Exploiting Ambipolarity in Graphene Field-Effect Transistors for Novel Designs on High-Frequency Analog Electronics.

Exploiting ambipolar electrical conductivity based on graphene field-effect transistors has raised enormous interest for high-frequency (HF) analog electronics. Controlling the device polarity, by biasing the graphene transistor around the vertex of the V-shaped transfer curve, enables to redesign and highly simplify conventional analog circuits, and simultaneously to seek for multifunctionalities, especially in the HF domain. This study presents new insights for the design of different HF applications such as power amplifiers, mixers, frequency multipliers, phase shifters, and modulators that specifically leverage the inherent ambipolarity of graphene-based transistors.

Investigation of the Optical Properties of Indium Tin Oxide Thin Films by Double Integration Sphere Combined with the Numerical IAD Method.

Transparent conductive electrodes have become essential components of numerous optoelectronic devices. However, their optical properties are typically characterized by the direct transmittance achieved by making use of spectrophotometers, avoiding an in-depth knowledge of the processes involved in radiation attenuation. A different procedure based on the Double Integration Sphere combined with the numerical Inverse Adding-Doubling (IAD) method is employed in this work to provide a comprehensive description of the physical processes limiting the light transmittance in commercial indium tin oxide (ITO) deposited on flexible PET samples, highlighting the noticeable contribution of light scattering on the total extinction of radiation. Moreover, harnessing their flexibility, the samples were subjected to different mechanical stresses to assess their impact on the material's optical and electrical properties.

Compact Modeling of Two-Dimensional Field-Effect Biosensors.

A compact model able to predict the electrical read-out of field-effect biosensors based on two-dimensional (2D) semiconductors is introduced. It comprises the analytical description of the electrostatics including the charge density in the 2D semiconductor, the site-binding modeling of the barrier oxide surface charge, and the Stern layer plus an ion-permeable membrane, all coupled with the carrier transport inside the biosensor and solved by making use of the Donnan potential inside the ion-permeable membrane formed by charged macromolecules. This electrostatics and transport description account for the main surface-related physical and chemical processes that impact the biosensor electrical performance, including the transport along the low-dimensional channel in the diffusive regime, electrolyte screening, and the impact of biological charges. The model is implemented in Verilog-A and can be employed on standard circuit design tools. The theoretical predictions obtained with the model are validated against measurements of a MoS2 field-effect biosensor for streptavidin detection showing excellent agreement in all operation regimes and leading the way for the circuit-level simulation of biosensors based on 2D semiconductors.

Functional Pyrazolo[1,5-a]pyrimidines: Current Approaches in Synthetic Transformations and Uses As an Antitumor Scaffold.

Pyrazolo[1,5-a]pyrimidine (PP) derivatives are an enormous family of N-heterocyclic compounds that possess a high impact in medicinal chemistry and have attracted a great deal of attention in material science recently due to their significant photophysical properties. Consequently, various researchers have developed different synthesis pathways for the preparation and post-functionalization of this functional scaffold. These transformations improve the structural diversity and allow a synergic effect between new synthetic routes and the possible applications of these compounds. This contribution focuses on an overview of the current advances (2015-2021) in the synthesis and functionalization of diverse pyrazolo[1,5-a]pyrimidines. Moreover, the discussion highlights their anticancer potential and enzymatic inhibitory activity, which hopefully could lead to new rational and efficient designs of drugs bearing the pyrazolo[1,5-a]pyrimidine core.

Inexpensive Graphene Oxide Heaters Lithographed by Laser.

In this paper, we present a simple and inexpensive method for the fabrication of high-performance graphene-based heaters on different large-scale substrates through the laser photothermal reduction of graphene oxide (laser-reduced graphene-oxide, LrGO). This method allows an efficient and localized high level of reduction and therefore a good electrical conductivity of the treated films. The performance of the heaters is studied in terms of steady-state temperature, power consumption, and time response for different substrates and sizes. The results show that the LrGO heaters can achieve stable steady-state temperatures higher than 200 °C when a voltage of 15 V is applied, featuring a time constant of around 4 s and a heat transfer coefficient of ~200 °C cm2/W. These characteristics are compared with other technologies in this field, demonstrating that the fabrication approach described in this work is competitive and promising to fabricate large-scale flexible heaters with a very fast response and high steady-state temperatures in a cost-effective way. This technology can be easily combined with other fabrication methods, such as screen printing or spray-deposition, for the manufacturing of complete sensing systems where the temperature control is required to adjust functionalities or to tune sensitivity or selectivity.

