Analyzing the Bolometric Performance of Vanadium Oxide Thin Films Modified by Carbon Nanotube Dispersions.

The influence of carbon nanotube (CNT) dispersions on the electrical properties and noise signal amplitude of VOx films is investigated. For a critical range of the CNT dispersion density on VOx films, the intrinsic properties of the VOx films are modified by the CNTs. The CNT concentrations reported in this work are about 0.3 µg/cm2 and 1.6 µg/cm2, allowing for low density and high density dispersions on the VOx film surface to be investigated. These values are higher than the percolation threshold of about 0.12 µg/cm2 for these films. The composite film exhibits a significant reduction in the temperature coefficient of resistance (TCR) (from ≈3.8% K-1 to ≈0.3% K-1) for high density dispersions. In contrast, while VOx-CNT composites with low density single wall CNT dispersions exhibit no significant change in TCR values, an approximate two orders of magnitude reduction in the low frequency 1/f noise is measured. The noise signal amplitude measured at 0.1 V and at 1.0 Hz reduces from 6 × 10-5V/(Hz) for VOx films to 5 × 10-7V/(Hz) for the low density SWCNT dispersion on VOx film and to 3 × 10-6V/(Hz) for the low density MWCNT dispersion on VOx film. The CNT concentration is the critical factor for yielding the observed changes in conductivity and low frequency noise. The results presented in this work provide a better understanding of VOx-based composites, thereby enabling the development of new, versatile and functional materials for device applications.

Growth of Highly-Ordered Metal Nanoparticle Arrays in the Dimpled Pores of an Anodic Aluminum Oxide Template.

A reliable, scalable, and inexpensive technology for the fabrication of ordered arrays of metal nanoparticles with large areal coverage on various substrates is presented. The nanoparticle arrays were formed on aluminum substrates using a two-step anodization process. By varying the anodization potential, the pore diameter, inter-pore spacing, and pore ordering in the anodic aluminum oxide (AAO) template were tuned. Following a chemical etch, the height of the pores in the AAO membrane were reduced to create a dimpled membrane surface. Periodic arrays of metal nanoparticles were subsequently created by evaporating metal on to the dimpled surface, allowing for individual nanoparticles to form within the dimples by a solid state de-wetting process induced by annealing. The ordered nanoparticle array could then be transferred to a substrate of choice using a polymer lift-off method. Following optimization of the experimental parameters, it was possible to obtain cm2 coverage of metal nanoparticles, like gold and indium, on silicon, quartz and sapphire substrates, with average sizes in the range of 50-90 nm. The de-wetting process was investigated for a specific geometry of the dimpled surface and the results explained for two different film thicknesses. Using a simple model, the experimental results were interpreted and supported by numerical estimations.

Impedance Analysis and Noise Measurements on Multi Walled Carbon Nanotube Networks.

The electrical impedance characteristics of multi-walled carbon nanotube (MWCNTs) networks were studied as a function of CNT concentrations in the frequency range of 1 kHz-1 MHz. The novelty of this study is that the MWCNTs were not embedded in any polymer matrix and so the response of the device to electrical measurements are attributed to the CNTs in the network without any contribution from a polymer host matrix. Devices with low MWCNT packing density (0.31-0.85 µg/cm2) exhibit a frequency independent plateau in the low-frequency regime. At higher frequencies, the AC conductivity of these devices increases following a power law, characteristic of the universal dynamic response (UDR) phenomenon. On the other hand, devices with high MWCNT concentrations (>1.0 µg/cm2) exhibit frequency independent conductivity over the entire frequency range (up to 1 MHz), indicating that conduction in these devices is due to direct contact between the CNTs in the network. A simple single-relaxation time electrical equivalent circuit with an effective resistance and capacitance is used to describe the device performance. The electrical noise measurements on devices with different MWCNT packing densities exhibit bias-dependent low-frequency 1/f noise, attributed to resistance fluctuations.

Analyzing growth kinematics and fractal dimensions of molybdenum disulfide films.

