Raman scattering efficiency of graphene Klar, P.; Lidorikis, E.; Eckmann, A. ...
Physical review. B, Condensed matter and materials physics,
05/2013, Letnik:
87, Številka:
20
Journal Article
Recenzirano
Odprti dostop
We determine the Raman scattering efficiency of the G and 2D peaks in graphene. Three substrates are used: silicon covered with 300 or 90 nm oxide, and calcium fluoride (CaF sub(2)). On Si/SiO ...sub(x), the areas of the G and 2D peak show a strong dependence on the substrate due to interference effects, while on CaF sub(2) no significant dependence is detected. Unintentional doping is reduced by placing graphene on CaF sub(2). We determine the Raman scattering efficiency by comparison with the 322 cm super(-1) peak area of CaF sub(2). At 2.41 eV, the Raman efficiency of the G peak is ~ 200 x 10 super(-5) m super(-1)Sr super(-1), and changes with the excitation energy to the power of 4. The 2D Raman efficiency is at least one order of magnitude higher than that of the G peak, with a different excitation energy dependence.
We study the statistical mechanics of a finite-dimensional non-linear Hamiltonian system (a chain of anharmonic oscillators) coupled to two heat baths (described by wave equations). Assuming that the ...initial conditions of the heat baths are distributed according to the Gibbs measures at two different temperatures we study the dynamics of the oscillators. Under suitable assumptions on the potential and on the coupling between the chain and the heat baths, we prove the existence of an invariant measure for any temperature difference, i.e., we prove the existence of steady states. Furthermore, if the temperature difference is sufficiently small, we prove that the invariant measure is unique and mixing. In particular, we develop new techniques for proving the existence of invariant measures for random processes on a non-compact phase space. These techniques are based on an extension of the commutator method of H\\örmander used in the study of hypoelliptic differential operators.
Abstract Background Assessment of the pattern of the RV outflow tract Doppler provides insights into the hemodynamics of chronic thromboembolic pulmonary hypertension (CTEPH). We studied whether ...pre-operative assessment of timing of the pulmonary flow systolic notch by Doppler echocardiography is associated with long-term survival after pulmonary endarterectomy (PEA) for CTEPH. Methods Fifty-nine out of 61 consecutive CETPH patients (mean age 53 ± 14 years, 34% male) whom underwent PEA between June 2002 and June 2005 were studied. Clinical, echocardiographic and hemodynamic variables were assessed pre-operatively and repeat echocardiography was performed 3 months after PEA. Notch ratio (NR) was assessed with pulsed Doppler and calculated as the time from onset of pulmonary flow until notch divided by the time from notch until end of pulmonary flow. Long-term follow-up was obtained between May 2021 and February 2022. Results Pre-operative mean pulmonary artery pressure (mPAP) was 45 ± 15 mmHg and pulmonary vascular resistance (PVR) was 646 ± 454 dynes.s.cm-5. Echocardiography before PEA showed that 7 patients had no notch, 33 had a NR < 1.0 and 19 had a NR > 1.0. Three months after PEA, echocardiography revealed a significant decrease in sPAP in long-term survivors with a NR < 1.0 and a NR > 1.0, while a significant increase in TAPSE/sPAP was only observed in the NR < 1.0 group. Mean long-term clinical follow-up was 14 ± 6 years. NR was significantly different between survivors and non-survivors (0.73 ± 0.25 vs. 1.1 ± 0.44, p < 0.001) but no significant differences were observed in mPAP or PVR. Long-term survival at 14 years was significantly better in patients with a NR < 1.0 compared to patients with a NR > 1.0 (83% vs. 37%, p = < 0.001). Conclusion Pre-operative assessment of NR is a predictor of long-term survival in CTEPH patients undergoing PEA, with low mortality risk in patients with NR < 1.0. Long-term survivors with a NR < 1.0 and NR > 1.0 had a significant decrease in sPAP after PEA. However, the TAPSE/sPAP only significantly increased in the NR < 1.0 group. In the NR < 1.0 group, the 6-min walk test increased significantly between pre-operative and at 1-year post-operative follow-up. NR is a simple echocardiographic parameter that can be used in clinical decision-making for PEA.
