Author: William M. Haynes
Publisher: CRC Press
ISBN: 1466571152
Category : Science
Languages : en
Pages : 2640
Book Description
Celebrating the 100th anniversary of the CRC Handbook of Chemistry and Physics, this 94th edition is an update of a classic reference, mirroring the growth and direction of science for a century. The Handbook continues to be the most accessed and respected scientific reference in the science, technical, and medical communities. An authoritative resource consisting of tables of data, its usefulness spans every discipline. Originally a 116-page pocket-sized book, known as the Rubber Handbook, the CRC Handbook of Chemistry and Physics comprises 2,600 pages of critically evaluated data. An essential resource for scientists around the world, the Handbook is now available in print, eBook, and online formats. New tables: Section 7: Biochemistry Properties of Fatty Acid Methyl and Ethyl Esters Related to Biofuels Section 8: Analytical Chemistry Gas Chromatographic Retention Indices Detectors for Liquid Chromatography Organic Analytical Reagents for the Determination of Inorganic Ions Section 12: Properties of Solids Properties of Selected Materials at Cryogenic Temperatures Significantly updated and expanded tables: Section 3: Physical Constants of Organic Compounds Expansion of Diamagnetic Susceptibility of Selected Organic Compounds Section 5: Thermochemistry, Electrochemistry, and Solution Chemistry Update of Electrochemical Series Section 6: Fluid Properties Expansion of Thermophysical Properties of Selected Fluids at Saturation Major expansion and update of Viscosity of Liquid Metals Section 7: Biochemistry Update of Properties of Fatty Acids and Their Methyl Esters Section 8: Analytical Chemistry Major expansion of Abbreviations and Symbols Used in Analytical Chemistry Section 9: Molecular Structure and Spectroscopy Update of Bond Dissociation Energies Section 11: Nuclear and Particle Physics Update of Summary Tables of Particle Properties Section 14: Geophysics, Astronomy, and Acoustics Update of Atmospheric Concentration of Carbon Dioxide, 1958-2012 Update of Global Temperature Trend, 1880-2012 Major update of Speed of Sound in Various Media Section 15: Practical Laboratory Data Update of Laboratory Solvents and Other Liquid Reagents Major update of Density of Solvents as a Function of Temperature Major update of Dependence of Boiling Point on Pressure Section 16: Health and Safety Information Major update of Threshold Limits for Airborne Contaminants Appendix A: Major update of Mathematical Tables Appendix B: Update of Sources of Physical and Chemical Data
CRC Handbook of Chemistry and Physics, 94th Edition
Author: William M. Haynes
Publisher: CRC Press
ISBN: 1466571152
Category : Science
Languages : en
Pages : 2640
Book Description
Celebrating the 100th anniversary of the CRC Handbook of Chemistry and Physics, this 94th edition is an update of a classic reference, mirroring the growth and direction of science for a century. The Handbook continues to be the most accessed and respected scientific reference in the science, technical, and medical communities. An authoritative resource consisting of tables of data, its usefulness spans every discipline. Originally a 116-page pocket-sized book, known as the Rubber Handbook, the CRC Handbook of Chemistry and Physics comprises 2,600 pages of critically evaluated data. An essential resource for scientists around the world, the Handbook is now available in print, eBook, and online formats. New tables: Section 7: Biochemistry Properties of Fatty Acid Methyl and Ethyl Esters Related to Biofuels Section 8: Analytical Chemistry Gas Chromatographic Retention Indices Detectors for Liquid Chromatography Organic Analytical Reagents for the Determination of Inorganic Ions Section 12: Properties of Solids Properties of Selected Materials at Cryogenic Temperatures Significantly updated and expanded tables: Section 3: Physical Constants of Organic Compounds Expansion of Diamagnetic Susceptibility of Selected Organic Compounds Section 5: Thermochemistry, Electrochemistry, and Solution Chemistry Update of Electrochemical Series Section 6: Fluid Properties Expansion of Thermophysical Properties of Selected Fluids at Saturation Major expansion and update of Viscosity of Liquid Metals Section 7: Biochemistry Update of Properties of Fatty Acids and Their Methyl Esters Section 8: Analytical Chemistry Major expansion of Abbreviations and Symbols Used in Analytical Chemistry Section 9: Molecular Structure and Spectroscopy Update of Bond Dissociation Energies Section 11: Nuclear and Particle Physics Update of Summary Tables of Particle Properties Section 14: Geophysics, Astronomy, and Acoustics Update of Atmospheric Concentration of Carbon Dioxide, 1958-2012 Update of Global Temperature Trend, 1880-2012 Major update of Speed of Sound in Various Media Section 15: Practical Laboratory Data Update of Laboratory Solvents and Other Liquid Reagents Major update of Density of Solvents as a Function of Temperature Major update of Dependence of Boiling Point on Pressure Section 16: Health and Safety Information Major update of Threshold Limits for Airborne Contaminants Appendix A: Major update of Mathematical Tables Appendix B: Update of Sources of Physical and Chemical Data
