Graphene-Based Adaptive Thermal Camouflage.

In nature, adaptive coloration has been effectively utilized for concealment and signaling. Various biological mechanisms have evolved to tune the reflectivity for visible and ultraviolet light. These examples inspire many artificial systems for mimicking adaptive coloration to match the visual appearance to their surroundings. Thermal camouflage, however, has been an outstanding challenge which requires an ability to control the emitted thermal radiation from the surface. Here we report a new class of active thermal surfaces capable of efficient real-time electrical-control of thermal emission over the full infrared (IR) spectrum without changing the temperature of the surface. Our approach relies on electro-modulation of IR absorptivity and emissivity of multilayer graphene via reversible intercalation of nonvolatile ionic liquids. The demonstrated devices are light (30 g/m2), thin (<50 µm), and ultraflexible, which can conformably coat their environment. In addition, by combining active thermal surfaces with a feedback mechanism, we demonstrate realization of an adaptive thermal camouflage system which can reconfigure its thermal appearance and blend itself with the varying thermal background in a few seconds. Furthermore, we show that these devices can disguise hot objects as cold and cold ones as hot in a thermal imaging system. We anticipate that, the electrical control of thermal radiation would impact on a variety of new technologies ranging from adaptive IR optics to heat management for outer space applications.

Graphene-gold supercapacitor as a voltage controlled saturable absorber for femtosecond pulse generation.

We report, for the first time to the best of our knowledge, use of a graphene-gold supercapacitor as a voltage controlled fast saturable absorber for femtosecond pulse generation. The unique design involving only one graphene electrode lowers the insertion loss of the device, in comparison with capacitor designs with two graphene electrodes. Furthermore, use of the high-dielectric electrolyte allows reversible, adjustable control of the absorption level up to the visible region with low bias voltages of only a few volts (0-2 V). The fast saturable absorber action of the graphene-gold supercapacitor was demonstrated inside a multipass-cavity Cr:forsterite laser to generate nearly transform-limited, sub-100 fs pulses at a pulse repetition rate of 4.51 MHz at 1.24 µm.

Dynamic tuning of plasmon resonance in the visible using graphene.

We report active electrical tuning of plasmon resonance of silver nanoprisms (Ag NPs) in the visible spectrum. Ag NPs are placed in close proximity to graphene which leads to additional tunable loss for the plasmon resonance. The ionic gating of graphene modifies its Fermi level from 0.2 to 1 eV, which then affects the absorption of graphene due to Pauli blocking. Plasmon resonance frequency and linewidth of Ag NPs can be reversibly shifted by 20 and 35 meV, respectively. The coupled graphene-Ag NPs system can be classically described by a damped harmonic oscillator model. Atomic layer deposition allows for controlling the graphene-Ag NP separation with atomic-level precision to optimize coupling between them.

Graphene-enabled electrically controlled terahertz spatial light modulators.

In this Letter, we demonstrate a broadband terahertz (THz) spatial light modulator using 5×5 arrays of large area graphene supercapacitors. Our approach relies on controlling spatial charge distribution on a passive matrix array of patterned graphene electrodes. By changing the voltage bias applied to the rows and columns, we were able to pattern the THz transmittance through the device with high modulation depth and low operation voltage. We anticipate that the simplicity of the device architecture with high contrast THz modulation over a broad spectral range could provide new tools for THz imaging and communication systems.

Compact terahertz harmonic generation in the Reststrahlenband using a graphene-embedded metallic split ring resonator array.

Harmonic generation is a result of a strong non-linear interaction between light and matter. It is a key technology for optics, as it allows the conversion of optical signals to higher frequencies. Owing to its intrinsically large and electrically tunable non-linear optical response, graphene has been used for high harmonic generation but, until now, only at frequencies < 2 THz, and with high-power ultrafast table-top lasers or accelerator-based structures. Here, we demonstrate third harmonic generation at 9.63 THz by optically pumping single-layer graphene, coupled to a circular split ring resonator (CSRR) array, with a 3.21 THz frequency quantum cascade laser (QCL). Combined with the high graphene nonlinearity, the mode confinement provided by the optically-pumped CSRR enhances the pump power density as well as that at the third harmonic, permitting harmonic generation. This approach enables potential access to a frequency range (6-12 THz) where compact sources remain difficult to obtain, owing to the Reststrahlenband of typical III-V semiconductors.

Alternative surgical approach for the management of uterine prolapse in young women: preliminary results.