Summary Ulcerative colitis is an idiopathic, chronic inflammatory disorder of the colonic mucosa, which starts in the rectum and generally extends proximally in a continuous manner through part of, ...or the entire, colon; however, some patients with proctitis or left-sided colitis might have a caecal patch of inflammation. Bloody diarrhoea is the characteristic symptom of the disease. The clinical course is unpredictable, marked by alternating periods of exacerbation and remission. In this Seminar we discuss the epidemiology, pathophysiology, diagnostic approach, natural history, medical and surgical management, and main disease-related complications of ulcerative colitis, and briefly outline novel treatment options. Enhanced understanding of how the interaction between environmental factors, genetics, and the immune system results in mucosal inflammation has increased knowledge of disease pathophysiology. We provide practical therapeutic algorithms that are easily applicable in daily clinical practice, emphasising present controversies in treatment management and novel therapies.
Abstract
Introduction
The notch ratio (NR) in the pulmonary flow predicts in-hospital mortality after pulmonary endarterectomy (PEA) for chronic thrombotic pulmonary hypertension (CTEPH).
Purpose
We ...studied whether the echocardiographic parameter NR can also discriminate long term outcome.
Methods
All patients who underwent PEA between June 2002 and June 2005 were studied. Clinical, hemodynamic and echocardiographic variables were assessed pre-operatively and at 3 months post-PEA. Clinical follow up ended in March 2022. NR was the time from onset pulmonary flow until notch divided by the time from notch until end of pulmonary flow assessed with pulsed Doppler.
Results
A total of 59 patient are included in this analysis. Mean age was 53±14 years, 34% were male patients and 66% of patients were NYHA class III or IV. Pre-operative mean pulmonary artery pressure (mPAP) was 45±15 mmHg and calculated total pulmonary resistance (TPR) was 870±511 dynes s cm–5. Pre-operatively, 7 patients had no notch, 33 had NR <1.0 and 19 had NR >1.
Six patients died in hospital and a total of 19 patients died during the follow up till March 2022. Between survivors and non-survivors, no significant differences were observed in 6-minute walking distance (409±114 m. vs. 364±110 m., p=0.22), plasma BNP (34±47 pmol/l vs. 57±52 pmol/l, p=0.10), mean PAP (43±14 mmHg vs. 49±15 mmHg, p=0.14), TPR (793±493 dynes s cm–5 vs. 1015±525 dynes s cm–5, p=0.13). NR was significant different between survivors and non-survivors (0.73±0.25 vs. 1.1±0.44, p<0.001).
Mean very long term follow-up of 14±6 years. The 1, 5, 8 and 14 year survival for patients with a NR <1 was respectively 100%, 100%, 95% and 83% was significantly better (p≤0.001) then for patients with a NR >1 (1, 5, 8 and 14 year survival was 68%, 53%, 42% and 37%, respectively). For patients without a notch (1, 5 and 8 year survival was 100% and 14 year survival was 86%).
Conclusion
NR predicts in-hospital and long term mortality in CTEPH patients undergoing PEA. NR >1.0 is associated with a higher risk of mortality. NR is a simple echocardiographic parameter that can be used in clinical decision making for PEA.
Funding Acknowledgement
Type of funding sources: None.
The isolation of various two-dimensional (2D) materials, and the possibility to combine them in vertical stacks, has created a new paradigm in materials science: heterostructures based on 2D ...crystals. Such a concept has already proven fruitful for a number of electronic applications in the area of ultrathin and flexible devices. Here, we expand the range of such structures to photoactive ones by using semiconducting transition metal dichalcogenides (TMDCs)/graphene stacks. Van Hove singularities in the electronic density of states of TMDC guarantees enhanced light-matter interactions, leading to enhanced photon absorption and electron-hole creation (which are collected in transparent graphene electrodes). This allows development of extremely efficient flexible photovoltaic devices with photoresponsivity above 0.1 ampere per watt (corresponding to an external quantum efficiency of above 30%).
Necrotizing skin and soft-tissue infections (NSTI) are rare but potentially life-threatening and disabling infections that often require intensive care unit admission.
To review all aspects of care ...for a critically ill individual with NSTI.
Literature search using Medline and Cochrane library, multidisciplinary panel of experts.
The initial presentation of a patient with NSTI can be misleading, as features of severe systemic toxicity can obscure sometimes less impressive skin findings. The infection can spread rapidly, and delayed surgery worsens prognosis, hence there is a limited role for additional imaging in the critically ill patient. Also, the utility of clinical scores is contested. Prompt surgery with aggressive debridement of necrotic tissue is required for source control and allows for microbiological sampling. Also, prompt administration of broad-spectrum antimicrobial therapy is warranted, with the addition of clindamycin for its effect on toxin production, both in empirical therapy, and in targeted therapy for monomicrobial group A streptococcal and clostridial NSTI. The role of immunoglobulins and hyperbaric oxygen therapy remains controversial.
