Cross-layer Design of Private MAC with TH-BPPM and TH-BPAM in UWB Ad-hoc Networks

Parvez, A.Al,Khan, M.A.,Hoque, M.E.,An, Xizhi,Kwak, Kyung-Sup The Korea Institute of Information and Commucation 2006 韓國通信學會論文誌 Vol.31 No.12A

Ultra-wideband(UWB) is a killer technology for short-range wireless communications. In the past, most of the UWB research focused on physical layer but the unique characteristics of UWB make it different to design the upper layer protocols than conventional narrow band systems. Cross-layer protocols have received high attention for UWB networks. In this paper, we investigate the performance of two physical layer schemes: Time Hopping Binary Pulse Position Modulation(TH-BPPM) and Time Hopping Binary Pulse Amplitude Modulation (TH-BPAM) with proposed private MAC protocol for UWB ad-hoc networks. From pulse level to packet level simulation is done in network simulator ns-2 with realistic network environments for varying traffic load, mobility and network density. Our simulation result shows TH-BPAM outperforms TH-BPPM in high traffic load, mobility and dense network cases but in a low traffic load case identical performance is achieved.

Comparative study of plasma and ion-beam treatment to reduce the oxygen vacancies in TiO₂ and recombination reactions in dye-sensitized solar cells

Parvez, Md.K.,Yoo, G.M.,Kim, J.H.,Ko, M.J.,Kim, S.R. North Holland 2010 Chemical physics letters Vol.495 No.1

Oxygen plasma and ion-beam treatments of nano-structured TiO<SUB>2</SUB> were carried out to enhance the efficiency of dye-sensitized solar cells (DSSCs). Relative changes in surface states and recombination reactions were examined. Comparative studies showed that the oxygen ion-beam treatment was more effective in reducing the number of oxygen vacancies in TiO<SUB>2</SUB> and the recombination reactions between TiO<SUB>2</SUB> conduction band electrons and I<SUB>3</SUB><SUP>-</SUP> ions in the electrolyte than the plasma treatment. Oxygen ion-beam treated TiO<SUB>2</SUB> film in the DSSC showed a 23mV increase in the open-circuit voltage (V<SUB>oc</SUB>) and an improvement in the photo-conversion efficiency from 5.05% to 6.64%.

Optimization of triboelectric energy harvesting from falling water droplet onto wrinkled polydimethylsiloxane-reduced graphene oxide nanocomposite surface

Parvez, Abu Naushad,Rahaman, Md Habibur,Kim, Hyeon Cheol,Ahn, Kyoung Kwan Elsevier Science Ltd 2019 Composites Part B, Engineering Vol.174 No.-

<P><B>Abstract</B></P> <P>This study investigates the triboelectric energy harvesting phenomenon of falling water droplets on a novel nanocomposite surface, chemically synthesized from reduced graphene oxide (rGO) and polydimethylsiloxane (PDMS) polymer. The prime concern of this work is to synthesize such a triboelectric nanocomposite film, which will pose optimized hydrophobicity along with ameliorated dielectric properties through proper optimization of filler quantity inclusion in PDMS matrix. Therefore, six samples including one pristine PDMS and five nanocomposites (PDMS-rGO) have been prepared by varying filler concentration. Optimization has been explained based on determination of several parameters and nano-characterization techniques such as thickness of rGO flakes, thickness of polymer and nanocomposite samples, water contact angles, dielectric properties, triboelectric outputs, FE-SEM, EDX, FTIR, XPS and Raman spectroscopic analyses. After analyzing the outputs of a single electrode mode triboelectric nanogenerator (SEM-TENG) based on Pristine PDMS and nanocomposite samples, it has been found that 0.5 mg rGO incorporated PDMS matrix of 141 μm thickness revealed highest water contact angle i.e.116.9°. Besides, highest output potential difference (V<SUB> <I>OC</I> </SUB>) of ∼2 V and close circuit current (I<SUB> <I>SC</I> </SUB>) of ∼2 nA have been obtained upon contact and separation of rolling water droplet over the same nanocomposite surface. This work demonstrates a unique way to get an optimized thin triboelectric nanocomposite film, which is able to harvest the kinetic energy of a tiny moving water droplet. Hence, we hope that this work may serve as a convenient platform for triboelectric energy harvesting from natural raindrops, fountains or any real-life phenomenon involving the movement of droplet.</P>

Comprehensive Substrate Characterization of 22 Antituberculosis Drugs for Multiple Solute Carrier (SLC) Uptake Transporters <i>In Vitro</i>

Parvez, M. M.,Kaisar, Nazia,Shin, Ho Jung,Lee, Yoon Jae,Shin, Jae-Gook American Society for Microbiology 2018 Antimicrobial Agents and Chemotherapy Vol.62 No.9

