Terahertz tomography is a promising method among non-destructive inspection techniques to detect faults and defects in dielectric samples. Recently, image quality was improved significantly through ...the incorporation of
information and off-axis data. However, this improvement has come at the cost of increased measurement time. To aim toward industrial applications, it is therefore necessary to speed up the measurement by parallelizing the data acquisition employing multi-channel setups. In this work, we present two tomographic frequency-modulated continuous wave (FMCW) systems working at a bandwidth of 230-320 GHz, equipped with an eight-channel detector array, and we compare their imaging results with those of a single-pixel setup. While in the first system the additional channels are used exclusively to detect radiation refracted by the sample, the second system features an f-θ lens, focusing the beam at different positions on its flat focal plane, and thus utilizing the whole detector array directly. The usage of the f-θ lens in combination with a scanning mirror eliminates the necessity of the formerly used slow translation of a single-pixel transmitter. This opens up the potential for a significant increase in acquisition speed, in our case by a factor of four to five, respectively.
Propolis is a resinous natural hive product derived from plant exudates collected by honeybees. Due to biological and pharmacological activities, it has been extensively used in folk medicine. The ...present study was designed to investigate the chemical composition, subchronic toxicity, antimicrobial activity of Iranian propolis ethanolic extract, which has not been studied previously. One hundred and nine compounds were identified by gas chromatography–mass spectrometry analysis. Forty-five days subchronic toxicity of oral propolis extract was investigated in male rats. During the study no significant behavioral and clinical toxicity has been seen in animals however, hematologic, blood biochemistry and histopathologic data studies exhibited some significant differences between the groups. The ethanolic extract of propolis inhibited the growth of all examined microorganisms including bacteria and fungi with the highest antimicrobial activity against Gram-positive bacteria such as
Staphylococcus aureus and
Staphylococcus epidermidis.
Propolis is a resinous natural hive product derived from plant exudates collected by honey bees. Due to biological and pharmacological activities, it has been extensively used in folk medicine. The ...present study was designed to measure the antioxidant power of ethanolic extracts of propolis samples from different parts of Iran with “ferric reducing ability of plasma” (FRAP) assay and compare the results with Trolox at concentrations of 100, 1000 and 2000
μg/ml. FRAP values of propolis ethanolic extracts were in the range of 31.5
±
14.6 to 1650
±
72
μM, whereas the values of Trolox ranged from 125.25
±
9.95 to 3381.64
±
113.83
μM. The FRAP values of Tehran propolis ethanolic extract and Trolox at concentration of 100
μg/ml did not show any significant difference (
P
>
0.05). Total flavonoid and polyphenol contents of ethanolic extracts of propolis samples, determined by using aluminum nitrate and Folin–Ciocalteu colorimetric methods, were in the range of 1.22
±
0.33–7.79
±
0.39
g/100 g and 3.08
±
0.02–8.46
±
0.03
g/100
g crude extract of propolis, respectively. The result of this experiment may show that propolis as a natural source of antioxidant compounds may be of use in prevention of free radical-related diseases.
Radar systems based on frequency-modulated continuous-wave (FMCW) technique are used in 3D terahertz imaging setups to construct volumetric images of dielectric samples in order to reveal internal ...structures and defects. In some applications, a mobile imaging system is preferred, to carry to the sample under test (SUT). We have integrated a single FMCW transceiver unit with opto-mechanical components to obtain 3D information faster, compared to single-point measurements with raster scan. A scanning module with aspherical telecentric f-9 lens as an optical objective system and a galvanometer scanner mirror are designed.
Many established terahertz imaging modalities are on one side restricted by the tradeoff between resolution and field of view such as in the case of focal plane arrays and on the other side suffer ...from a limited depth of field such as in the case of quasi-optical terahertz imaging configurations. Furthermore, typical scanning solutions require time-consuming measurement procedures and restrict significant potential industrial deployments of terahertz imaging technology. Imaging with sparse multistatic line arrays in combination with digital beam forming (DBF) techniques enables us to overcome these limitations and offer three-dimensional (3D) terahertz image reconstructions of the object. This contribution addresses the design of such terahertz imaging systems from a general point of view with the focus on the design of sparse line arrays, while considering objects scattering properties. Based on this design concept, the realization of a novel highly sparse 3D terahertz imaging system is discussed. The sparse line array of the system is operating within a frequency range from 75 to 110 GHz and is used in combination with a conveyor in order to generate a synthetic sampling aperture. The system is capable to generate 3D terahertz images with tens of megavoxels at feed motions of up to a few 10 cm/s. Also, a sparse array design in regard to an imaging system operating at 240 GHz with integrated SiGe sensor elements is discussed. In addition, three different DBF algorithms are compared in regard to their computational efficiency.
