Space-time Thermodynamics of the Glass Transition

We consider the probability distribution for fluctuations in dynamical action and similar quantities related to dynamic heterogeneity. We argue that the so-called "glass transition" is a manifestation of low action tails in these distributions where the entropy of trajectory space is sub-extensive in time. These low action tails are a consequence of dynamic heterogeneity and an indication of phase coexistence in trajectory space. The glass transition, where the system falls out of equilibrium, is then an order-disorder phenomenon in space-time occurring at a temperature T_g which is a weak function of measurement time. We illustrate our perspective ideas with facilitated lattice models, and note how these ideas apply more generally.Comment: 5 pages, 4 figure

Dynamics and Thermodynamics of the Glass Transition

The principal theme of this paper is that anomalously slow, super-Arrhenius relaxations in glassy materials may be activated processes involving chains of molecular displacements. As pointed out in a preceding paper with A. Lemaitre, the entropy of critically long excitation chains can enable them to grow without bound, thus activating stable thermal fluctuations in the local density or molecular coordination of the material. I argue here that the intrinsic molecular-scale disorder in a glass plays an essential role in determining the activation rate for such chains, and show that a simple disorder-related correction to the earlier theory recovers the Vogel-Fulcher law in three dimensions. A key feature of this theory is that the spatial extent of critically long excitation chains diverges at the Vogel-Fulcher temperature. I speculate that this diverging length scale implies that, as the temperature decreases, increasingly large regions of the system become frozen and do not contribute to the configurational entropy, and thus ergodicity is partially broken in the super-Arrhenius region above the Kauzmann temperature $T_K$. This partially broken ergodicity seems to explain the vanishing entropy at $T_K$ and other observed relations between dynamics and thermodynamics at the glass transition.Comment: 20 pages, no figures, some further revision

Role of Magnesium and its mitochondrial transporter MRS2 in the modulation of drug-induced apoptosis leading to multidrug resistance phenotype

Magnesium is an essential element for many biological processes crucial for cell life and proliferation. Growing evidences point out a role for this cation in the apoptotic process and in developing multi drug resistance (MDR) phenotype. The first part of this study aimed to highlight the involvement of the mitochondrial magnesium channel MRS2 in modulating drug-induced apoptosis. We generated an appropriate transgenic cellular system to regulate expression of MRS2 protein. The cells were then exposed to two different apoptotic agents commonly used in chemotherapy. The obtained results showed that cells overexpressing MRS2 channel are less responsiveness to pharmacological insults, looking more resistant to the induced apoptosis. Moreover, in normal condition, MRS2 overexpression induces higher magnesium uptake into isolated mitochondria respect to control cells correlating with an increment of total intracellular magnesium concentration. In the second part of this research we investigated whether magnesium intracellular content and compartmentalization could be used as a signature to discriminate MDR tumour cells from their sensitive counterparts. As MDR model we choose colon carcinoma cell line sensitive and resistant to doxorubicin. We exploited a standard-less approach providing a complete characterization of whole single-cells by combining X-Ray Fluorescence Microscopy , Atomic Force Microscopy and Scanning Transmission X-ray Microscopy. This method allows the quantification of the intracellular spatial distribution and total concentration of magnesium in whole dehydrated cells. The measurements, carried out in 27 single cells, revealed a different magnesium pattern for both concentration and distribution of the element in the two cellular strains. These results were then confirmed by quantifying the total amount of intracellular magnesium in a large populations of cells by using DCHQ5 probe and traditional fluorimetric technique

O ensino de ciências sociais na implementação do novo ensino médio : os espaços e significados da sociologia nas escolas de Gravataí-RS

O objetivo desta pesquisa exploratória é entender a atuação dos professores de sociologia da cidade de Gravataí, após um ano do início da implementação do Novo Ensino Médio (NEM), em 2022. O estudo se dá através da análise e reflexão das falas colhidas em entrevistas individuais de três docentes que lecionam o componente de sociologia na rede estadual de ensino do município. Os resultados desta análise apontam que não houve novos problemas a serem enfrentados pelos professores, mas sim que aqueles já enraizados no sistema de ensino pioraram e fragilizaram mais ainda o componente de sociologia no ensino médio. A piora se dá na sobrecarga dos docentes com a distribuição de componentes ainda mais fragmentada nas escolas, negociações mais difíceis para o trabalho em condições minimamente suportáveis; assim houve mais uma desvalorização da sociologia como componente escolar no NEM. Tudo isso com impacto direto sobre a qualidade de ensino e na pedagogia dos profissionais. O que por fim, pode-se afirmar, dificulta o desenvolvimento de um pensamento sociológico nos estudantes do ensino médio nas escolas estaduais do RS

Monitoring magnesium efflux cyclic AMP-induced in HL60 cells by using a new hydroxyquinoline fluorescent chemosensor