GFET Asymmetric Transfer Response Analysis through Access Region Resistances.

Graphene-based devices are planned to augment the functionality of Si and III-V based technology in radio-frequency (RF) electronics. The expectations in designing graphene field-effect transistors (GFETs) with enhanced RF performance have attracted significant experimental efforts, mainly concentrated on achieving high mobility samples. However, little attention has been paid, so far, to the role of the access regions in these devices. Here, we analyse in detail, via numerical simulations, how the GFET transfer response is severely impacted by these regions, showing that they play a significant role in the asymmetric saturated behaviour commonly observed in GFETs. We also investigate how the modulation of the access region conductivity (i.e., by the influence of a back gate) and the presence of imperfections in the graphene layer (e.g., charge puddles) affects the transfer response. The analysis is extended to assess the application of GFETs for RF applications, by evaluating their cut-off frequency.

Laser-Fabricated Reduced Graphene Oxide Memristors.

Finding an inexpensive and scalable method for the mass production of memristors will be one of the key aspects for their implementation in end-user computing applications. Herein, we report pioneering research on the fabrication of laser-lithographed graphene oxide memristors. The devices have been surface-fabricated through a graphene oxide coating on a polyethylene terephthalate substrate followed by a localized laser-assisted photo-thermal partial reduction. When the laser fluence is appropriately tuned during the fabrication process, the devices present a characteristic pinched closed-loop in the current-voltage relation revealing the unique fingerprint of the memristive hysteresis. Combined structural and electrical experiments have been conducted to characterize the raw material and the devices that aim to establish a path for optimization. Electrical measurements have demonstrated a clear distinction between the resistive states, as well as stable memory performance, indicating the potential of laser-fabricated graphene oxide memristors in resistive switching applications.

In-Depth Study of Laser Diode Ablation of Kapton Polyimide for Flexible Conductive Substrates.

This work presents a detailed study of the photothermal ablation of Kapton® polyimide by a laser diode targeting its electrical conductivity enhancement. Laser-treated samples were structurally characterized using Scanning Electron Microscopy (SEM), Raman spectroscopy, X-ray Photoelectron Spectroscopy (XPS), as well as Diffuse Reflectance Infrared Fourier Transform (DRIFT) spectroscopy. The results show that the laser-assisted ablation constitutes a simple one-step and environmental friendly method to induce graphene-derived structures on the surface of polyimide films. The laser-modified surface was also electrically characterized through the Transmission Line Method (TLM) aiming at the improvement of the conductivity of the samples by tuning the laser power and the extraction of the contact resistance of the electrodes. Once the laser-ablation process is optimized, the samples increase their conductivity up to six orders of magnitude, being comparable to that of graphene obtained by chemical vapor deposition or by the reduction of graphene-oxide. Additionally, we show that the contact resistance can be decreased down to promising values of ∼2 Ω when using silver-based electrodes.

High Photocurrent in Gated Graphene-Silicon Hybrid Photodiodes.

Graphene/silicon (G/Si) heterojunction based devices have been demonstrated as high responsivity photodetectors that are potentially compatible with semiconductor technology. Such G/Si Schottky junction diodes are typically in parallel with gated G/silicon dioxide (SiO2)/Si areas, where the graphene is contacted. Here, we utilize scanning photocurrent measurements to investigate the spatial distribution and explain the physical origin of photocurrent generation in these devices. We observe distinctly higher photocurrents underneath the isolating region of graphene on SiO2 adjacent to the Schottky junction of G/Si. A certain threshold voltage (VT) is required before this can be observed, and its origins are similar to that of the threshold voltage in metal oxide semiconductor field effect transistors. A physical model serves to explain the large photocurrents underneath SiO2 by the formation of an inversion layer in Si. Our findings contribute to a basic understanding of graphene/semiconductor hybrid devices which, in turn, can help in designing efficient optoelectronic devices and systems based on such 2D/3D heterojunctions.

Does Nasal Surgery Improve OSA in Patients with Nasal Obstruction and OSA? A Meta-analysis.

