Blast furnace hearth refractories are a key component in achieving long furnace lives. These refractories can be degraded by among other things reactions with coke ash products. Recent studies have ...shown that these coke ash products could be calcium aluminate based. To understand and characterize the effects of these calcium aluminates on hearth refractories a study has been carried out that investigates the reaction kinetics of CaO.Al2O3, CaO.2Al2O3 and CaO.6Al2O3 in contact with an aluminosilicate blast furnace hearth refractory. The experimental program covered the temperature range 1450° to 1550°C. The temperatures were chosen to represent the hot face temperatures of the hearth refractories. From this study it was found that the rate of reaction with the aluminosilicate refractory and CaO.6Al2O3 was much slower than that of CaO.Al2O3 and CaO.2Al2O3. The prevailing kinetics of the aluminosilicate refractory with CaO.Al2O3 and CaO.2Al2O3 was found to be consistent with the linear rate law. The slow rate of reaction of the refractory with CaO.6Al2O3 prohibited identification of the prevailing kinetic regime. In characterizing the reaction interface between the aluminosilicate and the calcium aluminates it was found that there was significant reaction between the refractory and CaO.Al2O3 and CaO.2Al2O3 but little reaction with the CaO.6Al2O3. The reaction layers formed at the interface between the couples were found to consist of CaO.2Al2O3, CaO.6Al2O3, corundum (Al2O3), plagioclase (CaO.Al2O3.2SiO2) and melilite (2CaO.Al2O3.SiO2). The formation of a layer with these phases could result in spalling/wear of the hearth refractory.
Understanding the degradation of blast furnace hearth refractories by coke ash products is a crucial component in achieving long furnace life. This study has been conducted to determine the ...reactivity of calcium aluminates (CaO·Al2O3, CaO·2Al2O3 and CaO·6Al2O3) in contact with an alumina-carbon refractory at representative hearth temperatures of 1450° to 1550°C. The rate of reaction between the alumina-carbon refractory and calcium aluminates was observed to increase with CaO content. The largest reaction layer was observed in CaO·Al2O3 followed by CaO·2Al2O3 and CaO·6Al2O3. The calcium aluminate (CaO·Al2O3, CaO·2Al2O3) and alumina-carbon reactions observed in this study were found to be consistent with the logarithmic rate law, with the exception of CaO·6Al2O3 where no reaction was observed. Energy dispersive spectroscopy analysis indicated the formation of CaO·2Al2O3, CaO·6Al2O3, corundum (Al2O3), plagioclase (CaO·Al2O3·2SiO2) and melilite (2CaO·Al2O3·SiO2) at the reaction interface of the reaction couples. The large volume changes due to the formation of these phases may result in spalling at the hot face of the hearth refractory.
In this study, the mineral matter layer that forms between coke, and liquid iron during carbon dissolution has been characterised. Rectangular prisms of coke were immersed in an iron–2 mass% carbon ...melt at representative ironmaking temperatures for 20 min then drop quenched. The quench sample was then sectioned and the coke–iron interface was examined in the SEM. A mineral matter layer was observed at the experimental temperatures 1400°C, 1450°C and 1500°C, but not at 1550°C. Though no layer was found at 1550°C a slag was observed on the metal surface. This slag was not evident at other temperatures. The formation of the mineral matter layer and its temperature dependence is described in terms of a temperature activated fusion process. Further the mineral matter layer and adjacent coke were found to be significantly depleted in SiO2. This has been explained in terms of SiO2 reduction.
The effects of sulfur concentration in liquid iron on mineral layer development between coke and iron as coke dissolves in a 2 mass pct carbon-iron liquid have been investigated at 1773 K (1500 °C). ...The initial sulfur in iron concentrations used ranged from 0.006 to 0.049 mass pct. Key findings include that the two-stage dissolution behavior exhibited in the carbon transfer from coke to iron, as reported in a previous study by the authors, at low initial sulfur in iron contents, was also apparent at the higher values used in this study. This two-stage behavior was attributed to a change in the mineral layer density as a result of changes in mineral morphology at the interface. In addition to confirming the two-stage behavior of the carbon-transfer kinetics at the higher sulfur concentration in iron levels, after a period of time, a solid calcium sulfide layer formed on the mineral layer. The sulfide layer formed after approximately 40 minutes, and the proportion of sulfide in the mineral layer increased with increased experimental time and initial sulfur concentration in iron. It was usually found at the iron side of the mineral layer and was associated with calcium-enriched calcium aluminates. Thermodynamic analysis of this layer confirmed that the sulfide is stabilized as the mineral layer is enriched by calcium.