Publisher: CRC Press
ISBN: 1466571152
Category : Science
Languages : en
Pages : 2640
Book Description
Celebrating the 100th anniversary of the CRC Handbook of Chemistry and Physics, this 94th edition is an update of a classic reference, mirroring the growth and direction of science for a century. The Handbook continues to be the most accessed and respected scientific reference in the science, technical, and medical communities. An authoritative resource consisting of tables of data, its usefulness spans every discipline. Originally a 116-page pocket-sized book, known as the Rubber Handbook, the CRC Handbook of Chemistry and Physics comprises 2,600 pages of critically evaluated data. An essential resource for scientists around the world, the Handbook is now available in print, eBook, and online formats. New tables: Section 7: Biochemistry Properties of Fatty Acid Methyl and Ethyl Esters Related to Biofuels Section 8: Analytical Chemistry Gas Chromatographic Retention Indices Detectors for Liquid Chromatography Organic Analytical Reagents for the Determination of Inorganic Ions Section 12: Properties of Solids Properties of Selected Materials at Cryogenic Temperatures Significantly updated and expanded tables: Section 3: Physical Constants of Organic Compounds Expansion of Diamagnetic Susceptibility of Selected Organic Compounds Section 5: Thermochemistry, Electrochemistry, and Solution Chemistry Update of Electrochemical Series Section 6: Fluid Properties Expansion of Thermophysical Properties of Selected Fluids at Saturation Major expansion and update of Viscosity of Liquid Metals Section 7: Biochemistry Update of Properties of Fatty Acids and Their Methyl Esters Section 8: Analytical Chemistry Major expansion of Abbreviations and Symbols Used in Analytical Chemistry Section 9: Molecular Structure and Spectroscopy Update of Bond Dissociation Energies Section 11: Nuclear and Particle Physics Update of Summary Tables of Particle Properties Section 14: Geophysics, Astronomy, and Acoustics Update of Atmospheric Concentration of Carbon Dioxide, 1958-2012 Update of Global Temperature Trend, 1880-2012 Major update of Speed of Sound in Various Media Section 15: Practical Laboratory Data Update of Laboratory Solvents and Other Liquid Reagents Major update of Density of Solvents as a Function of Temperature Major update of Dependence of Boiling Point on Pressure Section 16: Health and Safety Information Major update of Threshold Limits for Airborne Contaminants Appendix A: Major update of Mathematical Tables Appendix B: Update of Sources of Physical and Chemical Data
CRC Handbook of Chemistry and Physics, 96th Edition
Author: William M. Haynes
Publisher: CRC Press
ISBN: 1482260972
Category : Science
Languages : en
Pages : 2652
Book Description
Proudly serving the scientific community for over a century, this 96th edition of the CRC Handbook of Chemistry and Physics is an update of a classic reference, mirroring the growth and direction of science. This venerable work continues to be the most accessed and respected scientific reference in the world. An authoritative resource consisting of tables of data and current international recommendations on nomenclature, symbols, and units, its usefulness spans not only the physical sciences but also related areas of biology, geology, and environmental science. The 96th edition of the Handbook includes 18 new or updated tables along with other updates and expansions. A new series highlighting the achievements of some of the major historical figures in chemistry and physics was initiated with the 94th edition. This series is continued with this edition, which is focused on Lord Kelvin, Michael Faraday, John Dalton, and Robert Boyle. This series, which provides biographical information, a list of major achievements, and notable quotations attributed to each of the renowned chemists and physicists, will be continued in succeeding editions. Each edition will feature two chemists and two physicists. The 96th edition now includes a complimentary eBook with purchase of the print version. This reference puts physical property data and mathematical formulas used in labs and classrooms every day within easy reach. New Tables: Section 1: Basic Constants, Units, and Conversion Factors Descriptive Terms for Solubility Section 8: Analytical Chemistry Stationary Phases for Porous Layer Open Tubular Columns Coolants for Cryotrapping Instability of HPLC Solvents Chlorine-Bromine Combination Isotope Intensities Section 16: Health and Safety Information Materials Compatible with and Resistant to 72 Percent Perchloric Acid Relative Dose Ranges from Ionizing Radiation Updated and Expanded Tables Section 6: Fluid Properties Sublimation Pressure of Solids Vapor Pressure of Fluids at Temperatures Below 300 K Section 7: Biochemistry Structure and Functions of Some Common Drugs Section 9: Molecular Structure and Spectroscopy Bond Dissociation Energies Section 11: Nuclear and Particle Physics Summary Tables of Particle Properties Table of the Isotopes Section 14: Geophysics, Astronomy, and Acoustics Major World Earthquakes Atmospheric Concentration of Carbon Dioxide, 1958-2014 Global Temperature Trend, 1880-2014 Section 15: Practical Laboratory Data Dependence of Boiling Point on Pressure Section 16: Health and Safety Information Threshold Limits for Airborne Contaminants
