Reinforced concrete columns confined by steel tubes, also known as steel tube–confined reinforced concrete (STCRC) columns, are a kind of composite column in which the outer steel tube acts predominantly as hoop reinforcement. This is achieved by the provision of breaks to the longitudinal continuity of the steel tube. The compressive behavior and seismic performance of STCRC columns have been extensively studied in the last few decades. However, knowledge of the fire behavior of STCRC columns is very limited. Hence, experimental and numerical studies to investigate the response of STCRC columns under combined thermal (fire) and structural loading are presented herein. Four full-scale STCRC columns and one concrete-filled steel tubular (CFST) column were first axially loaded and then subjected to fire until failure. The measured furnace temperatures, specimen temperatures, axial displacement versus time curves, and fire resistance of the columns are presented and discussed. A nonlinear finite-element model employing a sequentially coupled thermal-stress analysis was then developed and validated against recent fire tests on STCRC and CFST columns reported in the literature. Following extensive parametric studies, a simplified method is proposed for predicting the temperatures of the steel tube, reinforcing bars, and concrete. Design rules are then proposed for predicting the load-bearing capacity of STCRC columns exposed to fire, which are consistent with the design method for STCRC columns at ambient temperature.
Abstract Design by GMNIA (Geometrically and Materially Nonlinear Analysis with Imperfections) allows the key behavioural features of structures to be directly captured in the analysis, dramatically reducing the need for subsequent design checks. Since the analysis of frames typically employs beam finite elements, which do not explicitly account for local buckling, cross‐section classification and capacity checks remain necessary. To resolve the step‐wise and overly conservative nature of traditional checks, the alternative use of strain limits, defined using the Continuous Strength Method, has been proposed. The framework allows cross‐sections of all classes to be treated in a consistent manner, and results in an accurate and consistent representation of the true behaviour of structures. To date, the accuracy of the design approach for stainless steel has been comprehensively demonstrated for isolated stainless steel members; the design method is extended to indeterminate stainless steel structural systems herein. The method is included in AISC 370 and prEN 1993‐1‐14; inclusion of this design framework in international codes of practice presents a step change for the future direction of efficient structural stainless steel design.
1. Venous plasma histamine and catecholamines were measured in stable asthmatic subjects by a recently developed specific and sensitive radioenzymatic assay. 2. Plasma histamine concentrations were significantly elevated in both extrinsic and intrinsic asthmatic subjects, compared with both normal controls and patients with chronic obstructive airways disease. There was no correlation between histamine concentration and severity of airways obstruction, however. 3. Elevated plasma histamine concentrations at rest-5-indicate increased release of mediators from ‘leaky’ mast cells in asthma. 4. Plasma catecholamine concentrations in asthmatic subjects did not differ from normal and there was no correlation with severity of broncho- constriction or with plasma histamine concentration.
We present observations of the (1,1), (2,2), (4,4) and (5,5) inversion transitions of para-ammonia (NH3) and 24 GHz continuum, taken with the Australia Telescope Compact Array toward 21 southern Galactic hot molecular cores traced by 6.7 GHz methanol maser emission. We detect NH3(1,1) emission toward all 21 regions and 24 GHz continuum emission toward 12 of the regions, including 6 with no reported 8 GHz continuum counterparts. In total, we find the 21 regions contain 41 NH3(1,1) cores. We extract characteristic spectra for every core at each of the NH3 transitions and present both integrated intensity maps and channel maps for each region. The NH3(4,4)+(5,5) emission is always unresolved and found at the maser position indicating that the methanol masers are found at the warmest part of the core. We observe large asymmetries in the NH3(1,1) hyperfine line profiles and conclude this is due to a number of dense, small clumps within the beam. We derive properties of the ionised gas and find the 24 GHz continuum sources not detected at 8 GHz are always coincident with both NH3 and methanol masers in contrast to those detected at 8 + 24 GHz which are generally offset from the methanol masers. We investigate the possibility that the former may be hyper-compact HII regions. Finally, we separate the cores into five groups, based on their association with NH3, methanol maser and continuum emission. From the different physical properties of the cores in the groups, we discuss the possibility that these groups may represent cores at different evolutionary stages of the massive star formation process.