We report a multichannel microfluidic droplet reactor for the large-scale, high temperature synthesis of nanocrystals. The reactor was applied here to the production of CdTe, CdSe and alloyed CdSeTe ...nanocrystals, and found in all cases to provide high quality quantum dots with spectral properties that did not vary between channels or over time. One hour test runs yielded 3.7, 1.5 and 2.1 g of purified CdTe, CdSe and the alloy, respectively, using 0.4 M cadmium precursor solutions and carrier and reagent phase flow rates of 4 and 2 ml min super(-1). A further nine hour test-run applied to CdTe, utilizing increased carrier and reagent flow rates of 5 and 3 ml min super(-1), yielded 54.4 g of dry purified material, corresponding to a production rate of 145 g per day. The reactor architecture is inherently scalable and, with only minimal modifications, should allow for straightforward expansion to the kilogram-per-day production levels sought by industry.
Abstract
Background
Cognitive impairment is reported as a common complication in adult tuberculous meningitis (TBM), yet few studies have systematically assessed the frequency and nature of ...impairment. Moreover, the impact of impairment on functioning and medication adherence has not been described.
Methods
A cognitive test battery (10 measures assessing 7 cognitive domains) was administered to 34 participants with human immunodeficiency virus (HIV)–associated TBM 6 months after diagnosis. Cognitive performance was compared with that a comparator group of 66 people with HIV without a history of tuberculosis. A secondary comparison was made between participants with TBM and 26 participants with HIV 6 months after diagnosis of tuberculosis outside the central nervous system (CNS). Impact on functioning was evaluated, including through assessment of medication adherence.
Results
Of 34 participants with TBM, 16 (47%) had low performance on cognitive testing. Cognition was impaired across all domains. Global cognitive performance was significantly lower in participants with TBM than in people with HIV (mean T score, 41 vs 48, respectively; P < .001). These participants also had lower global cognition scores than those with non-CNS tuberculosis (mean global T score, 41 vs 46; P = .02). Functional outcomes were not significantly correlated with cognitive performance in the subgroup of participants in whom this was assessed (n = 19).
Conclusions
Low cognitive performance following HIV-associated TBM is common. This effect is independent of, and additional to, effects of HIV and non-CNS tuberculosis disease. Further studies are needed to understand longer-term outcomes, clarify the association with treatment adherence, a key predictor of outcome in TBM, and develop context-specific tools to identify individuals with cognitive difficulties in order to improve outcomes in TBM.
Cognitive impairment following tuberculous meningitis is poorly described. In a case control study we demonstrate that low cognitive performance affects ∼50% of patients at 6 months following diagnosis HIV-associated TBM, and is significantly worse than that seen in HIV alone
Cognitive impairment in tuberculous meningitis Davis, Angharad; Dreyer, Anna J; Albertyn, Christine ...
Journal of neurology, neurosurgery and psychiatry,
11/2023, Volume:
94, Issue:
Suppl 1
Journal Article
Peer reviewed
Few studies have systematically assessed cognitive impairment following tuberculous meningitis (TBM). Moreover, the impact of impairment on functioning and medication adherence is not described.A ...cognitive test battery (10 measures, 7 cognitive domains) was administered to 34 participants with HIV-associated TBM 6 months post-diagnosis. Cognitive performance was compared to a comparator group of 66 people living with HIV (PLWH) without TB. A secondary comparison was made between TBM cases and 26 participants with HIV 6-months post-diagnosis of TB outside the central nervous system (CNS). Impact on functioning and medication adherence was assessed.In TBM, 16/34 (47%) of participants had low performance on cognitive testing with impairment across all domains. Global cognitive performance was significantly lower in TBM cases compared to PLWH (mean T-score 41 vs 48, p<0.001). TBM cases also had lower global cognition compared to those with non-CNS TB (mean global T score 41 vs 46, p=0.016). Functional outcomes did not significantly correlate with cognitive performance in a sub-group of participants (n=19).Low cognitive performance following TBM is common. This effect is independent of, and additional to, the effects of HIV and non-CNS TB disease. Larger studies are needed to better understand effect on functional outcome and treatment adherence.
