Zero-Bias Power-Detector Circuits based on MoS2 Field-Effect Transistors on Wafer-Scale Flexible Substrates.

The design, fabrication, and characterization of wafer-scale, zero-bias power detectors based on 2D MoS2 field-effect transistors (FETs) are demonstrated. The MoS2 FETs are fabricated using a wafer-scale process on 8 µm-thick polyimide film, which, in principle, serves as a flexible substrate. The performances of two chemical vapor deposition MoS2 sheets, grown with different processes and showing different thicknesses, are analyzed and compared from the single device fabrication and characterization steps to the circuit level. The power-detector prototypes exploit the nonlinearity of the transistors above the cut-off frequency of the devices. The proposed detectors are designed employing a transistor model based on measurement results. The fabricated circuits operate in the Ku-band between 12 and 18 GHz, with a demonstrated voltage responsivity of 45 V W-1 at 18 GHz in the case of monolayer MoS2 and 104 V W-1 at 16 GHz in the case of multilayer MoS2 , both achieved without applied DC bias. They are the best-performing power detectors fabricated on flexible substrate reported to date. The measured dynamic range exceeds 30 dB, outperforming other semiconductor technologies like silicon complementary metal-oxide-semiconductor circuits and GaAs Schottky diodes.

Wide Spectral Photoresponse of Layered Platinum Diselenide-Based Photodiodes.

Platinum diselenide (PtSe2) is a group-10 transition metal dichalcogenide (TMD) that has unique electronic properties, in particular a semimetal-to-semiconductor transition when going from bulk to monolayer form. We report on vertical hybrid Schottky barrier diodes (SBDs) of two-dimensional (2D) PtSe2 thin films on crystalline n-type silicon. The diodes have been fabricated by transferring large-scale layered PtSe2 films, synthesized by thermally assisted conversion of predeposited Pt films at back-end-of-the-line CMOS compatible temperatures, onto SiO2/Si substrates. The diodes exhibit obvious rectifying behavior with a photoresponse under illumination. Spectral response analysis reveals a maximum responsivity of 490 mA/W at photon energies above the Si bandgap and relatively weak responsivity, in the range of 0.1-1.5 mA/W, at photon energies below the Si bandgap. In particular, the photoresponsivity of PtSe2 in infrared allows PtSe2 to be utilized as an absorber of infrared light with tunable sensitivity. The results of our study indicate that PtSe2 is a promising option for the development of infrared absorbers and detectors for optoelectronics applications with low-temperature processing conditions.

Strain Gauges Based on CVD Graphene Layers and Exfoliated Graphene Nanoplatelets with Enhanced Reproducibility and Scalability for Large Quantities.

The two-dimensional material graphene promises a broad variety of sensing activities. Based on its low weight and high versatility, the sensor density can significantly be increased on a structure, which can improve reliability and reduce fluctuation in damage detection strategies such as structural health monitoring (SHM). Moreover; it initializes the basis of structure-sensor fusion towards self-sensing structures. Strain gauges are extensively used sensors in scientific and industrial applications. In this work, sensing in small strain fields (from -0.1% up to 0.1%) with regard to structural dynamics of a mechanical structure is presented with sensitivities comparable to bulk materials by measuring the inherent piezoresistive effect of graphene grown by chemical vapor deposition (CVD) with a very high aspect ratio of approximately 4.86 × 108. It is demonstrated that the increasing number of graphene layers with CVD graphene plays a key role in reproducible strain gauge application since defects of individual layers may become less important in the current path. This may lead to a more stable response and, thus, resulting in a lower scattering.. Further results demonstrate the piezoresistive effect in a network consisting of liquid exfoliated graphene nanoplatelets (GNP), which result in even higher strain sensitivity and reproducibility. A model-assisted approach provides the main parameters to find an optimum of sensitivity and reproducibility of GNP films. The fabricated GNP strain gauges show a minimal deviation in PRE effect with a GF of approximately 5.6 and predict a linear electromechanical behaviour up to 1% strain. Spray deposition is used to develop a low-cost and scalable manufacturing process for GNP strain gauges. In this context, the challenge of reproducible and reliable manufacturing and operating must be overcome. The developed sensors exhibit strain gauges by considering the significant importance of reproducible sensor performances and open the path for graphene strain gauges for potential usages in science and industry.

Coronary Artery Evaluation by Screening Echocardiogram in Intercollegiate Athletes.