<P>The substrate potentials of antituberculosis drugs on solute carrier (SLC) transporters are not well characterized to date, despite a well-established understanding of their drug dispositions and pharmacokinetics. In this study, we investigated comprehensively the substrate potentials of the 22 currently available antituberculosis drugs for SLC family transporter-mediated uptake, using Xenopus laevis oocytes and stably transfected HEK-293 cells in vitro. The result suggested that ethambutol, isoniazid, amoxicillin, and prothionamide act as novel substrates for the SLC transporters. In addition, in the presence of representative transporter inhibitors, the uptake of the antituberculosis drugs was markedly decreased compared with the uptake in the absence of inhibitor, suggesting involvement of the corresponding transporters. A cellular uptake study was performed, and the K-m values of ethambutol were found to be 526.1 +/- 15.6, 212.0 +/- 20.1, 336.8 +/- 20.1, and 455.0 +/- 28 mu M for organic cation transporter 1 (OCT1), OCT2, OCTN1, and OCTN2, respectively. Similarly, the K-m of prothionamide was 805.8 +/- 23.4 mu M for OCT1, while the K-m values of isoniazid and amoxicillin for organic anion transporter 3 (OAT3) were 233.7 +/- 14.1 and 161.4 +/- 10.6 mu M, respectively. The estimated in vivo drug-drug interaction indexes from in vitro transporter inhibition kinetics for verapamil, probenecid, and ibuprofen against ethambutol, prothionamide, isoniazid, and amoxicillin were found to show potential for clinical drug interactions. In conclusion, this is the first study that demonstrated 22 antituberculosis drug interactions with transporters. This study will be helpful for mechanistic understanding of the disposition, drug-drug interactions, and pharmacokinetics of these antituberculosis drugs.</P>

Inhibitory Interaction Potential of 22 Antituberculosis Drugs on Organic Anion and Cation Transporters of the SLC22A Family

Parvez, M. Masud,Kaisar, Nazia,Shin, Ho Jung,Jung, Jin Ah,Shin, Jae-Gook American Society for Microbiology 2016 Antimicrobial Agents and Chemotherapy Vol.60 No.11

<B>ABSTRACT</B><P>Twenty-two currently marketed antituberculosis drugs were comprehensively evaluated for their inhibitory effect on organic anionic transporter (OAT)- and organic cation transporter (OCT)-mediated uptake using stably transfected HEK293 cells<I>in vitro</I>. We observed moderate to strong inhibitory effects on OAT1- and OAT3-mediated<I>para</I>-aminohippurate (PAH) uptake and OCT1- and OCT2-mediated<I>N</I>-methyl-4-phenylpylidinium acetate (MPP<SUP>+</SUP>) uptake. Ciprofloxacin, linezolid,<I>para</I>-aminosalicylic acid (PAS), and rifampin were observed to have strong inhibitory effects, with the concentrations for a 50% inhibitory effect (IC50s) being 35.1, 31.1, 37.6, and 48.1 μM, respectively, for OAT1 and >100, 21.9, 24.6, and 30.2 μM, respectively, for OAT3. Similarly, pyrazinamide, rifabutin, and levofloxacin were observed to have inhibitory effects, with IC50values being 36.5, 42.7, and 30.3 μM, respectively, for OCT1 and with the IC50value for PAS being 94.2 μM for OCT2. In addition, we used zidovudine and metformin as clinically prescribed substrates of OATs and OCTs, respectively, and zidovudine and metformin uptake was also strongly inhibited by the antituberculosis drugs. Among the tested drugs, the highest drug-drug interaction (DDI) indexes were found for PAS, which were 9.3 to 13.9 for OAT1 and 12.0 to 17.7 for OAT3, and linezolid, which were 1.18 to 2.15 for OAT1 and 1.7 to 3.01 for OAT3. Similarly, the DDI indexes of pyrazinamide and levofloxacin were 0.57 and 0.30, respectively, for OCT1, and the DDI index of PAS was 3.8 for OCT2, suggesting a stronger possibility (DDI index value cutoff, >0.1) of<I>in vivo</I>DDIs. This is the first comprehensive report of the inhibitory potential of anti-TB drugs on OAT- and OCT-mediated uptake of prototype and clinically prescribed substrate drugs<I>in vitro</I>, providing an ability to predict DDIs between anti-TB drugs and other coprescribed drugs in clinical studies<I>in vivo</I>.</P>

Characterization of 22 Antituberculosis Drugs for Inhibitory Interaction Potential on Organic Anionic Transporter Polypeptide (OATP)-Mediated Uptake