AIM: To demonstrate an alternative surgical approach for the management of uterine prolapse in young women by a technique that was previously defined for post-hysterectomy vaginal vault suspension in published work and also to demonstrate successful operative results. METHODS: The study population consisted of 12 women aged 28-41 years who had stage 4 uterine prolapse and who were surgically treated by abdominal hysteropexy using autogenous rectus fascia strips. Operative results and postoperative follow-up Pelvic Organ Prolapse Quantification and Prolapse Quality of Life results were recorded. RESULTS: Mean age of patients was 35.5 ± 4.1 years (range, 28-41). Mean parity in the study group was 2.6 ± 1.0 (range, 1-5). Mean operation time was 32.0 ± 5.2 min (range, 25-42). All patients were discharged on the postoperative 3rd day and no complications were observed postoperatively. Mean follow-up period was 20 ± 7.0 months (range, 12-36). All of the patients had complete remission for uterine prolapse and none of the patients had complaints related to the operation. CONCLUSION: Abdominal hysteropexy operation using rectus fascia strips provides a safe and alternative approach for the management of uterine prolapse in young women who desire to preserve their uterus. But further analysis is needed to confirm our results.

Electrically Tunable Nonlinearity at 3.2 Terahertz in Single-Layer Graphene.

Graphene is a nonlinear material in the terahertz (THz) frequency range, with χ(3) ∼ 10-9 m2/V2 ∼ 15 orders of magnitude higher than that of other materials used in the THz range, such as GaAs or lithium niobate. This nonlinear behavior, combined with ultrafast dynamic for excited carriers, proved to be essential for third harmonic generation in the sub-THz and low (<2.5 THz) THz range, using moderate (60 kV/cm) fields and at room temperature. Here, we show that, for monochromatic high peak power (1.8 W) input THz signals, emitted by a quantum cascade laser, the nonlinearity can be controlled using an ionic liquid gate that tunes the graphene Fermi energy up to >1.2 eV. Pump and probe experiments reveal an intense absorption nonlinearity at 3.2 THz, with a dominant 3rd-order contribution at EF > 0.7 eV, hence opening intriguing perspectives per engineering novel architectures for light generation at frequencies > 9 THz.

Controlled Growth of Single-Crystal Graphene Wafers on Twin-Boundary-Free Cu(111) Substrates.

Single-crystal graphene (SCG) wafers are needed to enable mass-electronics and optoelectronics owing to their excellent properties and compatibility with silicon-based technology. Controlled synthesis of high-quality SCG wafers can be done exploiting single-crystal Cu(111) substrates as epitaxial growth substrates recently. However, current Cu(111) films prepared by magnetron sputtering on single-crystal sapphire wafers still suffer from in-plane twin boundaries, which degrade the SCG chemical vapor deposition. Here, it is shown how to eliminate twin boundaries on Cu and achieve 4 in. Cu(111) wafers with ≈95% crystallinity. The introduction of a temperature gradient on Cu films with designed texture during annealing drives abnormal grain growth across the whole Cu wafer. In-plane twin boundaries are eliminated via migration of out-of-plane grain boundaries. SCG wafers grown on the resulting single-crystal Cu(111) substrates exhibit improved crystallinity with >97% aligned graphene domains. As-synthesized SCG wafers exhibit an average carrier mobility up to 7284 cm2 V-1 s-1 at room temperature from 103 devices and a uniform sheet resistance with only 5% deviation in 4 in. region.

Near- and Far-Field Observation of Phonon Polaritons in Wafer-Scale Multilayer Hexagonal Boron Nitride Prepared by Chemical Vapor Deposition.

Polaritons in layered materials (LMs) are a promising platform to manipulate and control light at the nanometer scale. Thus, the observation of polaritons in wafer-scale LMs is critically important for the development of industrially relevant nanophotonics and optoelectronics applications. In this work, phonon polaritons (PhPs) in wafer-scale multilayer hexagonal boron nitride (hBN) grown by chemical vapor deposition are reported. By infrared nanoimaging, the PhPs are visualized, and PhP lifetimes of ≈0.6 ps are measured, comparable to that of micromechanically exfoliated multilayer hBN. Further, PhP nanoresonators are demonstrated. Their quality factors of ≈50 are about 0.7 times that of state-of-the-art devices based on exfoliated hBN. These results can enable PhP-based surface-enhanced infrared spectroscopy (e.g., for gas sensing) and infrared photodetector applications.

High frequency performance of individual and arrays of single-walled carbon nanotubes.

