Dr. Aziza Sarwar
Assistant Professor
Department of Chemistry , Faculty of Basic Sciences

aziza.sarwar@buitms.edu.pk
Extension No: 647

Qualification

Ph.D. (2013)
Materials Science and Engineering (Analytical Polymer Applied Chemistry)
University of Science and Technology Beijing, P.R.China, China

Teaching Courses

  • Advanced Analytical Chemistry
  • Material Science
  • Nanochemistry
  • Research Methodology
  • Polymer Chemistry
  • Recent Research in Chemistry
  • Advanced Composite Materials
  • Polymer Science
  • Thin PDLC films
  • Smart Glass Technology
  • Functional Materials
  • Advanced Separation Techniques
  • In-Organic Chemistry (General)

Teaching Method

  • Collaborative Learning
  • Visual, Audio, & Kinesthetic Teaching
  • Expeditionary Learning
  • Differentiated Instruction

Research Interest

  • Thin Films Composite Materials
  • Nanochemistry
  • Multi-functional Epoxy Monomers , Catalysts & Hardeners
  • energy-saving materials
  • Liquid crystal photonic devices
  • Light-responsive, temperature-sensitive, and electric field-sensitive
  • Waste water treatment
  • Smart Product( Smart organic soap, Paper, water straw, and Organic Leather)

Membership

  • American Chemical Society of USA
  • Royal Chemical Society (RCS) ,UK
  • The Chemical Society Of Palistan
  • The Chinese Academy of Chemical Sciences.
  • Pakistan Association for the Advancement of Science.
  • International Scientific Committee of Chemical and Materials Engineering
  • IUPAC Affiliate Fellow for the year 2015
  • Member of NIC, NIB, and GIL
  • Vice President Chemical Society of Pakistan (Balochistan Chapter).
  • HEC, APPROVED SUPERVISOR, Application Id # 31,839) https://www.hec.gov.pk/english/scholarshipsgrants ASA/Pages/APS-EPORTAL.aspx
  • Member of the Advanced studies and Research Board in BUITEMS
  • Member of the Academic Council University of Balochistan
  • Member of the Department of Chemistry Board of Studies
  • Committee member of “The EMN Liquid Crystal Meeting”, Nov: 26 to 30, 2017 was held inMauritius.
  • Member of HEC scrutiny committee of various projects
  • Member of PSF scrutiny committee of Materials, AI, and Nano projects.
  • Official Ambassador of IYC, USA ,2022-2023 from Pakistan
  • .Journal of Mountain Area Research
  • UniversalJournal of Materials Science (Horizon Research Publishing Corporation, USA)
  • Journal of Physical Science & Application (David Publishing Company, USA).
  • Journal of Material Science: Advanced Composite Materials (Whioce Publishing, Singapore).
  • International Journal for Research in Applied and Natural Science (Green Publication).
  • SCIREA Journal of Chemistry, (Publishing, Singapore).