INTRODUCTION: Coronary artery anomalies are the second most common congenital cause of sudden cardiac death in young athletes. Some centers have advocated for limited transthoracic echocardiogram (TTE) protocols in the screening of college athletes, which may miss important causes of sudden cardiac death. PURPOSE: The purpose of this study was to evaluate the ability of screening TTE to determine the origin and proximal course of the coronary arteries in intercollegiate athletes. METHODS: An institutional review board-approved retrospective review of all incoming National Collegiate Athletic Association Division-I athletes at a single institution for the 2013-2014 academic year was performed. Two pediatric cardiologists independently reviewed all TTE studies for right coronary artery (RCA) and left coronary artery (LCA) ostia, proximal course, and measurable course. Proximal course was defined as a measurable course >1 cm for the RCA and a measurable course >1 cm or observation of the bifurcation for the LCA. Measurable course was defined as the maximum continuously observable distance of coronary artery from a clearly delineable ostium. Results were compared among athlete characteristics, and interobserver reliability was evaluated. RESULTS: Chart review identified 146 athletes, representing 22 sports and 6 ethnicities. No coronary anomalies were found. The average measurable course was 2.1 cm for the RCA and 1.5 cm for the LCA. Both readers observed the RCA ostium in 143 athletes (98%), LCA ostium in 143 athletes (98%), RCA proximal course in 119 athletes (82%), and LCA proximal course in 118 athletes (81%). Statistical analysis showed good interobserver reliability for observation of the ostia and proximal course. CONCLUSIONS: The origin and proximal course of the coronary arteries were readily and reliably observed in the majority of athletes, suggesting coronary artery evaluation should be included in athlete screening TTE protocols.

Complex adult laryngotracheal reconstruction with a prefabricated flap: a case series.

BACKGROUND: Laryngotracheal stenosis (LTS) can cause persistent or recurrent airway obstruction. Although there is extensive literature on surgical techniques to treat LTS at onset, there are few techniques described for complex adult LTS after failed prior airway surgery. We describe a procedure used successfully in 3 patients who required structural augmentation for complex LTS. METHODS: Patients were treated with staged reconstruction using a prefabricated composite graft consisting of auricular cartilage and a radial forearm free flap. RESULTS: All patients underwent successful reconstruction with good wound healing and are tolerating oral diets. Two patients have been successfully decannulated. CONCLUSION: A delayed prefabricated graft using auricular cartilage in a radial forearm free flap is a viable surgical intervention in patients with complex adult LTS who are not candidates for conventional approaches.

Airway management after maxillectomy with free flap reconstruction.

BACKGROUND: Maxillectomy defects require complex 3-dimensional reconstructions often best suited to microvascular free tissue transfer. Postoperative airway management during this procedure has little discussion in the literature and is often dictated by surgical dogma. The purpose of this article was to review our experience in order to evaluate the effect of airway management on perioperative outcomes in patients undergoing maxillectomy with free flap reconstruction. METHODS: A retrospective chart review was performed on patients receiving maxillectomy with microvascular reconstruction at 2 institutions between 1999 and 2011. Patient's airways were managed with or without elective tracheotomy at the surgical team's discretion and different perioperative outcomes were measured. The primary outcome was incidence of airway complication including pneumonia and need for further airway intervention. Secondary outcome was measured as factors leading to perioperative performance of the tracheotomy. RESULTS: Seventy-nine of 143 patients received elective tracheotomy perioperatively. The incidence of airway complication was equivalent between groups (10.1% vs 9.4%; p = .89). Patients with cardiopulmonary comorbidities were more likely to receive perioperative tracheotomy (74.1% vs 50.9%; p = .03) without a difference in airway complications. Other patient cofactors did not have an impact on perioperative tracheotomy or airway complication rate. CONCLUSIONS: Elective tracheotomy may safely be avoided in a subset of patients undergoing maxillectomy with microvascular reconstruction. Elective tracheotomy should be considered in patients with cardiopulmonary risk factors.

Use of internal mammary vessels in head and neck microvascular reconstruction.

OBJECTIVE: To describe the use of the internal mammary vessels (IMVs) in microvascular head and neck reconstruction in a small case series with select donor sites. DESIGN: Retrospective medical record review study. SETTING: Oregon Health and Science University and University of Alabama. PATIENTS: Patients for whom IMVs were used for head and neck reconstruction from January 1, 1998, through December 31, 2010. MAIN OUTCOME MEASURES: Intraoperative or postoperative complications, flap survival, and morbidity due to the flap. RESULTS: Of 2721 free tissue transfers, 55 (2%) (in 48 patients) used IMVs. Use of IMVs was associated with ablative surgery with sternal resection (25 of 55 [45%]), a vessel depleted neck (23 of 55 [42%]), and fistula repair with gross contamination due to prior flap failure or chronic pharyngocutaneous fistula with vessel depleted neck (7 of 55 [13%]). Flaps included radial forearm (33 of 55 [60%]), jejunum (9 of 55 [16]), ulnar (5 of 55 [9%]), and other (8 of 55 [14%]). No vein grafts were used. Pneumothorax developed in 1 patient (2%). Postoperative fistulas were observed in 14 of 48 patients (29%); the fistulas healed conservatively in 7 patients (50%), rotation of flap tissue was required in 2 patients (14%), and the fistulas persisted in 5 patients (36%). The flap survival rate was 98%. CONCLUSION: Internal mammary vessels provide reliable recipient vessels for cervical and sternal microvascular reconstruction.

