Determination of mechanical properties of different sized silicon and silica nanowires tested in SEM

To push miniaturization in electronics forward, integration of silicon or silica nanowires into microelectromechanical based sensors (MEMS) becomes essential, because they were found to enhance the overall sensitivity and noise immunity. With respect to mechanical stress may develop in nanowires in operation of the MEMS system, their stability need to be checked to ensure long-term reliability. The monolithic fabrication includes a controlled two-step chip-on-wafer etching technique resulting in double-anchored wires with the minimum width of 35 nm, the maximum width of 74 nm and a height of 168 nm with clamped wire endings for silicon [1,2]. Based on this idea clamped silica wires with widths between 150 to 200 nm and heights of 50 nm and 372 nm were created due to prior coating of a silicon bulk with a silsesquioxane precursor in addition to subsequent e-beam irradiation [3]. Dimensions and shape of the wire cross-sections were exemplary investigated using transmission electron microscopy, while the determination of the respective wire´s length between the clamped endings of 2 to 12µm and the in-situ three-point-bending tests were carried out within a scanning electron microscope. A micromanipulator equipped with a piezo-resistive force sensor, shaped like a cantilever conventionally used for atomic force microscopes was loaded and unloaded at the wires mid-span and forces were detected. Simultaneously the systematic tests were recorded in scanning electron micrographs taken each second to extract force-displacement (f-d) curves of the different sized nano-objects. As expected for brittle material, silicon nanowires showed well-known f-d behavior. Considering a modulus of elasticity of 169 GPa for bulk [100] silicon and the influence of the native oxide finite element simulation (FEM) exactly fit to the experimental data leading to the conclusion that no size dependence for elastic properties was identified [4]. Same observations were made with silica wires until a stress level of about 0.1 to 0.4 GPa is reached and a superplastic deformation without fracture of the wires takes place. The validation of the f-d results from the systematic study of the fracture behavior of silicon wire is in progress. Due to the special wire geometry (small width in relation to height) buckling occurs during loading, implemented within a finite-element simulation, which needs still further refinement. Finally, this study will help to predict mechanical behavior (or vice versa the dimensions) of MEMS integrated silicon nanowires. The project leading to this application has received funding from the EMPIR programme Strength-ABLE co-financed by the Participating States and from the European Union’s Horizon 2020 research and innovation programme. [1] Z. Tasdemir, N. Wollschläger, W. Österle, Y. Leblebici and B. E. Alaca: A deep etching mechanism for trench-bridging silicon nanowires, Nanotechnology 27 (2016) 095303. [2] M. Yilmaz, Y. Kilinc, G. Nadar, Z. Tasdemir, N. Wollschläger, W. Österle, Y. Leblebici and B. E. Alaca: Top-down technique for scaling to nano in silicon MEMS, J. Vac. Sci. Technol. B 35 (2017) 022001-1 [3] M. Yilmaz, N. Wollschläger, M. Nasr Esfahani, Österle, Y. Leblebici and B. E. Alaca: Superplastic behavior of silica nanowires obtained by direct patterning of silsesquioxane-based precursors, Nanotechnology 28 (2017) 115302. [4] N. Wollschläger, Z. Tasdemir, I. Häusler, Y. Leblebici, W. Österle and B. E. Alaca: Determination of the Elastic Behavior of Silicon Nanowires within a Scanning Electron Microscope, J. Nanomat. (2016) 4905838-

Treatment of ventilator-associated pneumonia (VAP) caused by Acinetobacter: results of prospective and multicenter ID-IRI study

Ventilator-associated pneumonia (VAP) due to Acinetobacter spp. is one of the most common infections in the intensive care unit. Hence, we performed this prospective-observational multicenter study, and described the course and outcome of the disease. This study was performed in 24 centers between January 06, 2014, and December 02, 2016. The patients were evaluated at time of pneumonia diagnosis, when culture results were available, and at 72 h, at the 7th day, and finally at the 28th day of follow-up. Patients with coexistent infections were excluded and only those with a first VAP episode were enrolled. Logistic regression analysis was performed. A total of 177 patients were included; empiric antimicrobial therapy was appropriate (when the patient received at least one antibiotic that the infecting strain was ultimately shown to be susceptible) in only 69 (39%) patients. During the 28-day period, antibiotics were modified for side effects in 27 (15.2%) patients and renal dose adjustment was made in 38 (21.5%). Ultimately, 89 (50.3%) patients died. Predictors of mortality were creatinine level (OR, 1.84 (95% CI 1.279-2.657); p = 0.001), fever (OR, 0.663 (95% CI 0.454-0.967); p = 0.033), malignancy (OR, 7.095 (95% CI 2.142-23.500); p = 0.001), congestive heart failure (OR, 2.341 (95% CI 1.046-5.239); p = 0.038), appropriate empiric antimicrobial treatment (OR, 0.445 (95% CI 0.216-0.914); p = 0.027), and surgery in the last month (OR, 0.137 (95% CI 0.037-0.499); p = 0.003). Appropriate empiric antimicrobial treatment in VAP due to Acinetobacter spp. was associated with survival while renal injury and comorbid conditions increased mortality. Hence, early diagnosis and appropriate antibiotic therapy remain crucial to improve outcomes