Awards & Achivements

  • Ambassador Asian Council Science Editors( ACSE), UAE
    2026
  • Recognized Scientist National Scientist Directory (S.No. NSD.ChemSci-0004870) from the Ministry of the science & technology I.R.Pakistan
    2025
  • World recognized scientist list in Material Science & Analytical Chemistry, AD Scientific Index ID: 525086
    2025
  • Certificate of the Recognization and Appreciation of ACS Publications Peer Reviewer
    2024
  • How to develop an Operational research grant proposal
    2024
  • HEC-TDF-054 project Successful Story in 01-12-2022 BUITEMS, Quetta, Balochistan.
    2022
  • Secured 2 nd Prize 80,000/- PKR in ALL Pakistan DICE Agriculture and Food Sciences (DICE-AFS) Innovation Event on 2022 at MNS (Mian Nawaz Sharif) University of Agriculture Multan. Link # https://mnsuam.edu.pk/index.php/afs
    2022
  • SEE Pakistan 2022, National Startup Championship (NSC) held in the Expo Center Lahore 18 August 2022, secured special appreciation certificates with a cash prize. Link # https://seepakistan.com.pk/
    2022
  • Secured Special Prize 20,000/- PKR in ALL Pakistan DICE Agriculture and Food Sciences (DICEAFS) Innovation Event on 2021 at MNS (Mian Nawaz Sharif) University of Agriculture Multan. Link # https://mnsuam.edu.pk/index.php/winners-of-dice-afs-2021
    2021
  • Short list for Best Teacher award from HEC, 2021.
    2021
  • Secured I st Prize 40,000/- PKR in 4th Invention & Innovation Summit, in Balochistan University September 24-25, 2019. Link # http://www.innovationsummit.net/wp-content/uploads/2019/11/Cash-Award-Winner.pdf
    2019
  • Secured 2 nd Prize 80,000/- PKR in ALL Pakistan DICE Agriculture and Food Sciences (DICE-AFS) Innovation Event on 9-10 October 2019 at MNS (Mian Nawaz Sharif) University of Agriculture Multan. Link # https://mnsuam.edu.pk/index.php/winners-of-dice-afs-20019
    2019
  • Award as a productive scientist of Pakistan in 2017 according to Pakistan Council for Science and Technology.
    2017
  • Award as a productive scientist of Pakistan in 2016 according to Pakistan Council for Science and Technology.
    2016
  • 3 rd position in excellent international student scholarship of USTB for year of 2012.
    2012
  • Chancellor Scholarships of University of Science and Technology Beijing for Ph.D. Studies.
    2010
  • Rotary club international scholarship of youth merit award programme.
    2010
With a strong foundation in inorganic chemistry and a passion for synthesizing novel metal complexes, I have dedicated my research to exploring the fascinating world of coordination chemistry. My work focuses on designing and synthesizing Shiff-base ligands and their transition and Lanthanide metal complexes as well as nanomaterials investigating their potential applications in various fields such as Photoluminescence Studies, Antimicrobial Agents, Anti-inflammatory Agents anti-cancerous Agents and Antiviral Agents. I am proficient in various characterization techniques, including X-ray Characterization Techniques crystallography, NMR spectroscopy, IR spectroscopy, EDX studies, SEM studies, TGA/DTA studies, Uv-Visible spectroscopy, Elemental analysis and PXRD studies.

Publications

Development of the hybrid BWM-fuzzy preference programming approach using a two-phase model: A case study in the automotive after-sales services
Mojtaba Elahi, Ramin Enayati, Mehdi Keramatpour (2025) Iranian Journal of Fuzzy Systems vol. 22 no. 3 pp. 181-217
Smart Glass Technology
Mujtaba Ellahi Mahar, Shaista Taimur, Hamdullah Khan Tareen (2025) Cambridge Scholars Publishing vol. - no. - pp. -
Advanced Antistatic Composites for Electrostatic Dissipation: Development of EPDM Based Conductive Elastomeric Nanocomposites
Habiba Tanveer, Shaista Taimur, Mujtaba Ellahi, Talha Baig, Nazeeha S Alkayal, Ahsan Ali, Tariq Yasin, Wael A Altabey, Mohammad Noori, Sallam A Kouritem (2025) Polymer Testing vol. - no. - pp. 108917
CPEC Sustainable Development: Opportunities and Challenges
M. ELLAHI (2025) Pakistan Institute of Development Economics vol. - no. - pp. -
A fuzzy Delphi-SERVQUAL model using degree of belief structure for assessing customer satisfaction in automotive after-sales services
Mojtaba Elahi, Ramin Enayati, Mehdi Keramatpour (2025) Applied Soft Computing vol. - no. - pp. 113770
View All

Work Experience

July 2016 to Date
Assistant Prof: at Chemistry
BUITEMS
September 2014 to June 2016
Research Officer BPS-18 at H.E.J. Research Institute of Chemistry, University of Karachi
H.E.J. Research Institute of Chemistry, University of Karachi
September 2013 to September 2014
Assistant Prof: bps-19 (IPFP) at Department of Chemical Engineering, University of Karach
Department of Chemical Engineering, University of Karachi
August 2010 to September 2013
Ph.D. Research Fellow at Education
University of Science and Technology Beijing, P.R.China
October 2001 to August 2010
Lecturer in Chemistry, BPS-17 at Education
Mir Sher Muhammad Talpur Public College Mirpurkhas, Sindh