We have studied the high frequency performance limits of single-walled carbon nanotube (SWNT) transistors in the diffusive transport regime limited by the acoustic phonon scattering. The relativistic band structure of single-walled carbon nanotubes combined with the acoustic phonon scattering provides an analytical model for the charge transport of the radio frequency transistors. We were able to obtain the intrinsic high frequency performance such as the cut-off frequency and the linearity of the SWNT transistors. We have extended our model to include transistors based on arrays of SWNTs. The effect of electrostatic screening in a dense array of SWNTs on the cut-off frequency is studied.

Electrically Tunable Nonequilibrium Optical Response of Graphene.

The ability to tune the optical response of a material via electrostatic gating is crucial for optoelectronic applications, such as electro-optic modulators, saturable absorbers, optical limiters, photodetectors, and transparent electrodes. The band structure of single layer graphene (SLG), with zero-gap, linearly dispersive conduction and valence bands, enables an easy control of the Fermi energy, EF, and of the threshold for interband optical absorption. Here, we report the tunability of the SLG nonequilibrium optical response in the near-infrared (1000-1700 nm/0.729-1.240 eV), exploring a range of EF from -650 to 250 meV by ionic liquid gating. As EF increases from the Dirac point to the threshold for Pauli blocking of interband absorption, we observe a slow-down of the photobleaching relaxation dynamics, which we attribute to the quenching of optical phonon emission from photoexcited charge carriers. For EF exceeding the Pauli blocking threshold, photobleaching eventually turns into photoinduced absorption, because the hot electrons' excitation increases the SLG absorption. The ability to control both recovery time and sign of the nonequilibrium optical response by electrostatic gating makes SLG ideal for tunable saturable absorbers with controlled dynamics.

Balci technique for suspending vaginal vault at vaginal hysterectomy with reduced risk of vaginal vault prolapse.

AIM: The aim of this study was to evaluate the efficacy of a new technique of suspending the vaginal vault at vaginal hysterectomy (VH) for total uterine prolapse. MATERIAL AND METHODS: This prospective study included 65 patients (group 1) in whom VH was performed using the new technique and 110 patients (group 2) in whom VH was performed using the traditional method. Both groups were followed up for 4 years. The incidences of vaginal vault prolapse (VVP), total vaginal length (TVL) (location of vaginal cuff), intraoperative and postoperative complications and sexual function were compared. RESULTS: There were no statistically significant differences between the two groups regarding age, parity, body mass index (BMI), blood loss, intraoperative and postoperative complications, and sexual function. One (1.5%) patient had VVP in group 1, whereas 12 (10.9%) patients had VVP in group 2. TVL in group 1 was 8.9 ± 1.2 cm while in group 2 it was 5.9 ± 0.8 cm. The operation times were 57 ± 5 min and 76 ± 9 min in group 1 and group 2, respectively. There was a statistically significant difference between the two groups regarding VVP (P = 0.022), TVL (P < 0.001) and operation time (P < 0.001). The two groups were also compared regarding anterior and posterior prolapse after 4 years: group 1 had less anterior and posterior prolapse (stage II or more) than group 2 (P = 0.041, P = 0.047), respectively. CONCLUSION: In this new technique, compared to the traditional technique, there was a lower incidence of VVP, greater TVL was achieved and the duration of the operation was shorter.

Bilateral adnexal torsion due to postmenopausal hydatidiform mole.

Occurrence of gestational trophoblastic neoplasia (GTN) and adnexal torsion is rare in postmenopause. We report a 58-year-old postmenopausal woman with adnexal torsion caused by hydatidiform mole. The patient was admitted to our clinic complaining of acute abdominal pain, nausea and vomiting lasting one day. Ultrasonography showed an enlarged uterus including hypo/hyperechogenous cystic areas in the endometrial cavity and bilateral adnexal masses. ß-HCG level was investigated and determined as 157.000 IU/l, because of the suspicion of GTN in ultrasonography. Doppler sonography revealed enlarged left adnexa with absence of vascular flow. The patient underwent total abdominal hysterectomy and bilateral salpingo-oophorectomy. ß-HCG decreased to normal ranges in the fourth postoperative week. The resected uterus contained an endometrial, cystic, grapelike tumor. The ovaries were enlarged bilaterally with necrotic appearance. Histopathology revealed complete hydatidiform mole and theca lutein cysts. To our knowledge, the present case is the first hydatidiform mole associated with bilateral adnexal torsion caused by theca lutein cysts in postmenopausal period.

Effect of pre-amniocentesis counseling on maternal pain and anxiety.

