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"Ida, M"
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Emergent de Sitter cosmology near black hole horizon
A
bstract
We propose an effective model for an exponentially expanding universe in the brane-world scenario. The setup consists of a 5D black hole and a brane close to the black hole horizon. In case the brane acquires a specific configuration, which we deduce from stability arguments, the induced metric outside the black hole horizon on the brane becomes de Sitter in static coordinates. Studying the Einstein equations perturbatively we find the effective gravity on the brane at this level and derive the 4D gravitational constant. Considering a homogeneous and isotropic fluid in the corresponding FLRW coordinates we find that the bulk fluid density inside the brane, which has the same equation of state as the fluid on the brane, contributes to the energy density in the Friedmann equation and therefore in late time may be attributed to dark matter. Studying the stability of the setup we observe that the brane becomes stabilized, in the presence of matter on the brane, with a de Sitter length that is qualitatively of the order of Schwarzschild radius of the universe due to matter. We briefly discuss effects that can bound the de Sitter lifetime. In particular this model can provide a lifetime compatible with Trans-Planckian Censorship conjecture for the current de Sitter phase.
Journal Article
Graphene Oxide (GO): A Promising Nanomaterial against Infectious Diseases Caused by Multidrug-Resistant Bacteria
Infectious diseases are major threat due to it being the main cause of enormous morbidity and mortality in the world. Multidrug-resistant (MDR) bacteria put an additional burden of infection leading to inferior treatment by the antibiotics of the latest generations. The emergence and spread of MDR bacteria (so-called “superbugs”), due to mutations in the bacteria and overuse of antibiotics, should be considered a serious concern. Recently, the rapid advancement of nanoscience and nanotechnology has produced several antimicrobial nanoparticles. It has been suggested that nanoparticles rely on very different mechanisms of antibacterial activity when compared to antibiotics. Graphene-based nanomaterials are fast emerging as “two-dimensional wonder materials” due to their unique structure and excellent mechanical, optical and electrical properties and have been exploited in electronics and other fields. Emerging trends show that their exceptional properties can be exploited for biomedical applications, especially in drug delivery and tissue engineering. Moreover, graphene derivatives were found to have in vitro antibacterial properties. In the recent years, there have been many studies demonstrating the antibacterial effects of GO on various types of bacteria. In this review article, we will be focusing on the aforementioned studies, focusing on the mechanisms, difference between the studies, limitations and future directions.
Journal Article
Carotid plaque thickness is increased in chronic kidney disease and associated with carotid and coronary calcification
Chronic kidney disease accelerates both atherosclerosis and arterial calcification. The aim of the present study was to explore whether maximal carotid plaque thickness (cPTmax) was increased in patients with chronic kidney disease compared to controls and associated with cardiovascular disease and severity of calcification in the carotid and coronary arteries.
The study group consisted of 200 patients with chronic kidney disease stage 3 from the Copenhagen Chronic Kidney Disease Cohort and 121 age- and sex-matched controls. cPTmax was assessed by ultrasound and arterial calcification by computed tomography scanning.
Carotid plaques were present in 58% of patients (n = 115) compared with 40% of controls (n = 48), p = 0.002. Among participants with plaques, cPTmax (median, interquartile range) was significantly higher in patients compared with controls (1.9 (1.4-2.3) versus 1.5 (1.2-1.8) mm), p = 0.001. Cardiovascular disease was present in 9% of patients without plaques (n = 85), 23% of patients with cPTmax 1.0-1.9 mm (n = 69) and 35% of patients with cPTmax >1.9 mm (n = 46), p = 0.001. Carotid and coronary calcium scores >400 were present in 0% and 4%, respectively, of patients with no carotid plaques, in 19% and 24% of patients with cPTmax 1.0-1.9 mm, and in 48% and 53% of patients with cPTmax >1.9 mm, p<0.001.
This is the first study showing that cPTmax is increased in patients with chronic kidney disease stage 3 compared to controls and closely associated with prevalent cardiovascular disease and severity of calcification in both the carotid and coronary arteries.
Journal Article
On torsion contribution to chiral anomaly via Nieh–Yan term
In this note we present a solution to the question of whether or not, in the presence of torsion, the topological Nieh–Yan term contributes to chiral anomaly. The integral of Nieh–Yan term is non-zero if topology is non-trivial; the manifold has a boundary or vierbeins have singularities. Noting that singular Nieh–Yan term could be written as a sum of delta functions, we argue that the heat kernel expansion cannot end at finite steps. This leads to a sinusoidal dependence on the Nieh–Yan term and the UV cut-off of the theory (or alternatively the minimum length of spacetime). We show this ill-behaved dependence can be removed if a quantization condition on length scales is applied. It is expected as the Nieh–Yan term can be derived as the difference of two Chern class integrals (i.e. Pontryagin terms). On the other hand, in the presence of a cosmological constant, we find that indeed the Nieh–Yan term contributes to the index with a dimensionful anomaly coefficient that depends on the de Sitter length or equivalently inverse Hubble rate. We find similar result in thermal field theory where the anomaly coefficient depends on temperature. In both examples, the anomaly coefficient depends on IR cut-off of the theory. Without singularities, the Nieh–Yan term can be smoothly rotated away, does not contribute to topological structure and consequently does not contribute to chiral anomaly.
