Cross Metathesis Assisted Solid-Phase Synthesis of Glycopeptoids

Khan, Sharaf Nawaz,Kim, Arim,Grubbs, Robert H.,Kwon, Yong-Uk American Chemical Society 2012 Organic letters Vol.14 No.12

<P>A solid-phase synthesis of glycopeptoids was explored through olefin cross metathesis (CM). Peptoids and sugar derivatives with appropriate olefin moieties were coupled in the presence of an olefin metathesis catalyst to afford glycopeptoids in good yields. This systematic solid-phase CM study can provide facile access to the molecular sources of glycopeptidomimetics and postchemical modifications on various molecular scaffolds.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/orlef7/2012/orlef7.2012.14.issue-12/ol300808c/production/images/medium/ol-2012-00808c_0006.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/ol300808c'>ACS Electronic Supporting Info</A></P>

Joint routing, link capacity dimensioning, and switch port optimization for dynamic traffic in optical networks

Khan, Akhtar Nawaz,Khan, Zawar H.,Khattak, Khurram S.,Hafeez, Abdul Electronics and Telecommunications Research Instit 2021 ETRI Journal Vol.43 No.5

This paper considers a challenging problem: to simultaneously optimize the cost and the quality of service in opaque wavelength division multiplexing (WDM) networks. An optimization problem is proposed that takes the information including network topology, traffic between end nodes, and the target level of congestion at each link/ node in WDM networks. The outputs of this problem include routing, link channel capacities, and the optimum number of switch ports locally added/dropped at all switch nodes. The total network cost is reduced to maintain a minimum congestion level on all links, which provides an efficient trade-off solution for the network design problem. The optimal information is utilized for dynamic traffic in WDM networks, which is shown to achieve the desired performance with the guaranteed quality of service in different networks. It was found that for an average link blocking probability equal to 0.015, the proposed model achieves a net channel gain in terms of wavelength channels (𝛾_w) equal to 35.72 %, 39.09 %, and 36.93 % compared to shortest path first routing and 𝛾_w equal to 29.41 %, 37.35 %, and 27.47 % compared to alternate routing in three different networks.

Fiscal Convergence and Total Factor Productivity: Firm-Level Evidence from Pakistan

KHAN, Usman Shaukat,KHAN, Muhammad Arshad,NAWAZ, Saima,RAHMAN, Abdul Korea Distribution Science Association 2020 The Journal of Asian Finance, Economics and Busine Vol.7 No.10

This study examines the impact of corporate tax, a fiscal measure along with trade liberalization and research and development on total factor productivity for a panel of 153 industrial firms listed on the Pakistan Stock Exchange over the period 1997-2017. For empirical analysis, we employ the system generalized method of moment estimator. In the first step, we estimate industrial production function and the results reveal that raw material, industrial labour force and energy play vital role in enhancing industrial production. Whereas, industrial capital exerts negative impact on industrial output. We also measured total factor productivity using the production elasticities. In the second step, we examine the impact of corporate tax, trade liberalization and research and development on total factor productivity. The results indicate that higher level of corporate tax exerts negative impact on total factor productivity. The findings reveal that higher corporate taxation discourages industrial firms to undertake research and development thereby exerting adverse impact on total factor productivity of firms. The impact of trade liberalization proxied by average tariff is positive while customs duty and sales tax negatively impact firm-level total factor productivity. These findings provide useful insights for managers, investors and policy makers in Pakistan.

Impacts of Demographics on Citizen’s Access to Information: An Empirical Study of District Dera Ismail Khan, North Western Frontier Province, Pakistan

Najeebullah Khan,Bahadar Shah,Allah Nawaz 한국사회복지학회 2008 Asian Social Work and Policy Review Vol.2 No.2

The impact of demographic dimensions on local government behavior is well identified, analyzedand documented at the global level. Likewise, several studies are available on developing countries,but empirical evidence on the conditions of Pakistan is lacking. This study is an effort to unearthempirical evidence on access to information in the local government system exemplifying data fromthe district Dera Ismail Khan (DIK), North Western Frontier Province (NWFP). Most globalhypotheses for developing countries are accepted in this study but the statistics on local data arefar more different in terms of the value and weight of variables, relationships and impacts on theresearch concepts. The most dominant concept in the impact of access to information on the localgovernment system is ‘‘education for all.’’ Mass education is a leading concept in making or breakingthe role of people participation in the success or failure of local democracies. Data show thatilliteracy is causing many problems, including the mass population’s unawareness of their interestsand duties at the public level, thereby giving the ruling elite a free hand in exploiting publicresources for self-interest, at the cost of the public good.

