Journals
2018 EN
Jones Keaton R. · Nabinger Sarah C. · Lee Sangbin
+7 more
Background and Objectives Hepatocellular carcinoma (HCC) in patients with hepatitis B virus (HBV) exhibit lower tumor microRNA‐26a (miR‐26a) expression which is associated with worse outcomes. It is unknown if similar miR‐26a loss occurs in HCC developed in other liver diseases. We examined tumor miR‐26a expression and its impact on recurrence and mortality in a North American HCC cohort. Methods MiR‐26a levels from tumor and surrounding nontumor liver tissue in 186 subjects were collected. We defined lower tumor expression of miR‐26a as <1‐fold that of the adjacent nontumor liver tissue. Results Viral hepatitis (42%; 40% hepatitis C and 2% HBV), alcohol (19%), and nonalcoholic fatty liver disease (NAFLD) (18%) were the most common causes of liver disease. The prevalence of lower tumor miR‐26a expression was 68%, and it was evident in HCCs arising in all etiologies (viral hepatitis 60%, alcohol 61%, and NAFLD 76%). Subjects with lower tumor miR‐26a expression had significantly higher tumor recurrence (hazard ratio [HR], 2.45; 95% confidence interval [CI], 1.18 to 5.1; P = 0.016) and higher mortality of borderline significance (HR, 1.51; 95% CI, 0.94 to 2.41; P = 0.086). Conclusion Reduced miR‐26a expression is a common phenomenon in HCC arising in North American patients with different underlying liver diseases and may increase recurrence and mortality after surgery.
Journals
2018 EN
Sahu Kriti R. · De Udayan
Harmful electromagnetic (EM) interference (EMI) to living beings and various sensitive instruments by EM radiations from electronic and electrical gadgets and mobile towers is increasing rapidly. It inflicts illness, and presumably cancerous growth in human cells. EMI is minimized by wrapping the receiver and/or the emitter gaplessly by an efficient EM shielding sheet. Compared to the widely used and classical metallic shields, 2nd generation polymer composite EMI shields are lighter and more flexible. Conventional polymer composites use conducting polymers and metallic/carbon powders that have conducting electrons to reflect EM waves away. A polymeric binder, curing overnight to a soft and flexible sheet, has presently been selected for making the polymeric composites. We test EM shielding by certain non‐metallic composites. We review results for composites with fine metallic fibers (copper and brass turnings, available as waste from mechanical workshops) or conducting forms of cadmium oxide or ferroelectric materials (PbNb 2 O 6 [o‐PN] & BaTiO 3 [BT]) or their mixtures (52 samples). Small pieces of these cloth‐like polymeric sheets have been characterized in a Vector Network Analyzer (VNA), by measuring input power ( P in ), the reflected power ( P refl ), and the transmitted power ( P out ), over five frequency bands in 700 MHz to 40 GHz range to find Shielding Effectiveness (SE) = 10 log ( P out / P in ) and Reflection Effectiveness = 10 log ( P refl / P in ). Success of o‐PN, BT, conducting (fired) Cd‐O, metallic turnings and their combinations has been discussed, highlighting some new observations. Composites, developed in this work, include EMI Shielding materials and potential Radar Absorption Materials.
Journals
2018 EN
Sahu Bhagirath · Singh Soni · Meshram Manoj Kumar
+1 more
A compact lowpass filter (LPF) with wide stopband which uses four non‐uniform cascaded defected ground structure (DGS) units along with a 50 Ω microstrip line is reported in this article. Each DGS unit, which consists of a combination of three isosceles U‐shaped DGSs is analyzed in terms of an equivalent RLC circuit model. Every DGS of the DGS unit along with microstrip line provides one attenuation pole. It is found through performance comparison of the proposed U‐shaped DGS with dumbbell‐ and fork‐shaped DGSs that the proposed U‐shaped DGS is compact and provides higher quality factor. Further, the modeling of the proposed LPF is carried out using equivalent RLC circuit model. The results obtained through numerical and circuit simulations are compared. The proposed LPF has size of 14.44 mm × 3.4 mm, 3‐dB cut‐off frequency of 14.2 GHz, and greater than 40 dB and 22 dB stopband rejection up to 21.8 GHz and 30 GHz respectively. The proposed LPF is fabricated and experimentally tested. The experimental results are nearly in agreement with corresponding numerical/circuit simulation results.
Journals
2018 EN
Sahu Nikesh Kumar · Das Gourab · Gangwar Ravi Kumar
A dielectric resonator (DR) based circularly polarized multi‐input‐multi‐output (MIMO) antenna is studied in this article for wireless local area network (WLAN) applications. In this work, two self‐complementary L‐shaped dielectric resonators are used as two radiators and each radiator is excited by a 50 Ω coaxial probe feed network. The position of the feed network is selected in such a way that it directly generates a pair of orthogonal modes inside the DR. Along with this, diversity in the radiated beam direction is observed to provide low field correlation and a defected ground structure (DGS) is implemented to provide low inter‐port correlation. Experimental test results show that the proposed MIMO structure possesses a 10‐dB impedance bandwidth of 15.6% (5.2‐6.08 GHz) and a 3‐dB axial ratio (AR) bandwidth of 7.05% (5.2‐5.58 GHz). Besides, MIMO suitability of the proposed structure is evaluated by means of envelope correlation coefficient (ECC), diversity gain (DG), and channel capacity loss (CCL).
