Lens Dimensions Research Articles

Autostereoscopic 3D viewing can change the dimensions of the crystalline lens in myopes.

Autostereoscopic displays have become increasingly common, but their impact on ocular dimensions remains unknown. We sought to identify changes in the crystalline lens dimensions induced by autostereoscopic three-dimensional (3D) viewing. Forty young adults (age: 22.6 ± 2.0 years, male/female: 15/25) were consecutively enrolled and randomly divided into two groups (3D and two-dimensional [2D] viewing groups) to watch a 30-min movie clip displayed in 3D or 2D mode on a tablet computer. The lens thickness (LT), diameter, curvature, decentration and tilt were measured with anterior segment optical coherence tomography under both non-accommodating (static) and accommodating conditions. In the static condition, the LT decreased by 0.03 ± 0.03 mm (p < 0.001) and the anterior radius of curvature (ARC) increased by 0.49 ± 0.59 mm (p = 0.001) post-3D viewing. In contrast, following 2D viewing, the ARC decreased by 0.23 ± 0.25 mm (p = 0.001). Additionally, the increase in the steep ARC post-3D viewing was greater in high-myopic eyes than low to moderate myopic eyes (p = 0.04). When comparing the accommodative with the static (non-accommodative) condition, for 3D viewing the lens decentration decreased (-0.03 ± 0.05 mm, p = 0.02); while for 2D viewing, the posterior curvature radius (-0.14 ± 0.20 mm, p = 0.006) and diameter (-0.13 ± 0.20 mm, p = 0.01) decreased. Viewing with the autostereoscopic 3D tablet could temporally decrease the thickness and curvature of the lens under non-accommodating conditions. However, its long-term effect requires further exploration.

Effects of electric and magnetic fields on the electronic properties in the asymmetrical biconvex lens-shaped GaAs/GaAlAs quantum dots

Theoretical investigation of electronic properties in asymmetric biconvex lens-shaped GaAs/GaAlAs quantum dots is considered in the presence of the external magnetic and electric fields. In addition, the effects of the dot size and the asymmetry of the structure on the electronic properties are also investigated. The shape of this quantum dot corresponds to the intersection of two differently centered spheres. The energy levels and wave functions of the shallow hydrogenic impurity in the structure with a finite potential are calculated numerically in cylindrical coordinates with the effective mass approach using a complex eigenvalue formalism through a two-dimensional axisymmetrical and three-dimensional finite element methods. The results reveal significant dependence of the calculated physical properties on lens dimensions, axial impurity position, and intensities of applied electric and magnetic fields.

Distribution and associated factors of crystalline lens volume in noncataract adolescents and adults and patients with cataract in a Chinese population.

To explore the distribution of lens volume (VOL) and its associated factors in noncataract adolescents and adults and patients with cataract in a Chinese population. Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangzhou, China. Cross-sectional study. 1674 eyes from 1674 Chinese participants (690 adolescents and 363 adults without cataract, and 621 patients with cataract) aged from 7 to 90 years were included. Lens thickness (LT) and lens diameter (LD) were measured using swept-source anterior segment optical coherence tomography (SS-AS OCT) to calculate VOL. Axial length (AL) was measured by IOL-Master 700. Pearson correlation analysis and multivariate linear regression models were used to evaluate the potential associated factors of lens dimensions. The mean VOL was 167.74 ± 12.18 mm 3 in noncataract adolescents, 185.20 ± 14.95 mm 3 in noncataract adults, and 226.10 ± 49.25 mm 3 in patients with cataract. VOL had no significant correlation with AL in patients with cataract ( P > .05), neither in noncataract adolescents nor noncataract adults, when adjusted with LT, LD, age, and sex ( P > .05). On the other hand, eyes with longer ALs tended to have smaller LTs and larger LDs in all groups (all P -trend < .05). Larger VOL was associated with older age in all groups (all P < .001). A data set of VOLs in Chinese eyes over a wide age range was presented. It is inaccurate to predict VOL, LT, and LD solely according to AL. The direct measurement and calculation of VOL in vivo and the establishment of the normal range of VOL could help predict the size of lens capsular bag and plan cataract surgery.