Projects

Studies on synthesis of Morita Baylis Hillman (MBH) adducts derivative
No. 01/ Research Completed /- Projects/ ORIC/ BUITEMS/ 2011/ 487, National , Funded , 2020, Completed
One International paper published.
Synthesis and Evaluation of Biological Potential of Thiazolidines by using Aliphatic Hydrazones as Synthetic
No. 01/ Research Completed FY 2018- Million Projects/ ORIC/ 19 PKR. BUITEMS/ 2011/ 337, National , Funded , 2019, Completed
One International paper published.
Preparation and Characterization of di,tri and block co-polymers epoxy based thin PDLC films (Smart glass)"
No.9356/Balochistan/ NRPU/R&D/HEC/, National , Funded , 2018, Completed
One International book published with CAMBRIDGE, UK PUBLISHING and a filed patent. One MS student co...
Studies on synthesisof Schiff bases and evaluating scope of Morita Baylis Hillman (MBH) adducts
No. 01/ Research Completed FY 2018- Million Projects/ ORIC/ 19 PKR. BUITEMS/ 2011/ 325, National , Funded , 2018, Completed
One International paper published.
Study the effects of epoxy/tetra functional thiol structure based PDLCs film
No. 01/ Research Completed FY 2018- PKR. Projects/ ORIC/ 19 BUITEMS/ 2011/ 340, National , Funded , 2018, Completed
One International paper published with Two International conference papers. One BS-STUDENT SUPERVISE...
Study on the effects of silver nano particles (AgNPs) inepoxy monomers based PDLC films (Smart glass)
HEC-No. TDF02-054, National , Funded , 2017, Completed
Two Patents filed. Two MS students supervised with Two BS-students. Two International papers with Tw...
Preparation of thin Smart glass films viaPIPS Method Using TYETA Hardener
No. 01/ Research Projects/ ORIC/ BUITEMS/ 2011/ 610, National , Funded , 2017, Completed
One International paper has been published with Two International conference Papers. One BS-Student ...
Single crystalline Nano Octahedron of NiFe2O4: Gram scaleSynthesis, magnetic and optical properties
Supported by FY 2014- Yuan National Natural 2016 Science Foundation of P.R. CHINA (Grant nos: 51371105 and 51071023, International , Funded , 2014, Completed
Two International papers with two international conference papers published.
Study on the effects of isotropic cross-linked pristine morphology and electro-optical properties of PDLC films
Supported by the National Natural 16 Science Foundation P.R. CHINA (Grant No.51272026 and 51273022),, International , Funded , 2013, Completed
Two International papers with two international conference papers published. Filed Chinese Patent.

