Explore the vast range of titles available.

The investigation on metalenses have been rapidly developing, aiming to bring compact optical devices with superior properties to the market. Realizing miniature optics at the UV frequency range in particular has been challenging as the available transparent materials have limited range of dielectric constants. In this work we introduce a low absorption loss and low refractive index dielectric material magnesium oxide, MgO, as an ideal candidate for metalenses operating at UV frequencies. We theoretically investigate metalens designs capable of efficient focusing over a broad UV frequency range (200–400 nm). The presented metalenses are composed of sub-wavelength MgO nanoblocks, and characterized according to the geometric Pancharatnam–Berry phase method using FDTD method. The presented broadband metalenses can focus the incident UV light on tight focal spots (182 nm) with high numerical aperture ( NA ≈ 0.8 ). The polarization conversion efficiency of the metalens unit cell and focusing efficiency of the total metalens are calculated to be as high as 94%, the best value reported in UV range so far. In addition, the metalens unit cell can be hybridized to enable lensing at multiple polarization states. The presented highly efficient MgO metalenses can play a vital role in the development of UV nanophotonic systems and could pave the way towards the world of miniaturization.

The growing demand for complex nanophotonic devices that operate in the ultraviolet (UV) range necessitates the development of innovative compatible optical devices, particularly for use in lithography applications. In this context, we introduce the first non-contrast dielectric flat metalenses that offer tunable multi-focal polarization channeling in the UV region. The metalens we have developed consists of equally spaced Al O nanoblocks carved on an Al O substrate. We demonstrate that controlling the arrangement of nanoblocks on the substrate provides a sufficient geometric phase (Pancharatnam-Berry phase) for developing spatially tunable quadruple-focal metalens in the UV region. While illuminating with the linear polarized light, precise manipulation of the phase profile generates multiple tightly confined focal points, where each possesses different controllable circular polarization states. This feature makes the offered approach a suitable strategy for spatially controlled polarization filtering and channeling. Our design also shows high polarization conversion efficiency in the whole UV spectrum. As proof of concept, we show the focusing characteristics of our designed metalens at four chosen wavelengths. This study demonstrates a promising basis for further development of UV nanophotonic devices and potentially opens up new opportunities for future employment of flat optics in a variety of industrial applications in the UV range.

Mission resilience is a primary consideration for naval platforms operating in contested maritime environments. It is a concept that encapsulates a platform’s ability to endure, and to survive threats that affect the achievement of mission objectives. Historically, platform survivability analysis was constrained by “stove piping” the analysis within individual survivability domains (susceptibility, vulnerability and recoverability). However, the trade-space combining susceptibility, vulnerability and recoverability in a temporal framework enables holistic survivability analysis. This is referred to as “Integrated Survivability”. To demonstrate the utility of Integrated Survivability analysis, and its contribution to mission resilience, a naval platform survivability case study was developed. The case study examined the achievement of a mission objective for four platform configurations exposed to a detonating weapon threat. There were three primary outcomes. Firstly, the case study demonstrated a platform general arrangement configuration change to improve crew access, instead of a technological solution, provided the best outcome for achieving the mission objective. Secondly, the case study demonstrated the use of a warship computer model specifically designed for naval platform survivability analysis. This warship model is an unclassified, generalised naval platform representation designed to foster collaboration and for documenting research in the open literature. Finally, the case study enabled the development of a workflow to facilitate Integrated Survivability analysis for the enhancement of the fleet-in-being and assessment of future naval platform acquisitions.

We theoretically investigate a multi-resonant plasmonic metamaterial perfect absorber operating between 600 and 950 nm wavelengths. The presented device generates 100% absorption at two resonance wavelengths and delivers an ultra-narrow band (sub-20 nm) and high quality factor (Q=44) resonance. The studied perfect absorber is a metal–insulator–metal configuration where a thin MgF2 spacer is sandwiched between an optically thick gold layer and uniformly patterned gold circular nanodisc antennas. The localized and propagating nature of the plasmonic resonances are characterized and confirmed theoretically. The origin of the perfect absorption is investigated using the impedance matching and critical coupling phenomenon. We calculate the effective impedance of the perfect absorber and confirm the matching with the free space impedance. We also investigate the scattering properties of the top antenna layer and confirm the minimized reflection at resonance wavelengths by calculating the absorption and scattering cross sections. The excitation of plasmonic resonances boost the near-field intensity by three orders of magnitude which enhances the interaction between the metamaterial surface and the incident energy. The refractive index sensitivity of the perfect absorber could go as high as S=500 nm/RIU. The presented optical characteristics make the proposed narrow-band multi-resonant perfect absorber a favorable platform for biosensing and contrast agent based bioimaging.