A closer look at integrated reporting quality: a systematic review and agenda of future research

PurposeThis paper aims to conduct a systematic review of the literature on the quality of integrated reports (IR) and highlight the gaps in the existing research to provide directions and suggestions for future research.Design/methodology/approachThis study was conducted through a systematic literature review using content analysis based on 40 papers from the Scopus, Web of Science and EBSCOhost databases on IR quality. While reading the full-text papers, the authors found six additional papers referenced by the literature being reviewed that were relevant to IR quality. Thus, there were 46 papers in the final review. The analysis begins with the definition and dimension of IR quality and theoretical lenses. Furthermore, this study outlines constructs or variables used in the previous literature.FindingsThe authors found that most studies used the quantitative method (41 papers or 89%). Five papers in the literature used qualitative methods (11%). Most researchers (34 papers or 72%) defined IR quality as consistent with the International Integrated Reporting Council framework, specifically the eight content elements. In particular, with the constructs that make up the quality of the IR, variations between researchers were found. Furthermore, there were some gaps that could be the directions for future research.Research limitations/implicationsThe literature that provides academic knowledge about IR quality is still limited, and research on IR is still growing. The literature review conducted by this study can provide an overview of the current research positions on the quality of IR and directions for future research in this area.Practical implicationsThis study intends to show corporate executives a framework demonstrating the quality of corporate reporting. It can impact not only investors as a specific stakeholder group but also other stakeholder groups.Originality/valueTo the best of the authors’ knowledge, this study is the first literature review to examine the quality of IR, thus providing a map of current research to suggest directions for future research. Most of the previous literature reviews have been focused on integrated reporting (IR) in general and not quality.

The Design Methods and Experiments for a 220-GHz Quasi-Optical Cryogenic Schottky Subharmonic Mixer of High Performance

In this article, we present systematic design methods and experimental verifications of a 220-GHz quasi-optical cryogenic Schottky subharmonic mixer. To maximize device performance over a wide bandwidth and overcome the difficulties in conjugate matching designs, an impedance optimization-based cooperative design method is proposed for such quasi-optical mixer that includes the on-chip antenna and heterodyne mixing circuit. A coplanar waveguide (CPW) tuning network is utilized and optimized to offset the parasitic reactance effect of Schottky diodes. Besides, a dual-band log-periodic-slot integrated lens antenna is presented for coupling the radio frequency and local oscillator radiations with high efficiency. A reversed field tracing method is proposed to acquire the position and size of the equivalent Gaussian waists at both frequencies, thus offering the guidance for optimizing the substrate thickness and lens dimensions for improved antenna gain and radiation pattern. A 220-GHz quasi-optical mixer prototype was fabricated and experimentally verified at both room and cryogenic temperatures. At 134 K, the single-sideband noise factor and the conversion loss are around 4.2–8.5 and 6–11 dB over a wide intermediate-frequency bandwidth of 0.5–20 GHz, showing the superior device performance at the comparable bands.

Species independence of eye lens dimensions in teleosts and elasmobranchs.

The vertebrate eye lens grows incrementally, adding layers of elongated, tightly packed lens fiber cells at the outer margin of the lens. With subsequent growth, previously-deposited fiber cells degrade, leaving a region of fully denucleated and organelle-free cells which are responsible for the high transparency and low light scattering characteristics of the lens. The objective of this study was to determine if the horizon separating the gelatinous outer cortex of the lens from its hardened interior occurred at a consistent location within the lens of several teleost and elasmobranch fish species, and could be linked to fiber cell morphology or function. A fixed ratio of 0.69±0.01 of hardened eye lens diameter (HD) to overall eye lens diameter (LD) was observed in a broad size range of Atlantic cod (Gadus morhua), haddock (Melanogrammus aeglefinus), thorny skate (Amblyraja radiata) and round ray (Rajella fyllae). The location of the hardened lens horizon was similar to that reported for optical plasticity and spherical aberration, but not that of fiber cell denucleation, suggesting that fiber cell dehydration continues after the loss of internal organelles. Our findings support a previous suggestion that the maintenance of optical quality during fish eye lens growth requires a precisely-fixed HD:LD ratio, while the ubiquity of a fixed ratio across fish taxa may suggest that many fish species possess a common refractive index profile. The linear relationship between HD and fish length should allow fish length to be backcalculated from the diameter of the isolated lens core, thus aiding research using isotope ratios of lens laminae or inner cores to reconstruct early life history events.

A Wideband GRIN Dielectric Lens Antenna for 5G Applications.

