Design of Cognitive Radios

Cognitive radios are expected to perform spectrum sensing and communication in the frequency range of tens of megahertz to about 10 GHz. As such, they pose tough architecture and circuit design problems. This paper deals with issues such as broadband, low-noise amplification, multidecade carrier frequency synthesis, and spectrum sensing. The paper also describes the effect of nonlinearity and local oscillator harmonics, demonstrating that cognitive radios entail more difficult challenges than do software-defined radios. Multi-decade synthesis techniques and RF-assisted sensing methods are also presented

Thyroid dysfunction in women with polycystic ovarian syndrome: a comparative study

Background: Polycystic ovary syndrome (PCOS) is the most common endocrinopathy in reproductive age women. Some of the PCOS women show presence of hypothyroidism.Methods: This study was conducted at tertiary care centre Indira Gandhi Government Medical College and Hospital (IGGMC), Nagpur, Maharashtra, India. The study group had 50 diagnosed patients of PCOS and 50 age matched normal regular menstruating women were taken as controls.Results: In this study, PCOS patients showed higher mean TSH level than control group (4.024±1.09 and 2.84±0.83 respectively). And more women were diagnosed with overt hypothyroidism in the PCOS group (6%) than in the control group (2%).Conclusions: The findings of the study showed that PCOS is associated with hypothyroidism as compared to normal population

Peptide dendrimer-conjugates of ketoprofen: synthesis and ex vivo and in vivo evaluations of passive diffusion, sonophoresis and iontophoresis for skin delivery

The aim of this study was to evaluate skin delivery of ketoprofen when covalently tethered to mildly cationic (2or 4) peptide dendrimers prepared wholly by solid phase peptide synthesis. The amino acids glycine, arginine and lysine formed the dendrimer with ketoprofen tethered either to the lysine side-arm (N) or periphery of dendrimeric branches. Passive diffusion, sonophoresis- and iontophoresis-assisted permeation of each peptide dendrimer-drug conjugate (D1–D4) was studied across mouse skin, both in vitro and in vivo. In addition, skin toxicity of dendrimeric conjugates when trialed with iontophoresis or sonophoresis was also evaluated. All dendrimeric conjugates improved aqueous solubility at least 5-fold, compared to ketoprofen alone, while also exhibiting appreciable lipophilicity. In vitro passive diffusion studies revealed that ketoprofen in its native form was delivered to a greater extent, compared with a dendrimer-conjugated form at the end of 24\ua0h (Q(μg/cm): ketoprofen (68.06\ua0±\ua03.62)\ua0>\ua0D2 (49.62\ua0±\ua02.92)\ua0>\ua0D4 (19.20\ua0±\ua00.89)\ua0>\ua0D1 (6.45\ua0±\ua00.40)\ua0>\ua0D3 (2.21\ua0±\ua00.19). However, sonophoresis substantially increased the skin permeation of ketoprofen-dendrimer conjugates in 30\ua0min (Q(μg/cm): D4 (122.19\ua0±\ua07.14)\ua0>\ua0D2 (66.74\ua0±\ua03.86)\ua0>\ua0D1 (52.10\ua0±\ua03.22)\ua0>\ua0D3 (41.66\ua0±\ua03.22)) although ketoprofen alone again proved superior (Q: 167.99\ua0±\ua09.11\ua0μg/cm). Next, application of iontophoresis was trialed and shown to considerably increase permeation of dendrimeric ketoprofen in 6\ua0h (Q(μg/cm): D2 (711.49\ua0±\ua039.14)\ua0>\ua0D4 (341.23\ua0±\ua016.43)\ua0>\ua0D3 (89.50\ua0±\ua04.99)\ua0>\ua0D1 (50.91\ua0±\ua02.98), with a Qvalue of 96.60\ua0±\ua05.12\ua0μg/cmfor ketoprofen alone). In vivo studies indicated that therapeutically relevant concentrations of ketoprofen could be delivered transdermally when iontophoresis was paired with D2 (985.49\ua0±\ua043.25\ua0ng/mL). Further, histopathological analysis showed that the dendrimeric approach was a safe mode as ketoprofen alone. The present study successfully demonstrates that peptide dendrimer conjugates of ketoprofen, when combined with non-invasive modalities, such as iontophoresis can enhance skin permeation with clinically relevant concentrations achieved transdermally

Role of sparger design on gas dispersion in mechanically agitated gas-liquid contactors

Critical impeller speeds for gas dispersion and gas recirculation were measured in 0.57, 1.0 and 1.5 m i.d. vessels, using visual observations, measurements of power consumption and liquid-phase mixing time. A pitched blade down-flow turbine impeller (PTD) was used. Design parameters of the PTD impeller such as diameter (0.22T to 0.57T), blade width (0.25D to 0.4D) and blade thickness (2.8, 4.3 and 6.4 mm) were studied. The effect of sparger type and geometry on NCD has been investigated. For this purpose, pipe, ring, conical and concentric ring spargers were employed. Design details of the ring sparger such as ring diameter, number of holes and hole size were also studied in detail. The sparger location with respect to the impeller was found to be the most important parameter. Correlations have been developed for NCD and NCR

Mechanism of solid suspension

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Effect of addition of alcohol on the design parameters of mechanically agitated three-phase reactors

The effect of the presence of isopropyl alcohol on the design parameters of gas-liquid-solid systems has been studied in a vessel with an internal diameter of 0.57 m. A pitched blade downflow turbine was used as an impeller. Isopropyl alcohol concentration was varied from 0 to 2 vol.%. Air and quartz particles of 2000 μ m in size were used as the gas and solid phase, respectively. The solid loading (X) was varied from 0 to 15 wt.%. The impeller speed and superficial gas velocity were varied in the range of 2.4 to 10 rev s−1 and 0 to 9.4 mm s−1 respectively. The variations of power number and mixing time with respect to impeller speed were found to be similar. The effect of isopropanol concentration on the power consumption, liquid phase mixing time, critical impeller speed for gas dispersion, critical impeller speed for solid suspension and fractional gas hold up have been studied

Effect of impeller design on liquid phase mixing in mechanically agitated reactors

Liquid phase mixing time (θmix) was measured in mechanically agitated contactors of internal diameter 0.57 m, 1.0 m and 1.5 m. Tap water was used as the liquid phase. The impeller speed was varied in the range of 0.4-9.0 r/s. Three types of impellers, namely disc turbine (DT), pitched blade downflow turbine (PTD) and pitched-blade upflow turbine (PTU) were employed. The ratio of impeller diameter to vessel diameter (D/T) and the ratio of impeller blade width to impeller diameter (W/D) were varied over a wide range. The effects of impeller clearance from the tank bottom (C), the blade angle (φ), the number of blades (nb), the blade thickness (k) and the total liquid height (H/T) were studied in detail. Mixing time was measured using the conductivity method. Mixing time was found to have a strong dependance on the flow pattern generated by the impeller. Mixing time was found to decrease by decreasing the impeller clearance in the case of DT and PTU. However in the case of PTD it increases with a decrease in the impeller clearance. Similar trend of the effect of impeller clearance on θmix, was observed for all the other PTD impellers with different diameter, number of blades and blade angle (except 60° and 90°). All the impeller designs were compared on the basis of power consumption and on this basis optimum design recommendations have been made. For PTD impellers, a correlation has been developed for the dimensionless mixing time