Parvez, M. Masud,Jung, Jin Ah,Shin, Ho Jung,Kim, Dong Hyun,Shin, Jae-Gook American Society for Microbiology 2016 Antimicrobial Agents and Chemotherapy Vol.60 No.5

<B>ABSTRACT</B><P>We investigated the inhibitory interaction potential of 22 currently marketed antituberculosis (TB) drugs on organic anion-transporting polypeptide 1B1 (OATP1B1)-, OATP2B1-, and OATP1B3-mediated uptake using<I>in vitro</I>Xenopusoocytes and HEK cells. Rifabutin, ethambutol, amoxicillin, linezolid,<I>p</I>-amino salicylic acid, and rifapentine exhibited mild to moderate inhibitory effects on OATP-mediated uptake of estrone-3 sulfate, estradiol 17β-d-glucuronide, and rosuvastatin. The 50% inhibitory concentration (IC50) values of rifabutin, amoxicillin, ethambutol,<I>p</I>-amino salicylic acid, and linezolid were 35.4, 36.2, 57.6, 72.6, and 65.9 μM, respectively, for uptake mediated by organic anionic transporter polypeptide 1B1 (OATP1B1) and 28.8, 28.9, 53.9, 31.5, and 61.0 μM, respectively, for uptake mediated by organic anionic transporter polypeptide 1B3 (OATP1B3). Streptomycin and linezolid showed greater inhibition of organic anionic transporter polypeptide 2B1 (OATP2B1)-mediated uptake, with IC50values of 33.2 and 35.6 μM, respectively, along with mild inhibition of other drugs. Furthermore, rifabutin, amoxicillin, and rifapentine significantly inhibited OATP1B1-mediated rosuvastatin uptake, with IC50values of 12.3, 13.0, and 11.0 μM, respectively, which showed a similar profile to estrone-3 sulfate uptake. The calculated<I>R</I>values ([<I>I</I>]<I>u inlet,max</I>/<I>Ki</I>, where [<I>I</I>]<I>u inlet,max</I>represents the maximum estimated inhibitor concentration inlet to the liver and<I>Ki</I>is the inhibition constant) as the drug-drug interaction (DDI) indexes of PAS, ethambutol, and amoxicillin were 26.1, 6.5, and 4.3 for OATP1B1 and 52.0, 8.0, and 4.6 for OATP1B3, and those for streptomycin, amikacin, and linezolid were 5.0, 4.2, and 4.4 for OATP2B1, respectively, suggesting a higher possibility of<I>in vivo</I>DDIs. This study is the first comprehensive report to show the novel inhibitory potential of 22 marketed anti-TB drugs on OATP-mediated uptake, providing evidence for future<I>in vivo</I>clinical DDI studies.</P>

Evaluation of <i>para</i>-Aminosalicylic Acid as a Substrate of Multiple Solute Carrier Uptake Transporters and Possible Drug Interactions with Nonsteroidal Anti-inflammatory Drugs <i>In Vitro</i>

Parvez, M. Masud,Shin, Ho Jung,Jung, Jin Ah,Shin, Jae-Gook American Society for Microbiology 2017 Antimicrobial Agents and Chemotherapy Vol.61 No.5

<P>para-Aminosalicylic acid (PAS) is a second-line antituberculosis drug that has been used to treat multidrug-resistant and extensively drug-resistant tuberculosis for more than 60 years. Renal secretion and glomerular filtration are the major pathways for the elimination of PAS. We comprehensively studied PAS transport by using cell lines that overexpressed various transporters and found that PAS acts as a novel substrate of an organic anionic polypeptide (OATP1B1), organic cationic transporters (OCT1 and OCT2), and organic anion transporters (OAT1 and OAT3) but is not a substrate of any ATP-binding cassette (ABC) transporters. Net PAS uptake was measured, and the transport affinities (K-m values) for OATP1B1, OCT1, OCT2, OAT1, and OAT3 were found to be 50.0, 20.3, 28.7, 78.1, and 100.1 mu M, respectively. The net uptake rates suggested that renal OAT1 and OAT3 play relatively major roles in PAS elimination. The representative inhibitors rifampin for OATP1B1, probenecid for OAT1 and OAT3, and verapamil for OCT1 and OCT2 greatly inhibited PAS uptake, suggesting that PAS is dependent on multiple transporters for uptake. We also evaluated nonsteroidal anti-inflammatory drugs (NSAIDs), proton pump inhibitors (PPIs), and metformin for the inhibition of PAS uptake via these transporters. Half-maximal (50%) inhibitory concentrations (IC(50)s) were kinetically determined and used to predict the drug-drug interactions (DDIs) affecting these transporters' activity toward PAS. We found that rifampin, probenecid, ibuprofen, naproxen, cimetidine, and quinidine each exhibited a significant potential for in vivo DDIs with PAS. In this study, PAS was found to be a novel substrate of several transporters, and drugs that inhibit these transporters can reduce PAS elimination.</P>