This paper proposes a graded effective refractive indexes (GRIN) dielectric lens for 5G applications. The inhomogeneous holes in the dielectric plate are perforated to provide GRIN in the proposed lens. The constructed lens employs a collection of slabs that correspond to the specified graded effective refractive index. The thickness and the whole lens dimensions are optimized based on designing a compact lens with optimum lens antenna performance (impedance matching bandwidth, gain, 3 dB beamwidth, and sidelobe level). A wideband (WB) microstrip patch antenna is designed to be operated over the entire band of interest from 26 GHz to 30.5 GHz. For the 5G mm-wave band of operation, the behavior of the proposed lens along with a microstrip patch antenna is analyzed at 28 GHz for various performance parameters, including impedance matching bandwidth, 3 dB beamwidth, maximum gain, and sidelobe level. It has been observed that the antenna exhibits good performance over the entire band of interest in terms of gain, 3 dB beamwidth, and sidelobe level. The numerical simulation results are validated using two different simulation solvers. The proposed unique and innovative configuration is well-suited for 5G high gain antenna solutions with a low-cost and lightweight antenna structure.

Printing Polymeric Convex Lenses to Boost the Sensitivity of a Graphene-Based UV Sensor.

Ultraviolet (UV) is widely used in daily life as well as in industrial manufacturing. In this study, a single-step postprocess to improve the sensitivity of a graphene-based UV sensor is studied. We leverage the advantage of electric-field-assisted on-demand printing, which is simply applicable for mounting functional polymers onto various structures. Here, the facile printing process creates optical plano-convex geometry by accelerating and colliding a highly viscous droplet on a micropatterned graphene channel. The printed transparent lens refracts UV rays. The concentrated UV photon energy from a wide field of view enhances the photodesorption of electron-hole pairs between the lens and the graphene sensor channel, which is coupled with a large change in resistance. As a result, the one-step post-treatment has about a 4× higher sensitivity compared to bare sensors without the lenses. We verify the applicability of printing and the boosting mechanism by variation of lens dimensions, a series of UV exposure tests, and optical simulation. Moreover, the method contributes to UV sensing in acute angle or low irradiation. In addition, the catalytic lens provides about a 9× higher recovery rate, where water molecules inside the PEI lens deliver fast reassembly of the electron-hole pairs. The presented method with an ultimately simple fabrication step is expected to be applied to academic research and prototyping, including optoelectronic sensors, energy devices, and advanced manufacturing processes.

Accommodative movements of the choroid in the optic nerve head region of human eyes, and their relationship to the lens

The ciliary muscle (CM) powers the accommodative response, and during accommodation the CM pulls the choroid forward in the region of the ora serrata. Our goal was to elucidate the accommodative movements of the choroid in the optic nerve region in humans and to determine whether these movements are related to changes in the lens dimensions that occur with aging, in the unaccommodated and accommodated state.Both eyes of 12 human subjects (aged 18–51 yrs) were studied. Homatropine (1 drop/5%) was used to relax the ciliary muscle (unaccommodated or “resting” eye) and pilocarpine was used to induce the maximum accommodative response (2 drops/4%) (accommodated eye). Images of the fundus and choroid were collected in the region of the optic nerve (ON) via Spectralis OCT (infrared and EDI mode), and choroidal thickness was determined. Ultrasound biomicroscopy (UBM; 50 MHz, 35 MHz) images were collected in the region of the lens/capsule and ciliary body. OCT and UBM images were collected in the resting and accommodated state.The unaccommodated choroidal thickness declined significantly with age (p = 0.0073, r = 0.73) over the entire age range of the subjects studied (18–51 years old). The choroidal thickness was significantly negatively correlated with lens thickness in the accommodated (p = 0.01) and the unaccommodated states (p = 0.005); the thicker the lens the thinner the choroid.Choroid movements around the optic nerve during accommodation were statistically significant; during accommodation the choroid both thinned and moved centrifugally (outward/away from the optic nerve head). The accommodative choroid movements did not decline significantly with age and were not correlated with accommodative amplitude.Measurement of the choroidal thickness is possible with the Spectralis OCT instrument using EDI mode and can be used to determine the accommodative changes in choroidal thickness. The choroidal thickness decreased with age and during accommodation. It may be that age-related choroidal thinning is due to changes in the geometry of the accommodative apparatus to which it is attached (i.e., ciliary muscle/lens complex) such that when the lens is thicker, the choroid is thinner. Accommodative decrease in choroidal thickness and stretch of the retina/choroid may indicate stress/strain forces in the region of the optic nerve during accommodation and may have implications for glaucoma.