Journal Article
Viral Loads and Duration of Viral Shedding in Adult Patients Hospitalized with Influenza
BackgroundThe goal of this study was to characterize viral loads and factors affecting viral clearance in persons with severe influenza MethodsThis was a 1-year prospective, observational study involving consecutive adults hospitalized with influenza. Nasal and throat swabs were collected at presentation, then daily until 1 week after symptom onset. Real-time reverse-transcriptase polymerase chain reaction to determine viral RNA concentration and virus isolation were performed. Viral RNA concentration was analyzed using multiple linear or logistic regressions or mixed-effect models ResultsOne hundred forty-seven inpatients with influenza A (H3N2) infection were studied (mean age ± standard deviation, 72±16 years). Viral RNA concentration at presentation positively correlated with symptom scores and was significantly higher than that among time-matched outpatients (control subjects). Patients with major comorbidities had high viral RNA concentration even when presenting >2 days after symptom onset (mean ± standard deviation, 5.06±1.85 vs 3.62±2.13 log10 copies/mL; P=.005; β, +0.86 [95% confidence interval, +0.03 to +1.68]). Viral RNA concentration demonstrated a nonlinear decrease with time; 26% of oseltamivir-treated and 57% of untreated patients had RNA detected at 1 week after symptom onset. Oseltamivir started on or before symptom day 4 was independently associated with an accelerated decrease in viral RNA concentration (mean β [standard error], −1.19 [0.43] and −0.68 [0.33] log10 copies/mL for patients treated on day 1 and days 2–3, respectively; P<.05) and viral RNA clearance at 1 week (odds ratio, 0.10 [95% confidence interval, 0.03–0.35] and 0.30 [0.10–0.90] for patients treated on day 1–2 and day 3–4, respectively). Conversely, major comorbidities and systemic corticosteroid use for asthma or chronic obstructive pulmonary disease exacerbations were associated with slower viral clearance. Viral RNA clearance was associated with a shorter hospital stay (7.0 vs 13.5 days; P=.001) ConclusionPatients hospitalized with severe influenza have more active and prolonged viral replication. Weakened host defenses slow viral clearance, whereas antivirals started within the first 4 days of illness enhance viral clearance
Journal Article
Naturalistic stimuli reveal a dominant role for agentic action in visual representation
Naturalistic, dynamic movies evoke strong, consistent, and information-rich patterns of activity over a broad expanse of cortex and engage multiple perceptual and cognitive systems in parallel. The use of naturalistic stimuli enables functional brain imaging research to explore cognitive domains that are poorly sampled in highly-controlled experiments. These domains include perception and understanding of agentic action, which plays a larger role in visual representation than was appreciated from experiments using static, controlled stimuli.
•Responses evoked by movies reflect agentic action across a large expanse of cortex.•Agentic action dominates representations in both dorsal and ventral visual pathways.•Representation of action in the ventral pathway is consistent with prior literature.
Journal Article
Synthesis of a copper-supported triplet nitrene complex pertinent to copper-catalyzed amination
Terminal copper-nitrenoid complexes have inspired interest in their fundamental bonding structures as well as their putative intermediacy in catalytic nitrene-transfer reactions. Here, we report that aryl azides react with a copper(I) dinitrogen complex bearing a sterically encumbered dipyrrin ligand to produce terminal copper nitrene complexes with near-linear, short copper–nitrenoid bonds [1.745(2) to 1.759(2) angstroms]. X-ray absorption spectroscopy and quantum chemistry calculations reveal a predominantly triplet nitrene adduct bound to copper(I), as opposed to copper(II) or copper(III) assignments, indicating the absence of a copper–nitrogen multiple-bond character. Employing electron-deficient aryl azides renders the copper nitrene species competent for alkane amination and alkene aziridination, lending further credence to the intermediacy of this species in proposed nitrene-transfer mechanisms.
Journal Article
Carotid plaque thickness predicts cardiovascular events and death in patients with chronic kidney disease
Background
Classical risk scoring systems underestimate the risk of cardiovascular disease in chronic kidney disease (CKD). Coronary artery calcium score (CACS) has improved prediction of cardiovascular events in patients with CKD. The maximal carotid plaque thickness (cPTmax) measured in ultrasound scans of the carotid arteries has demonstrated similar predictive value as CACS in the general population. This is the first study to investigate whether cPTmax can predict cardiovascular events in CKD and to compare the predictive value of cPTmax and CACS in CKD.
Method
Two hundred patients with CKD stage 3 from the Copenhagen CKD Cohort underwent ultrasound scanning of the carotid arteries. The assessment consisted of locating plaque and measuring the thickest part of the plaque, cPTmax. Based on the distribution of cPTmax, the participants were divided into 3 groups: No plaques, cPTmax 1.0–1.9 mm and cPTmax > 1.9 mm (median cPTmax = 1.9 mm among patients with plaques). To measure CACS, 175 of the patients underwent a non-contrast CT scan of the coronary arteries. The follow-up time spanned between the ultrasound scan and a predefined end-date or the time of first event, defined as a composite of major cardiovascular events or death of any cause (MACE).
Results
The median follow-up time was 5.4 years during which 45 patients (22.5%) developed MACE. In a Cox-regression adjusted for classical cardiovascular risk factors, patients with cPTmax > 1.9 mm had a significantly increased hazard ratio of MACE (HR 3.2, CI: 1.1–9.3),
p
= 0.031) compared to patients without plaques. C-statistics was used to evaluate models for predicting MACE. The improvement in C-statistics was similar for the two models including classical cardiovascular risk factors plus cPTmax (0.247, CI: 0.181–0.312) and CACS (0.243, CI: 0.172–0.315), respectively, when compared to a model only controlled for time since baseline (a Cox model with no covariates).
Conclusion
Our results indicate that cPTmax may be useful for predicting MACE in CKD. cPTmax and CACS showed similar ability to predict MACE.
Journal Article