Certifications

Invited Speaker
Institute of Chemistry, Shah Abdul Latif University (SALU), Khairpur & ACS Chapter I.R.Pakistan, Pakistan, 2026
Invited Speaker
4th International Conference on Emerging Trends in Chemistry (CCUMT-2026), held from June 4-6, 2026, at the School of Science, UMT, Lahore, Pakistan, 2026 Learn More
Selected for the Second Scientific Activity “Advanced Manufacturing Techniques” From 6th to 10th July, 2026
International Nathiagali Summer College Islamabad, Pakistan, Pakistan, 2026 Learn More
Theories of Research: Ontology, Epistemology, and Axiology of the Research Methodology 2026 Course
Center for Learning and Teaching (CLT), HEC, Pakistan, 2026
Getting Published: Best Practice In Scholarly Publishing and Editorial workflows
Asian Council Of Science Editors , United Arab Emirates, 2026
The art of teaching with cases (HEC)
Emerald Publishing, Germany, 2026
The author's journey : from manuscript to global market - an expert session on academic book publishing
Elsevier , Research Academy at HEC Pakistan, United Kingdom, 2026
Power user in locating technical resources: an in-depth dive with IEEE Xplore digital library
IEEE-China, China, 2026
Artificial intelligence in libraries & HEC Playgiarism policy
Pakistan Science Foundation (PSF) , Pakistan, 2026
Getting Academic AI Rights
Clarivate : Web of science, United States, 2026
Ebook central research assistant: driving student research success
Clarivate : web of science, United States, 2026
The art of filteration 4.0 - Practical strategies for mannual and automated workflows
Merck Company, Germany, Germany, 2026
Uncover aggregation ASAP for proteins,peptides and ADCs on stunner
Drug Discovery News, Development & Diagnostics (DDN), United States, 2026
How to respond to reviewer's comments
Elsevier , Virtual Event, Germany, 2025
Citation Manager: Mendeley of the Research Methodology
Forman Christian College (A Chartered University) , Pakistan, 2025
Qualitative and Quantitative analysis of polymers using TGA, DSC, and FT-IR
Chemical Research & Innovation society , Saudi Arabia, 2025
OIC -COMSTECH & NINGO UNIVERSITY CERTIFICATE COURSE ON THE APPLIED BIOMEDICAL AI
OIC-COMSTECH , Pakistan, 2025
World startup Championship
See Pakistan 2025, Pakistan, 2025
Invited Speaker
ACSE, EMERGING SCIENTIST 2025 , UAE, DUBAI, United Arab Emirates, 2025 Learn More
Invited Speaker
23rd International & 35th National CHEMISTRY CONFERENCE OF EMERGING TRENDS IN CHEMISTRY ,GCU ,FAISALABAD, Pakistan, 2025 Learn More
RECOGNISATION & APPRECIATIONS AS 2024 ACS PUBLICATIONS & PEER REVIEWERS
AMERICAN CHEMICAL SOCIETY (ACS) PUBLICATIONS, United States, 2024
Application of data science in Genomics and drugs deliver
ACS ,Virtual Mode, United States, 2024
Students Ambassader Orientation and Training HEC
EMERALD PUBLISHING, United Kingdom, 2024
Author workshop - Essential a research article in high impact journal of writing
Elsevier , Virtual Event, United Kingdom, 2024
Navigating Peer Review
Wiley , Virtual Mode, Germany, 2024
Pushing the boundries of microanalysis in SEM with the BEX Techniques
Oxford Instruments ,UK, United Kingdom, 2024
Trends in open research
Wiley , (Online Wbinar), Germany, 2024
How GENERATIVE AI change information discovery
Wiley , Virtual Mode, Germany, 2024
Invited Speaker
ACSE-UAE DUBAI, 2024, United Arab Emirates, 2024 Learn More
Invited Speaker
22ND International & 34TH National CHEMISTRY CONFERENCE OF EMERGING TRENDS IN CHEMISTRY ,MALAKAND UNIVERSITY, KPK, Pakistan, 2024 Learn More
Invited Speaker
5th International Conference on Advances in Materials Science (AIMS-2023) University of Lahore ,Punjab, Pakistan, 2024 Learn More
Invited Speaker
2nd International Industrial Chemistry Conference (IICC – 2023), Pakistan, 2023
Invited Speaker
21st International & 33rd National CHEMISTRY CONFERENCE OF EMERGING TRENDS IN CHEMISTRY ,QAU, ISLAMABAD, Pakistan, 2023 Learn More
Invited Speaker
4th International Conference on Advances in Materials Science (AIMS-2023) University of Lahore ,Punjab, Pakistan, 2023 Learn More
Crystal orientation with the Laue method
Elsevier , Virtual Event, United States, 2023
Exploring NMR Spectroscopy , Principals, Techniques ,and Applications
OIC Ministerial Standing Committee on scientific & technological co-operation (COMSTECH),Islamabad, Pakistan, 2023
How to secure funding by International Research Organizations
By SAGE, United States, 2023
Engaging of open science of 2023:PREPRINTS
Intech Open Journals, United Kingdom, 2023
Bio- Chemistry Symposium [A Future with Bio-Chemistry]
UIT, University of Karachi, Pakistan, 2023
International Youth Conference
USA, Florida, United States, 2023