Indications for pedicled pectoralis major flap in a free tissue transfer practice.

BACKGROUND: The pedicled pectoralis major myocutaneous flap (PMMF) was highly used over the last 3 decades. The current era of free tissue transfer has gradually relegated the PMMF to a secondary role. METHODS: In a retrospective review of all patients undergoing pedicled PMMF from 2002 to now, we sought to determine the current role and assess the outcomes of the PMMF in a primary microvascular head and neck reconstructive center. RESULTS: Fifty-five PMMFs were performed in 53 patients (24 myocutaneous and 31 myofascial); group 1 consisted of 20 patients (38%) who underwent a secondary PMMF after a free flap complication (flap failure 9/20, fistula 5/20, wound breakdown with great vessel exposure 3/20, loss of soft tissue skin paddle 2/20, and delayed hematoma in 1/20); group 2 included 18 patients (33%) who had a simultaneous free flap with a PMMF for dead space filler or cervical skin/great vessel coverage reconstruction, whereas the remaining 15 patients (29%) in group 3 underwent primary PMMF for reconstruction of cervical skin defect, great vessel coverage, pharyngocutaneous fistula, infection, and dead space filler. Complications of PMMF included 3 hematomas, 2 partial dehiscences, 1 chest wall abscess, and 1 case of mastitis. Because of cervical tethering, 14 of 53 patients underwent secondary pectoralis myectomy with cervical contracture release at a mean of 10.3 months after initial surgery. CONCLUSION: The pedicled PMMF continues to serve an important role in head and neck reconstruction in the microvascular era with notable uses for free flap rescue, with simultaneous free flap reconstruction and for primary reconstruction in select circumstances with an overall acceptable short- and long-term morbidity profile.

Reconstruction of the jejunoesophageal anastomosis with a circular mechanical stapler in total laryngopharyngectomy defects.

BACKGROUND: The aim of this study was to demonstrate the technical feasibility and potential benefits of using a circular mechanical stapler with free jejunal transfer for jejunoesophageal anastomosis in total laryngopharyngectomy reconstruction while comparing the rates of fistula and stricture. METHODS: This study was a retrospective review of 12 free jejunal flaps completed with circular mechanical stapler for the jejunoesophageal anastomosis with comparison to 17 jejunal free flaps where all anastomoses were hand sewn. RESULTS: In all, 29 patients underwent free jejunal transfer: 12 had jejunal free flap with circular mechanical stapler for jejunoesophageal anastomosis, whereas 17 patients had hand-sewn anastomosis. Corresponding rates of fistula and stricture were 0/12 fistulas and 3/12 strictures in the stapler cohort and 2/17 fistulas with 0/17 strictures in the hand-sewn cohort. No statistically significant difference in rate of fistula was observed between each cohort, whereas a trend toward increased rate of stricture (p = .06) was observed in the stapled anastomosis cohort. CONCLUSIONS: Use of circular mechanical stapler appears to be a safe and effective technique at the jejunoesophageal anastomosis for total laryngopharyngeal defects with comparable fistula and stricture rates to grafts that are hand sewn.

Superficial ulnar artery: a contraindication to radial forearm free tissue transfer.

OBJECTIVES: Superficial ulnar artery is a vascular anomaly that may be encountered during elevation of forearm flaps for head and neck reconstruction. This anomaly should be considered in patients with a positive Allen's test. STUDY DESIGN: Case report and retrospective review of forearm flaps performed at our institution. METHODS: A 72-year-old man with a history of total laryngectomy presented for closure of a pharyngocutaneous fistula with radial forearm flap. A positive Allen's test and undetectable Doppler over the thenar eminence with radial artery occlusion was noted. An ulnar flap was felt to be the best alternative. A superficial ulnar artery was discovered upon elevation of the ulnar flap. Despite its anomalous course, the artery provided several fasciocutaneous branches, and the flap was successfully used to repair the patient's fistula. A retrospective review of forearm flaps and the incidence of superficial ulnar artery at our institution is presented. RESULTS: A total of 690 forearm flaps (571 radial, 51 ulnar, and 68 osteocutaneous radial) were performed from 1998 to 2010. Superficial ulnar artery was encountered three times, yielding an incidence of 0.43%. In each case, the preoperative Allen's test suggested a dominant radial artery circulation. In all cases, a fasciocutaneous ulnar flap was successfully used. CONCLUSIONS: Superficial ulnar artery should be considered with a positive Allen's test. An ulnar fasciocutaneous flap based on the superficial ulnar artery is a safe alternative to the radial fasciocutaneous flap in this setting.