A novel photonic terahertz measurement system based on a frequency‐modulated continuous‐wave (FMCW) radar approach is presented. In previous works, fast frequency modulation has been demonstrated in ...connection with a continuous wave terahertz spectroscopy setup based on the photomixing principle. In this paper, a terahertz radar based on both a photomixing transmitter and a photomixing receiver, in contrast to the rigid spectroscopy approach, is reported. Hereby, frequency modulation bandwidths of more than 1.65 THz in radar operation is achieved. This corresponds to an order of magnitude more than what is previously achieved by terahertz radar systems. At the same time, measurement rates can be achieved that are comparable with radar systems based on Monolithic Microwave Integrated Circuits (MMICs) according to the current state of the art. Within the scope of the work, two operating modes are realized, one with a measurement rate of about 560 Hz at 600 GHz modulation bandwidth and one with 200 Hz at 1.65 THz modulation bandwidth, which can be set within the spectrum from 50 GHz to about 4.5 THz. The possibility to adjust the operating range of the radar without necessary hardware adaptations is another unique feature of the presented system, which allows the operator to choose a suitable frequency band that corresponds best to a certain measurement scheme via software settings. Besides the potential for multi‐layer thickness inspections, the capabilities of this technique for terahertz imaging applications are presented.
A novel photonic terahertz measurement system based on a frequency‐modulated continuous‐wave radar approach is presented. Hereby, frequency modulation bandwidths of more than 1.65 THz are achieved. The possibility of adjusting the operating range of the radar without necessary hardware adaptations is another unique feature. Besides the potential for multi‐layer thickness inspections, the capabilities for terahertz imaging applications are highlighted.
Abstract Background: The present study assessed the therapeutic effects of dalteparin in patients who had recent onset central retinal vein occlusion (CRVO) as compared with those of acetylsalicylic ...acid (ASA). Methods: Patients with recent onset of CRVO were randomly assigned to receive dalteparin subcutaneously every day for 20 days or ASA daily for the same period. Complete ophthalmic examinations were conducted at baseline and at each follow-up interval: 1 week and 1, 2, 3, 4, and 6 months later. Best-corrected visual acuity was assessed by an investigator blind to the treatment group. Results: The mean 6-month change in logMAR visual acuity for dalteparin-treated patients was an increase of 5.5 letters (Early Treatment Diabetic Retinopathy Study chart) (−0.11 SD 0.71 logMAR) and for ASA-treated patients was a decrease of 14 letters (+0.28 SD 0.79 logMAR), representing a significant difference between the 2 groups ( p = 0.016). One patient in the dalteparin group and 14 in the ASA group showed iris neovascularization (NVI) (2.1% vs. 30.4%, p = 0.0001). Interpretation: Dalteparin was found to be superior to ASA in terms of improving visual acuity and preventing NVI over the first 6 months of treatment. Similar studies are recommended of other newer types of anticoagulants, especially those that could be used orally.
To explore the multifocal electroretinogram in patients with nonproliferative diabetic retinopathy with clinically-significant macular edema.
Forty-one eyes with clinically significant macular edema ...were tested. The latencies and amplitudes of average responses of 5 eccentric rings from 0 to 26 degrees relative to the fixation point were compared with normal values obtained from 13 nondiabetic subjects.
Local electroretinogram responses were significantly delayed and decreased in amplitude in patients with clinically-significant macular edema.
Multifocal electroretinogram can be used to quantify the visual function in clinically significant macular edema.
We report on the development of a handheld three-dimensional (3D) terahertz scanning system with an aspherical telecentric 3D-printed f-θ lens using selective laser sintering. The lens covers a ...broader scan line of 50 mm with its larger aperture, compared to the 20 mm range in our initial work, which was presented at the European Microwave Week 2021. In order to evaluate the adaptability of the optomechanical components with different sensor units, two different integrated frequency-modulated continuous wave radar modules based on monolithic microwave integrated circuit technology, operating in W- and D-bands are tested within the measurement scheme. The optomechanical part consists of a galvanometer scanner mirror and the f-θ lens. The optical system enables B-scans perpendicular to the manual translational movement of the sensor unit by its user. An integrated guiding wheel system with rotary encoder makes it possible to correlate the measurement points to their respective locations, enabling complete 3D volumetric inspection of the corresponding structures, which is particularly useful for the inspection along cracks and welds.
Retinal vein occlusion is the second most common vascular disease of retina after diabetic retinopathy, affecting 1.6% of the population above the age of 40. The aim of this study was to compare the ...effect of dalteparin and aspirin in patients with recent-onset branch retinal vein occlusion.
A randomized clinical trial was conducted on patients with branch retinal vein occlusion of less than 30 days' duration. Ophthalmic, systemic, and hematologic evaluations were made. Visual acuity was measured with Early Treatment Diabetic Retinopathy Study chart. Patients in the dalteparin group received subcutaneous dalteparin 100 IU/kg twice daily for 10 days, then 100 IU/kg once daily for another 10 days while the patients in the aspirin group were given aspirin 100 mg daily throughout the study.
Seventy-eight patients were enrolled, 37 in the dalteparin and 41 in the aspirin group. The patients were followed for six months. The visual outcomes of the two groups were compared. Although dalteparin improved mean visual acuity slightly more than aspirin, no statistically significant differences were found between the groups at one (P=0.37), two (P=0.16), three (P=0.11), or six (P=0.13) months. Resolution of macular edema and development of new vessels made no statistically significant difference between the groups (P=0.08) and (P=0.49), respectively.
In recent-onset branch retinal vein occlusion, no significant difference was found in the final visual acuity between the patients treated by dalteparin or aspirin. A further study with larger sample size is recommended.
PDF