Study of the accuracy of the design method based on aberration theory for collimating lenses

The method was proposed choosing the initial construction and for the design of collimation and side-emitting lenses which includes the lens profile generating on the base of the conic curves using simple theoretical expressions from the third-order aberration theory. Compared to the other methods, this one gives the possibility to evaluate the necessary size and basic parameters of conic curves without any time-consuming procedures. In the paper, the accuracy of the solutions obtained on the basis of aberration theory has been analyzed from the viewpoint of lens efficiency and the forming surfaces’ shape both for different lens types and extended LED sources. The goal of the work was in researching how close to the more exact configuration the proposed solution was obtained using optimization technique. For different cases of lens size and lens dimensions, we have demonstrated that the deviation of the lens profile is comparable to the surface manufacturing accuracy. Thus, the method using aberration theory provides a basis for the fast automatic and visual tool for designing illumination lenses.

Variable-focus optoacoustic lens with wide dynamic range and long focal length by using a flexible polymer nano-composite membrane

We demonstrate a variable-focus optoacoustic lens (VFOL) by pneumatically controlling a flexible polymer nano-composite membrane, which can produce laser-generated focused ultrasound (LGFU) with a high peak amplitude (>30 MPa) and a tight focal dimension (several hundred μm) over a wide dynamic range of focus variation (>20 mm) together with a long focal length up to 60 mm, each of which is widest and longest among optoacoustic lenses developed so far. Two different designs in lens dimension have been fabricated and characterized: VFOL-L with a 40-mm diameter and VFOL-S with 10 mm. VFOL-L exhibits a wide dynamic range of focal length variation from 38.52 to 60.39 mm with a center frequency near ~ 10 MHz, which is proper for practical long-range applications with several-cm depth. In comparison, VFOL-S covers a focal variation range from 6.75 to 11.1 mm with ~ 14 MHz, producing a relatively higher-pressure amplitude, which allows the inception of acoustic cavitation at an impedance-mismatched boundary. The nano-composite membrane of VFOL is actuated from a planar to deeply curved shape by externally injecting liquid into the VFOL, resulting in a focal gain up to 255 and a positive peak pressure of > 30 MPa in the VFOL-L case. The minimum-geometrical f-number as low as 0.963 is achieved at the shortest focal length (38.52 mm) with 6-dB lateral and axial spot dimensions of 304 μm and 2.86 mm, respectively. We expect that the proposed VFOL-based LGFU with a high peak pressure, a wide dynamic axial range, and a tight focal dimension are suitably applied for depth-dependent characterization of tissues and shockwave treatment, taking advantages of optoacoustic pulses as input with inherent broadband high-frequency characteristics.

Relationship of the cornea and globe dimensions to the changes in adult human crystalline lens diameter, thickness and power with age

It is well known that human crystalline lens shape, dimensions and optical properties change throughout life and influence whole eye refraction. However, it is not clear if lens properties are associated with other ocular parameters. The purpose of the present study was to investigate the relationship of corneal and external globe dimensions with adult lens diameter (LD), lens thickness (LT) and lens power (LP) in order to determine if external factors influence lens properties. Postmortem human eyes (n = 66, age = 20–78 years) were obtained from the Ramayamma International Eye Bank, Hyderabad, India. Globe antero-posterior length (GAPL) and mean (average of horizontal and vertical) diameters of cornea (MCD) and globe (MGD) were measured using digital calipers. Eyes were dissected to produce ocular structures that contain the lens maintained in its accommodating framework, including intact zonules, ciliary body and sections of sclera. Specimens were mounted in a mechanical lens stretching system. LD, LT and LP were measured using high magnification retro-illumination photography, slit illumination photography and Scheiner principle-based optical system respectively in the unstretched (accommodated) state. Relationships between external globe and corneal dimensions and LD, LT or LP were assessed by multiple regression analysis. Age (0.012 ± 0.003 mm/year; p<0.001) and GAPL (0.185 ± 0.045 mm/mm; p<0.001) were significant (p<0.0001) predictors of LD. After adjusting for age-related increases, LD appears to be positively correlated with GAPL. Age (0.010 ± 0.004 mm/year; p = 0.009) and GAPL (−0.143 ± 0.060 mm/mm; p = 0.02) were significant (p = 0.001) predictors of LT. After adjusting for the age-related increase, LT appears to be negatively correlated with GAPL. Only age was a significant predictor of LP (−0.26 ± 0.04 D/year; p<0.001). The results suggest that, apart from aging, lens diameter and thickness are dependent on the anteroposterior length of the eye globe. Lens power is not influenced by globe dimensions.