Mathematics learning inequality among children of private and public schools

Parvez, Aquib,Laxminarayana, K. 서울대학교 교육연구소 2022 Asia Pacific Education Review Vol.23 No.2

In this study, we research the gap in average mathematics learning between the children of private and public schools at two points. We have divided them into two groups on the basis of the type of school they are attending or last attended. We first skim through their various background characteristics at these two points. We then explore these background characteristics and using the threefold Blinder–Oaxaca decomposition, we find that it is the difference in the average endowments between the two which consistently explains the gap in average performance between them. We also find the role of differential impact of the background characteristics on the average learning outcome of children on the first point. The most important and consistent contributor to the endowment effect is the schooling cost and the time allocation on studies. One striking result is the now significant contribution of the gap in average years of schooling which is worrying because these children are from the same age group. We conclude that with the average features and returns of the private school children, the gap in learning between them would have been removed. Moreover, the public school children would have performed better than the private school children.

Tyrosinase inhibitors of Galla Rhois and its derivative components

Parvez Shoukat,Amin Muhammad Haider,배현수 경희대학교 융합한의과학연구소 2021 Oriental Pharmacy and Experimental Medicine Vol.21 No.2

Two hundred forty-three oriental herbs were screened for their tyrosinase inhibitory activity. Among them, methanol extract of Galla Rhois was shown to be the most potent tyrosinase inhibitory activity. The IC50 values for Galla Rhois, kojic acid, ascorbic acid, arbutin and 5 HMF were 0.163, 0.019, 0.316, 1.520 and 2.511 mg/mL, respectively. Anti-tyrosinase activity of Galla Rhois is higher about two, nine and 15-fold of anti-tyrosinase activity of ascorbic acid, arbutin and 5-HMF while lesser than kojic acid. To isolate active compounds, the 50% aqueous methanol extracts was evaporated to vacuo, and the fractionated by the Diaion HP-20, Sepadex LH-20 column chromatography and repeated the preparative HPLC procedure. Three major phenolic compounds were isolated, and characterized, one of them exhibiting tyrosinase inhibitory activity stronger than L-ascorbic acid (IC50 = 90 μg/mL) was identified as Methyl gallate ((IC50 = 40 μg/mL) by UV, IR, C-NMR, and FAB-MS spectroscopy. The compound isolated from Galla Rhois exhibited non-competitive inhibition against oxidation of l-3-4-dihydroxyphenylalanine (l-DOPA) by mushroom tyrosinase. As a naturally occurring tyrosinase inhibitor, methyl gal-late may be useful as a new agent to inhibit the oxidation of l-DOPA by mushroom tyrosinase. This is the first HPLC analysis containing ascorbic acid, 5-HMF and arbutin, Galla Rhois exert varying degrees of inhibition on tyrosinase-dependent and these result suggesting that Galla Rhois may serve as candidates for depigmenting agents. Further studies on the application of Methyl gallate is needed in cosmetics and as anti-melanogenic agents.

Model Predictive Control of Bidirectional AC-DC Converter for Energy Storage System

Md. Parvez Akter,Saad Mekhilef,Nadia Mei Lin Tan,Hirofumi Akagi 대한전기학회 2015 Journal of Electrical Engineering & Technology Vol.10 No.1

Energy storage system has been widely applied in power distribution sectors as well as in renewable energy sources to ensure uninterruptible power supply. This paper presents a model predictive algorithm to control a bidirectional AC-DC converter, which is used in an energy storage system for power transferring between the three-phase AC voltage supply and energy storage devices. This model predictive control (MPC) algorithm utilizes the discrete behavior of the converter and predicts the future variables of the system by defining cost functions for all possible switching states. Subsequently, the switching state that corresponds to the minimum cost function is selected for the next sampling period for firing the switches of the AC-DC converter. The proposed model predictive control scheme of the AC-DC converter allows bidirectional power flow with instantaneous mode change capability and fast dynamic response. The performance of the MPC controlled bidirectional AC-DC converter is simulated with MATLAB/Simulink® and further verified with 3.0kW experimental prototypes. Both the simulation and experimental results show that, the AC-DC converter is operated with unity power factor, acceptable THD (3.3% during rectifier mode and 3.5% during inverter mode) level of AC current and very low DC voltage ripple. Moreover, an efficiency comparison is performed between the proposed MPC and conventional VOC-based PWM controller of the bidirectional AC-DC converter which ensures the effectiveness of MPC controller.