Development of low cost nanolithography tools for precisely creating a variety of nanostructure shapes and arrangements in a high-throughput fashion is crucial for next generation biophotonic technologies. Although existing lithography techniques offer tremendous design flexibility, they have major drawbacks such as low-throughput and fabrication complexity. In addition the demand for the systematic fabrication of sub-100 nm structures on flexible, stretchable, non-planar nanoelectronic/photonic systems and multi-functional materials has fueled the research for innovative fabrication methods in recent years. This thesis research investigates a novel lithography approach for fabrication of engineered plasmonic nanostructures and metamaterials operating at visible and infrared wavelengths. The technique is called Nanostencil Lithography (NSL) and relies on direct deposition of materials through nanoapertures on a stencil. NSL enables high throughput fabrication of engineered antenna arrays with optical qualities similar to the ones fabricated by standard electron beam lithography. Moreover, nanostencils can be reused multiple times to fabricate series of plasmonic nanoantenna arrays with identical optical responses enabling high throughput manufacturing. Using nanostencils, very precise nanostructures could be fabricated with 10 nm accuracy. Furthermore, this technique has flexibility and resolution to create complex plasmonic nanostructure arrays on the substrates that are difficult to work with e-beam and ion beam lithography tools. Combining plasmonics with polymeric materials, biocompatible surfaces or curvilinear and non-planar objects enable unique optical applications since they can preserve normal device operation under large strain. In this work, mechanically tunable flexible optical materials and spectroscopy probes integrated on fiber surfaces that could be used for a wide range of applications are demonstrated. Finally, the first application of NSL fabricated low cost infrared nanoantenna arrays for plasmonically enhanced vibrational biospectroscopy is presented. Detection of immunologically important protein monolayers with thickness as small as 3 nm, and antibody assays are demonstrated using nanoantenna arrays fabricated with reusable nanostencils. The results presented indicate that nanostencil lithography is a promising method for reducing the nano manufacturing cost while enhancing the performance of biospectroscopy tools for biology and medicine. As a single step and low cost nanofabrication technique, NSL could facilitate the manufacturing of biophotonic technologies for real-world applications.

Introduction Critically ill patients are frequently encountered in the emergency department (ED) and requiring rapid diagnosis and treatment. It has been shown that fingerstick tests shorten examination and treatment durations in the ED. The aim of this study was to assess the agreement between fingerstick creatinine measurements and serum creatinine values obtained by laboratory enzymatic testing. Methods This study was conducted as a single center, prospective, observational study. 250 patients aged 18 years and over who applied to the adult emergency department between 12.12.2023 and 30.12.2023 and underwent the necessary serum biochemistry examination were included in the study. In addition to the blood biochemistry tests were requested by the patients’ doctors, blood samples taken from the patients’ fingertips were scanned using the i-STAT device and a creatinine cartridge. Intraclass correlation coefficient (ICC) was used to examine the consistency between serum creatinine values measured in the laboratory and fingerstick creatinine values, and the type 1 error level was set as 0.05. A graphical approach, the Bland-Altman plot was used to examine the agreement between measurements. A significance level of 0.05 was used for all comparisons. Results In this study, after exclusion of 4 patients due to kit problems, 133 patients (54.16%) were female and 113 patients (45.94%) were male. The median age was found to be 55.5. A strong agreement was found between the measured values (ICC: 0.996). Patients when analyzed among themselves in terms of admission complaints, existing diseases, age, gender, admission vital signs and glomerular filtration rates, a strong agreement was observed between fingertip creatinine and serum creatinine in each group. Conclusion In conclusion, the fingerstick creatinine test may be considered for early use in patients presenting to the ED, as it is easily applicable in examination and treatment management and has strong agreement rates with laboratory values.

Little is known about the impact of COVID-19 on the outcomes of patients undergoing surgery and intervention. This study was conducted between 20 March and 20 May 2020 in six hospitals in Istanbul, and aimed to investigate the effects of surgery and intervention on COVID-19 disease progression, intensive care (ICU) need, mortality and virus transmission to patients and healthcare workers. Patients were examined in three groups: group I underwent emergency surgery, group II had an emergency non-operating room intervention, and group III received inpatient COVID-19 treatment but did not have surgery or undergo intervention. Mortality rates, mechanical ventilation needs and rates of admission to the ICU were compared between the three groups. During this period, patient and healthcare worker transmissions were recorded. In total, 1273 surgical, 476 non-operating room intervention patients and 1884 COVID-19 inpatients were examined. The rate of ICU requirement among patients who had surgery was nearly twice that for inpatients and intervention patients, but there was no difference in mortality between the groups. The overall mortality rates were 2.3% in surgical patients, 3.3% in intervention patients and 3% in inpatients. COVID-19 polymerase chain reaction positivity among hospital workers was 2.4%. Only 3.3% of infected frontline healthcare workers were anaesthesiologists. No deaths occurred among infected healthcare workers. We conclude that emergency surgery and non-operating room interventions during the pandemic period do not increase postoperative mortality and can be performed with low transmission rates.

