Density functional theory with B3LYP hybrid functional and all-electron basis set was applied to study the AlN (SWAlNNTs) and GaN (SWGaNNTs) single-walled nanotubes.The structural and electronic ...properties were analyzed in function of its diameter and chiralities. Additionally, the elastic and piezoelectric constants were calculated for armchair, zigzag and chiral nanotubes. The simulations showed that both, SWAlNNTs and SWGaNNTs, are easily formed from the graphene-like surface than from the respective bulk. As the diameter increases, the band gap energy also increases, but converges to the band gap energy of its precursor surface. The calculated elastic constants for bulk, graphene-like surface and nanotubes of AlN and GaN show that AlN, in all configurations, is more rigid than GaN. This effect can be related to the more pronounced ionic character of Al–N bond, which confers the stiffness of material. This stiffness affects the AlN nanotube formation, especially that with small diameter, that has the higher energy strain and formation energy for all chiralities. The AlN configurations have piezoelectric response ~ 25% greater than GaN. The AlN zigzag nanotube has the higher piezoelectric constant
e
11
, i.e., 0.84 C/m
2
. Compared to AlN bulk, the
e
11
of nanotube is less than the
e
33
of its bulk, 1.44 C/m
2
, but is higher when compared with the others’ piezoelectric constants of bulk and surface. Therefore, although the nanotubes present the same stability in diameters above 20 Å, AlN and GaN differ in their band gap energy, piezoelectric response and elastic constant, which will interfere directly with their application in electronic and piezoelectric devices, besides a possible functionalization, such as doping or molecule adsorption.
Autonomous radiation monitoring of small vessels Ziock, K.P.; Cheriyadat, A.; Fabris, L. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
10/2011, Letnik:
652, Številka:
1
Journal Article
Recenzirano
Small private vessels are one avenue by which nuclear materials may be smuggled across international borders. While one can contemplate using the land-based approach of radiation portal monitors on ...the navigable waterways that lead to many ports, these systems are ill-suited to the problem. In contrast to roadways, where lanes segregate vehicles, and motion is well controlled by inspection booths; channels, inlets, and rivers present chaotic traffic patterns populated by vessels of all sizes. A unique solution to this problem is based on a portal-less portal monitor designed to handle free-flowing traffic on roadways with up to five-traffic lanes. The instrument uses a combination of visible-light and gamma-ray imaging to acquire and link radiation images to individual vehicles. This paper presents the results of a recent test of the system in a maritime setting.
Tumour microenvironment is a complex, multicellular functional compartment that, particularly when assembled as an abundant desmoplastic reaction, may profoundly affect the proliferative and invasive ...abilities of epithelial cancer cells. Tumour microenvironment comprises not only stromal cells, mainly cancer‐associated fibroblasts, but also immune cells of both the innate and adaptive system (tumour‐associated macrophages, neutrophils, natural killer cells, and T and B lymphocytes), and endothelial cells. This results in an intricate web of mutual communications regulated by an extensively remodelled extracellular matrix, where the tumour cells are centrally engaged. In this regard, cholangiocarcinoma, in particular the intrahepatic variant, has become the focus of mounting interest in the last years, largely because of the lack of effective therapies despite its rising incidence and high mortality rates worldwide. On the other hand, recent studies in pancreatic cancer, which similarly to cholangiocarcinoma, is highly desmoplastic, have argued against a tumour‐promoting function of the tumour microenvironment. In this review, we will discuss recent developments concerning the role of each cellular population and their multifaceted interplay with the malignant biliary epithelial counterpart. We ultimately hope to provide the working knowledge on how their manipulation may lead to a therapeutic gain in cholangiocarcinoma.
