Síntese de criptomelana

Cryptomelane was synthetised from several runs by methods whose reproductibility was proved. The best conditions of temperature and pH for the synthesis, the influence of the digestion time on the degree of crystallinity, and the role of the presence of Zn and K ions in the cryptomelane structure as a function of aging of the mineral in contact with the mother solution, were studied. By reduction of KMnO4 with HC1 or Zn/H2 SO4 , the highest degree of crystallinity was found at temperatures above 60ºC in an extended digestion time. The behavior of constituent ions as a function of digestion time indicates that the crystallinity of the cryptomelane is improved by increasing incorporation of K and Mn (IV) ions and decreasing of Mn (II) content, H2O and Zn ions. The probable mechanism of cryptomelane formation is thought to occur under conditions of low pH with K+ present, nucleation being induced mainly by H3O+.Foram efetuadas dezenas de sínteses de criptomelanas por métodos de reprodutibilidade testada e comprovada. Estudou-se a melhor temperatura de síntese, a influência do tempo de digestão no grau de cristalinidade, pH e a influência da incorporação de íons Zn e K na estrutura da criptomelana em função do tempo de envelhecimento do mineral em contato com a solução nutriente. As sínteses foram obtidas pela redução de KMnO4 com HC1 e com Zn/H2SO4, obtendo-se melhor grau de cristalinidade em temperaturas superiores a 60ºC e tempo de digestão prolongado. O estudo do comportamento dos íons constituintes da criptomelana em função do tempo de digestão indicou que o aperfeiçoamento cristalino leva a um acréscimo dos íons K, Mn (IV) e diminuição de Mn (II), H2O+ e Zn. Este estudo permitiu estabelecer um provável mecanismo de formação da criptomelana, que deve ocorrer em condições de pH baixos e presença de K+, sendo a nucleação induzida principalmente através dos cátions oxônios

Delayed enzymatic debridement in severe burns: Proof of concept

Introduction Enzymatic debridement (ED) is a novel powerful therapy for debridement of severe burns. Standard ED is usually performed within 72 h after injury following a presoaking phase. Little evidence exists on the effectiveness of ED later than 72 h after trauma. In this retrospective study, we compared outcomes of burn patients treated within versus later than 72 h after injury. Patients and Methods 110 patients with severe burns treated with ED between 2016 and 2020 were evaluated. Patients treated later than 72 h after trauma were identified and matched to a control group treated within 72 h. Matching criteria included age, area treated with ED, and localization of ED. Exclusion criteria were abbreviated burn severity index (ABSI) greater than 12 and death within the first 10 days after burn injury. Primary outcomes were time to full epithelialization and number of secondary surgical interventions. Results 16 patients (11 female, 5 male) matched the inclusion criteria and were assigned to the late treatment group. Mean age was 54.0 ± 19.0 years, the = and mean ABSI score 6.3 ± 3.2. 16 matched patients were assigned to the early ED group. Secondary surgical procedures were performed in 62.5% of cases in both groups with a mean of 1.7 (late treatment) vs. 2.2 (control; p = 0.29) secondary procedures in each group, respectively. No significant difference between groups regarding time to complete epithelialization (28.2 days vs. 27.3 days, p = 0.45) was observed. Infection rate was higher (18.8% vs. 6.3%, p = 0.28) in the delayed group. Conclusion Delayed ED is a feasible procedure as part of personalized care in burn surgery. In our retrospective study, we could not identify r safety issues except a slightly higher infection rate. This may however be attributed to delayed initiation of burn treatment itself

Strontium as a tracer of weathering processes in a silicate catchment polluted by acid atmospheric inputs, Strengbach, France

This paper determines the weathering and atmospheric contributions of Ca in surface water from a small spruce forested silicate catchment (N–E France) receiving acid atmospheric inputs. The bedrock is a granite with K-feldspar and albite as dominant phases. The calcium content in plagioclase is low and the Ca/Na ratio in surface water is high, reflecting other sources of calcium from those expected from the weathering of major mineral phases. The biotite content is low. Only traces of apatite were detected while no calcite was found in spite of a major hydrothermal event having affected the granite. The strontium isotopic ratio 87Sr/86Sr and Sr content was used as a tracer of weathering and was determined in minerals and bulk bedrock, open field precipitation, throughfall, soil solution, spring and stream water. The Sr isotopic ratio of the reacting weathering end-member was predicted by simulating the alteration of the granite minerals by incorporating strontium into the water–rock interaction kinetic code KINDIS. In the early stages of water–rock interaction, K-feldspar and biotite strongly influence the isotopic composition of the weathering solution whereas, the Na-rich plagioclase appears to be the main long-term reactive weathering end-member. Approximately 50% of dissolved Sr in streamwater are atmospherically derived. The 87Sr/86Sr ratios of exchangeable Sr in the fine fraction at 1-m depth from a soil profile indicate that the amount of exchangeable Sr seems essentially controlled by atmospheric inputs. The exception is the deep saprolite where weathering processes could supply the Sr (and Ca). Na-Plagioclase weathering obviously control the chemistry and the isotopic composition of surface waters. The weathering of trace mineral plays a secondary role, the exception is for apatite when plagioclase is absent. Our hydrochemical, mineralogical and isotopic investigations show that a major part of the strong Ca losses detected in catchment hydrochemical budgets that result from the neutralization of acid precipitation has an atmospheric origin. Consequently, in the long term, in such areas, the availability of such an exchangeable base cation might be strongly limited and surface waters consequently acidified

