels between groups with favorable or unfavorable clinical outcomes (0.16 SD vs. 0.54 SD p-value = 0.167). There was higher mortality in patients with subtherapeutic levels (18% vs. 0%), and additionally, there was a greater rate of renal failure in the group with higher therapeutic levels (50% vs. 20.7%). Due to the loss of power of the study, we were unable to demonstrate a possible difference between colistin levels related to favorable or unfavorable clinical outcomes at day 7. However, we recommend further studies to evaluate the impact of measuring levels in terms of mortality and security.

A Generalized Approach for Evaluating the Mechanical Properties of Polymer Nanocomposites Reinforced with Spherical Fillers.

In this work, the effective mechanical reinforcement of polymeric nanocomposites containing spherical particle fillers is predicted based on a generalized analytical three-phase-series-parallel model, considering the concepts of percolation and the interfacial glassy region. While the concept of percolation is solely taken as a contribution of the filler-network, we herein show that the glassy interphase between filler and matrix, which is often in the nanometers range, is also to be considered while interpreting enhanced mechanical properties of particulate filled polymeric nanocomposites. To demonstrate the relevance of the proposed generalized equation, we have fitted several experimental results which show a good agreement with theoretical predictions. Thus, the approach presented here can be valuable to elucidate new possible conceptual routes for the creation of new materials with fundamental technological applications and can open a new research avenue for future studies.

Is There a Role for the Therapeutic Drug Monitoring of Colistin? An Overview.

Colistin is used as a last-line antibiotic for the treatment of Gram-negative multiresistant bacteria. Due to its high nephrotoxicity, Therapeutic Drug Monitoring (TDM) is recommended for dose adjustment. We aimed to evaluate the available evidence of TDM in patients given colistin to treat Gram-negative infections. In this paper, we offer an overview, using an electronic search of the literature (published up to June 2019, without language restrictions) that compares the clinical outcomes and measurements of colistin TDM. Ultimately, the Therapeutic Drug Monitoring (TDM) of colistin in Plasma could prevent nephrotoxicity risk.

Surface-Bulk Interplay in Vapor-Deposited Glasses: Crossover Length and the Origin of Front Transformation.

Thin film stable glasses transform into a liquid by a moving front that propagates from surfaces or interfaces with higher mobility. We use calorimetric data of vapor-deposited glasses of different thicknesses and stabilities to identify the role of glassy and liquid dynamics on the transformation process. By invoking the existence of an ultrathin intermediate layer whose transformation strongly depends on the properties of both the liquid and the glass, we show that the recovery to equilibrium is driven by the mismatch in the dynamics between glass and liquid. The lifetime of this intermediate layer associated with the moving front is the geometric mean between the bulk transformation time and the alpha relaxation time. Within this view, we explain the observed dependencies of the growth front velocity and the crossover length with both stability and temperature. Extrapolation of these results points towards ordinary thin film glasses transforming via a frontlike transformation mechanism if heated sufficiently fast, establishing a close connection between vapor-deposited and liquid-cooled glasses.

Incidence of antiretroviral drug-related problems in the treatment of HIV among hospitalized patients in the Hospital Santa Clara, Bogotá / Incidencia de los problemas relacionados con los medicamentos antirretrovirales para el tratamiento de la infección por HIV en pacientes hospitalizados en el Hospital Santa Clara de Bogotá

Introduction: The antiretroviral therapy for the treatment of the human immunodeficiency virus (HIV) is a therapeutic strategy linked to drug-related problems that cause or can cause the appearance of negative results associated with the medication. It is important, therefore, to identify their incidence, characterize them, and classify them to design strategies to minimize their impact. Objective: To estimate the overall incidence and the incidence of each one of the antiretroviral drugs-related problems in the treatment of the HIV infection in a cohort of hospitalized patients in Bogotá, Colombia. Materials and methods: We conducted a descriptive, retrospective cohort study in patients aged 18 years or more diagnosed with HIV infection and under antiretroviral treatment hospitalized between January 1st, 2015, and December 31st, 2016, in the Hospital Santa Clara, Bogotá. Results: The overall incidence of antiretroviral drug-related problems was 0.90 (95% CI: 0.85-0.93). The incidence of drug-drug interactions was 0.85 (95% CI: 0.80-0.90), 0.28 (95% CI: 0.22-0.35) for adverse reactions, and 0.12 (CI 95%: 0.08-0.17) for prescription errors. Conclusion: Drug-related problems should be studied, diagnosed, prevented, and treated. Their knowledge can enable health care professionals to anticipate their emergence, reduce their incidence, implement risk management plans, and optimize adherence to antiretroviral treatment.