Diffusion-weighted imaging in the head and neck region: usefulness of apparent diffusion coefficient values for characterization of lesions

PURPOSEWe aimed to evaluate the role of apparent diffusion coefficient (ADC) values calculated from diffusion-weighted imaging for head and neck lesion characterization in daily routine, in comparison with histopathological results.METHODSNinety consecutive patients who underwent magnetic resonance imaging (MRI) at a university hospital for diagnosis of neck lesions were included in this prospective study. Diffusion-weighted echo-planar MRI was performed on a 1.5 T unit with b factor of 0 and 1000 s/mm2 and ADC maps were generated. ADC values were measured for benign and malignant whole lesions seen in daily practice.RESULTSThe median ADC value of the malignant tumors and benign lesions were 0.72×10-3 mm2/s, (range, 0.39–1.51×10-3 mm2/s) and 1.17×10-3 mm2/s, (range, 0.52–2.38×10-3 mm2/s), respectively, with a significant difference between them (P < 0.001). A cutoff ADC value of 0.98×10-3 mm2/s was used to distinguish between benign and malignant lesions, yielding 85.3% sensitivity and 78.6% specificity. The median ADC value of lymphomas (0.44×10-3 mm2/s; range, 0.39–0.58×10-3 mm2/s) was significantly smaller (P < 0.001) than that of squamous cell carcinomas (median ADC value 0.72×10-3 mm2/s; range, 0.65–1.06×10-3 mm2/s). There was no significant difference between median ADC values of inflammatory (1.13×10-3 mm2/s; range, 0.85–2.38×10-3 mm2/s) and noninflammatory benign lesions (1.26×10-3 mm2/s; range, 0.52–2.33×10-3 mm2/s).CONCLUSIONDiffusion-weighted imaging and the ADC values can be used to differentiate and characterize benign and malignant head and neck lesions

Effect of Native Oxide on Stress in Silicon Nanowires : Implications for Nanoelectromechanical Systems

Understanding the origins of intrinsic stress in Si nanowires (NWs) is crucial for their successful utilization as transducer building blocks in next-generation, miniaturized sensors based on nanoelectromechanical systems (NEMS). With their small size leading to ultrahigh-resonance frequencies and extreme surface-to-volume ratios, silicon NWs raise new opportunities regarding sensitivity, precision, and speed in both physical and biochemical sensing. With silicon optoelectromechanical properties strongly dependent on the level of NW intrinsic stress, various studies have been devoted to the measurement of such stresses generated, for example, as a result of harsh fabrication processes. However, due to enormous NW surface area, even the native oxide that is conventionally considered as a benign surface condition can cause significant stresses. To address this issue, a combination of nanomechanical characterization and atomistic simulation approaches is developed. Relying only on low-temperature processes, the fabrication approach yields monolithic NWs with optimum boundary conditions, where NWs and support architecture are etched within the same silicon crystal. Resulting NWs are characterized by transmission electron microscopy and micro-Raman spectroscopy. The interpretation of results is carried out through molecular dynamics simulations with ReaxFF potential facilitating the incorporation of humidity and temperature, thereby providing a close replica of the actual oxidation environment in contrast to previous dry oxidation or self-limiting thermal oxidation studies. As a result, consensus on significant intrinsic tensile stresses on the order of 100 MPa to 1 GPa was achieved as a function of NW critical dimension and aspect ratio. The understanding developed herein regarding the role of native oxide played in the generation of NW intrinsic stresses is important for the design and development of silicon-based NEMS

Nanomechanical Modeling of the Bending Response of Silicon Nanowires

Understanding the mechanical behavior of silicon nanowires is essential for the implementation of advanced nanoscale devices. Although bending tests are predominantly used for this purpose, their findings should be properly interpreted through modeling. Various modeling approaches tend to ignore parts of the effective parameter set involved in the rather complex bending response. This oversimplification is the main reason behind the spread of the modulus of elasticity and strength data in the literature. Addressing this challenge, a surface-based nanomechanical model is introduced in this study. The proposed model considers two important factors that have so far remained neglected despite their significance: (i) intrinsic stresses composed of the initial residual stress and surface-induced residual stress and (ii) anisotropic implementation of surface stress and elasticity. The modeling study is consolidated with molecular dynamics-based study of the native oxide surface through reactive force fields and a series of nanoscale characterization work through in situ three-point bending test and Raman spectroscopy. The treatment of the test data through a series of models with increasing complexity demonstrates a spread of 85 GPa for the modulus of elasticity and points to the origins of ambiguity regarding silicon nanowire properties, which are some of the most commonly employed nanoscale building blocks. A similar conclusion is reached for strength with variations of up to 3 GPa estimated by the aforementioned nanomechanical models. Precise consideration of the nanowire surface state is thus critical to comprehending the mechanical behavior of silicon nanowires accurately. Overall, this study highlights the need for a multiscale theoretical framework to fully understand the size-dependent mechanical behavior of silicon nanowires, with fortifying effects on the design and reliability assessment of future nanoelectromechanical systems