Spinal anaesthesia is the most preferred anaesthetic technique for elective as well as for unplanned Caesarean sections. Spinal-induced hypotension remains the most important side effect with a ...reported incidence between 20% and 100%. It can cause -maternal discomfort (nausea and vomiting) and impaired utero-placental perfusion. The present study was designed to examine the influence of epidural volume effect on the spread and duration of low-dose hyperbaric levobupivacaine. The aim of this study was to evaluate the influence of epidural restriction (injection of saline) on the distribution of anaesthesia as well as the incidence of hypotension during the spinal anaesthesia.After the approval by the ethics committee, 60 full-term parturient women (ASA I or II) with uncomplicated pregnancies were prospectively randomized into 2 groups: the SA group (single shot spinal anaesthesia) included 37 patients and the CSE-EVR group (combined spinal-epidural anaesthesia) included 39 patients in whom we induced the restriction of the spinal space by epidural volume compression. The blocks were performed at the L2/3 or L3/4 level in a sitting position, in the CSE-EVR group using the needle-through-needle technique. The initial dose for CSE-EVR was exactly half of the SA dose (0.5 mg per 10 cm height of hyperbaric levobupivacaine and 20 microg fentanyl). After spinal injection, an epidural catheter was located in the CSE-EVR and a volume of 20 mL saline solution injected. After injection, the women were turned supine with a left uterine displacement. Surgery was allowed when a sensory block at or above the T8 dermatome was established. We evaluated the height of the block by the pinprick method and the motor block by the Bromage scale, 10 min after spinal injection, during the operation time and at the end of surgery. Haemodynamic monitoring (NIBP, HR) was assessed every 2 min until the childbirth, then every 5 min during operative time. Anaesthetic efficacy was evaluated for breakthrough pain by visual analogue pain score (VAPS), Apgar score at birth, umbilical artery pH, and epinephrine consumption.The level of anaesthesia 10 min after the induction was significantly higher in the spinal group (SA) than in the CSE-EVR T5 (T4-T7) vs. T7 (T6-T8) group.The SA group experienced complete motor block during the time of anaesthesia, while the CSE-EVR group demonstrated significantly faster motor recovery. The incidence of hypotension and ephedrine supplementation was significantly lower in the CSE-EVR group (19 vs. 35 patients) than in the SA group (p<0.05).The neonatal outcome and umbilical artery pH were higher in the CSE-EVR group. Both groups were comparable in demographic data, VAS scores, preloading and infusion volume, atropine or ephedrine use, and adverse effects such as nausea or skin pruritus.We demonstrated a possible restriction of the spread of spinal anaesthesia by using epidural volume restriction with 20 mL saline as part of a combined spinal epidural technique. The study shows that CSE with EVR using only 50% of the levobupivacaine dose provided adequate anaesthesia for elective Caesarean delivery, as well as better maternal haemodynamic stability.
We report the first measurement of coherent elastic neutrino-nucleus scattering (CEvNS) on argon using a liquid argon detector at the Oak Ridge National Laboratory Spallation Neutron Source. Two ...independent analyses prefer CEvNS over the background-only null hypothesis with greater than 3σ significance. The measured cross section, averaged over the incident neutrino flux, is (2.2±0.7)×10^{-39} cm^{2}-consistent with the standard model prediction. The neutron-number dependence of this result, together with that from our previous measurement on CsI, confirms the existence of the CEvNS process and provides improved constraints on nonstandard neutrino interactions.
Motivated by our previous work on pristine Na2SiO3, we proceeded with calculations on the structural, electronic, mechanical and piezoelectric properties of complex glass-like Na2Si1−xGexO3 (x = 0.0, ...0.25, 0.50, 0.75, 1.0) by using density functional theory (DFT). Interestingly, the optimized bond lengths and bond angles of Na2SiO3 and Na2GeO3 resemble each other with high similarity. On doping we report the negative formation energy and feasibility of transition of Na2SiO3 → Na2GeO3 while the structural symmetry is preserved. Analyzing the electronic profile, we have observed a reduced band gap on increasing x = Ge concentration at Si-sites. All the systems are indirect band gap (Z–Γ) semiconductors. The studied systems have shown mechanical stabilities by satisfying the Born criteria for mechanical stability. The calculated results have shown highly anisotropic behaviour and high melting temperature, which are a signature of glass materials. The piezoelectric tensor (both direct and converse) is computed. The results thus obtained predict that the systems under investigation are potential piezoelectric materials for energy harvesting.
We have constructed a unique instrument for use in the search for orphan sources. The system uses gamma-ray imaging to ldquosee throughrdquo the natural background variations that effectively limit ...the sensitivity of current devices. The imager is mounted in a 4.9-m-long trailer and can be towed by a large personal vehicle. Source locations are determined both in range and along the direction of travel as the vehicle moves. A fully inertial platform coupled to a Global Positioning System receiver is used to map the gamma-ray images onto overhead geospatial imagery. The resulting images provide precise source locations, allowing rapid follow-up work. The instrument simultaneously searches both sides of the street to a distance of 50 m (100-m swath) for millicurie-class sources with excellent performance as determined using source injection studies and receiver-operator-characteristic techniques.
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