Close collaboration between intensive care, surgery, microbiology and infectious diseases, and centralization of care is fundamental in the approach to the severely ill patient with NSTI. As many aspects of management of these rare infections are supported by low-quality data only, multicentre trials are urgently needed.
We study metastable behavior in a discrete nonlinear Schrödinger equation from the viewpoint of Hamiltonian systems theory. When there are
n
<
∞
sites in this equation, we consider initial conditions ...in which almost all the energy is concentrated in one end of the system. We are interested in understanding how energy flows through the system, so we add a dissipation of size
γ
at the opposite end of the chain, and we show that the energy decreases extremely slowly. Furthermore, the motion is localized in the phase space near a family of breather solutions for the undamped system. We give rigorous, asymptotic estimates for the rate of evolution along the family of breathers and the width of the neighborhood within which the trajectory is confined.
Bacterial communities directly influence ecological processes in the ocean, and depth has a major influence due to the changeover in primary energy sources between the sunlit photic zone and dark ...ocean. Here, we examine the abundance and diversity of bacteria in Monterey Bay depth profiles collected from the surface to just above the sediments (e.g., 2000 m). Bacterial abundance in these Pacific Ocean samples decreased by >1 order of magnitude, from 1.22 ±0.69 ×106 cells ml-1 in the variable photic zone to 1.44 ± 0.25 ×105 and 6.71 ± 1.23 ×104 cells ml-1 in the mesopelagic and bathypelagic, respectively. V1-V2 16S rRNA gene profiling showed diversity increased sharply between the photic and mesopelagic zones. Weighted Gene Correlation Network Analysis clustered co-occurring bacterial amplicon sequence variants (ASVs) into seven subnetwork modules, of which five strongly correlated with depth-related factors. Within surface-associated modules there was a clear distinction between a 'copiotrophic' module, correlating with chlorophyll and dominated by e.g., Flavobacteriales and Rhodobacteraceae, and an 'oligotrophic' module dominated by diverse Oceanospirillales (such as uncultured JL-ETNP-Y6, SAR86) and Pelagibacterales. Phylogenetic reconstructions of Pelagibacterales and SAR324 using full-length 16S rRNA gene data revealed several additional subclades, expanding known microdiversity within these abundant lineages, including new Pelagibacterales subclades Ia.B, Id, and IIc, which comprised 4-10% of amplicons depending on the subclade and depth zone. SAR324 and Oceanospirillales dominated in the mesopelagic, with SAR324 clade II exhibiting its highest relative abundances (17±4%) in the lower mesopelagic (300-750 m). The two newly-identified SAR324 clades showed highest relative abundances in the photic zone (clade III), while clade IV was extremely low in relative abundance, but present across dark ocean depths. Hierarchical clustering placed microbial communities from 900 m samples with those from the bathypelagic, where Marinimicrobia was distinctively relatively abundant. The patterns resolved herein, through high resolution and statistical replication, establish baselines for marine bacterial abundance and taxonomic distributions across the Monterey Bay water column, against which future change can be assessed.
Lysozyme dextran nanogels (NG) have great potential in vitro as a drug delivery platform, combining simple chemistry with rapid uptake and cargo release in target cells with "stealth" properties and ...low toxicity. In this work, we study for the first time the potential of targeted NG as a drug delivery platform in vivo to alleviate acute pulmonary inflammation in animal model of LPS-induced lung injury. NG are targeted to the endothelium via conjugation with an antibody (Ab) directed to Intercellular Adhesion Molecule-1(ICAM-NG), whereas IgG conjugated NG (IgG-NG) are used for control formulations. The amount of Ab conjugated to the NG and distribution in the body after intravenous (IV) injection have been quantitatively analyzed using a tracer isotope-labeled 125IIgG. As a proof of concept, Ab-NG are loaded with dexamethasone, an anti-inflammatory therapeutic, and the drug uptake and release kinetics are measured by HPLC. In vivo studies in mice showed that: i) ICAM-NG accumulates in mouse lungs (∼120% ID/g vs ∼15% ID/g of IgG-NG); and, ii) DEX encapsulated in ICAM-NG, but not in IgG-NG practically blocks LPS-induced overexpression of pro-inflammatory cell adhesion molecules including ICAM-1 in the pulmonary inflammation.
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