Magnetic resonance imaging of the normal canine eye using a T1‐weighted volumetric acquisition

MRI is becoming increasingly available within the veterinary profession, and eyes are frequently included as part of a cranial study. The advantages of volumetric imaging are numerous, when compared to traditional two-dimensional imaging, and could be utilised within the veterinary setting. This report describing the normal MRI appearance of the canine eye, aimed to establish a standard reference range on a T1w volumetric acquisition. This study retrospectively assessed 62 eyes from 31 dogs that had undergone MRI at the Small Animal Hospital, Langford Vets, University of Bristol between 2016 and 2018 using a standardised MRI protocol. Dogs were excluded if they had presented with any reported ocular or orbital abnormalities. Measurements were performed from the 3D T1w volumetric sequence by a single observer using a previously published technique. Mean axial globe length was 2.13 cm and equatorial width 2.16 cm. Mean anteroposterior depth of the anterior chamber was 0.40 cm and 0.97 cm for the vitreous chamber. The mean anteroposterior and equatorial distance of the lens was 0.75 cm and 1.15 cm, respectively. Mean optic nerve width was 0.15 cm, and the mean width of the entire optic nerve sheath was 0.43 cm. Statistically significant relationships were noted between age and axial globe length and both lens dimensions. Highly significant relationships were noted between all variables, except lens dimensions and body weight Conclusion: This study provides reference values to assist in the interpretation of ocular structures during MRI on a T1w volumetric acquisition.

3D Printed Contact Lenses.

Although the manufacturing processes of contact lenses are well established, the use of additive manufacturing for their fabrication opens many new possibilities to explore. The current study demonstrates the fabrication of personalized smart contract lenses utilizing additive manufacturing. The study includes 3-dimensional (3D) modeling of contact lenses with the assistance of a computer aided designing tool based on standard commercial contact lens dimension, followed by the selection of the suitable materials and 3D printing of contact lenses. The 3D printing parameters were optimized to achieve the desired lens geometries, and a post processing treatment was performed to achieve a smooth surface finish. The study also presents functionalized contact lenses with built-in sensing abilities by utilizing microchannels at the contact lens edges. Tinted contact lenses were printed and nanopatterns were textured onto the contact lens surfaces through holographic laser ablation. 3D printed contact lenses have advantages over conventional contact lenses, offering customized ophthalmic devices and the capability to integrate with optical sensors for diagnostics.

3D printed micro-optics for quantum technology: Optimised coupling of single quantum dot emission into a single-mode fibre

Future quantum technology relies crucially on building quantum networks with high fidelity. To achieve this challenging goal, it is of utmost importance to connect individual quantum systems such that their emitted single photons overlap with the highest possible degree of coherence. This requires perfect mode overlap of the emitted light from different emitters, which necessitates the use of single-mode fibres. Here, we present an advanced manufacturing approach to accomplish this task. We combined 3D printed complex micro-optics, such as hemispherical and Weierstrass solid immersion lenses, as well as total internal reflection solid immersion lenses, on top of individual indium arsenide quantum dots with 3D printed optics on single-mode fibres and compared their key features. We observed a systematic increase in the collection efficiency under variations of the lens geometry from roughly 2 for hemispheric solid immersion lenses up to a maximum of greater than 9 for the total internal reflection geometry. Furthermore, the temperature-induced stress was estimated for these particular lens dimensions and results to be approximately 5 meV. Interestingly, the use of solid immersion lenses further increased the localisation accuracy of the emitters to less than 1 nm when acquiring micro-photoluminescence maps. Furthermore, we show that the single-photon character of the source is preserved after device fabrication, reaching a $ g^{(2)} (0)$ value of approximately 0.19 under pulsed optical excitation. The printed lens device can be further joined with an optical fibre and permanently fixed.This integrated system can be cooled by dipping into liquid helium using a Stirling cryocooler or by a closed-cycle helium cryostat without the necessity for optical windows, as all access is through the integrated single-mode fibre. We identify the ideal optical designs and present experiments that demonstrate excellent high-rate single-photon emission.

