Performance Enhancement of Cavity Assisted Photonic Crystal De-Multiplexer in Slow Light Regime

Mohammad-Hashem Vadjed-Samiei,Hassan Aghababaeian 한국광학회 2016 Current Optics and Photonics Vol.20 No.3

This study first proposes a new version of a photonic crystal based de-multiplexer operating under theslow light regime, secondly analyses the structure numerically to demonstrate de-multiplexing operationand finally studies the impact of light speed on the performance of the proposed structure. The operationwavelength is 1.55 μm. The study indicates that, by adjusting the speed of light, around 0.1C, in the mainwaveguide and in the output channels’ waveguides, an enhancement in the performance of the de-multiplexerwill be gained.

The Effect of Melanocyte Stimulating Hormone and Hydroxyapatite on Osteogenesis in Pulp Stem Cells of Human Teeth Transferred into Polyester Scaffolds

Marziyeh Aghazadeh,Mohammad Samiei,Vahideh Raeisdasteh Hokmabad,Effat Alizadeh,Neda Jabbari,Alexander Seifalian,Roya Salehi 한국섬유공학회 2018 Fibers and polymers Vol.19 No.11

Presently, tissue engineering is employed in the restoration and repair of tissue defects. Degradable scaffolds, stem cells and stimulating factors are employed in this method. In this study, the effect of melanocyte-stimulating hormone (MSH) and/or hydroxyapatite (HA) on proliferation, osteoblast differentiation, and mineralization of human dental pulp stem cells (hDPSCs) seeded on PLLA-PCL nanofibrous scaffolds was evaluated. For this aim, PLLA-PCL-HA nanofibrous scaffolds were fabricated using electrospinning method. FE-SEM images exhibited that all nanofibers had bead-free morphologies with average diameters ranging from 150-205 nm. Human DPSCs seeded into PLLA-PCL nanofibers were treated with MSH. Cell viability, proliferation, morphology, osteogenic potential, and the expression of tissue-specific genes were assessed by means of MTT assay, FE-SEM, alizarin red S staining, and RT-PCR analysis. hDPSCs exhibited improved adhesion and proliferation capacity on the PLLA-PCL-HA nanofibers treated with MSH compared to other groups (p<0.05). Additionally, PLLA-PCL-HA nanofibers treated with MSH exhibited significantly higher mineralization and alkaline phosphatase activity than other groups. RT-PCR results confirmed that PLLA-PCL-HA nanofibers enriched with MSH could significantly unregulated the gene expression of BMP2, osteocalcin, RUNX2 and DSPP that correlated to osteogenic differentiation (p<0.05). Based on results, incorporation of HA nanoparticles in PLLA-PCL nanofibers and addition of MSH in media exhibited synergistic effects on the adhesion, proliferation, and osteogenesis differentiation of hDPSCs, and therefore assumed to be a favorable scaffold for bone tissue engineering applications.

Compact and Temperature Independent Electro-optic Switch Based on Slotted Silicon Photonic Crystal Directional Coupler

Hassan Aghababaeian,Mohammad-Hashem Vadjed-Samiei 한국광학회 2012 Current Optics and Photonics Vol.16 No.3

In this paper, we have proposed a principle to design a compact and temperature independent electro-optic switch based on a slotted photonic crystal directional coupler (SPCDC). Infiltration of the slotted silicon photonic crystal with polymer enhances the slow light and decreases the switching length,whereas the different signs of thermo-optic coefficients of the polymer and silicon make the proposed switch stable within 25℃ to 85℃ temperature range. The SPCDC structure is modified to increase poling efficiency of the polymer in the slot and to flatten the dispersion diagram of the even mode to minimize the switching length.

Temperature Stabilization of Group Index in Silicon Slotted Photonic Crystal Waveguides

Hassan Aghababaeian,Mohammad-Hashem Vadjed-Samiei,Nosrat Granpayeh 한국광학회 2011 Current Optics and Photonics Vol.15 No.4

In this paper, we have proposed a principle to design wideband, low dispersion and temperature stabilized slow light structure in slotted photonic crystal waveguide (SPCW). The infiltration of the silicon photonic crystal with polymer will enhance the slow light and increase the group index, whereas the different signs of thermo-optic coefficients of polymer and silicon make the proposed structure stable on temperature variation over 60℃ and improves the group index-bandwidth products of the designed structure. The SPCW structure is modified to maximize the slow light effect and minimize the dependence of the group index and hence the group velocity dispersion to temperature.

