Rectangular split-ring resonators with single-split and two-splits under different excitations at microwave frequencies

In this work, transmission characteristics of rectangular split-ring resonators with single-split and two-splits are analyzed at microwave frequencies. The resonators are coupled with monopole antennas for excitation. The scattering parameters of the devices are investigated under different polarizations of E and H fields. The magnetic resonances induced by E and H fields are identified and the differences in the behavior of the resonators due to orientations of the fields are explained based on simulation and experimental results. The addition of the second split of the device is investigated considering different configurations of the excitation vectors. It is demonstrated that the single-split and the two-splits resonators exhibit identical transmission characteristics for a certain excitation configuration as verified with simulations and experiments. The presented resonators can effectively function as frequency selective media for varying excitation conditions

MEMS-Based Terahertz Detectors

A MEMS based novel THz detector structure is designed and realized by micro fabrication. The detector is then characterized to extract its mechanical performance. Operating in 1-5 THz band, the detector has a pixel size of 200 μm × 200 μm. Bimaterial suspension legs consist of Parylene-C and titanium, the pair of which provides a high mismatch in coefficients of thermal expansion. The pixel is a suspended Parylene-C structure having a 200 nm-thick titanium metallization. Operation principle relies on conversion of absorbed THz radiation into heat energy on the pixel. This increases the temperature of the free-standing microstructure that is thermally isolated from the substrate. The increase in temperature induces mechanical deflection due to bimaterial springs. The detector is designed to deliver a noise equivalent temperature difference (NETD) less than 500 mK and a refresh rate of 30 Hz

A micromachined freestanding terahertz absorber with an array of metallic patches

An array of square metallic patches on a thin suspended dielectric layer is introduced as an effective terahertz absorber. The suspended structure is placed on a metalized substrate and the device exhibits metamaterial behavior at specific frequencies determined by the size of the patches. It is feasible to place patches with different sizes in an array formation for a broadband absorber. In array configuration, individual elements induce distinct resonances yielding narrow band absorption regions. Design of the absorber is described using electromagnetic simulations. The absorber structure was fabricated on a silicon wafer using standard microfabrication techniques. The characteristics of the absorber were measured using a terahertz time domain spectroscope. The measured data match well the simulations indicating strong absorption peaks in a band of 0.5-2 THz

Embroidered Rectangular Split-Ring Resonators for the Characterization of Dielectric Materials

In this paper, we report an embroidered rectangular split-ring resonator (SRR) operating at S band for material characterization based on the differences in dielectric parameters. We designed, fabricated and characterized SRR sensors on a conventional fabric that can be conformally attached over the surface of samples under investigation. The structures are made of conductive threads and can be embroidered on any dielectric fabric at low cost using conventional embroidery methods. We have demonstrated material characterization capability of the sensors using a specific design with a length of 60 mm and a width of 30 mm. We wrapped the sensors on low-density polyethylene (LDPE) bottles filled with deionized (DI) water and common solvents (ethanol, methanol, isopropanol and acetone) in our experiments. We measured the nominal resonant frequency of a specific sensor wrapped around an empty bottle as 2.07 GHz. The shifts in resonant frequencies when the bottle was filled with the solvents follow the dielectric constants of the solvents

A Suspended Array of Square Patch Metamaterial Absorbers for Terahertz Applications

A suspended array of square metallic patches on a thin dielectric layer is introduced as a terahertz absorber. The absorber is fabricated on a metalized substrate and the device exhibits metamaterial behavior at specific frequencies determined by the size of the patches. It is feasible to place patches with different sizes in an array formation for a broadband absorber. Design of the absorber is described using electromagnetic simulations. The absorber structure was fabricated on a silicon wafer and its characteristics were measured using a terahertz time domain spectroscope. The measured data match well the simulations indicating strong absorption peaks in a band of 0.5-2 THz

A Microwave Ring Resonator Based Glucose Sensor

A microwave ring resonator based glucose detecting biosensor incorporating glucose oxidase enzyme is presented. Sensor uses a split ring resonator as a transducer, where the sensing operation is done by the observation of shifts in its resonant frequency. Resonator was fabricated with basic fabrication techniques and the enzyme was immobilized via conductive polymer agent PEDOT:PSS. Experimentally observed redshift of resonant frequency of the sensor in response to different loading conditions are in agreement with simulation results and theoretical expectations. Sensor selectivity is confirmed with control experiments conducted with NaCl solutions. Experiments done with different glucose solution concentrations yielded a sensor sensitivity of 0.174MHz/mgml-1

Integrating microfluidics and biosensing on a single flexible acoustic device using hybrid modes

Integration of microfluidics and biosensing functionalities on a single device holds promise in continuous health monitoring and disease diagnosis for point-of-care applications. However, the required functions of fluid handling and biomolecular sensing usually arise from different actuation mechanisms. In this work, we demonstrate that a single acoustofluidic device, based on a flexible thin film platform, is able to generate hybrid waves modes, which can be used for fluidic actuation (Lamb waves) and biosensing (thickness shear waves). On this integrated platform, we show multiple and sequential functions of mixing, transport and disposal of liquid volumes using Lamb waves, whilst the thickness bulk shear waves allow us to sense the chemotherapeutic Imatinib, using an aptamer-based strategy, as would be required for therapy monitoring. Upon binding, the conformation of the aptamer results in a change in coupled mass, which has been detected. This platform architecture has the potential to generate a wide range of simple sample-to-answer biosensing acoustofluidic devices

