Ultrafast Optical Spectroscopy of Micelle-Suspended Single-Walled Carbon Nanotubes

We present results of wavelength-dependent ultrafast pump-probe experiments on micelle-suspended single-walled carbon nanotubes. The linear absorption and photoluminescence spectra of the samples show a number of chirality-dependent peaks, and consequently, the pump-probe results sensitively depend on the wavelength. In the wavelength range corresponding to the second van Hove singularities (VHSs), we observe sub-picosecond decays, as has been seen in previous pump-probe studies. We ascribe these ultrafast decays to intraband carrier relaxation. On the other hand, in the wavelength range corresponding to the first VHSs, we observe two distinct regimes in ultrafast carrier relaxation: fast (0.3-1.2 ps) and slow (5-20 ps). The slow component, which has not been observed previously, is resonantly enhanced whenever the pump photon energy resonates with an interband absorption peak, and we attribute it to radiative carrier recombination. Finally, the slow component is dependent on the pH of the solution, which suggests an important role played by H$^+$ ions surrounding the nanotubes.Comment: 6 pages, 8 figures, changed title, revised, to be published in Applied Physics

EPIdemiology of Surgery-Associated Acute Kidney Injury (EPIS-AKI) : Study protocol for a multicentre, observational trial

More than 300 million surgical procedures are performed each year. Acute kidney injury (AKI) is a common complication after major surgery and is associated with adverse short-term and long-term outcomes. However, there is a large variation in the incidence of reported AKI rates. The establishment of an accurate epidemiology of surgery-associated AKI is important for healthcare policy, quality initiatives, clinical trials, as well as for improving guidelines. The objective of the Epidemiology of Surgery-associated Acute Kidney Injury (EPIS-AKI) trial is to prospectively evaluate the epidemiology of AKI after major surgery using the latest Kidney Disease: Improving Global Outcomes (KDIGO) consensus definition of AKI. EPIS-AKI is an international prospective, observational, multicentre cohort study including 10 000 patients undergoing major surgery who are subsequently admitted to the ICU or a similar high dependency unit. The primary endpoint is the incidence of AKI within 72 hours after surgery according to the KDIGO criteria. Secondary endpoints include use of renal replacement therapy (RRT), mortality during ICU and hospital stay, length of ICU and hospital stay and major adverse kidney events (combined endpoint consisting of persistent renal dysfunction, RRT and mortality) at day 90. Further, we will evaluate preoperative and intraoperative risk factors affecting the incidence of postoperative AKI. In an add-on analysis, we will assess urinary biomarkers for early detection of AKI. EPIS-AKI has been approved by the leading Ethics Committee of the Medical Council North Rhine-Westphalia, of the Westphalian Wilhelms-University Münster and the corresponding Ethics Committee at each participating site. Results will be disseminated widely and published in peer-reviewed journals, presented at conferences and used to design further AKI-related trials. Trial registration number NCT04165369

Structure and function of glucose binding protein-single walled carbon nanotube complexes.

Understanding the structure and function of glucose binding proteins (GBP) complexed with single walled carbon nanotubes (SWNTs) is important for the development of applications including fluorescent sensors and nanostructure particle tracking. Herein, circular dichroism (CD), thermal denaturation, photo-absorption spectroscopy and atomic force microscopy are used to study these nanostructures. The protein retains its glucose-binding activity after complexation and is thermally stable below 36 °C. However, the SWNT lowers the midpoint denaturation temperature (Tm) by 5 °C and 4 °C in the absence and presence of 10 mM glucose, respectively. This data highlights that using techniques such as CD and thermal denaturation may be necessary to fully characterize such protein-nanomaterial nanostructures

Fine Structure of the Dorsal Surface of Ostrich`s (Struthio camelus) Tongue

The tongue of birds fills the oral cavity and has a beak-like shape. Morphological studies of birds reveal a correlation between the structure of the tongue and the mechanism of food intake and the type of food. However, several studies have shown morphological differences among the tongues of bird species. The aim of this study was to analyze ostrich tongue morphology and ultrastructural features using scanning electron microscopy. Tongues from 12 adult ostriches were examined. Six tongues were sectioned sagittally into lateral and middle portions, fixed in 10% formaldehyde solution, and examined under light microscopy. The other six samples were sectioned longitudinally, and the dorsal and ventral surfaces were separated, Immersion-fixed In modified Karnovsky solution, and examined under scanning electron microscopy. The tongue surface of the ostrich was smooth, without lingual papillae, and covered by stratified non-keratinized epithelium. In the submucosal layer, mucous salivary glands were surrounded by connective-tissue capsules, with septa dividing the glands Into lobes. Numerous salivary gland ducts of different sizes and connective-tissue laminae dividing each opening could be clearly seen in scanning electron microscope Images. The ventral surface had fewer openings than the dorsal surface. In samples treated with NaOH, connective-tissue papillae from the dorsal region were oriented posteriorly

Insight into the reaction dynamics of proton drip-line nuclear system .sup.17F+.sup.58Ni at near-barrier energies

The mechanism of reactions with weakly-bound proton-rich nuclei at energies near the Coulomb barrier is a long-standing open question owing to the paucity of experimental data. In this study, a complete kinematics measurement was performed for the proton drip-line nucleus .sup.17F interacting with .sup.58Ni at four energies near the Coulomb barrier. Thanks to the powerful performance of the detector array, exhaustive information on the reaction channels, such as the differential cross sections for quasielastic scattering, exclusive and inclusive breakup, as well as for fusion-evaporation protons and alphas, was derived for the first time. The angular distributions of quasielastic scattering and exclusive breakup can be described reasonably well by the continuum-discretized coupled-channels calculations. The inclusive breakup was investigated using the three-body model proposed by Ichimura, Austern, and Vincent, and results indicate the non-elastic breakup is the dominant component. The total fusion cross sections were determined by the fusion-evaporation protons and alphas. Based on the measured exclusive breakup data, the analysis of the classical dynamical simulation code PLATYPUS demonstrates that the incomplete fusion plays a minor role. Moreover, compared with .sup.16O+.sup.58Ni, both the reaction and total fusion cross sections of .sup.17F+.sup.58Ni exhibit an enhancement in the sub-barrier energy region, which mainly arises from couplings to the continuum states. This work indicates that the information of full reaction channels is crucially important to comprehensively understand the reaction mechanisms of weakly bound nuclear systems.Academi

Dimer-covering resonating-valence-bond treatment of single-walled zigzag carbon nanotubes

Single-walled zigzag carbon nanotubes with h hexagons around the carbon nanotube, h ranging from 3 to 19, have been investigated from a resonating-valence-bond point of view. The energies calculated for the undoped h=3n–1 zigzag carbon nanotubes, n integer, suggest that the two lowest-lying phases are degenerate. Therefore, de-confined low-energy topological spin defects would occur. Then, these carbon nanotubes should be conductors, in analogy to polyacethylene. In clear contrast, no such degeneracy is obtained for either, h=3n+1 or h=3n, so bound pairs of topological spin defects are expected to occur in these cases. Our findings provide further insights into electron correlation and exchange effects in carbon nanotubes. Copyright EDP Sciences, SIF, Springer-Verlag Berlin Heidelberg 2011