OBJECTIVE: To perform a systematic review and meta-analysis to determine if isolated nasal surgery in patients with obstructive sleep apnea and nasal airway obstruction improves obstructive sleep apnea. DATA SOURCES: Computerized searches were performed in PubMed, EMBASE, and the Cochrane Library through October 2014. Manual searches and subject matter expert input was also solicited. REVIEW METHODS: A search protocol was defined a priori, and 2 independent investigators performed the data extraction, focusing on relevant data, including quality data polysomnography data, and taking note of methodological quality and risk for bias. RESULTS: The 10 studies meeting criteria included a total of 320 patients. There were 2 randomized controlled trials, 7 prospective studies, and 1 retrospective study. There was a significant improvement in the pooled results of both Epworth Sleepiness Scale (ESS; difference 3.53, 95% confidence interval [CI] [0.64, 6.23]) and Respiratory Disturbance Index (RDI; 11.06, 95% CI [5.92, 16.19]) scores with isolated nasal surgery. There was no significant improvement in the Apnea Hypopnea Index (AHI) in the random effects model (4.83, 95% CI [-1.6, 11.62]). CONCLUSIONS: The pooled results showed that isolated nasal surgery for patients with nasal obstruction and obstructive sleep apnea improved some sleep parameters, as shown by significant improvements in ESS and RDI, but had no significant improvements on AHI. Future controlled studies with larger groups are needed to confirm the benefits of isolated nasal surgery in this patient population.

Facial lesions negatively impact affect display.

OBJECTIVE: To evaluate the impact of facial lesions on affect display in patients as compared with individuals without lesions. STUDY DESIGN: Prospective randomized controlled experiment. Setting Academic tertiary referral center. SUBJECTS AND METHODS: Forty-five normal observers viewed photographs of normal faces in repose and faces with lesions in repose. Observers classified the affect display of the patients and the normals using a survey containing choices of primary emotions and personal attributes. Latent class analysis was used to find the unmeasured or "latent" classes. Latent class regression was used to determine the impact of lesion size and location on class membership. Finally, lesion classes and normal classes were checked for differences. RESULTS: Latent class analysis identified 4 independent latent classes for faces with lesions. The normal data were best fit by 3 latent classes. As a group, faces with lesions were most likely to be classified as either negative-sad or negative-angry, accounting for a combined probability of 44%. This was in contrast to the normal group, where 62% were classified as positive and only 13.9% as negative. Size and location significantly affected negative class membership. There were significant differences in the lesion classes as compared with the normal classes. CONCLUSION: Faces with lesions were reported to display different affect in repose than normal faces in repose. The classification of the lesion faces was dependent on lesion size and location. These findings provide the first objective evidence of the affect display penalty caused by facial lesions.

Impact of crooked nose rhinoplasty on observer perceptions of attractiveness.

OBJECTIVES/HYPOTHESIS: To evaluate the impact of a crooked nose on observer perceptions of facial asymmetry and attractiveness and the ability of rhinoplasty to minimize it. We hypothesized that the presence of a crooked nose would penalize symmetry and attractiveness ratings as compared to normal faces. We further hypothesized that straightening rhinoplasty would restore symmetry and improve attractiveness. STUDY DESIGN: Randomized controlled experiment. METHODS: A group of 39 naïve observers viewed pictures of patients with crooked noses before and after straightening rhinoplasty, and normal patients. Observers rated the overall asymmetry and attractiveness, and the asymmetry of facial subunits using a survey with a rating scale of 1 to 10 for each category. RESULTS: For asymmetry, patient group (preoperative, postoperative, normal) was statistically significant by multivariate analysis of the variance. Post-analysis of variance showed significant differences in asymmetry scores for overall, nose subunit, and mouth subunit. Pairwise testing then showed significantly different overall asymmetry scores between normal and preoperative (P < .001), and preoperative and postoperative (P < .001), but not between normal and postoperative (P = .215) groups. Mixed linear regression analysis showed that decreasing nasal asymmetry by 1 point increases attractiveness by 0.18 points or 0.082 attractiveness standard deviations (P < .001). CONCLUSIONS: Faces with crooked noses were rated less symmetrical overall and less symmetrical at the nose and mouth subunits as compared to normal and postoperative faces. Straightening rhinoplasty diminished overall facial asymmetry and subunit asymmetry scores. Decreasing nasal asymmetry led to significant improvements in facial attractiveness. These data provide objective evidence supporting the idea that a straightening rhinoplasty can improve attractiveness.

Not just another face in the crowd: society's perceptions of facial paralysis.