Correlation of Intraoperative Optical Coherence Tomography of Crystalline Lens Diameter, Thickness, and Volume with Biometry and Age

To characterize crystalline lens dimensions derived from invivo spectral-domain optical coherence tomography (SD-OCT) and identify associations among these parameters, ocular biometry, and age. In this retrospective study, lens thickness (LT), lens diameter (LD), and lens volume (LV) were measured intraoperatively using SD-OCT in 293 eyes undergoing lens surgery. Correlations among LT, LD, LV, age, axial length (AL), and anterior chamber depth (ACD) were analyzed. Multiple regression analysis was performed to determine whether a combination of biometric data could predict LD and LV. Wide variations were observed in LT (3.6-5.7mm), LD (7.5-11.9mm), and LV (119.9-312.4mm3) of aging eyes. Correlations among the 3 lens dimensions were statistically significant (LV-LT: r= 0.785; P < .001; LV-LD: r= 0.696; P < .001; and LT-LD: r= 0.121; P= .039). With age, the correlation coefficients of LT, LD, and LV were 0.526, 0.326, and 0.573, respectively (P < .001). Although there was significant correlation of AL with LT (r=-0.137; P= .002) and LD (r= 0.268; P < .001), it was not significant with LV (r= 0.084; P= .15). Subgroup analysis revealed that 19.8% of long eyes had LD >1 standard deviation (SD) above and that 5.2% had LD <1 SD below the mean LD. Dimensions of the aging lens vary considerably and are most accurately characterized by direct measurement of LT, LD, and LV, rather than making assumptions based on AL. These findings challenge historically proposed relationships between LD and AL and represent a normative dataset of contemporary geometric features of the aging lens, possibly aiding in surgical decision making and future developments in lens surgery.

Morphometric analysis of in vitro human crystalline lenses using digital shadow photogrammetry

There is a great need for accurate biometric data on human lenses. To meet this, a compact tabletop optical comparator, the minishadowgraph, was built for measuring isolated eye lens shape and dimensions while the lens was fully immersed in supporting medium. The instrument was based around a specially designed cell and an illumination system which permitted image recording in both sagittal and equatorial (coronal) directions. Data were acquired with a digital camera and analyzed using a specially written MATLAB program as well as by manual measurements in image analysis software. The possible effect of lens orientation and gravity on the dimensions was examined by measuring dimensions with anterior or posterior surfaces up and by measuring lenses with calipers after removal from the minishadowgraph cell.Dimensions, curvatures and shape factors were obtained for 134 fully accommodated lenses ranging in age from birth to 88 years postnatal. Of these, 41 were from donors aged under 20 years, ages which are generally of limited availability. Thickness and diameter showed the same age-related trends described in previous studies but, for the lenses measured in air, age-dependent differences were observed in thickness (−5 to 0%) and diameter (+5 to 0%), consistent with gravitational sag. Anterior and posterior radii of curvature of the central 3 or 6 mm, depending on lens diameter, increase with age, with the anterior increase greater than the posterior. The anterior surface shape of the neonatal lens is that of a prolate ellipse and the posterior, an oblate ellipse. Both surfaces become hyperbolic after age 20.The data presented here on dimensions, shape and sagging will be of great value in assessing age-related changes in the optical and mechanical performance of the lens. In particular, the comprehensive data set from donors aged under 20 years provides a unique and valuable insight to the changes in size and shape during the early dynamic growth period of the lens.

Effect of Dielectric Substrate Parameters Which Dimensions of Lens and Distance From Antenna on The Gain Enhancement of Microstrip Antenna with Metamaterial