Background Gastric cancer (GC) has a high mortality rate due to the diagnosis in advanced stages. Aberrant DNA methylation is the earliest event in carcinogenesis and can be noninvasively detected in cell-free DNA (cfDNA) from gastric cancer patients. Methods A total of 143 serum samples were analyzed, including 33 GC patients, 30 chronic gastritis (ChG) patients, and 80 healthy individuals. Additionally, tissue samples were collected from 30 GC patients (stages I–IV) and 38 ChG patients. Methylation patterns of ten genes were examined in GC cells, as well as in serum and tissue samples from GC, ChG, and control groups using methylation-specific qPCR. Statistical evaluations were conducted on various parameters including Ct differences, categorical variables, sensitivity, and specificity. Results APC, CDH1, RASSF1A, hMLH1, RUNX3, p16, SFRP2, RNF180, PCDH10, and RPRM were all significantly hypermethylated in the tissues of GC patients compared to those with ChG ( P  < 0.001). SFRP2, RPRM, APC, PCDH10, and RNF180 genes were analyzed in sera of 3 groups. Among them, SFRP2 methylation was detected in 71.87% of GC, 16.6% of ChG and 8.8% of the control group. The methylation frequencies of RPRM were 66.6% in GC, 13.3% in ChG, and 7.5% in the control group. In a dual-gene panel assay combining SFRP2 and RPRM, the sensitivity and specificity for detecting gastric cancer in serum samples were 57.58% and 96.25%, respectively, when comparing the cancer and control groups. The sensitivity was 78.79%, the specificity was 90.00% and AUC was 0.931 for GC and control groups ( P  < 0.0001). The sensitivity was 78.79%, the specificity was 83.33% and AUC was 0.879 for the discrimination of GC and ChG ( P  < 0.0001). Conclusions Methylation of 10 genes were studied and a prototype early diagnosis tool for GC utilizing SFRP2 and RPRM with high sensitivity and specificity was developed.

Purpose To investigate the treatment outcomes of extracranial oligometastatic colorectal cancer (CRC) patients treated with stereotactic body radiotherapy (SBRT). Materials and methods The clinical data of 388 extra-cranial oligometastatic CRC (≤ 5 lesions) patients and 463 lesions treated with SBRT at 19 cancer institutions were retrospectively analyzed. The prognostic factors predicting overall survival (OS), progression-free survival (PFS), and local control (LC) were assessed in uni- and multivariable analyses. Results The median age was 62 years (range, 29–92 years). The majority of the patients (90.5%) received surgery and systemic treatment for their primary tumor, had ≤ 2 metastasis (83.3%), had single organ involvement (90.3%), and staged using flouro-deoxyglucose positron emission tomography (FDG-PET/CT) (76%). The median fraction and total radiation doses were 10 Gy (range: 6–34 Gy) and 50 Gy (range: 8–64 Gy), respectively, delivered in a median of 4 fractions (range: 1–8). The median follow-up time for the entire cohort was 30.7 months (interquartile range: 27.0–34.3 months). The 3‑year OS, PFS, and LC rates were 64.0%, 42.3%, and 72.7%, respectively. The 3‑year LC rate was significantly higher in patients receiving BED 10  ≥ 100 Gy than those receiving BED 10  < 100 Gy (76.0% vs. 67.3%; p  = 0.04). The 3‑year PFS and OS rates were higher in patients receiving BED 10  ≥ 100 Gy than those receiving BED 10  < 100 Gy (33.2% vs. 25.2%; p  = 0.03; 53.7% vs.  44.8%; p  = 0.02). Single metastasis and complete response after SBRT were independent prognostic factors for survival in multivariable analysis. Conclusions In this multi-center study, we demonstrated that SBRT is an effective treatment option of metastatic lesions in oligometastatic CRC patients by providing promising LC rates. Higher SBRT doses beyond BED 10  ≥ 100 Gy were associated with improved LC and survival. LC of treated lesion and lower tumor burden after SBRT were associated with better outcomes.

Objective This study evaluates various craniospinal irradiation (CSI) techniques used in Turkish centers to understand their advantages, disadvantages and overall effectiveness, with a focus on enhancing dose distribution. Methods Anonymized CT scans of adult and pediatric patients, alongside target volumes and organ-at-risk (OAR) structures, were shared with 25 local radiotherapy centers. They were tasked to develop optimal treatment plans delivering 36 Gy in 20 fractions with 95% PTV coverage, while minimizing OAR exposure. The same CT data was sent to a US proton therapy center for comparison. Various planning systems and treatment techniques (3D conformal RT, IMRT, VMAT, tomotherapy) were utilized. Elekta Proknow software was used to analyze parameters, assess dose distributions, mean doses, conformity index (CI), and homogeneity index (HI) for both target volumes and OARs. Comparisons were made against proton therapy. Results All techniques consistently achieved excellent PTV coverage (V95 > 98%) for both adult and pediatric patients. Tomotherapy closely approached ideal Dmean doses for all PTVs, while 3D-CRT had higher Dmean for PTV_brain. Tomotherapy excelled in CI and HI for PTVs. IMRT resulted in lower pediatric heart, kidney, parotid, and eye doses, while 3D-CRT achieved the lowest adult lung doses. Tomotherapy approached proton therapy doses for adult kidneys and thyroid, while IMRT excelled for adult heart, kidney, parotid, esophagus, and eyes. Conclusion Modern radiotherapy techniques offer improved target coverage and OAR protection. However, 3D techniques are continued to be used for CSI. Notably, proton therapy stands out as the most efficient approach, closely followed by Tomotherapy in terms of achieving superior target coverage and OAR protection.