Revolutionizing the Health Sector-Com parative Analysis of e-Health Implementation in Pakistan, Sri Lanka and Mongolia

( Kamran Nawaz Khan ),( Dollamullege Tekla Manori Ranasinghe ),( Gerelsuren Bayarsaikhan ) 한국정책학회 2015 한국정책학회 추계학술발표논문집 Vol.2015 No.-

Countries around the world are turning to e-Health to extend service delivery in health sector. Developing countries like located in South Asia or the Indian Subcontinent like Pakistan, Sri Lanka, Nepal, India, among others have taken bold steps towards revolutionizing the health sector with the use of e-Health. This will utilize the immense opportunities presented by cutting edge technologies to provide costs effective method and enhance the quality of health services delivery. Many e-Health projects were launched in the last decade in these countries. Nonetheless, a lot of these projects failed. It seems to be difficult to understand how to implement e-Health services in today``s complex and conservative cultural environment. In addition, legal and ethical issues need to be addressed to promote the integration ICT tools to facilitate e-Health care. The issue that this paper addresses is the lack of embedded e-Health framework that fits on the conditions and circumstances of a South Asian nation. To address this problem, the purpose of this paper is to determine and identify various challenges or factors (e.g., environmental, cultural, legal, technical, etc.) that may directly or indirectly affect the implementation of e-Health in Pakistan, Sri Lanka and Mongolia. The data to be used in the study will be derived mainly from available documents (secondary data such as from WHO, WB, among others) and interview from subject matter experts (SMEs). The documents will be reviewed and the interviews will be transcribed and analyzed. The results of the study will help develop an effective mechanism in the implementation of reforms in the health sector for efficient and effective health surveillance, obliteration of epidemics, and a large-scale health service delivery for the citizens.

Congestion-Aware Handover in LTE Systems for Load Balancing in Transport Network

Safdar Nawaz Khan Marwat,Sven Meyer,Thushara Weerawardane,Carmelita Goerg 한국전자통신연구원 2014 ETRI Journal Vol.36 No.5

Long-Term Evolution employs a hard handoverprocedure. To reduce the interruption of data flow,downlink data is forwarded from the serving eNodeB(eNB) to the target eNB during handover. In cellularnetworks, unbalanced loads may lead to congestion inboth the radio network and the backhaul network,resulting in bad end-to-end performance as well ascausing unfairness among the users sharing the bottlenecklink. This work focuses on congestion in the transportnetwork. Handovers toward less loaded cells can helpredistribute the load of the bottleneck link; such amechanism is known as load balancing. The results showthat the introduction of such a handover mechanism intothe simulation environment positively influences thesystem performance. This is because terminals spendmore time in the cell; hence, a better reception is offered. The utilization of load balancing can be used to furtherimprove the performance of cellular systems that areexperiencing congestion on a bottleneck link due to anuneven load.

Synthesis and biological activities of 3-polyamino-5b-cholane-7a,24-diols

Sharaf Nawaz Khan,Hong-Seok Kim 한국공업화학회 2009 Journal of Industrial and Engineering Chemistry Vol.15 No.4

A series of 3-polyaminochenodeoxycholic acid derivatives were synthesized and their in vitro antimicrobial and antifungal activities were assessed. The antimicrobial activity was evaluated against Gram-positive and Gram-negative bacteria, and the antifungal activity was assessed against two strains Candida albicans (ATCC MYA-1003) and Aspergillus fumigatus (ATCC 16424). The introduction of an amine group to steroid was accomplished by reductive amination of 3-oxosteroid 9 with Boc-spermidine and Boc-spermine, in the presence of NaBH(OAc)3. This afforded a high yield of 3-polyaminosteroids of 10–13. The 3b-sperminyl-5b-cholane 6 showed the highest antimicrobial activity against Streptococcus pyogenes 308A, Staphylococcus aureus 503, Escherichia coli DC2 and Pseudomonas aeruginosa 9027 with a MIC value of 3.13 mg/mL.