OBJECTIVES/HYPOTHESIS: There is a paucity of data showing the perception penalty caused by facial paralysis. Our objective was to measure society's perception of facial paralysis on the characteristic of beauty. We hypothesized that patients with paralysis would be considered by society as less attractive than normals, a difference amplified by smiling. STUDY DESIGN: Randomized controlled experiment. METHODS: Forty subjects viewed photographs of normal and paralyzed faces. They rated attractiveness, identified paralysis if present, its severity, and the feature most affected. RESULTS: There were significant differences in attractiveness scores for normal and paralyzed faces (Wilcoxon rank sum test, z = 16.912; P < .001). A mixed effects regression model was used to explain differences in the scores. The fixed portion of the model shows paralyzed faces were 1 standard deviation less attractive than normal faces. Smiling increased attractiveness for normals (constant, 5.9; smile effect, 0.735; P < .001). The smile × paralysis interaction term was -0.892; P < .001, but not significantly different from the smile term (χ(2) (1) = 0.87; P = .352). The random effects model showed an intersubject rating variability of 1.32. CONCLUSIONS: The attractiveness penalty imposed by facial paralysis is significant, with paralyzed faces considered markedly less attractive than normals. However, the ratings did not change significantly when patients smiled, despite the increased asymmetry that occurs through smiling. Observers were moderately good at identifying the presence of facial paralysis, but less good at distinguishing side of involvement. These results have important implications for patient counseling and management of facial paralysis patients in an evidence-based manner.

How facial lesions impact attractiveness and perception: differential effects of size and location.

OBJECTIVES/HYPOTHESIS: To determine the effect of facial lesion size and location on perceptions of attractiveness and importance for repair. We hypothesized that attractiveness scores and importance for repair would be dependent on lesion size and location. STUDY DESIGN: Randomized controlled experiment. METHODS: Forty-five subjects viewed 35 photographs of normal faces and faces with lesions of different sizes and locations. They rated attractiveness, how disfiguring, how bothered, and how important they considered repair. RESULTS: Iterated factor analysis showed "bothered, disfigured, and important to repair" addressed the same domain, so a disfigured/bothersome/repair factor score (DBRFS) was used. A mixed-effects regression model for attractiveness showed small-central and small-peripheral coefficients were not significantly different, χ(2) (1) = 0.03, P = 1.000; but large-central and large-peripheral differences and small-central and large-peripheral differences were significantly different, χ(2) (1) = 10.34, P = 0.004; and χ(2) (1) = 50.55, P < .001, respectively. DBRFS and attractiveness were poorly correlated (χ = -0.29). A mixed-effects regression for DBRFS showed small-central to large-central and the small-central to large-peripheral coefficients were significantly different, χ(2) (1) = 129.20, P < .001; and χ(2) (1) = 115.25, P < .001; but large-central to large-peripheral coefficients were not, χ(2) (1) = 0.14, P = 1.000. CONCLUSIONS: The attractiveness penalty caused by a lesion was correlated with size but not location. Importance to repair was correlated with how disturbing and bothersome it was but not with how the lesion diminished attractiveness. All large lesions and small central lesions were considered important to repair by observers. These results will help us predict the true impact of lesions and support evidence-based treatment plans.

What faces reveal: impaired affect display in facial paralysis.

OBJECTIVES/HYPOTHESIS: To evaluate affect display in patients with facial paralysis as compared with normal subjects. We hypothesized that patients with facial paralysis would have impaired affect display and be perceived as displaying a negative affect as compared with normal subjects. STUDY DESIGN: Randomized controlled experiment. METHODS: Forty naive observers viewed pictures of patients with facial paralysis and normal faces. Observers classified the affect display of the patients and normal subjects by using a survey containing choices regarding primary emotions and personal attributes. RESULTS: An exploratory latent class analysis was performed on the survey results, and the faces were categorized into three types: positive, negative, and neutral. The probability of interpreting normal smiling faces as positive was 98%; the probability of interpreting those in repose as neutral or positive was 60%. The faces with facial paralysis were much more likely to be regarded as negative or neutral. The probability for classification into the negative class was 73% for the paralyzed faces in repose and 69% for the paralyzed smiling faces. In the latent class regression, smiling normal faces were six times more likely to be classified as positive, and smiling paralyzed faces were three times less likely to be in that class. CONCLUSIONS: Patients with facial paralysis were classified as having a negative affect display the vast majority of the time. Antithetically, normal faces in repose were classified as neutral the majority of the time; they were classified as positive the majority of the time when smiling. These novel results demonstrate the impact of the facial paralysis defect on perception by observers. Laryngoscope, 2011.

The straight truth: measuring observer attention to the crooked nose.