Cellular homeostasis of magnesium is still unclear. Several studies documented the occurrence of fluxes of magnesium across the plasmamembrane within minutes from the application of metabolic or hormonal stimuli. These fluxes, however, result in limited variation of free Mg2+ intracellular concentration and large changes in total Mg content. It has been reported that a stimulation with cyclic AMP caused a movement of total magnesium within 10 min after treatment in cardiomyocytes. In this study we tested this hypothesis in HL60 leukemic cells, not excitable but highly proliferating cell model. We evaluated Mg flux by DCHQ5, the phenyl-derivative of hydroxyquinoline fluorescent probe family. We observed a drastic decrease of intracellular total magnesium in the first 3 min. We also verified that at least 10% of the total intracellular amount of magnesium moved in the supernatant of stimulated cells

Intracellular magnesium content changes during mitochondria-mediated apoptosis: in depth study of early events on mitochondrial membrane potential

A recent study showed the antitumor activity of a new indole-derivative – MM-67 – inducing mitochondria-mediated apoptosis and a decrease of intracellular magnesium (Mg) concentration in HT29 colon cancer cells. Aim of this work was to assess cellular Mg levels throughout MM-67-induced apoptosis from the early to the final stage of the process and to evaluate the correlation with mitochondrial membrane potential (ΔΨm) variations. All analysis were performed by flow cytometry: ΔΨm was assessed by using mitochondrial potential sensitive dye DiOC6, while free and total intracellular cation concentrations were assessed by using the commercial probe MagFluo4-AM (Kd=4.7 mM), and the new synthesized DCHQ5 (Kd=8.3 mM), respectively. Our results evidenced that the MM67 induced apoptosis is characterized by a direct correlation between ΔΨ and free intracellular Mg content variations

Imbalance of Mg Homeostasis as a Potential Biomarker in Colon Cancer

Background: Increasing evidences support a correlation between magnesium (Mg) homeostasis and colorectal cancer (CRC). Nevertheless, the role of Mg and its transporters as diagnostic markers in CRC is still a matter of debate. In this study we combined X-ray Fluorescence Microscopy and databases information to investigate the possible correlation between Mg imbalance and CRC. Methods: CRC tissue samples and their non-tumoural counterpart from four patients were collected and analysed for total Mg level and distribution by X-Ray Fluorescence Microscopy. We also reviewed the scientific literature and the main tissue expression databases to collect data on Mg transporters expression in CRC. Results: We found a significantly higher content of total Mg in CRC samples when compared to non-tumoural tissues. Mg distribution was also impaired in CRC. Conversely, we evidenced an uncertain correlation between Mg transporters expression and colon malignancies. Discussion: Although further studies are necessary to determine the correlation between different cancer types and stages, this is the first report proposing the measurement of Mg tissue localisation as a marker in CRC. This study represents thus a proof-of-concept that paves the way for the design of a larger prospective investigation of Mg in CRC

Efficacy, safety, and dose of Pafuramidine, a new oral drug for treatment of first stage sleeping sickness, in a phase 2a clinical study and phase 2b randomized clinical studies

Sleeping sickness (human African trypanosomiasis [HAT]) is caused by protozoan parasites and characterized by a chronic progressive course, which may last up to several years before death. We conducted two Phase 2 studies to determine the efficacy and safety of oral pafuramidine in African patients with first stage HAT.; The Phase 2a study was an open-label, non-controlled, proof-of-concept study where 32 patients were treated with 100 mg of pafuramidine orally twice a day (BID) for 5 days at two trypanosomiasis reference centers (Angola and the Democratic Republic of the Congo [DRC]) between August 2001 and November 2004. The Phase 2b study compared pafuramidine in 41 patients versus standard pentamidine therapy in 40 patients. The Phase 2b study was open-label, parallel-group, controlled, randomized, and conducted at two sites in the DRC between April 2003 and February 2007. The Phase 2b study was then amended to add an open-label sequence (Phase 2b-2), where 30 patients received pafuramidine for 10 days. The primary efficacy endpoint was parasitologic cure at 24 hours (Phase 2a) or 3 months (Phase 2b) after treatment completion. The primary safety outcome was the rate of occurrence of World Health Organization Toxicity Scale Grade 3 or higher adverse events. All subjects provided written informed consent.; Pafuramidine for the treatment of first stage HAT was comparable in efficacy to pentamidine after 10 days of dosing. The cure rates 3 months post-treatment were 79% in the 5-day pafuramidine, 100% in the 7-day pentamidine, and 93% in the 10-day pafuramidine groups. In Phase 2b, the percentage of patients with at least 1 treatment-emergent adverse event was notably higher after pentamidine treatment (93%) than pafuramidine treatment for 5 days (25%) and 10 days (57%). These results support continuation of the development program for pafuramidine into Phase 3