In this study, it was aimed to determine the effect of dielectric substrate parameters which dimensions of lens and distance from antenna used as lens layer in front of antenna on antenna gain for the 2.45 GHz Wifi frequency band and calculate the effect of dielectric substrate on increasing the gain of classical microstrip antenna by using metamaterial lens layer (Square split ring resonator). For this purpose, a conventional microstrip antenna with a center resonant frequency of 2.45 GHz was first designed with the help of an electromagnetic simulation program. Then, the dielectric lens layer's size and distance from the antenna parameters were optimized and a maximum gain of 16% was obtained. In addition, it was determined that the dielectric lens layer size had more effect on increase of gain than the distance between antenna and lens layers. Then, the dielectric lens layer, 5λ / 16 antenna size and λ / 4 antenna distance which selected randomly, was designed and placed as a lens in front of the antenna (without using metamaterial). It was observed that the dielectric lens layer had an effect of antenna gain of about 7% for the single layer and 22% for the double layer. A square split ring resonator-shaped metamaterial lens layer with the same parameters as the resulting dielectric lens layer was then designed and placed in front of the conventional microstrip patch antenna for the 2.45 GHz Wifi frequency. It was observed that the lens layer with metamaterial increased the gain of the antenna by about 22% by placing it in single layer and 87% by placing it in double layer in front of the conventional microstrip amenna.

Quantitative Analysis of Retinal Structure and Function in Two Chromosomally Altered Mouse Models of Down Syndrome

PurposeOphthalmic disorders are among the most prevalent Down syndrome (DS) comorbidities. Therefore, when studying mouse models of DS, ignoring how vision is affected can lead to misinterpretation of results from assessments dependent on the integrity of the visual system. Here, we used imaging and electroretinography (ERG) to study eye structure and function in two important mouse models of DS: Ts65Dn and Dp(16)1Yey/+.MethodsCornea and anterior segment were examined with a slit-lamp. Thickness of retinal layers was quantified by optical coherence tomography (OCT). Eye and lens dimensions were measured by magnetic resonance imaging (MRI). Retinal vasculature parameters were assessed by bright field and fluorescent imaging, and by retinal flat-mount preparations. Ganzfeld ERG responses to flash stimuli were used to assess retinal function in adult mice.ResultsTotal retinal thickness is significantly increased in Ts65Dn and Dp(16)1Yey/+ compared with control mice, because of increased thickness of inner retinal layers, including the inner nuclear layer (INL). Increased retinal vessel caliber was found in both chromosomally altered mice when compared with controls. ERG responses in Ts65Dn and Dp(16)1Yey/+ mice showed subtle alterations compared with controls. These, however, seemed to be unrelated to the thickness of the INL, but instead dependent on the anesthetic agent used (ketamine, tribromoethanol, or urethane).ConclusionsWe provide evidence of retinal alterations in Ts65Dn and Dp(16)1Yey/+ mice that are similar to those reported in persons with DS. Our ERG results are also a reminder that consideration should be given to the choice of anesthetic agents in such experiments.

Interview

Mikko Kokkonen Mikko Kokkonen, from the University of Oulu, Finland, talks to us about his group's submission “Focal length of a low permittivity plano-convex lens at frequencies 30–600 GHz” page 223 One of the exciting research focuses in the microelectronics department at the University of Oulu is research into lenses for sub-terahertz (0.1 THz–1 THz) band applications, which is part of the 6G flagship program (https://www.oulu.fi/6gflagship/). Lenses can be used for focusing the radiation patterns toward a desired direction, which can improve communication between units and reduce the need for higher signal power. Additionally, from the materials side, low-loss and low-permittivity lens materials are an attractive choice for research, as they can be made from novel, sustainable materials. The Letter examines a hemi-spherical lens with geometric optics coupled with a finite element method and compares the results. Geometric optics is a form of optical theory where the wave is assumed to be a line, so it has no information about the waveform. However, the finite element method takes the waveform into account. In this Letter, we have presented simulated results for a hemi-spherical lens and show how different frequencies propagate through and beyond the lens. When using the lens on the front of the receiver to collect radio-waves, it is important to have at least some idea of ​​where to place the lens. As can be seen from the results, different distances mean different electrified intensities that affect antenna performance, so proper placement is important. The biggest challenge we faced is the lack of information relating to lens behaviour for different radio frequencies. There are plenty of research papers out there that are within the realms of the topic, but there is little to no coherent information about how frequency changes should be taken into account with regards to lens dimensions when designing lenses. I'm still fairly new to this field, but I have seen the frequency band increasing from tens of gigahertz to hundreds of gigahertz, and I'm convinced that it will rise even higher! The sixth generation of mobile wireless networks (6G) is tentatively envisioned to launch in the next ten years, so I guess that there will be a lot of different kind of devices utilising the 0.1 THz–1 THz frequency band. Also, I think we can expect to see lots of information on how lenses should and should not be utilised at the sub-terahertz band.