Introducción. El tratamiento antirretroviral de la infección por el virus de la inmunodeficiencia humana (HIV) se ha relacionado con diversos problemas de los medicamentos que causan o pueden causar la aparición de resultados negativos. En este contexto, es importante determinar su incidencia, caracterizarlos y clasificarlos para diseñar estrategias que minimicen su impacto. Objetivo. Estimar la incidencia global y de cada uno de los problemas relacionados con los medicamentos antirretrovirales utilizados en el tratamiento del HIV en una cohorte de pacientes hospitalizados en una institución de tercer nivel de Bogotá. Materiales y métodos. Se hizo un estudio descriptivo y retrospectivo de cohorte en pacientes de 18 años o más de edad con diagnóstico de infección por el HIV y en tratamiento antirretroviral, hospitalizados entre el 1° enero de 2015 y el 31 de diciembre de 2016 en el Hospital Santa Clara de Bogotá. Resultados. La incidencia global de los problemas relacionados con los medicamentos antirretrovirales fue de 0,90 (IC95% 0,85-0,93). La incidencia de las interacciones medicamentosas fue de 0,85 (IC95% 0,80-0,90), la de las reacciones adversas de 0,28 (IC95% 0,22-0,35) y la del error de prescripción de 0,12 (IC95% 0,08-0,17). Conclusión. Los problemas relacionados con los medicamentos deben estudiarse, diagnosticarse, prevenirse y tratarse para que el personal de salud pueda anticiparse a su aparición, disminuir su incidencia, implementar planes de manejo del riesgo y optimizar el cumplimiento del tratamiento antirretroviral.

Incidencia de los problemas relacionados con los medicamentos antirretrovirales para el tratamiento de la infección por HIV en pacientes hospitalizados en el Hospital Santa Clara de Bogotá / Incidence of antiretroviral drug-related problems in the treatment of HIV among hospitalized patients in the Hospital Santa Clara, Bogotá

Resumen Introducción. El tratamiento antirretroviral de la infección por el virus de la inmunodeficiencia humana (HIV) se ha relacionado con diversos problemas de los medicamentos que causan o pueden causar la aparición de resultados negativos. En este contexto, es importante determinar su incidencia, caracterizarlos y clasificarlos para diseñar estrategias que minimicen su impacto. Objetivo. Estimar la incidencia global y de cada uno de los problemas relacionados con los medicamentos antirretrovirales utilizados en el tratamiento del HIV en una cohorte de pacientes hospitalizados en una institución de tercer nivel de Bogotá. Materiales y métodos. Se hizo un estudio descriptivo y retrospectivo de cohorte en pacientes de 18 años o más de edad con diagnóstico de infección por el HIV y en tratamiento antirretroviral, hospitalizados entre el 1° enero de 2015 y el 31 de diciembre de 2016 en el Hospital Santa Clara de Bogotá. Resultados. La incidencia global de los problemas relacionados con los medicamentos antirretrovirales fue de 0,90 (IC95% 0,85-0,93). La incidencia de las interacciones medicamentosas fue de 0,85 (IC95% 0,80-0,90), la de las reacciones adversas de 0,28 (IC95% 0,22-0,35) y la del error de prescripción de 0,12 (IC95% 0,08-0,17). Conclusión. Los problemas relacionados con los medicamentos deben estudiarse, diagnosticarse, prevenirse y tratarse para que el personal de salud pueda anticiparse a su aparición, disminuir su incidencia, implementar planes de manejo del riesgo y optimizar el cumplimiento del tratamiento antirretroviral.