PFAS Analysis - What's possible with unique technologies?
LUMS , Virtual Event, Pakistan, 2023
Wolters Kluwer OVID data base
Wiley (Online Wbinar), Italy, 2022
International Symposium of Excellence Science
HEJ, University of Karachi, Pakistan, 2022
Research Data Management: why it matter and how to manage
At Elsevier Asia Pacific , Islamabad, Pakistan, 2022
Which competence do teachers educator need in supporting teacher online
British council , Islamabad, Pakistan, 2022
Invited Speaker
20th-international-and-32nd-national-chemistry-conference-chemical-sciences, Pakistan, 2022 Learn More
Invited Speaker
ICCS-MA , SALU, KHAIRPUR, Pakistan, 2022 Learn More
Invited Speaker
3rd International Conference on Advances in Materials Science (AIMS-2022) , Pakistan, 2022
Invited Speaker
2nd-international-conference-on-physical-sciences, Pakistan, 2022 Learn More
Invited Speaker
1st International Conference on Applied Physics and Engineering (ICAPE 2021), Pakistan, 2021 Learn More
Invited Speaker
19th International & 31st National CHEMISTRY CONFERENCE OF EMERGING TRENDS IN CHEMISTRY ,UMT LAHORE , Pakistan, 2021 Learn More
Invited Speaker
International Conference of energy,water, and environment , UET Lahore, Pakistan, 2021 Learn More
Protection of Intellectual Property: Filing Process & Prosecution of Patents
Organized by Oric UMT ,Lahore, Pakistan, 2021
UV-Vis spectroscopy for validate Pharmaceutical testing
Wiley (Online Wbinar), Germany, 2021
BIO Remediation: ECO Sustainable green technology
Pastic, Karachi, Pakistan, 2021
Seminar / Poster & Project Exhibition
BUITEMS, Pakistan, 2021
Oxford Machine Learning Summer School
Oxford University (Online Wbinar), United Kingdom, 2020
Annual Innovation Summit
Willey , United States, 2020
Wiley Analytical Science Conference
Wiley (Virtual Event), Germany, 2020
Invited Speaker
International Conference on Technology and Science Techno- Science 2020, Antalya, Turkey, Turkey, 2020 Learn More
Invited Speaker
1 st International Conference on Advances in Engineering and Technology (ICAET- 2018). BUITEMS, QUETTA, Pakistan, 2018 Learn More
Pharmacopeia Modernization: How Will Your Chromatography Workflow Benefit?
Cambridge University (Online Wbinar), United Kingdom, 2018
Efficient Microstructure Characterization of Metals using Light Microscopy
Willey (Online Webinar), Germany, 2018
University Teaching
BUITEMS, Pakistan, 2017
Intellectual Property, Patent & Trademark
BUITEMS, Pakistan, 2017
Invited Speaker
Collaborative Conference on Materials Research (CCMR) 2017, Jesu Island, South Korea, South Korea, 2017 Learn More
Invited Speaker
INTERNATIONAL CONFERENCE ON NANO- COMPOSITES AND MULTI-FUNCTIONAL, MATERIALS (ICNMM), NUST; ISLAMABD. I.R. PAKISTAN, Pakistan, 2017 Learn More
Keynote Speaker
EMN Meeting on Liquid Crystal, at the Radisson Resort Orlando-Celebration Hotel, Orlando, USA., United States, 2016 Learn More
Keynote Speaker
3D and Materials Research (CC3DMR), in Cheon /Seoul, South Korea., South Korea, 2016 Learn More
Invited Speaker
14th EURASIA CONFERENCE ON CHEMICAL SCIENCES (EuAsC2S-14) DECEMBER 15 – 18, 2016, KARACHI, I.R. PAKISTAN, Pakistan, 2016 Learn More
Invited Speaker
INTERNATIONAL CONFERENCE ON ADVANCED MATERIALS AND EMERGING TECHNOLOGIES 2016 (ICAMET 2016), UET , Lahore, I.R. PAKISTAN, Pakistan, 2016 Learn More
Professional Development Training Program
BUITEMS, Pakistan, 2016
Orientation Workshop on SPSS & STATA
BUITEMS, Pakistan, 2016
EMN Meeting on Liquid Crystal
Radisson Resort OrlandoCelebration Hotel, Orlando, USA, United States, 2016
5th International Symposium-cumTraining Course on Molecular Medicine & Drug Research
Université of Karachi, Pakistan, 2015
Two days’ Workshop on “Intellectual PropertyRights Management Through Patents
University of Karachi, Pakistan, 2015
Effective management skills a course attend in professional skill development program,
Université of Karachi., Pakistan, 2015
Seminar cum workshop on new trends in Electro-chemistry
LEJ,Research Institute of Chemistry, at Université of Karachi., Pakistan, 2015
Webinar International prospective on industrial chemical safety & security, Jointly organized by the ICCBS & CRDF Global (USA)
LEJ,Research Institute of Chemistry, at Université of Karachi., Pakistan, 2015
Invited Speaker
Materials and Process Engineering, at the NED University Science and Technology, I.R. PAKISTAN, Pakistan, 2015 Learn More
Invited Speaker
The 2NDInternational Conference on Engineering & Applied Sciences (ICEAS-2013) at Tokyo, Japan., Japan, 2013
Invited Speaker
International Conference on Engineering & Applied Sciences (ICEAS-2012) Beijing, P.R. China, China, 2012

