Multiple Imputation Using Gaussian Copulas

Missing observations are pervasive throughout empirical research, especially in the social sciences. Despite multiple approaches to dealing adequately with missing data, many scholars still fail to address this vital issue. In this paper, we present a simple-to-use method for generating multiple imputations using a Gaussian copula. The Gaussian copula for multiple imputation (Hoff, 2007) allows scholars to attain estimation results that have good coverage and small bias. The use of copulas to model the dependence among variables will enable researchers to construct valid joint distributions of the data, even without knowledge of the actual underlying marginal distributions. Multiple imputations are then generated by drawing observations from the resulting posterior joint distribution and replacing the missing values. Using simulated and observational data from published social science research, we compare imputation via Gaussian copulas with two other widely used imputation methods: MICE and Amelia II. Our results suggest that the Gaussian copula approach has a slightly smaller bias, higher coverage rates, and narrower confidence intervals compared to the other methods. This is especially true when the variables with missing data are not normally distributed. These results, combined with theoretical guarantees and ease-of-use suggest that the approach examined provides an attractive alternative for applied researchers undertaking multiple imputations

Sidewall depletion in nano-patterned LAO/STO heterostructures

We report the fabrication of nanostructures from the quasi-two-dimensional electron gas (q2DEG) formed at the LaAlO$_{3}$/ SrTiO$_{3}$ (LAO/STO) interface. The process uses electron beam lithography in combination with reactive ion etching. This technique allows to pattern high-quality structures down to lateral dimensions as small as $100$nm while maintaining the conducting properties without inducing conductivity in the STO substrate. Temperature dependent transport properties of patterned Hall bars of various widths show only a small size dependence of conductivity at low temperature as well as at room temperature. The deviation can be explained by a narrow lateral depletion region. All steps of the patterning process are fully industry compatible.Comment: 5 pages, 4 figure

Solubility and Permeability Studies of Aceclofenac in Different Oils

Purpose: To measure the extent of solubility of the lipophilic drug,   aceclofenac, in 13 oils as well as its in vitro permeability from these oils in order to develop optimized topical microemulsion and  microemulsion-based gel for improved bioavailability.Methods: UV spectrophotometeric method was used at the wavelength of 276 nm to measure the dissolved quantity of aceclofenac in each of the oils (almond oil, oleic acid, castor oil, paraffin oil, cinnamon oil, clove oil, canola oil, sesame oil, isopropyl myristate (ipm), sunflower oil, corn oil, coconuts oil and eucalyptus oil) at 25 °C. The in-vitro permeability of aceclofenac in each of these oils was determined at 32 ± 0.5 °C using Franz diffusion cell with phosphate buffer (pH 7.4) as medium with 0.45ì cellulose acetate membrane. The solubility and permeability of aceclofenac were compared with the hydroalcoholic solution of aceclofenac.Results: The highest solubility values of 9.153 and 8.560 mg/ml for  aceclofenac were obtained with almond oil and oleic acid, respectively (p < 0.05). However the solubility and permeability of aceclofenac in hydro-alcoholic solution were 150.65 mg/ml and 14.91± 0.05 ìg/cm2/h,  respectively. Aceclofenac also showed higher permeability values (1.45± 0.04 and 1.21 ± 0.06) in almond oil and oleic acid, respectively, than in the other oils (p < 0.05).Conclusion: These findings show that almond oil and oleic acid are  promising vehicles for aceclofenac as its enhanced solubility and  permeability in these vehicles are suggestive of improved bioavailability.Keywords: Aceclofenac, Almond oil, Solubility; Permeability, Oleic acid, Bioavailability

Analysis of Simvastatin using a Simple and Fast High Performance Liquid Chromatography-Ultra Violet Method: Development, Validation and Application in Solubility Studies