Abstract Introduction: The antiretroviral therapy for the treatment of the human immunodeficiency virus (HIV) is a therapeutic strategy linked to drug-related problems that cause or can cause the appearance of negative results associated with the medication. It is important, therefore, to identify their incidence, characterize them, and classify them to design strategies to minimize their impact. Objective: To estimate the overall incidence and the incidence of each one of the antiretroviral drugs-related problems in the treatment of the HIV infection in a cohort of hospitalized patients in Bogotá, Colombia. Materials and methods: We conducted a descriptive, retrospective cohort study in patients aged 18 years or more diagnosed with HIV infection and under antiretroviral treatment hospitalized between January 1st, 2015, and December 31st, 2016, in the Hospital Santa Clara, Bogotá. Results: The overall incidence of antiretroviral drug-related problems was 0.90 (95% CI: 0.85-0.93). The incidence of drug-drug interactions was 0.85 (95% CI: 0.80-0.90), 0.28 (95% CI: 0.22-0.35) for adverse reactions, and 0.12 (CI 95%: 0.08-0.17) for prescription errors. Conclusion: Drug-related problems should be studied, diagnosed, prevented, and treated. Their knowledge can enable health care professionals to anticipate their emergence, reduce their incidence, implement risk management plans, and optimize adherence to antiretroviral treatment.

An Approach to Measuring Colistin Plasma Levels Regarding the Treatment of Multidrug-Resistant Bacterial Infection.

Antimicrobial resistance to antibiotic treatment has significantly increased during recent years, causing this to become a worldwide public health problem. More than 70% of pathogenic bacteria are resistant to at least one of the currently used antibiotics. Polymyxin E (colistin) has recently been used as a "last line" therapy when treating Gram-negative multi-resistant bacteria. However, little is known about these molecules' pharmacological use as they have been discontinued because of their high toxicity. Recent research has been focused on determining colistimethate sodium's pharmacokinetic parameters to find the optimal dose for maintaining a suitable benefit-risk balance. This review has thus been aimed at describing the use of colistin on patients infected by multi-drug resistant bacteria and the importance of measuring this drug's plasma levels in such patients.

Pseudomonas aeruginosa Coharboring BlaKPC-2 and BlaVIM-2 Carbapenemase Genes.

Pseudomonas aeruginosa, a bacterium commonly isolated from hospital settings, exhibits intrinsic resistance to a number of antibiotics and can acquire resistance during antibiotic therapy. Resistance towards carbapenems is increasing due to its overuse in the treatment of infections caused by extended-spectrum ß-lactamase (ESBL) producing organisms. Nonetheless, carbapenems are essential for the treatment of high-risk infections and are one of the remaining weapons in the fight against "extreme drug resistance" of Gram-negative/positive bacilli. Herein, we describe a case report of infections caused by P. aeruginosa strains that carry blaVIM-2 and blaKPC-2 carbapenemase genes simultaneously, identified in five patients who were admitted to a high complexity health institution in Colombia. Molecular characterization included PCR screening for blaKPC, blaGES, blaOXA-48, blaIMP, blaNDM, and blaVIM carbapenemase and other resistance genes as well as analysis of the genetic relationships by genome macro-restriction and Pulsed-Field Gel Electrophoresis (PFGE) separation. In conclusion, these infections represent a major challenge to public health due to the risk of the infection spreading compounded by the fact that limited treatment options are available, thereby increasing the risk of increased morbidity and mortality.

Biosimilars: An Approach to some Current Worldwide Regulation Frameworks.

Developing new biologics has led to regulations and norms aimed at guaranteeing their safety, quality and effectiveness, in terms of marketing, prescription, use, interchangeability and switching. Biologics are of great importance in treating patients suffering from rheumatic, autoimmune, inflammatory and neoplastic diseases. The expiry/lapse of reference biologics or originators' patents has meant that developing biosimilars involves accompanying legal requirements for their approval in countries worldwide. This paper has thus approached the situation of biosimilar regulation worldwide, the pertinent technical concepts and regulatory differences in some countries of interest.

The Genetic Diagnosis of Neurodegenerative Diseases and Therapeutic Perspectives.