Though the positive role of alkali halides in realizing large area growth of transition metal dichalcogenide layers has been validated, the film-growth kinematics has not yet been fully established. This work presents a systematic analysis of the MoS2morphology for films grown under various pre-treatment conditions of the substrate with sodium chloride (NaCl). At an optimum NaCl concentration, the domain size of the monolayer increased by almost two orders of magnitude compared to alkali-free growth of MoS2. The results show an inverse relationship between fractal dimension and areal coverage of the substrate with monolayers and multi-layers, respectively. Using the Fact-Sage software, the role of NaCl in determining the partial pressures of Mo- and S-based compounds in gaseous phase at the growth temperature is elucidated. The presence of alkali salts is shown to affect the domain size and film morphology by affecting the Mo and S partial pressures. Compared to alkali-free synthesis under the same growth conditions, MoS2film growth assisted by NaCl results in ≈81% of the substrate covered by monolayers. Under ideal growth conditions, at an optimum NaCl concentration, nucleation was suppressed, and domains enlarged, resulting in large area growth of MoS2monolayers. No evidence of alkali or halogen atoms were found in the composition analysis of the films. On the basis of Raman spectroscopy and photoluminescence measurements, the MoS2films were found to be of good crystalline quality.

Late onset metastasis from renal cell carcinoma masquerading as a gallbladder polyp.

Renal cell carcinoma (RCC) accounts for approximately 3% of all adult malignancies. A third of people with RCC have metastatic lesions when diagnosed, and another third develop metachronous metastasis during follow-up or after surgical treatment. We report a case of gallbladder metastasis from clear-cell RCC in a 71-year-old woman 13 years after RCC of her right kidney. Preoperative imaging studies showed a suspicious, progressively enlarged gallbladder polyp. The patient underwent open cholecystectomy and lymph node dissection along the hepatoduodenal ligament. The pathology report was compatible with metastatic disease from the kidney that was previously resected. Gallbladder metastasis can occur from RCC several years after initial management. Physicians should be aware of this rare pathology, and intensive follow-up is essential after surgery for RCC.

Minimally invasive oesophagectomy for cancer in patients with HIV/AIDS: considerations and future directions.

The impact of HIV/AIDS on the treatment of oesophageal neoplasms remains undefined due to a lack of adequate data. We present our experience in treating patients with HIV/AIDS who have oesophageal cancer using minimally invasive techniques and discuss important key factors during perioperative management. Two men with HIV/AIDS underwent minimally invasive oesophagectomies in our department, with adequate clinical and oncological outcomes. Minimally invasive oesophagectomy can be safe and has the well-established benefits of minimally invasive techniques, offering good perioperative results and oncological outcomes in patients with HIV/AIDS. Multimodality therapy is crucial.

Laparoscopic repair of late perforation following Heller myotomy due to overeating.

Laparoscopic Heller myotomy is the mainstay surgical treatment of oesophageal achalasia and has proven to be safe and effective over the course of time. Oesophageal perforation after myotomy can be a serious complication with devastating outcomes. Most commonly, mucosal perforation are detected intraoperatively or early postoperatively. We present an extremely rare case of late oesophageal perforation in a 28-year-old man treated with laparoscopic Heller myotomy for type II oesophageal achalasia, and its successful minimally invasive repair with laparoscopic primary suturing.

Minimally invasive oesophagectomy and emerging complications: intercostal lung hernia.

Lung herniation is a rare entity, defined as a protrusion of the lung above the normal confines of thorax; it is caused by increased intrathoracic pressure and defects or weakness of the chest wall. Intercostal lung hernia can occur spontaneously or following thoracic trauma or surgery. Postoperative hernias are more commonly associated with less extensive surgical procedures, such as thoracoscopic surgery or mini-thoracotomy incisions, rather than with major thoracic procedures. We describe the first reported case of postoperative intercostal lung hernia following two-stage totally minimally invasive oesophagectomy for cancer, together with its successful surgical repair.