Calpain-3 mutations in Turkey

Abstract Autosomal recessive limb-girdle muscular dystrophies (LGMD2s

The interrelations of radiologic findings and mechanical ventilation in community acquired pneumonia patients admitted to the intensive care unit: a multicentre retrospective study

BACKGROUND: We evaluated patients admitted to the intensive care units with the diagnosis of community acquired pneumonia (CAP) regarding initial radiographic findings. METHODS: A multicenter retrospective study was held. Chest x ray (CXR) and computerized tomography (CT) findings and also their associations with the need of ventilator support were evaluated. RESULTS: A total of 388 patients were enrolled. Consolidation was the main finding on CXR (89%) and CT (80%) examinations. Of all, 45% had multi-lobar involvement. Bilateral involvement was found in 40% and 44% on CXR and CT respectively. Abscesses and cavitations were rarely found. The highest correlation between CT and CXR findings was observed for interstitial involvement. More than 80% of patients needed ventilator support. Noninvasive mechanical ventilation (NIV) requirement was seen to be more common in those with multi-lobar involvement on CXR as 2.4-fold and consolidation on CT as 47-fold compared with those who do not have these findings. Invasive mechanical ventilation (IMV) need increased 8-fold in patients with multi-lobar involvement on CT. CONCLUSION: CXR and CT findings correlate up to a limit in terms of interstitial involvement but not in high percentages in other findings. CAP patients who are admitted to the ICU are severe cases frequently requiring ventilator support. Initial CT and CXR findings may indicate the need for ventilator support, but the assumed ongoing real practice is important and the value of radiologic evaluation beyond clinical findings to predict the mechanical ventilation need is subject for further evaluation with large patient series

THE ROLE OF MAGNETIC RESONANCE IMAGING WITH DYNAMIC SUBTRACTION IN DETERMINING LIVER LESIONS WITH CIRRHOSIS

WOS: 000318755100007Introduction: The aim of this study is to evaluate the role of the Magnetic Resonance Imaging (MRI) with Dynamic Subtraction in determining liver lesions with cirrhosis. Materials and Method: We investigated the presence of lesions in the liver with standard MRI protocol among 30 patients with cirrhosis. Subsequently, subtraction process was applied to the dynamic images. Images obtained with standard and subtraction methods were analyzed; and the sensitivity, specificity, positive and negative predictive values were investigated. Results: The age range was 45-86, the average age was 65.6 and the median age was 64.5 years. On standard and subtraction images, no lesion was found in 14 patients. In 16 patients, after evaluation with standard protocol, 20 lesions were found. On dynamic images, 21 lesions were identified. When compared to standard protocol, with dynamic subtraction imaging, sensitivity to detect a lesion was found as 95.5%, whereas specificity was 87.5%, positive predictive value was 90.5%, negative predictive value was 93.3% and the accuracy was 91.6%. Conclusion: In the identification of the number of liver lesions, subtraction imaging was not superior to the standard protocole alone. However, the addition of subtraction images on the standard protocol improves the evaluation quality for lesions detected in cirrhotic liver

Maksiller sinüste monostotik fibröz displazi: Olgu sunumu

Fibröz displazi, yavaş ilerleme gösteren, benign ka-rakterli nadir bir kemik hastalığıdır. Paranazal sinüslerin monostotik tutulumu nadirdir. İki yılı aşkın bir süredir yüz asimetrisi, kronik sinüzit, tekrarlayıcı baş ağrısı ve nefes darlığı şikayetleri olan 54 yaşındaki kadın hastanın çekilen düz grafilerinde opasifikasyon ve maksiller sinüste genişleme gözlendi. Aksiyel ve koronal bilgisayarlı tomografi görüntülerinde maksiller sinüste genişlemeye, burun tıkanıklığına ve maksillada kortikal kalınlaşmaya yol açan heterojen kitle belirlendi. Kortikal kemikte herhangi bir erozyon ya da bozulma belirtileri yoktu. Hastaya endonazal endoskopik biyopsi yapıldı ve fibröz displazi tansı histolojik olarak doğrulandı.Fibrous dysplasia is an uncommon benign disease of the bone, with slow progression. Monostotic involvement of the paranasal sinuses is rare. We report a 54-year-old woman who had complaints of facial asymmetry, chronic sinusitis, recurrent headaches, and nasal obstruction for two years. Conventional radiography showed opacification and expansion of the maxillary sinus. Axial and coronal computed tomography scans showed a heterogeneous mass that expanded the right maxillary sinus, leading to nasal obstruction and cortical thickening of the maxilla. No signs of destruction or erosion in the cortical bone were identified. An endonasal endoscopic biopsy was performed and the diagnosis of fibrous dysplasia was confirmed histologically