Association of Methylenetetrahydrofolate Reductase C677T Polymorphism with Hyperhomocysteinemia and Deep Vein Thrombosis in the Iranian Population

Habib Ghaznavi,Zahra Soheili,Shahram Samiei,Mohammad Soleiman Soltanpour 대한혈관외과학회 2015 Vascular Specialist International Vol.31 No.4

Purpose: Deep venous thrombosis (DVT) is a common but elusive condition characterized by a high morbidity and mortality rate. The aim of the present study was to investigate the correlation between methylenetetrahydrofolate reductase (MTHFR) C677T polymorphism with plasma total homocysteine (tHcy) levels and DVT risk in an Iranian population. Materials and Methods: Our study population consisted of 67 patients with a diagnosis of DVT and 67 healthy subjects as controls. Genotyping of MTHFR C677T polymorphism was performed by the polymerase chain reaction technique combined with restriction enzyme fragment length polymorphism (PCR-RFLP) and measurement of tHcy levels was done by enzyme immunoassay method. Results: Plasma tHcy levels were significantly higher in DVT patients than controls (18.09±7.6 vs. 10.5±4.3, P=0.001). Also, plasma tHcy levels were significantly higher in MTHFR 677TT genotypes compared to 677CC genotypes in both DVT patients (P=0.016) and controls (P=0.03). Neither heterozygote nor homozygote genotypes of MTHFR C677T polymorphism was significantly correlated with DVT (P>0.05). The distribution of MTHFR C677T genotypes was similar between men and women in both DVT patients and controls (P>0.05). Moreover, the frequency of mutant 677T allele did not differ significantly between the two groups (28.3% vs. 21.6%, P=0.15). Conclusion: Based on this study, we propose that hyperhomocysteinemia but not homozygosity for MTHFR C677T polymorphism is a significant risk factor for DVT in the Iranian population. Also, MTHFR 677TT genotype is a determinant of elevated plasma tHcy levels.

Role of Hyperhomocysteinemia and Methylene Tetrahydrofolate Reductase C677T Polymorphism in Idiopathic Portal Vein Thrombosis

Habib Ghaznavi,Zahra Soheili,Shahram Samiei,Mohammad Soleiman Soltanpour 대한혈관외과학회 2016 Vascular Specialist International Vol.32 No.1

Purpose: Portal vein thrombosis (PVT) is a rare and life-threatening vascular disorder characterized by obstruction or narrowing of the portal vein. Hyperhomocysteinemia and methylenetetrahydrofolate reductase (MTHFR) C677T polymorphism has been studied in PVT patients with conflicting results. In the present study the association of hyperhomocysteinemia and MTHFR C677T polymorphism with PVT risk was investigated in Iranians. Materials and Methods: Our study population consisted of 10 idiopathic PVT patients and 80 healthy control subjects matched for age and sex. MTHFR C677T polymorphism was genotyped by the polymerase chain reaction technique combined with restriction enzyme fragment length polymorphism (PCR-RFLP) technique and plasma total homocysteine (tHcy) levels were determined by enzyme immunoassay method. Results: Mean plasma tHcy levels were significantly higher in PVT patients(20.2±6.8) than control subjects (10.9±4.7) (P=0.001). Moreover, plasma tHcy levels were significantly higher in 677T allele carriers relative to 677C allele carriers in both PVT patients (P=0.01) and control subjects (P=0.03). Neither homozygote nor heterozygote genotypes of MTHFR C677T polymorphism correlated significantly with PVT risk (P>0.05). Moreover, MTHFR C677T polymorphism didn’t increase the risk of PVT under dominant (CT+TT vs. CC) or recessive (TT vs. CC+CT) genetic models analyzed (P>0.05). The difference in frequency of minor 677T allele between PVT patients and control subjects was not statistically significant (P>0.05). Conclusion: Based on the current study, we suggest that hyperhomocysteinemia constitutes a significant and common risk factor for PVT. Also, MTHFR C677T polymorphism is not a risk factor for PVT but is a contributing factor for elevated plasma tHcy levels.