Galactic chemical abundance evolution in the solar neighborhood up to the Iron peak

We have developed a detailed standard chemical evolution model to study the evolution of all the chemical elements up to the iron peak in the solar vicinity. We consider that the Galaxy was formed through two episodes of exponentially decreasing infall, out of extragalactic gas. In a first infall episode, with a duration of $\sim$ 1 Gyr, the halo and the thick disk were assembled out of primordial gas, while the thin disk formed in a second episode of infall of slightly enriched extragalactic gas, with much longer timescale. The model nicely reproduces the main observational constraints of the solar neighborhood, and the calculated elemental abundances at the time of the solar birth are in excellent agreement with the solar abundances. By the inclusion of metallicity dependent yields for the whole range of stellar masses we follow the evolution of 76 isotopes of all the chemical elements between hydrogen and zinc. Those results are confronted with a large and recent body of observational data, and we discuss in detail the implications for stellar nucleosynthesis.Comment: 19 pages, 14 figures, submitted to A&

The influence of sentinel lymph node tumour burden on additional lymph node involvement and disease-free survival in cutaneous melanoma – a retrospective analysis of 392 cases

Twenty per cent of sentinel lymph node (SLN)-positive melanoma patients have positive non-SLN lymph nodes in completion lymph node dissection (CLND). We investigated SLN tumour load, non-sentinel positivity and disease-free survival (DFS) to assess whether certain patients could be spared CLND. Sentinel lymph node biopsy was performed on 392 patients between 1999 and 2005. Median observation period was 38.8 months. Sentinel lymph node tumour load did not predict non-SLN positivity: 30.8% of patients with SLN macrometastases (⩾2 mm) and 16.4% with micrometastases (⩽2 mm) had non-SLN positivity (P=0.09). Tumour recurrences after positive SLNs were more than twice as frequent for SLN macrometastases (51.3%) than for micrometastases (24.6%) (P=0.005). For patients with SLN micrometastases, the DFS analysis was worse (P=0.003) when comparing those with positive non-SLNs (60% recurrences) to those without (17.6% recurrences). This difference did not translate into significant differences in DFS: patients with SLN micrometastasis, either with (P=0.022) or without additional positive non-SLNs (P<0.0001), fared worse than patients with tumour-free SLNs. The 2-mm cutoff for SLN tumour load accurately predicts differences in DFS. Non-SLN positivity in CLND, however, cannot be predicted. Therefore, contrary to other studies, no recommendations concerning discontinuation of CLND based on SLN tumour load can be deduced

Oxidative stress-driven parvalbumin interneuron impairment as a common mechanism in models of schizophrenia.

Parvalbumin inhibitory interneurons (PVIs) are crucial for maintaining proper excitatory/inhibitory balance and high-frequency neuronal synchronization. Their activity supports critical developmental trajectories, sensory and cognitive processing, and social behavior. Despite heterogeneity in the etiology across schizophrenia and autism spectrum disorder, PVI circuits are altered in these psychiatric disorders. Identifying mechanism(s) underlying PVI deficits is essential to establish treatments targeting in particular cognition. On the basis of published and new data, we propose oxidative stress as a common pathological mechanism leading to PVI impairment in schizophrenia and some forms of autism. A series of animal models carrying genetic and/or environmental risks relevant to diverse etiological aspects of these disorders show PVI deficits to be all accompanied by oxidative stress in the anterior cingulate cortex. Specifically, oxidative stress is negatively correlated with the integrity of PVIs and the extracellular perineuronal net enwrapping these interneurons. Oxidative stress may result from dysregulation of systems typically affected in schizophrenia, including glutamatergic, dopaminergic, immune and antioxidant signaling. As convergent end point, redox dysregulation has successfully been targeted to protect PVIs with antioxidants/redox regulators across several animal models. This opens up new perspectives for the use of antioxidant treatments to be applied to at-risk individuals, in close temporal proximity to environmental impacts known to induce oxidative stress

Linking early-life NMDAR hypofunction and oxidative stress in schizophrenia pathogenesis.

Molecular, genetic and pathological evidence suggests that deficits in GABAergic parvalbumin-positive interneurons contribute to schizophrenia pathophysiology through alterations in the brain's excitation-inhibition balance that result in impaired behaviour and cognition. Although the factors that trigger these deficits are diverse, there is increasing evidence that they converge on a common pathological hub that involves NMDA receptor hypofunction and oxidative stress. These factors have been separately linked to schizophrenia pathogenesis, but evidence now suggests that they are mechanistically interdependent and contribute to a common schizophrenia-associated pathology