Purpose: To develop and validate an accurate, rapid and reproducible reversed-phase high performance liquid chromatography (RP-HPLC) analytical method for the lipid lowering drug, simvastatin, and to apply the developed method to study the solubility of the drug in various oils andsurfactants.Methods: Isocratic RP-HPLC system with a UV-vis detector, and a column with dimensions 4.6 mm x 150 mm and 5ì particle size, was employed. The mobile phase consisted of methanol and 0.01M KH2PO4 phosphate buffer (80:20) at pH 5.5 adjusted with phosphoric acid (2M) and pumped at a flow rate of 1 ml/min. Validation parameters, viz, limit of detection (LOD), limit of quantification (LOQ) linearity, accuracy, precision, and sensitivity, were established. Solubility study was performed in various oils and surfactants at 25°C and the developed HPLC method was applied to analyze all samples.Results: The developed HPLC method showed good linearity (R2 = 0.9958 ± 0.0040. The intra- and inter-day % accuracy was more than 98 %. LOQ and LOQ were 0.160 and 0.484 ìg/ml respectively. Simvastatin showed the highest solubility in sesame oil (15 mg/ml) and in Tween 80 (11 mg/ml) at 25oC.Conclusion: An accurate, rapid and robust HPLC-UV method has been developed, validated and applied successfully to determine the solubility of simvastatin in oils.Keywords: Simvastatin, Validation, Solubility, Sesame oil, Tween 80

Limb Defects in Developing Chick Embryos after Administration of Glucose

Objective: To assess the role of administered glucose on gross development of limbs of the chick embryos, in comparison with age matched controls. Materials and Methods: Fertilized eggs of Egyptian Fayyumi breed were injected with glucose (5% weight/volume solution) into egg albumen. The eggs were put in the incubator under standard conditions of temperature and humidity. Eggs were divided in two groups, control (A) and experimental (B). Each group is subdivided in two subgroups comprising of 30 eggs each. Eggs were opened on day 10 of incubation in subgroup (A1, B1) while eggs from subgroup (A2, B2) were allowed to hatch on day 21 or day 22 of incubation. The exposed embryos were compared with age matched control subgroups. Effects of glucose were assessed by observing limb defects in the embryos from two groups. Results: The experimental animals had limb defects manifested as absent, one hind limb in 5 out of 53 (9.433%). Both hind limbs were absent in 6/53 (11.32%). In turned phalanges with inability to stand and limping gait was found in 8/53 (13.79%). No embryo of the control group demonstrated such findings. Conclusion: Administration of glucose resulted malformation such as limb defects and turned digits in growing chick embryos.&nbsp

Teratogenic Effect of Sodium Phenytoin on Limb Development in Chick Embryos is Time-Mediated as Evident by Stereomicroscope

Background: Women suffering from seizure-related illnesses are prescribed phenytoin during pregnancy if the benefits outweigh the risks. But the teratogenic effect of this drug on limb development needs exploration. This study was designed to investigate the time-mediated teratogenic effect of sodium phenytoin on limb development of chick embryos on days 04 and 09 of development using the stereomicroscope and at the time of hatching. Material and Methods: This randomized control trial comprised of two main groups of fertilized chicken eggs (Egyptian Fayoumi breed), control group A and experimental group B, each having 90 eggs. Each experimental egg was injected with sodium phenytoin (3.5 mg, teratogenic dose) just before incubation. Both the groups were divided into three subgroups each A1, A2, & A3/B1, B2 & B3. Stereomicroscope was used to observe the limb buds and cartilaginous elements in subgroups 1 and 2 on days 04 and 09 of development respectively. The embryos of subgroups 3 were assessed for gross limb deformities on hatching. Survival was noted in all the subgroups.Results: The difference in limb bud size between experimental and controls was statistically insignificant. There was no variation or deformity in the bones. The experimental group 3 had gross limb defects on hatching and the difference in survival was also statistically significant in subgroups 3.Conclusion: Prenatal administration of sodium phenytoin induces limb defects in chick embryos as evident after hatching but limb anomalies are not observed on days 04 and 09 of development as investigated by stereomicroscope. We conclude that the teratogenic effect of phenytoin is time-mediated

Barley-Based cropping systems and weed control strategies influence weed infestation, soil properties and barley productivity