OBJECTIVES/HYPOTHESIS: Quantify attentional distraction to crooked noses pre- and postoperatively as compared with normal noses by using an established metric of attention in a pilot study. STUDY DESIGN: Prospective, randomized, controlled experiment with crossover. METHODS: An eye-tracker system was used to record the eye-movement patterns, called scanpaths, of 40 naive observers gazing at pictures of faces with crooked noses preoperatively or postoperatively and pictures of faces without a crooked nose included as "normals." The fixation durations within the nasal area for each group of faces presented were compared. RESULTS: A mixed-design univariate analysis of variance was performed to test the hypothesis that mean fixation times in the nasal region varied by face group. The results were highly statistically significant, F(2,116) = 20.28, P = .000, η(2) = 0.029. Marginal means were calculated for each nasal area of interest group with confidence intervals (normal, 2.32 [2.26-2.38]; preoperative, 2.66 [2.58-2.75]; postoperative, 2.43 [2.35-2.51]). Post hoc testing with Bonferroni correction for three comparisons showed differences between the normal and preoperative groups (χ(2) 41.38, P = .000) and between the preoperative and postoperative groups (χ(2) 14.41, P = .000) but not between the normal and postoperative groups (χ(2) 4.19, P = .12). CONCLUSIONS: There were highly statistically significant differences in attention paid to the nasal area of crooked noses preoperatively and postoperatively, and there were no differences in attention to the nasal area between the postoperative noses and the normal noses. This represents a novel method for objectively evaluating attention and success of surgical procedures to minimize the appearance of deformities.

Bacterial pattern in chronic sinusitis and cystic fibrosis.

OBJECTIVE: To assess the association between pathogenic bacteria found in bronchoalveolar lavages and paranasal cavity cultures in patients with cystic fibrosis (CF) who underwent endonasal endoscopic sinus surgery. The authors hypothesized that the pathogenic bacterial pattern of the upper airway would be associated with that of the lower airway. STUDY DESIGN: Prospective case series with planned data collection. SETTING: Tertiary referral center. SUBJECTS AND METHODS: A group of 16 patients with diagnosis of CF who underwent endonasal endoscopic sinus surgery from July 2001 to August 2009 participated in the study. Culture samples were obtained from bronchoalveolar lavages and paranasal cavities. A Fisher exact test was performed to examine the significance of the association between upper airway and lower airway cultures. RESULTS: The most frequent microorganisms in cultures of para-nasal cavities and bronchoalveolar lavages were Pseudomonas aeruginosa, Staphylococcus aureus, and Streptococcus viridans. Statistical analysis revealed a significant association between upper airway cultures (paranasal cavities) and lower airway cavities (bronchoalveolar lavages) for the 2 most frequent microorganisms, P. aeruginosa and S. aureus (P = .007 and P = .030, respectively). CONCLUSION: The authors confirmed their initial hypothesis that a significant association between bronchoalveolar lavages and sinus cultures was established, once more confirming the idea of a unified airway. They found chronic rhinosinusitis with polyps to be a common clinical presentation in patients with CF. Further studies are required to indicate the role of antibiotics and the pathogenesis of the microorganisms as a manifestation of clinical severity.

The nasal obstruction symptom evaluation survey as a screening tool for obstructive sleep apnea.

OBJECTIVE: To determine if clinical data and Nasal Obstruction Symptom Evaluation (NOSE) scores can be used to identify patients at risk for obstructive sleep apnea (OSA). DESIGN: Intake surveys using the NOSE, Epworth Sleepiness Scale (ESS), and Snore Outcomes Scale (SOS) were administered to new patients visiting a facial plastic surgery practice and a rhinology practice. SETTING: An academic facial plastic surgery practice and an academic rhinology practice. PATIENTS: New patients to both practices. MAIN OUTCOME MEASURES: NOSE score and presence of septal deviation. RESULTS: The odds ratio (OR) for an ESS score higher than 10 was 2.98 (95% confidence interval [CI], 1.17-7.57) when snoring was present; 5.5 (95% CI, 1.35-22.58) when the NOSE score was 10 or higher; and 3.3 (95% CI, 0.98-11.0) when a deviated septum was found on clinical examination. The probability of an elevated ESS score was 88% when all 3 factors were present and 56% when the NOSE score was not elevated. Receiver operating characteristic analysis with predictors "snore" and NOSE score of 10 or higher had an area under the curve of 0.72. With a probability cutoff of 0.5, the sensitivity was 30%, and the specificity 90%. CONCLUSIONS: Sinonasal surgery is among the most common outpatient procedures performed in the United States each year. Many patients undergoing sinonasal surgery have undiagnosed OSA or nasal obstruction, a known risk factor for OSA. Patients with OSA have unique perioperative needs. In patients with nasal obstruction, a deviated septum, and/or snoring, there is an association between the NOSE score and the ESS score. The NOSE survey may serve as a simple screening instrument instead of the ESS for patients at risk for undiagnosed OSA and special perioperative needs.