Adolescents obviously do not always act in ways that serve their own best interests, even as defined by them. Sometimes their perception of their own risks, even of survival to adulthood, is larger ...than the reality; in other cases, they underestimate the risks of particular actions or behaviors. It is possible, indeed likely, that some adolescents engage in risky behaviors because of a perception of invulnerability?the current conventional wisdom of adults' views of adolescent behavior. Others, however, take risks because they feel vulnerable to a point approaching hopelessness. In either case, these perceptions can prompt adolescents to make poor decisions that can put them at risk and leave them vulnerable to physical or psychological harm that may have a negative impact on their long-term health and viability.
A small planning group was formed to develop a workshop on reconceptualizing adolescent risk and vulnerability. With funding from Carnegie Corporation of New York, the Workshop on Adolescent Risk and Vulnerability: Setting Priorities took place on March 13, 2001, in Washington, DC. The workshop's goal was to put into perspective the total burden of vulnerability that adolescents face, taking advantage of the growing societal concern for adolescents, the need to set priorities for meeting adolescents' needs, and the opportunity to apply decision-making perspectives to this critical area. This report summarizes the workshop.
We assessed whether remote ischemic preconditioning (RIPC) improves myocardial, renal, and lung protection after on-pump coronary surgery.
This was a single-center, prospective, randomized (1:1), ...placebo-controlled trial. Patients, investigators, anesthetists, surgeons, and critical care teams were blinded to group allocation. Subjects received RIPC (or placebo) stimuli (×3 upper limb (or dummy arm), 5-minute cycles of 200 mm Hg cuff inflation/deflation) before aortic clamping. Anesthesia, perfusion, cardioplegia, and surgical techniques were standardized. The primary end point was 48-hour area under the curve (AUC) troponin T (cTnT) release. Secondary end points were 6-hour and peak cTnT, ECG changes, cardiac index, inotrope and vasoconstrictor use, renal dysfunction, and lung injury. Hospital survival was 99.4%. Comparing placebo and RIPC, median (interquartile range) AUC 48-hour cTnT (ng/mL(-1)/48 h(-1)); 28 (19, 39) versus 30 (22, 38), 6-hour cTnT (ng/mL(-1)); 0.93(0.59, 1.35) versus 1.01(0.72, 1.43), peak cTnT (ng/mL(-1)); 1.02 (0.74, 1.44) versus 1.04 (0.78, 1.51), de novo left bundle-branch block (4% versus 0%) and Q waves (5.3% versus 5.5%), serial cardiac indices, intraaortic balloon pump usage (8.5% versus 7.5%), inotrope (39% versus 50%) and vasoconstrictor usage (66% versus 64%) were not different. Dialysis requirement (1.2% versus 3.8%), peak creatinine (median interquartile range, 1.2 mg/dL(-1) (1.1, 1.4) versus 1.2 (1.0, 1.4)), and AUC urinary albumin-creatinine ratios 69 (40, 112) versus 58 (32, 85) were not different. Intubation times; median (interquartile range), 937 minutes(766, 1402) versus 895(675, 1180), 6-hour; 278 (210, 338) versus 270 (218, 323) and 12-hour pO(2):FiO(2) ratios 255 (195, 323) versus 263 (210, 308) were similar.
In contrast to prior smaller studies, RIPC did not reduce troponin release, improve hemodynamics, or enhance renal or lung protection. Clinical Trial Registration-URL: http://www.ukcrn.org.uk. Unique identifier: 4659.
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