Barley-based cropping systems (BCS) alter barley production by influencing weed infestation rates and soil nutrient dynamics. This two-year field study evaluated the interactive effects of five BCS and five weed control strategies (WCS) on soil properties and the growth and yield of barley. Barley was planted in five different cropping systems, i.e., fallow-barley (FB), maize-barley (MaB), cotton-barley (CB), mungbean-barley (MuB) and sorghum-barley (SB). Similarly, five different WCS, weed-free (control, WF), weedy-check (control, WC), false seedbeds (FS), chemical control (CC) and use of allelopathic water extracts (AWE), were included in the study. The SB system had the highest soil bulk density (1.48 and 1.47 g cm−3 during the period 2017–2018 and 2018–2019, respectively) and lowest total soil porosity (41.40 and 41.07% during the period 2017–2018 and 2018–2019, respectively). However, WCS remained non-significant for bulk density and total soil porosity during both years of the study. Barley with WF had a higher leaf area index (5.28 and 4.75) and specific leaf area (65.5 and 64.9 cm−2 g−1) compared with barley grown under WC. The MuB system under WC had the highest values of extractable NH4-N (5.42 and 5.58 mg kg−1), NO3-N (5.79 and 5.93 mg kg−1), P (19.9 and 19.5 mg kg−1), and K (195.6 and 194.3 mg kg−1) with statistically similar NO3-N in the MaB system under WC and extractable K in the MuB system under FS. Grain yield ranged between 2.8–3.2 and 2.9–3.3 t ha−1 during the period 2017–2018 and 2018–2019, respectively, among different WCS. Similarly, grain yield ranged between 2.9–3.2 and 3.0–3.2 t ha−1 during the period 2017–2018 and 2018–2019, respectively, within different BCS. Among WCS, the highest grain yield (3.29 and 3.32 t ha−1) along with yield-related traits of barley were in WF as compared to WC. Overall, MuB system recorded better yield and yield-related traits, whereas the lowest values of these traits were recorded for FB systems. In conclusion, the MuB system with WF improved soil characteristics and barley yield over other cropping systems. The AWE significantly suppressed weeds and was equally effective as the chemical control. Therefore, MuB and AWE could be used to improve barley productivity and suppress weeds infestation

The influence of different row spacing and weed control intervals on weed infestation and yield-related traits of American (Gossypium hirsutum L.) and Desi (Gossypium arboreum) cotton

Narrow row spacing has attracted significant attention due to its beneficial impacts on weed management in cotton. This study compared the effects of normal and ultra-narrow row spacing on critical periods of weed control in American (Gossypium hirsutum L.) and ‘Desi’ (Gossypium arboreum) cotton. Two different row spacings (i.e., recommended (75 cm) and ultra-narrow (30 cm)) and three weed control intervals (i.e., weed control at 30, 60 and 90 days after sowing (DAS)) were included in the study. Weedy-check and weed-free treatments were included in the experiment as controls for comparison. ‘Desi’ cotton grown under ultra-narrow spacing recorded the lowest weed density and individual density of Trianthema portulacastarum L., Cyperus rotundus L., Cynodon dactylon L., Echinochloa colona (L.) Link and Digera muricata (L.) Mart. Moreover, ‘Desi’ cotton sown under ultra-narrow spacing with weed-free and weed control at 30 DAS resulted in the highest leaf area index (LAI), leaf area duration (LAD), net assimilation late (NAR), root elongation rate (RER) and root growth rate (RGR) at all sampling dates. Likewise, ‘desi’ cotton sown under recommended row spacing and weed-free conditions produced the highest number of sympodial and monopodial branches, number of flowers and bolls per plant, whereas the highest seed cotton yield of ‘Desi’ cotton was noted under ultra-narrow spacing and weed-free conditions. It is concluded that sowing both cotton types in ultra-narrow row spacing and controlling weeds at 30 DAS will result in lower weed infestation and higher seed cotton yield

SimE/TS fuzzy hybrid for multiobjective VLSI placement

A hybrid heuristic for multiobjective VLSI cell placement is presented, which draws from the memory concept of Tabu search (TS) and the goodness feature of Simulated Evolution (SimE). Experimental results using ISCAS-89 benchmark circuits illustrate improvement in quality as compared to our best canonical TS implementation

Wearable Internet of Things - from Human Activity Tracking to Clinical Integration

Wearable devices for human activity tracking have been rapidly emerging. Most of them are capable of sending health statistics to smartphones, smartwatches or smart bands. However, they only provide the data for individual analysis and their data is not integrated into clinical practice. Leveraging on the Internet of Things (IoT), edge and cloud computing technologies, we propose an architecture which is capable of providing cloud based clinical services using human activity data. Such services could supplement the shortage of staff in primary healthcare centers thereby reducing the burden on healthcare service providers. The enormous amount of data created from such services could also be utilized for planning future therapies by studying recovery cycles of existing patients. We provide a prototype based on our architecture and discuss its salient features. We also provide use cases of our system in personalized and home based healthcare services. We propose an International Telecommunication Union based standardization (ITU-T) for our design and discuss future directions in wearable IoT