AIM: The aim of this study was to evaluate the levels of anticipated and perceived pain and anxiety in expectant mothers at the times of pre-counseling, post-counseling, and post-amniocentesis and to investigate the effect of pre-amniocentesis counseling on the level of pain and anxiety. MATERIALS AND METHODS: This prospective study was carried out on 240 women with singleton pregnancies at mid-trimester. The maternal pain and anxiety levels associated with the procedure were evaluated using the visual analogue scale. Perceived pain and anxiety were assessed before and after counseling the pregnant woman about amniocentesis, and after amniocentesis. RESULTS: Median anticipated pain levels before (pain 1) and after pre-procedure counseling (pain 2) were 5 and 4, respectively. The actual pain after the procedure (pain 3) was 3. Median levels of anxiety felt by the patients before (anxiety 1) and after pre-procedure counseling (anxiety 2) were 6 and 3, respectively, while the median anxiety after the procedure (anxiety 3) was 5. For the pain and anxiety measurements, the results for each of the comparison times were significantly different from the results for the other two comparison times (P < 0.001). CONCLUSION: Adequate pre-amniocentesis counseling effectively reduces the actual level of pain and anxiety felt by the mother undergoing mid-trimester amniocentesis.

Management and outcomes of adnexal torsion: a 5-year experience.

PURPOSE: To discuss the surgical results of patients with diagnosis of adnexal torsion. METHODS: One hundred and fifty patients with diagnosis of adnexal torsion who presented to our clinic between January 2005 and December 2009 were included in this retrospective analysis. Data regarding age, gravidity, parity, size of mass, operation time, and duration of hospitalization were recorded and compared between the patients who had laparoscopy to those who had laparotomy. The pathological results of patients were also recorded. RESULTS: Fifty-eight patients were treated laparoscopically while 92 patients had laparotomy. The most frequent presenting symptom was pelvic pain (96%). Laparoscopy group consisted of young patients with low parity; operation and hospital stay time was shorter in laparoscopy group. Velocity loss in Doppler ultrasonography was noted in 81.3% of the patients. Of the laparotomy group 35 postmenopausal patients had hysterectomy and bilateral salpingo-oopherectomy, and staging surgery was done for 16 of them. The pathological finding was found to be malignant in four and borderline serous tumor in four patients. CONCLUSION: Laparoscopy is preferred for young patients who want to preserve their fertility. Because of high risk of malignancy in postmenopausal ovarian masses presenting with torsion; frozen section should be used. If not possible or not conclusive, staging surgery is more appropriate especially if there is suspicion of malignancy.

Long-Term Results of an Imperforate Hymen Procedure that Leaves the Hymen Intact.

PURPOSE OF THE STUDY: The aim of this study was to show the clinical results of postoperative evaluation of cases of imperforate hymen that presented at our center during a 21-year period. METHODS: A Foley's catheter was inserted in 74 patients of imperforate hymen who reported to the Department of Obstetrics and Gynecology, Meram Faculty of Medicine, Necmettin Erbakan University, between January 1, 1996, and December 31, 2016 with history of pelvic pain. In each case, the hymen was opened via a circular incision from the central of the distended. A Foley's catheter was inserted, and estrogen cream was prescribed for application on the hymenal structure for 14 days. The catheter was removed after 14 days. RESULTS: The mean age of the patients at the time of this study was 28.3 ± 2.6 years, and the mean age at diagnosis was 13.2 ± 2.5 years. Twenty-nine (96.6%) patients had experienced vaginal bleeding during their first sexual intercourse experience, and one patient (3.4%) had not. Fourteen out of the 30 married women had become pregnant, of whom nine had delivered vaginally and five had delivered via a cesarean section. After undergoing renal ultrasound, none of the patients had any apparent anomalies. Only one patient had a uterine anomaly, which was a bicornuate uterus. CONCLUSION: A circular incision with insertion of Foley's catheter prevents many social problems by preserving the hymen's architecture and allowing vaginal bleeding to occur during the first sexual intercourse experience.

Chip-Scalable, Room-Temperature, Zero-Bias, Graphene-Based Terahertz Detectors with Nanosecond Response Time.

The scalable synthesis and transfer of large-area graphene underpins the development of nanoscale photonic devices ideal for new applications in a variety of fields, ranging from biotechnology, to wearable sensors for healthcare and motion detection, to quantum transport, communications, and metrology. We report room-temperature zero-bias thermoelectric photodetectors, based on single- and polycrystal graphene grown by chemical vapor deposition (CVD), tunable over the whole terahertz range (0.1-10 THz) by selecting the resonance of an on-chip patterned nanoantenna. Efficient light detection with noise equivalent powers <1 nWHz-1/2 and response time ∼5 ns at room temperature are demonstrated. This combination of specifications is orders of magnitude better than any previous CVD graphene photoreceiver operating in the sub-THz and THz range. These state-of-the-art performances and the possibility of upscaling to multipixel architectures on complementary metal-oxide-semiconductor platforms are the starting points for the realization of cost-effective THz cameras in a frequency range still not covered by commercially available microbolometer arrays.