Journals
2018 EN
Panda Asit K. · Sahu Sudhakar · Mishra Rabindra K.
This article analyzes the radiation principle of a slot‐coupled hemispherical dielectric resonator antenna (DRA) integrated with a single‐layer metamaterial (MTM) superstrate, investigating it both numerically and experimentally. It creates a compact high directive DRA incorporating MTM superstrate. The proposed MTM medium consists of broadside coupled planar E‐shaped resonator periodic unit cell exhibiting low loss and a low refractive index over a broad frequency band. Measurements on fabricated prototypes to verify numerical results from full‐wave simulations, and they show more than 6 dB increase in directivity of the DRA.
Journals
2018 EN
Dash Upali Aparajita · Sahu Sudhakar
A physically accomplished truncated conical dielectric ring resonator (DRR) is designed and experimented to validate the performance parameters. The DRR loaded on brass ground plane fed by coaxial probe resonates in three frequencies: 12.5, 19.7, and 23.5 GHz. Among three resonances, the first one is radiating and shows reasonable broadside gain of 4.3 dBi. The higher resonances are nonradiating and offer very low gain. The frequency selective metasurface walls are realized by complementary split Ring resonators and positioned sensitively near the conical DRR. The gain performance at 12.5 GHz has been improved to 18 dBi with ‐10 dB impedance bandwidth of 900 MHz (12.2‐13.1 GHz) by incorporation of lateral frequency selective surface wall with suppression of higher nonradiating modes. The proposed antenna structure has been designed, simulated with the commercially available HFSS software to achieve the optimized dimension and validated with the measurement results.
Journals
2018 EN
Dash Upali Aparajita · Sahu Sudhakar
A conical sectored dielectric resonator antenna (DRA) loaded on S‐shaped slot square patch for wideband circular polarization is investigated. Wideband circular polarization (CP) is achieved by single tab extended at right top corner of the square patch along with the introduction of sectors on the top of DRA and S‐shaped slot on the patch. Calculated size of slot along with optimized height and size of DRA through parametric study helps to get wide impedance bandwidth. In addition, optimized size of single tab gives the wide axial ratio bandwidth. The −10 dB impedance bandwidth is 100.18% (2.1–6.0 GHz) and 3‐dB axial ratio (AR) bandwidth is 69.52% (3.0–6.2 GHz). The gain variation is around 3 dBi and radiation efficiency is around 80%–95% within the AR bandwidth. The proposed model is fabricated and measured which agree well with the simulated results.
Journals
2018 EN
Sahu Nikesh Kumar · Das Gourab · Gangwar Ravi Kumar
In this article, a dual polarized triple‐band dielectric resonator based hybrid multiple‐input multiple‐output (MIMO) antenna is presented. The proposed MIMO antenna is designed with the help of two cylindrical dielectric resonators along with two symmetrical modified Y‐shaped microstrip printed lines. Two metallic strips and a slot on the ground plane are used to enhance the isolation. A prototype of the proposed design is fabricated and tested to validate the simulation outcomes. The measured outcomes confirmed that the proposed antenna can be utilized in three different frequency bands such as 2.21–3.13, 3.40–3.92, and 5.30–6.10 GHz with fractional bandwidth of 34.45%, 14.2%, and 14%, respectively. The modified Y‐shaped printed line is used to obtain circular polarization in the upper frequency band with fractional axial ratio (AR) bandwidth of 4.18%. Besides, MIMO performance has also been examined in terms of diversity parameters like envelope correlation coefficient (ECC), mean effective gain (MEG), diversity gain (DG), and channel capacity loss (CCL).
Journals
2018 EN
Sahu Nikesh Kumar · Sharma Anand · Gangwar Ravi Kumar
In this article, a dual‐sense circularly polarized (CP) hybrid antenna is reported. The proposed hybrid antenna comprises of an asymmetrical square ring‐shaped printed line and a rectangular dielectric resonator (RDR). The asymmetricity present in the square ring is responsible for creating CP radiation with the opposite sense characteristics in the proposed antenna. Also, modified printed ring is used to excite TE 111 mode in the loaded RDR. This loading enhances the overall impedance bandwidth of the proposed antenna. For practical verification, a prototype of the proposed antenna is fabricated and tested. The measured outcomes indicate a close concurrence with the simulated outcomes. The proposed antenna works over the frequency range 3.28 GHz–5.78 GHz with a fractional bandwidth of 55.18%. Dual CP wave with dual‐sense characteristics (Axial Ratio < 3 dB) are created in the frequency range 3.81–4.28 GHz and 4.98–5.28 GHz respectively. These responses make the proposed antenna suitable for WLAN and WiMAX applications.
Journals
2018 EN
Sahu Nikesh Kumar · Das Gourab · Gangwar Ravi Kumar
A novel dielectric resonator (DR)‐based wideband circularly polarized multiple input multiple output (MIMO) antenna with pattern diversity is proposed in this article for wireless local area network applications. In this proposed MIMO antenna, 2 rectangular DRs and a single square DR are stepped together to generate circular polarization characteristics as well as pattern diversity. Along with this, an orthogonal probe feeding network is deployed in the design to limit the inter‐port coupling. Experimentally tested outcomes revealed that the proposed radiator has a 10‐dB impedance bandwidth of 21.51% and a 3‐dB axial ratio bandwidth of 13.23%. Besides, results of MIMO diversity performance parameters demonstrate that the proposed antenna is well suitable for MIMO applications.