Genetics has led to a new focus regarding approaches to the most prevalent diseases today. Ascertaining the molecular secrets of neurodegenerative diseases will lead to developing drugs that will change natural history, thereby affecting the quality of life and mortality of patients. The sequencing of candidate genes in patients suffering neurodegenerative pathologies is faster, more accurate, and has a lower cost, thereby enabling algorithms to be proposed regarding the risk of neurodegeneration onset in healthy persons including the year of onset and neurodegeneration severity. Next generation sequencing has resulted in an explosion of articles regarding the diagnosis of neurodegenerative diseases involving exome sequencing or sequencing a whole gene for correlating phenotypical expression with genetic mutations in proteins having key functions. Many of them occur in neuronal glia, which can trigger a proinflammatory effect leading to defective proteins causing sporadic or familial mutations. This article reviews the genetic diagnosis techniques and the importance of bioinformatics in interpreting results from neurodegenerative diseases. Risk scores must be established in the near future regarding diseases with a high incidence in healthy people for defining prevention strategies or an early start for giving drugs in the absence of symptoms.

NeuroEPO Preserves Neurons from Glutamate-Induced Excitotoxicity.

Many experimental studies show that erythropoietin (EPO) has a neuroprotective action in the brain. EPO in acute and chronic neurological disorders, particularly in stroke, traumatic brain injury, Alzheimer's disease, Parkinson's disease, and amyotrophic lateral sclerosis, has neuroprotective effects. We previously reported the neuroprotective effect of NeuroEPO, a low sialic form of EPO, against oxidative stress induced by glutamate excitotoxicity. In this paper, we analyze the effect of NeuroEPO against apoptosis induced by glutamate excitotoxicity in primary neuronal cultures obtained from the forebrains of Wistar rat embryos after 17 days of gestation. Excitotoxicity was induced after nine days of in vitro culture by treatment with a culture medium containing 100µM glutamate for 15 min. To withdraw glutamate, a new medium containing 100 ng NeuroEPO/mL was added. Apoptosis was analyzed after 24 h. Images obtained by phase contrast microscopy show that neurons treated with glutamate exhibit cell body shrinkage, loss of dendrites that do not make contact with neighboring cells, and that NeuroEPO was able to preserve the morphological characteristics of the control. Immunocytochemistry images show that the culture is essentially pure in neurons; that glutamate causes cell mortality, and that this is partially avoided when the culture medium is supplemented with NeuroEPO. Activation of intrinsic apoptotic pathways was analyzed. The decreases in Bcl-2/Bax ratio, increase in the release of cytochrome c, and in the expression and activity of caspase-3 observed in cells treated with glutamate, were restored by NeuroEPO. The results from this study show that NeuroEPO protects cortical neurons from glutamate-induced apoptosis via upregulation of Bcl-2 and inhibit glutamate-induced activation of caspase-3.

Microencapsulation of Carvacrol Using Pectin/Aloe-gel as a Novel Wound Dressing Films.

Recently, Pectin (PEC) and Aloe-Gel (AG) have received great attention for their use in the encapsulation of hydrophobic bioactive compounds such as Carvacrol (CAR). The aim of this study is to assess the physical, chemical and biological properties of a novel PEC/AG film and evaluate its capability to entrap CAR into microencapsulates. For this purpose, the casting method was used to prepare the PEC/AG membranes (70:30 % w/w). The CAR-loaded PEC/AG film was prepared adding different proportions of CAR (0.25%, 0.50% and 1.00% v/v) to the mixture of PEC/AG, previously emulsified with tween 80 (1.0%). The optical properties, Water Vapor Permeability (WVP), ATR-FTIR spectroscopy, microstructure, antibacterial activity and size of microcapsules were evaluated. The PEC/AG membranes loaded with CAR showed yellowish appearance and they were transparent to the UV electromagnetic radiation (190, 200 and 280 nm). The film prepared with the lowest amount of CAR (PC/AG-CAR-0.25%) showed the highest values of WVP (66.2%) and, according to SEM micrograph, the largest microcapsules (≈1005± 39 µm3). The FTIR analysis showed the characteristic absorption peaks located at 1015 cm-1 to 1030 cm-1 and a small shoulder to 990 cm-1 of benzene ring 1:2:4 substituted that suggested the presence of CAR-loaded in the PC/AG film. On the other hand, E. coli O157:H7 showed the highest sensitivity to the PEC/AG-CAR-1.00% film, while S. aureus was not sensitive.

New ABCC2 rs3740066 and rs2273697 Polymorphisms Identified in a Healthy Colombian Cohort.