The Census of Highand Medium-mass Protostars (CHaMP) is the first large-scale, unbiased, uniform mapping survey at ∼parsec-scale resolution of 90GHz line emission from massive molecular clumps in the Milky Way. We present the first Mopra (ATNF) maps of the CHaMP survey region in the Carina arm using the HCOJ=1→0 line, a common “high-density” tracer, which shows emission from an ensemble of massive molecular clumps. From these maps we derive the physical parameters of the clumps, using standard molecular spectral-line analysis techniques, and find that there exists a large population of weakly-emitting (but easily detectable) massive molecular clumps, the properties of which are distinct from brighter massive star-forming regions that are more typically studied. These massive clumps (comprising 90% of our clumps by number) are typically optically thin, and with the possible exception of the brightest 10% of sources, are of significantly lower density than the line’s critical density: thus, their HCO is subthermally excited. The weakly-emitting clump masses range from ∼10 to ∼3000M⊙, with the brighter sub-population only in the top decade of this range (although the upper limit of the mass range may be systematically underestimated). Thus because of their number, the weakly-emitting clumps may also comprise the bulk (up to 80%) of the molecular mass in the Galaxy. Our clump population shows a relationship between the Virial and measured mass (e.g., as measured by the α parameter) that is similar to the Bertoldi & McKee (1992) prediction. They also have a wide range of velocity dispersions at low brightness, but a much smaller range of dispersions among the brighter clumps. This supports the idea that the weakly-emitting clumps are not gravitationally bound, but rather pressure-confined by their overlying GMC envelopes.
No abstract is provided for this article.
Epigenetics is defined as heritable changes that affect gene expression without altering the DNA sequence. Epigenetic regulation of gene expression is facilitated through different mechanisms such as DNA methylation, histone modifications and RNA-associated silencing by small non-coding RNAs. All these mechanisms are crucial for normal development, differentiation and tissue-specific gene expression. These three systems interact and stabilize one another and can initiate and sustain epigenetic silencing, thus determining heritable changes in gene expression. Histone acetylation regulates diverse cellular functions including inflammatory gene expression, DNA repair and cell proliferation. Transcriptional coactivators possess intrinsic histone acetyltransferase activity and this activity drives inflammatory gene expression. Eleven classical histone deacetylases (HDACs) act to regulate the expression of distinct subsets of inflammatory/immune genes. Thus, loss of HDAC activity or the presence of HDAC inhibitors can further enhance inflammatory gene expression by producing a gene-specific change in HAT activity. For example, HDAC2 expression and activity are reduced in lung macrophages, biopsy specimens, and blood cells from patients with severe asthma and smoking asthmatics, as well as in patients with chronic obstructive pulmonary disease (COPD). This may account, at least in part, for the enhanced inflammation and reduced steroid responsiveness seen in these patients. Other proteins, particularly transcription factors, are also acetylated and are targets for deacetylation by HDACs and sirtuins, a related family of 7 predominantly protein deacetylases. Thus the acetylation/deacetylation status of NF-κB and the glucocorticoid receptor can also affect the overall expression pattern of inflammatory genes and regulate the inflammatory response. Understanding and targeting specific enzymes involved in this process might lead to new therapeutic agents, particularly in situations in which current anti-inflammatory therapies are suboptimal.
Purpose of review Multicenter studies showed that the characterization of coronary atherosclerosis by coronary computed tomography (CT) angiography (CCTA) provides independent and incremental prognostic value above and beyond traditional measures of coronary artery disease (CAD) and is able to identify patients at risk of future event. Aim of the present review is to expound the major imaging plaque features associated with increased risk of coronary event and to review the data supporting the usefulness of CCTA as tool for plaque assessment and for monitoring the changes in atherosclerotic burden. Recent findings The evaluation of coronary atherosclerosis, including the measurement of imaging risk scores (e.g. CT-adapted Leaman score) was demonstrated as independent long-term predictor of acute coronary events. In particular, qualitative (remodelling index, low-attenuation plaque, napkin-ring sign, small spotty calcifications) and quantitative (plaque burden, total-, noncalcific- and fibrofatty plaque volume) plaque features were associated with increased risk. CCTA was also demonstrated to accurately quantify plaque volume vs. intravascular ultrasound and findings from PARADIGM and EVAPORATE studies supported the use of CCTA as noninvasive tool to follow the effect of medication on plaque progression/regression. Finally, interesting relationship between plaque features, coronary physiology and biomarkers have been described. Summary Latest guidelines on the management of patients with stable CAD recommended CCTA in Class I of evidence, particularly when ‘information on atherosclerosis are desired’, underlining the usefulness of CCTA to characterize and quantify the atherosclerotic burden.