Oncogenic mutations on Rac1 affect global intrinsic dynamics underlying GTP and PAK1 binding

Rac1 is a small member of the Rho GTPase family. One of the most important downstream effectors of Rac1 is a serine/threonine kinase, p21-activated kinase 1 (PAK1). Mutational activation of PAK1 by Rac1 has oncogenic signaling effects. Here, although we focus on Rac1-PAK1 interaction by atomic-force-microscopy-based single-molecule force spectroscopy experiments, we explore the effect of active mutations on the intrinsic dynamics and binding interactions of Rac1 by Gaussian network model analysis and molecular dynamics simulations. We observe that Rac1 oncogenic mutations are at the hinges of three global modes of motion, suggesting the mechanical changes as potential markers of oncogenicity. Indeed, the dissociation of wild-type Rac1-PAK1 complex shows two distinct unbinding dynamic states that are reduced to one with constitutively active Q61L and oncogenic Y72C mutant Rac1, as revealed by single-molecule force spectroscopy experiments. Q61L and Y72C mutations change the mechanics of the Rac1-PAK1 complex by increasing the elasticity of the protein and slowing down the transition to the unbound state. On the other hand, Rac1’s intrinsic dynamics reveal more flexible GTP and PAK1-binding residues on switches I and II with Q61L, Y72C, oncogenic P29S and Q61R, and negative T17N mutations. The cooperativity in the fluctuations of GTP-binding sites around the p-loop and switch I decreases in all mutants, mostly in Q61L, whereas some PAK1-binding residues display enhanced coupling with GTP-binding sites in Q61L and Y72C and within each other in P29S. The predicted binding free energies of the modeled Rac1-PAK1 complexes show that the change in the dynamic behavior likely means a more favorable PAK1 interaction. Overall, these findings suggest that the active mutations affect intrinsic functional dynamic events and alter the mechanics underlying the binding of Rac1 to GTP and upstream and downstream partners including PAK1

Construct validity of auditory verbal learning test

Amaç: İşitsel Sözel Öğrenme Testi (Auditory Verbal Learning Test: AVLT) nöropsikoloji yazınında, belleğin kapsamlı değerlendirilmesi için sıklıkla kullanılan bir ölçüm aracıdır. Test sözel öğrenmeyi; anlık ve gecikmeli serbest hatırlama, tanıma türü hatırlama, geriye ve ileri doğru bozucu etki olarak ölçmektedir. Türk toplumuna uyarlama çalışmaları yapılmış olan AVLT’nin araştırma ve geliştirme (AR-GE) çalışmaları sürmektedir. Mevcut çalışmanın amacı; testin AR-GE sürecine katkı sağlamak amacıyla kurutlu geçerliğini incelemektir. Yöntem: Mevcut amaç doğrultusunda 20-69 yaş aralığında, tanılanmış herhangi bir psikiyatrik veya nörolojik rahatsızlığın bulunmayan; düzeltilmemiş görme ve işitme bozukluğu bulunmayan 78 sağlıklı katılımcıdan veriler elde edilmiştir. AVLT bu testi uygulama eğitimi almış iki psikolog tarafından, katılımcılara bireysel olarak uygulanmıştır. Bulgular: AVLT puanlarının temsil ettikleri özellik kümelerini incelemek amacıyla uygulanan temel bileşenler analizi, testin yapısıyla uyumlu olarak öğrenme ve serbest hatırlama, tanıma türü hatırlama bileşenlerini ayrı ayrı içermiştir. Yapısal Eşitlik Modeli (YEM) çalışmasında ise bu iki bileşene çeldiricilerin etkisi eklenmiştir. Yaş, eğitim ve cinsiyetin AVLT puanlarıyla ilişkisini belirlemek amacıyla, betimsel düzeyde incelemeler yapılmıştır. Sonuç: Belleğin gelişimsel süreçten etkilendiği yolundaki yazınla uyumlu olan bu bulgular AVLT’nin öğrenme/serbest hatırlama, tanıma ve çeldirici puanlarının kuramsal bilgiyle uyumlu bir bileşen örüntüsü gösterdiğini ortaya koymaktadır. Bu sonuç Türk toplumunda testin, geçerli bir ölçme aracı olduğuna işaret etmektedir.Objective: Auditory Verbal Learning Test (AVLT) is frequently used in neuropsychology literature to comprehensively assess the memory. The test measures verbal learning as immediate and delayed free recall, recognition, and retroactive and proactive interference. Adaptation of AVLT to the Turkish society has been completed, whereas research and development studies are still underway. The purpose of the present study is to investigate the construct validity of the test in order to contribute to the research and development process. Method: In line with this purpose, the research data were obtained from 78 healthy participants aged between 20 and 69. The exclusion criteria included neurological and/or psychiatric disorders as well as untreated auditory/visual disorders. AVLT was administered to participants individually by two trained psychologists. Results: Principal component analysis that is used to investigate the components represented by the AVLT scores consisted of learning, free recall and recognition, in line with the construct of the test. Distractors were also added to these two components in structural equation model. Analyses were carried out on descriptive level to establish the relatioships between age, education, gender and AVLT scores. Conclusion: These findings, which are consistent with the literature indicating that memory is affected by the developmental process, suggest that learning/free recall, recognition, and distractor scores of the AVLT demonstrate a component pattern consistent with theoretical knowledge. This conclusion suggests that AVLT is a valid measurement test for the Turkish society