Multidrug resistance-associated proteins (MRP) 1 and 2 belong to the ABC (ATP-Binding Cassette) transporters. These transport proteins are involved in the removal of various drugs and xenobiotics, as well as in multiple physiological, pathological, and pharmacological processes. There is a strong correlation between different polymorphisms and their clinical implication in resistance to antiepileptic drugs, anticancer, and anti-infective agents. In our study, we evaluated exon regions of MRP1 (ABCC1)/MRP2 (ABCC2) in a Colombian cohort of healthy subjects to determine single nucleotide polymorphisms (SNPs) and to determine the allelic and genomic frequency. Results showed there are SNPs in our population that have been previously reported for both MRP1/ABCC1 (rs200647436, rs200624910, rs150214567) and MRP2/ABCC2 (rs2273697, rs3740066, rs142573385, rs17216212). Additionally, 13 new SNPs were identified. Evidence also shows a significant clinical correlation for polymorphisms rs3740066 and rs2273697 in the transport of multiple drugs, which suggests a genetic variability in regards to that reported in other populations.

Label-Free Quantification of Anti-TNF-α in Patients Treated with Adalimumab Using an Optical Biosensor.

This study describes the development of an immunosensory label-free quantification methodology based on surface plasmon resonance (SPR) and its applicability in measuring/evaluating therapeutic drug monitoring (TDM) of anti-TNF-α monoclonal antibody (adalimumab) in rheumatoid arthritis (RA) patients. The experimental parameters evaluated in this study were immobilising ligands by pre-concentration assays, sensor surface regeneration, ascertaining the method's sensitivity and correlating the results from quantifying plasma samples by ELISA immunoassay. The results showed that TNF-α quantification values (in RU) were significantly different when comparing patients (~50-250 RU) to controls (~10-20 RU). Likewise, there was 0.97 correlation for patients and 0.91 for healthy volunteers using SPR and ELISA comparison methodologies. SPR immunosensory detection provided a precise, sensitive strategy, along with real-time determination, for quantifying adalimumab, having great potential for clinical routine regarding TDM.

Fractional Debye-Stokes-Einstein behaviour in an ultraviscous nanocolloid: glycerol and silver nanoparticles.

One of the major features of glass forming ultraviscous liquids is the decoupling between translational and orientational dynamics. This paper presents studies of this phenomenon in glycerol, an accepted molecular glass former, concentrating on the impact of two exogenic factors: high pressures (P) up to the extreme 1.5 GPa and silver (Ag) nanoparticles (NPs). The analysis is focused on the fractional Debye-Stokes-Einstein (FDSE) relationship: σ(T,P)(τ(T,P))(S) = const, linking DC electric conductivity (σ) and primary (alpha, structural) relaxation time (τα). In glycerol and its nanocolloid (glycerol + Ag NPs) at atmospheric pressure only negligible decoupling (S ∼ 1) was detected. However, in the compressed nanocolloid, a well-defined transformation (at P = 1.2 GPa) from S ∼ 1 to the very strongly decoupled dynamics (S ∼ 0.5) occurred. For comparison, in pressurized 'pure' glycerol the stretched shift from S ∼ 1 to S ∼ 0.7 took place. This paper also presents the general discussion of FDSE behavior in ultraviscous liquids, including the new link between the FDSE exponent, fragility and the apparent activation enthalpy and volume.

Fragility and basic process energies in vitrifying systems.

The concept of 'fragility' constitutes a central point of the glass transition science serving as the 'universal' metric linking previtreous dynamics of qualitatively distinct systems. Finding the fundamental meaning of fragility is the 'condicio sine qua' for reaching the long expected conceptual breakthrough in this domain. This report shows that fragility is determined by the ratio between two fundamental process energies, viz. the activation enthalpy and activation energy. The reasoning, avoiding any underlying physical model, is supported by the experimental evidence ranging from low molecular weight liquids and polymers to plastic crystals and liquid crystals. All these lead to the new general scaling plot for dynamics of arbitrary glass former. The limited adequacy of broadly used so far semi-empirical relationships between fragility and the activation energy is shown. Results presented remain valid for an arbitrary complex system and collective phenomena if their dynamics is described by the general super-Arrhenius relation.