Generalized Parity-Time Symmetry Condition for Enhanced Sensor Telemetry

Wireless sensors based on micro-machined tunable resonators are important in a variety of applications, ranging from medical diagnosis to industrial and environmental monitoring.The sensitivity of these devices is, however, often limited by their low quality (Q) factor.Here, we introduce the concept of isospectral party time reciprocal scaling (PTX) symmetry and show that it can be used to build a new family of radiofrequency wireless microsensors exhibiting ultrasensitive responses and ultrahigh resolution, which are well beyond the limitations of conventional passive sensors. We show theoretically, and demonstrate experimentally using microelectromechanical based wireless pressure sensors, that PTXsymmetric electronic systems share the same eigenfrequencies as their parity time (PT)-symmetric counterparts, but crucially have different circuit profiles and eigenmodes. This simplifies the electronic circuit design and enables further enhancements to the extrinsic Q factor of the sensors

Comparison of Charge-Coupled Devices and Photostimulable Phosphor Storage Plates for Detection of Vertical Root Fractures in Endodontically Treated Teeth: An In Vitro Study

Objective: Vertical root fracture (VRF) is among the most common causes of endodontic treatment failures. This study aims to compare charge-coupled devices (CCD) and photostimulable phosphor plates (PSP) for detection of vertical root fractures in endodontically treated teeth.Methods: In this diagnostic in vitro study, 40 maxillary anterior teeth were selected and after preparation and root canal filling, their crowns were cut 2mm above the cementoenamel junction (CEJ). The teeth were embedded in a piece of dried bone and radiographed using CCD and PSP with equal geometry at zero and 15° horizontal angles. VRFs were then induced and the fractured fragments were reattached. The teeth were radiographed again. Three observers evaluated the radiographs for detection of fracture line. Data were analyzed using the Proportion test and Wilcoxon’s Signed Ranks test.Results: No significant difference was found between the two sensors in detection of VRFs [p-value (complete)= 0.592, p-value (absolute)= 1]. The sensitivity of the two sensors for detection of buccolingual and mesiodistal fractures was not significantly different [p-value BL (absolute)= 0.109, p-value BL (complete) 0.180] [p-value MD (complete)=0.593, p-value MD (absolute)= 0.102]. The sensitivity of both sensors for detection of buccolingual fracture was higher than for mesiodistal fractures (p<0.001).Conclusion: CCD and PSP had equal efficacy for detection of VRFs in endodontically treated teeth

Langerhans' cell histiocytosis with multiple radiolucent lesions in the body of the mandible,report of a case

Introduction: Langerhans cell histiocytosis (LCH) refers to a group of rare reticuloendothelial system disorders and it occurs most often in young adults and children. A 57-year-old edentulous female patient who complained of dull pain in the posterior region of the mandible referred to the dental office, with a complaint of dull pain in the posterior region of the mandible. The lesion was diagnosed as LCH. Oral manifestations could be the first signs of Langerhans' cell histiocytosis. Therefore, the dentist must be aware of the oral symptoms so in order that the disease is not overlooked

Age Estimation from Pulp/Tooth Area Ratio Using Digital Panoramic Radiography

Background and Aim: To estimate the age in forensic identification, when none of the other identification methods are feasible, the teeth are used. The aim of the present study was to estimate the age from pulp/tooth area ratio (AR) by digital panoramic radiography in patients referred to a radiology clinic. Materials and Methods: In this diagnostic study, digital panoramic radiographs of 120 cases were assessed. The chronological age was calculated by subtracting the date of birth from the date of radiographs and the AR was calculated with "AutoCAD" software. Using the regression model, the age was estimated. In this study, the role of sex was also assessed. Results: The mean difference between the chronological and the estimated age was 0.11 years in male group. The correlation coefficient was -0.180 and the correlation between age and AR was not statistically significant (p= 0.169). The mean difference between the chronological and estimated age was 0.36 years in female group. Correlation coefficient was -0.336 and the correlation between age AR was significant (p= 0.004). Negative cor-relation indicates that AR decreases by aging. Conclusion: According to the results, AR cannot be used for age estimation alone but it can be used in combination with other indices for this purpose

Giant Photoresponsivity of Midinfrared Hyperbolic Metamaterials in the Photon-Assisted-Tunneling Regime

We explore broadband and omnidirectional midinfrared rectification based on nanopatterned hyperbolic metamaterials, composed of two dissimilar metals separated by an ultrathin dielectric layer. The exotic slow-light modes supported by such periodically trenched hyperbolic metamaterials efficiently trap incident radiation in massively parallel metal-insulator-metal tunnel junctions producing ultrafast infrared rectification via photon-assisted tunneling. This leads to a highly efficient photon-to-electron transduction with obtained photocurrent orders of magnitude larger than conventional lumped-element devices, such as nanorectennas and point-contact rectifiers. Our results promise an impact on infrared energy harvesters and plasmonic photodetectors.Electrical and Computer Engineerin

Low-Threshold Lasing and Coherent Perfect Absorption in the Generalized PT-Symmetric Optical Structures