The clinical value of preoperative and intraoperative assessments in the management of endometrial cancer.

OBJECTIVE: In this study, we aimed to investigate the diagnostic accuracy of preoperative assessment and frozen-section analysis (FSA) in endometrial cancer by comparing postoperative histopathology. METHODS: A total of 72 consecutive patients with endometrial cancer were included in this study. Comprehensive surgical staging was performed in all patients. After abdominal hysterectomy, the uterus was investigated for FSA. For preoperative analysis, histological grade and histological subtypes were investigated. In FSA, all the specimens were reviewed for histological subtype, histological grade, depth of myometrial invasion, lymphovascular space invasion (LVI), and cervical involvement. These results were compared with final histopathology. Data were statistically analyzed. RESULTS: The accuracy of preoperative examination was 95.8% (69/72) for histological type and 90% (65/72) for histological grade. In the frozen section, the accuracies of histological grade and subtype were found to be 92% and 98%, respectively. However, histological grade had 43% sensitivity in preoperative and intraoperative assessments. Myometrial invasion and LVI were correctly diagnosed in 93% and 94% of the cases, respectively. The risk assessment was correctly determined in 63 (87%) of 72 patients. Five patients were underclassified, and there was no lymph node invasion in these patients after final histopathology. Lymph node invasion was higher in patients with grade 3 classification, deep myometrial invasion, positive cervical involvement, and LVI. CONCLUSIONS: Frozen-section analysis is a feasible method for the management of the patients with endometrial cancer. However, preoperative and intraoperative assessment of histological grade has lower sensitivity in endometrial cancer.

Comparison of modified biophysical profile and doppler ultrasound in predicting the perinatal outcome at or over 36 weeks of gestation.

AIMS: In this study, modified biophysical profile (MBP) and uterine and umbilical artery Doppler ultrasonographic (USG) analysis were compared in predicting the perinatal outcome of pregnancies at > or =36 weeks. METHODS: Three hundred and fifteen pregnant women were included in this study. Following routine examination, amniotic fluid index, uterine and umbilical artery Doppler indices were evaluated. Nonstress test (NST) was done and MBP was generated. Non-reassuring fetal status (NRFS), perinatal mortality, 5-min APGAR score and umbilical artery pH results were used in evaluating the perinatal outcome. RESULTS: In groups with abnormal MBP and Doppler analysis the results of all parameters were bad. The statistical difference between the groups of normal and abnormal MBP and Doppler analysis was significant. In predicting the NRFS, MBP sensitivity was 60%, umbilical artery Doppler was 50% and uterine artery Doppler was 30%. In case of combination of findings of MBP and umbilical artery Doppler, the sensitivity rose to 70%. CONCLUSION: MBP was proved to be more significant than Doppler analysis in prediction of NRFS and perinatal results, but the sensitivity was increased when both were combined, so combination of MBP and Doppler analysis instead of MBP alone is more significant in antenatal assessment.

The effect of antenatal steroids on fetal lung maturation between the 34th and 36th week of pregnancy.

AIM: To evaluate the effect of antenatal treatment with a single dose of betamethasone between the 34th and the 36th week of pregnancy on the maturation of fetal lung. METHODS: To study 100 pregnant women in their 34th-36th week of pregnancy who were diagnosed as susceptible to have preterm delivery. Fifty patients did not receive betamethasone (group 1). The other 50 patients were administered 12 mg betamethasone in a single dose (group 2). Patients who delivered at least 24 h after the administration of betamethasone were included in this study. After delivery, the Apgar score and the development of respiratory distress syndrome (RDS) in the neonates were compared. RESULTS: Group 2 babies had better Apgar scores when compared to group 1, and the difference was statistically significant. Sixteen (32%) neonates of group 1 and 7 (14%) neonates of group 2 required resuscitation, and the difference was statistically significant (p = 0.032; OR = 0.34, 95% CI 0.12-0.93). RDS was detected in 8 newborns of group 1 and 2 of group 2. The difference was statistically significant (p = 0.046; OR = 0.21, 95% CI 0.04-1.08). CONCLUSION: The administration of a single dose of betamethasone to pregnant women in their 34th-36th week of pregnancy who are likely to have preterm delivery reduces RDS development. There is a need for larger studies to confirm these results.