Design and numerical analysis of a photonic crystal fiber (PCF)-based flattened dispersion THz waveguide

Optical Review - We present the modeling of a porous core dispersion flatten photonic crystal fiber (PCF) for the fruitful transmission of THz signals. The model comprises only rectangular holes in...     

Spatial and seasonal behaviour of organotin compounds in protected subtropical estuarine ecosystems in Okinawa,Japan

The spatial and temporal behaviours of the organotin compounds (OTCs) (butyl- and phenyltin) were investigated in the Manko and Okukubi protected estuarine ecosystems on Okinawa Island, Japan from February to October 2006. Butyltin compounds (BTCs) were frequently detected in all seasons, while phenyltin (PhTs) were found in winter and early spring. In Manko estuary, the total mean concentrations of BTCs and PhTs were 22.78?±?30.85, (mean?±?SD, n?=?53) and 0.08?±?0.27?ng(Sn)?L^?1, respectively. In Okukubi estuary, BTCs and PhTs were 12.58?±?23.96 and 0.47?±?1.67 (n?=?55) ng(Sn)?L^?1, respectively. The Manko sediments can be classified as lightly contaminated, while the Okukubi sediments were uncontaminated with tributyltin (TBT). The mean levels of TBT shown in Manko estuary exceeded the threshold level and represent an ecotoxicological risk to sensitive aquatic life. Generally, the present study reports the occurrence and continuous input of OTCs in the protected estuaries, even 16 years after legal restriction of TBT usage in coastal waters was implemented by the Japanese Environmental Authorities.     

Conditional Gradient Method for Double-Convex Fractional Programming Matrix Problems

We consider the problem of optimizing the ratio of two convex functions over a closed and convex set in the space of matrices. This problem appears in several applications and can be classified as a double-convex fractional programming problem. In general, the objective function is nonconvex but, nevertheless, the problem has some special features. Taking advantage of these features, a conditional gradient method is proposed and analyzed, which is suitable for matrix problems. The proposed scheme is applied to two different specific problems, including the well-known trace ratio optimization problem which arises in many engineering and data processing applications. Preliminary numerical experiments are presented to illustrate the properties of the proposed scheme.     

Effect of Clay Addition on the Properties of Carbon Nanotubes-Filled Immiscible Polyethylene/Polypropylene Blends

The effects of organically modified clay (OMC) incorporation on the microstructure and the electrical and mechanical properties of polypropylene (PP)/polyethylene (PE) blends filled with carbon nanotubes (CNT) were investigated. All blends were prepared by melt mixing in a batch mixer. The microstructures were characterized by scanning electron microscopy. In the OMC:CNT filled blends, the CNT were found to selectively localize within the PE phase, while the clay particles were observed in the PP phase. The electrical resistivity of OMC:CNT filled blends did not show any significant change as a result of the clay addition since it was localized in the CNT-free phase. On the other hand, the addition of clay degraded the blends' mechanical properties due to the poor adhesion between the OMC and the PP matrix.     

Optimization of an ammonia-cooled rectangular microchannel heat sink using multi-objective non-dominated sorting genetic algorithm (NSGA2)

The ever decreasing size of modern electronic packaging has induced researchers to search for an effective and efficient heat removal system to handle the continuously increasing power density. Investigations have involved different geometry, material and coolant to address the thermal management issues. This paper reports the potential improvement in the overall performance of a rectangular microchannel heat sink using a new gaseous coolant namely ammonia gas. Using a multi-objective general optimization scheme with the thermal resistance model as an analysis method in combination with a non-dominated sorting genetic algorithm as an optimization technique, it was found that significant reduction in the total thermal resistance up to 34?% for ammonia-cooled compared to air-cooled microchannel heat sink under the same operating conditions is achievable. In addition, a considerable decrease in the microchannel heat sink’s mass up to 30?% was achieved due to the different heat sink’s material used.     

Novel Pyrimidine‐based Ferrocenyl substituted Organometallic Compounds: Synthesis,Characterization and Biological Evaluation

Some novel pyrimidine‐based ferrocenyl substituted organometallic compounds were synthesized via multistep reactions, well characterized by different spectroscopic techniques and elemental analyses and evaluated for in vitro antiprotozoal susceptibility against HM1: IMSS strain of Entamoeba histolytica. The results of antiprotozoal susceptibility unveiled these compounds, as new leads in protozoal chemotherapy as most of the organometallics displayed an exceptionally higher antiamoebic activity (IC₅₀ = 0.055 μM ‐ 0.815 μM) than the reference drug metronidazole which gave IC₅₀ (50% inhibitory concentration) value 1.781 μM in our experiments, concluding that newly synthesized organometallic compounds have potential to be employed as effective antiamoebic agents and these organometallics can be very useful for further optimization work on amoebic chemotherapy.     

Reassignment of the structures of condensation products of α-keto α′-formylarylhydrazones with ethyl cyanoacetate: a novel route to ethyl 5-arylazo-2-hydroxynicotinates

The condensation of α-keto α′-formylarylhydrazones with ethyl cyanoacetate afforded ethyl 5-arylazo-2-hydroxy-6-aryl (or alkyl) nicotinates. The structures of the reaction products could be established based on X-ray crystal structure determination.