Personalized long term vital prognosis plays a key role in deciding between percutaneous coronary intervention (PCI) and CABG in patients with complex coronary artery disease. The FASTTRACK CABG trial enrolls patients with the sole guidance of coronary computed tomographic angiography (CCTA) and fractional flow reserve CCTA (FFRCT). The feasibility/non-feasibility of this approach is determined by the surgeon request to have access to the invasive coronary angiography.This interim analysis, which was requested by the Data and Safety Monitoring Board (DSMB), compared the treatment decision of the "on site" Heart team to the recommended treatment as per the SYNTAX Score II 2020 (SS-2020), which was prospectively assessed by the central core laboratory in the first 57 consecutive patients (half of the planned population) enrolled in this First in Man study.The average anatomical SYTAX Score is 35.6 ± 11.5. The SS-2020 predicted 5-year MACE and 10-year all-cause mortality are 14.7 % and 21.6 % following CABG, and 23.0 % and 30.4 % following PCI. Among the enrolled patients the SS-2020 predicts long-term PCI outcomes similar to CABG (absolute risk difference ≤0 % in favor of PCI) in only two patients whilst the remaining 55 patients had a predicted survival benefit with CABG.According to the SS-2020, the first 57 patients recruited into the FASTTRACK CABG trial received the appropriate modality of revascularization and the DSMB allowed the investigators to complete the study.
Objectives This study sought to investigate in vivo the vascular response at the proximal and distal edges of the second-generation ABSORB everolimus-eluting bioresorbable vascular scaffold (BVS). Background The edge vascular response after implantation of the BVS has not been previously investigated. Methods The ABSORB Cohort B trial enrolled 101 patients and was divided into B1 (n = 45) and B2 (n = 56) subgroups. The adjacent (5-mm) proximal and distal vessel segments to the implanted ABSORB BVS were investigated at either 6 months (B1) or 1 year (B2) with virtual histology intravascular ultrasound (VH-IVUS) imaging. Results At the 5-mm proximal edge, the only significant change was modest constrictive remodeling at 6 months (Δ vessel cross-sectional area: −1.80% [−3.18; 1.30], p < 0.05), with a tendency to regress at 1 year (Δ vessel cross-sectional area: −1.53% [−7.74; 2.48], p = 0.06). The relative change of the fibrotic and fibrofatty (FF) tissue areas at this segment were not statistically significant at either time point. At the 5-mm distal edge, a significant increase in the FF tissue of 43.32% [−19.90; 244.28], (p < 0.05) 1-year post-implantation was evident. The changes in dense calcium need to be interpreted with caution since the polymeric struts are detected as “pseudo” dense calcium structures with the VH-IVUS imaging modality. Conclusions The vascular response up to 1 year after implantation of the ABSORB BVS demonstrated some degree of proximal edge constrictive remodeling and distal edge increase in FF tissue resulting in nonsignificant plaque progression with adaptive expansive remodeling. This morphological and tissue composition behavior appears to not significantly differ from the behavior of metallic drug-eluting stents at the same observational time points.
Clinical trials have recently demonstrated that using a budesonide/formoterol combination inhaler as regular maintenance treatment twice daily but also as a rescue therapy for breakthrough symptoms can provide more effective control of asthma, particularly in reducing exacerbations, than using a short-acting beta2-agonist or formoterol as rescue therapy. This suggests that the corticosteroid component of the combination therapy plays an important role in rescue therapy. Formoterol as a rescue therapy is effective in relieving symptoms by relaxing airway smooth muscle but is also likely to have important inhibitory effects on mast cells, plasma exudation and neutrophilic inflammation. Inhaled corticosteroids have much more rapid suppressing effects on airway inflammation than previously recognised and the increased dose used as rescue therapy may prevent the increase in airway inflammation that occurs during the evolution of an exacerbation, thus preventing its development. It is likely that the molecular interactions between beta2-agonists and corticosteroids also enhance the effect of the combination therapy as rescue therapy. There is now a strong scientific rationale for single inhaler therapy in asthma, but more research is now needed to better understand the mechanisms involved.