Achieving exact balance between spatially separated gain and loss is generally regarded as a necessary condition for parity-time- (PT-)symmetric optical systems. We introduce generalized PT- (GPT-)symmetric optical structures, which have an asymmetric and unbalanced gain-loss profile, while exhibiting similar scattering properties and phase transitions as their traditional PT-symmetric counterparts. In particular, we show that the concept of GPT symmetry may help to reduce the threshold gain in achieving newly discovered PT-enabled applications, such as the coherent perfect absorber laser and exceptional points. The concept proposed herein will facilitate the practice of PT-symmetric optical and photonic devices by offering greater design flexibility to tailor gain-loss profiles and their thresholds

Comparison of the Absorbed Dose of Target Organs in Conventional and Digital Lateral Cephalometric Radiography

Background and Aim: Due to the widespread use of lateral cephalometric radiography especially in orthodontic therapy and orthognathic surgery, obtaining radiographs of high quality with the least amount of radiation exposure is of utmost importance. The aim of this study was to compare the absorbed dose of head and neck target organs in conventional and digital lateral cephalometric radiography .   Materials and Methods : In this experimental study, RANDO phantom was used for absorbed dose estimation in thyroid, parotid, pituitary and submandibular glands, bone marrow and ocular lens. The phantom was exposed 60 times: 30 times with CRANEX Tome, Soredex and 30 times with CRANEX D, Soredex with standard exposure settings. TLD (GR-200) dosimeters were used to measure organ doses. A total of 69 TLDs were used with 9 TLDs for background radiation. T-test was used for statistical analysis .   Results: The mean absorbed dose of target organs was 0.04±0.005 mSv for conventional and 0.01±0.002 mSv for digital technique. The difference in absorbed dose in all target organs except for the thyroid gland (P=0.08) between the two techniques of conventional and digital was statistically significant. (P=0.01 ).   Conclusion: Use of digital lateral cephalometric system causes a significant reduction in absorbed dose compared to the conventional film-screen syste

Diagnostic Accuracy of CBCT with Different Voxel Sizes and Intraoral Digital Radiography for Detection of Periapical Bone Lesions: An Ex-Vivo Study

Objectives: This study sought to assess the diagnostic accuracy of cone beam computed tomography (CBCT) with different voxel sizes and intraoral digital radiography with photostimulable phosphor (PSP) plate for detection of periapical (PA) bone lesions. Materials and Methods: In this ex vivo diagnostic study, one-millimeter defects were created in the alveolar sockets of 15 bone blocks, each with two posterior teeth. A no-defect control group was also included. Digital PA radiographs with PSP plates and CBCT scans with 200, 250 and 300μ voxel sizes were obtained. Four observers evaluated the possibility of lesion detection using a 5-point scale. Sensitivity, specificity, positive predictive value (PPV) and negative predicative value (NPV) were analyzed using one-way ANOVA and Tamhane’s post hoc test. Kappa and weighted kappa statistics were applied to assess intraobserver and interobserver agreements. Results: Cochrane Q test showed no significant difference between PSP and CBCT imaging modalities in terms of kappa and weighted kappa statistics (P=0.675). The complete sensitivity and complete NPV for 200 and 250 μ voxel sizes were higher than those of 300 μ voxel size and digital radiography (P<0.001). No significant difference was noted in other parameters among other imaging modalities (P=0.403). Conclusions: The results showed that high-resolution CBCT scans had higher diagnostic accuracy than PSP digital radiography for detection of artificially created PA bone lesions. Voxel size (field of view) must be taken into account to minimize patient radiation dose.

Generalized parity–time symmetry condition for enhanced sensor telemetry

Wireless sensors based on micromachined tunable resonators are important in a variety of applications, ranging from medical diagnosis to industrial and environmental monitoring. The sensitivity of these devices is, however, often limited by their low quality (Q) factor. Here, we introduce the concept of isospectral party–time–reciprocal scaling (PTX) symmetry and show that it can be used to build a new family of radiofrequency wireless microsensors exhibiting ultrasensitive responses and ultrahigh resolution, which are well beyond the limitations of conventional passive sensors. We show theoretically, and demonstrate experimentally using microelectromechanical-based wireless pressure sensors, that PTX-symmetric electronic systems share the same eigenfrequencies as their parity–time (PT)-symmetric counterparts, but crucially have different circuit profiles and eigenmodes. This simplifies the electronic circuit design and enables further enhancements to the extrinsic Q-factor of the sensors

Correction: Generalized parity-time symmetry condition for enhanced sensor telemetry (Nature Electronics (2018) DOI: 10.1038/s41928-018-0072-6)

© 2018 The Author(s). In the version of this Article originally published, a division symbol was mistakenly omitted from both of the y axis labels in Fig. 5a. The label in the left panel should have read \u27Re((ω×ω0)/2π) (MHz)\u27 and the label in the right panel should have read \u27Im((ω×ω0)/2π) (MHz)\u27. This has now been corrected