Patent

Di-(4-sulfonic acid) dibutyltetramethylethylene diammonium di (hydrogensulfate), Di-(4-sulfonic acid) dibutyl triethylene diammonium di (hydrogensulfate), 1,4-sultone-pyridinium hydrogensulfate and Cobalt Silicate, Copper Silicate, Zinc Silicate Based Catalysts System for biodiesel Production
Inventor(s): Zahoor Ullah, Hakim Ullah, Muhammad Nawaz, Amir Sada Khan, Mamoon-Ur- Rashid, Mujtaba Ellahi
Patent #:Application No: 511/2021 and SI. No: 144519Published: 2025 Country: Pakistan
Preparation of the PET/ITO Coated Sustainable Display Technology
Inventor(s): Dr. Mujtaba Ellahi Mahar,Dr. Hamdullah Khan Taren,Dr. M. Furqan Ali,,Mahnoor Gull ,and Abdul Haleem
Patent #:926/2025Published: 2025 Country: Pakistan
https://ipo.gov.pk/system/files/251215.pdf
Preparation of the smart organic anti-freeze liquid doping Al2O3 NPs via solution method
Inventor(s): Dr. Mujtaba Ellahi Mahar,Dr. Hamdullah Khan Treen,Dr. M. Furqan Ali,Dr. Zahoorullah ,and Abdul Haleem
Patent #:927/2025Published: 2025 Country: Pakistan
https://ipo.gov.pk/system/files/251215.pdf
Preparation of the smart organic zaqqum (Cactus) leather
Inventor(s): Mujtaba Ellahi,Shaista Tamur, Hamdullah khan,Shabana Mengal
Patent #:Application No. & Dated 832/2024)[Published: 2024 Country: Pakistan
https://ipo.gov.pk/system/files/241129.pdf
Smart organic life straw: A Sustainable product using membrane technology
Inventor(s): Mujtaba Ellahi,Shaista Tamur, Hamdullah khan, Islam khan
Patent #:Application No. & Dated 831/2024Published: 2024 Country: Pakistan
https://ipo.gov.pk/system/files/241129.pdf
Development of anti-viral smart organic soap with Silver Nanoparticles (AgNPs)
Inventor(s): Mujtaba Ellahi,Hamdullah khan, Hameeda Panezai,Mahnoor Gul
Patent #:Application No. & Dated 312/2022)Published: 2022 Country: Pakistan
https://ipo.gov.pk/system/files/220521.pdf
Preparation of epoxy based thin PDLC films (Switchable Smart Glass) doped with muti-functional Nanoparticles
Inventor(s): Mujtaba Ellahi,Shaista Taimur, Hamdullah khan, Zahoorullah,Aslam Bhutta
Patent #:Application No. & Dated 619/2022Published: 2022 Country: Pakistan
https://ipo.gov.pk/system/files/221004.pdf
Preparation of the ecofriendly smart organic biodegradable paper soap
Inventor(s): Mujtaba Ellahi,Shaista Tamur, Hamdullah khan
Patent #:(Application No. & Dated 630/2022)Published: 2022 Country: Pakistan
https://ipo.gov.pk/system/files/221007.pdf
“Preparation of the Anti-viral Covid-19 Smart Soap by the effective index method
Inventor(s): Mujtaba Ellahi, Naeem shahwani,Hameeda Panezai, Faisal khan
Patent #:(Application No. & Dated 584/2021)Published: 2021 Country: Pakistan
https://ipo.gov.pk/system/files/210914.pdf
Preparation of the smart Organic Based Shampoo
Inventor(s): Mujtaba Ellahi,Hameeda Panezai, Aslam Bhutta
Patent #:(Application No. & Dated 970/2021)Published: 2021 Country: Pakistan
https://ipo.gov.pk/system/files/220120.pdf
Preparation ofsmart glass panel via PIPS method
Inventor(s): Mujtaba Ellahi, Naeem Shahwani, Aslam Bhutta, Mehak Lashari
Patent #:(Application No. & Dated 764/2020Published: 2020 Country: Pakistan
https://ipo.gov.pk/system/files/210105.pdf