Intensive care unit outcomes following orthotopic liver transplantation: single-center experience and review of the literature.

BACKGROUND/AIM: Orthotopic Liver Transplantation (OLT) is the treatment of choice for patients with end stage liver disease, acute liver failure, hepatocellular carcinoma and metabolic disorders. As a result of improvement in surgical and anesthesiological skills, advanced understanding of transplant immunology and better critical care management of complications, patients survive longer after liver transplantation. It has been gradually achieved one-year survival rates of 80-90%. During the early post-operative period, all patients undergoing OLT are admitted to the intensive care unit, as they need a management of both preexisting patient's conditions and post-operative complications, usually due to either adverse intra-operative or post-operative events. The purpose of this review is the detailed recording, understanding and interpretation of immediate post-operative complications occurred in patients undergoing OLT, in intensive care unit. This could help to improve patient's treatment and reduce the incidence of complications, with further reduction of morbidity-mortality and cost. We also present our experience from the first 32 OLT patients from Liver Transplantation Unit of Laiko General Hospital, the only Liver Transplantation Unit in Athens. MATERIALS AND METHODS: This literature review was performed using the MEDLINE database. The key words were; Orthotopic liver transplantation; intensive care unit; post-operative complications; outcomes. One hundred-sixteen articles published in English until 2018 were used. We also use all the results from our 32 patients from our Liver Transplantation Unit during the period 07/2006 to 07/2009. RESULTS: All patients undergoing OLT admitted to the intensive care unit for a period of time, depending on the occurrence of post-operative complications. The incidence of primary failure ranges between 2-14%, whereas post-operative bleeding ranges between 7-15%. The treatment is usually conservative, although surgical repair may need in 10-15%. Acute renal failure post-operative is not an infrequent problem too, and has been reported to occur in 9% to 78% of cases. Acute rejection normally occurs 7-14 days after OLT. Additionally, the delay of the weaning from mechanical ventilation in the immediate post-operative period could increase the complications. Infectious complications are quite common almost from the first post-operative day in intensive care unit. CONCLUSIONS: Prolonged intensive care stay could increase the complications post-operative Infectious complications, renal and respiratory impairment are among the most common causes of early post-transplant morbidity and mortality.

Stoichiometry dependent electron transport and gas sensing properties of indium oxide nanowires.

The effect of stoichiometry of single crystalline In2O3 nanowires on electrical transport and gas sensing was investigated. The nanowires were synthesized by vapor phase transport and had diameters ranging from 80 to 100 nm and lengths between 10 and 20 µm, with a growth direction of [001]. Transport measurements revealed n-type conduction, attributed to the presence of oxygen vacancies in the crystal lattice. As-grown In2O3 nanowires were shown to have a carrier concentration of ≈5 × 10(17) cm(-3), while nanowires that were annealed in wet O2 showed a reduced carrier concentration of less than 10(16) cm(-3). Temperature dependent conductivity measurements on the as-grown nanowires and analysis of the thermally activated Arrhenius conduction for the temperature range of 77-350 K yielded an activation energy of 0.12 eV. This is explained on the basis of carrier exchange that occurs between the surface states and the bulk of the nanowire, resulting in a depleted surface layer of thickness of the order of the Debye length (LD), estimated to be about 3-4 nm for the as-grown nanowires and about 10 times higher for the more stoichiometric nanowires. Significant changes in the electrical conductance of individual In2O3 nanowires were also observed within several seconds of exposure to NH3 and O2 gas molecules at room temperature, thus demonstrating the potential use of In2O3 nanowires as efficient miniaturized chemical sensors. The sensing mechanism is dominated by the nanowire channel conductance, and a simple energy band diagram is used to explain the change in conductivity when gas molecules adsorbed on the nanowire surface influence its electrical properties. Less stoichiometric nanowires were found to be more sensitive to oxidizing gases while more stoichiometric nanowires showed significantly enhanced response to reducing gases.