A 33.3% Power Efficiency RF Energy Harvester with -25dBm Sensitivity using Threshold Compensation Scheme

Danial Khan,Hamed Abbasizadeh,Zaffar Hayat Nawaz Khan,이강윤 한국과학기술원 반도체설계교육센터 2017 IDEC Journal of Integrated Circuits and Systems Vol.3 No.3

This paper presents an ultra-low power RF-DC voltage multiplier using auxiliary transistors block to dynamically control the threshold voltage of the main chain transistors. The proposed scheme enhances the forward conduction current and reduces the reverse current by controlling the gate to source voltage of the main chain transistors. The proposed 5-stage scheme attains maximum post-layout simulated power conversion efficiency (PCE) of 33.3% at -16dBm input level and delivers 2.63 V output DC voltage to 1MΩ load. The proposed RF-DC voltage multiplier has been designed in a standard 180 nm CMOS technology.

Design of an efficient RF-DC voltage multiplier for RF Energy Harvesting Applications

Danial Khan,Hamed Abbasizadeh,Zaffar Hayat Nawaz Khan,Truong Thi Kim Nga,Sang Yun Kim,Ho Cheol Ryu,Kang Yoon Lee 대한전자공학회 2017 대한전자공학회 학술대회 Vol.2017 No.1

In this paper, a RF-DC voltage multiplier is presented to efficiently convert RF signals to DC voltages. The proposed circuit uses an internal threshold voltage cancellation (IVC) scheme with auxiliary block to reduce the threshold voltage of forward-biased transistors and minimizes the reverse leakage current of the reverse-biased by dynamically controlling the gate-source voltage of the transistors in the main rectification chain. The proposed circuit is designed in 0.18 um CMOS technology. A three-stage voltage multiplier results in a maximum power conversion efficiency (PCE) of 49.1% at input power level of 0 dBm and at frequency of 900 MHz. The proposed circuit produces an output voltage of 4.94 V at 50 KΩ load.

Cross Metathesis-Assisted Syntheses of Glycopeptoids

Sharaf Nawaz Khan,Arim Kim,Robert H. Grubbs,Yong-Uk Kwon 한국당과학회 2011 한국당과학회 학술대회 Vol.2011 No.1

Glycosylation, the attachment of sugars to proteins, is one of the most abundant post translational modifications in all living cells. It plays very important roles in protein folding, stabilization, embryogenesis, neuronal development, cell-cell adhesion and recognition. Glycosylation produces huge structural diversity in proteins which is necessary for the functionalization of nascent proteins. While peptides are an attractive class of molecules to synthesize glycopeptides, they possess undesirable drawbacks including sensitivity to proteases, limited cell permeability and poor bioavailability. Thus, there have been increasing needs for new peptidomimetics with improved pharmacokinetic characteristics. Among them, peptoids, N-alkylated glycine oligomers where side chains are directly attached to nitrogen atom rather than α-carbon of peptide, possess many advantages over peptides. Attachments of sugars to peptoid backbone generate glycopeptoids which have interesting features by mimicking glycopeptides. Our strategy was to install sugar derivatives to alkenyl moiety-containing peptoids through solid-phase cross metathesis approach. The peptoids were prepared on bead having strategically positioned alkenyl moieties in different length. O-linked sugar-alkene derivatives based upon glucose, mannose, and galactose monomers were also made. Initially, we screened reaction condition parameters such as catalyst, concentration of sugar derivative, temperature, solvent, and reaction time. HG2 was proved to be a better catalyst than G1 and G2. The length of alkenyl moieties was critical on cross metathesis. The cross metathesis was facilitated easily with 3-butenyl group over allyl group. We have successfully synthesized glycopeptoids on solid-phase through cross metathesis in very good yields. This systematic study into the use of solid-phase cross metathesis for the synthesis of glycopeptoids provides a particularly valuable tool for easy access to the molecular sources of glycopeptidomimetics and the rapid generation of glycopeptoid libraries.