Publisher: CRC Press
ISBN: 1482260972
Category : Science
Languages : en
Pages : 2652
Book Description
Proudly serving the scientific community for over a century, this 96th edition of the CRC Handbook of Chemistry and Physics is an update of a classic reference, mirroring the growth and direction of science. This venerable work continues to be the most accessed and respected scientific reference in the world. An authoritative resource consisting of tables of data and current international recommendations on nomenclature, symbols, and units, its usefulness spans not only the physical sciences but also related areas of biology, geology, and environmental science. The 96th edition of the Handbook includes 18 new or updated tables along with other updates and expansions. A new series highlighting the achievements of some of the major historical figures in chemistry and physics was initiated with the 94th edition. This series is continued with this edition, which is focused on Lord Kelvin, Michael Faraday, John Dalton, and Robert Boyle. This series, which provides biographical information, a list of major achievements, and notable quotations attributed to each of the renowned chemists and physicists, will be continued in succeeding editions. Each edition will feature two chemists and two physicists. The 96th edition now includes a complimentary eBook with purchase of the print version. This reference puts physical property data and mathematical formulas used in labs and classrooms every day within easy reach. New Tables: Section 1: Basic Constants, Units, and Conversion Factors Descriptive Terms for Solubility Section 8: Analytical Chemistry Stationary Phases for Porous Layer Open Tubular Columns Coolants for Cryotrapping Instability of HPLC Solvents Chlorine-Bromine Combination Isotope Intensities Section 16: Health and Safety Information Materials Compatible with and Resistant to 72 Percent Perchloric Acid Relative Dose Ranges from Ionizing Radiation Updated and Expanded Tables Section 6: Fluid Properties Sublimation Pressure of Solids Vapor Pressure of Fluids at Temperatures Below 300 K Section 7: Biochemistry Structure and Functions of Some Common Drugs Section 9: Molecular Structure and Spectroscopy Bond Dissociation Energies Section 11: Nuclear and Particle Physics Summary Tables of Particle Properties Table of the Isotopes Section 14: Geophysics, Astronomy, and Acoustics Major World Earthquakes Atmospheric Concentration of Carbon Dioxide, 1958-2014 Global Temperature Trend, 1880-2014 Section 15: Practical Laboratory Data Dependence of Boiling Point on Pressure Section 16: Health and Safety Information Threshold Limits for Airborne Contaminants
CRC Handbook of Chemistry and Physics
Author: William M. Haynes
Publisher: CRC Press
ISBN: 1439880506
Category : Science
Languages : en
Pages : 2633
Book Description
Mirroring the growth and direction of science for a century, the Handbook, now in its 93rd edition, continues to be the most accessed and respected scientific reference in the world. An authoritative resource consisting tables of data, its usefulness spans every discipline. This edition includes 17 new tables in the Analytical Chemistry section, a major update of the CODATA Recommended Values of the Fundamental Physical Constants and updates to many other tables. The book puts physical formulas and mathematical tables used in labs every day within easy reach. The 93rd edition is the first edition to be available as an eBook.
Publisher: CRC Press
ISBN: 1439880506
Category : Science
Languages : en
Pages : 2633
Book Description
Mirroring the growth and direction of science for a century, the Handbook, now in its 93rd edition, continues to be the most accessed and respected scientific reference in the world. An authoritative resource consisting tables of data, its usefulness spans every discipline. This edition includes 17 new tables in the Analytical Chemistry section, a major update of the CODATA Recommended Values of the Fundamental Physical Constants and updates to many other tables. The book puts physical formulas and mathematical tables used in labs every day within easy reach. The 93rd edition is the first edition to be available as an eBook.
Handbook of Differential Equations
Author: Daniel Zwillinger
Publisher: Academic Press
ISBN: 1483220966
Category : Mathematics
Languages : en
Pages : 694
Book Description
Handbook of Differential Equations is a handy reference to many popular techniques for solving and approximating differential equations, including exact analytical methods, approximate analytical methods, and numerical methods. Topics covered range from transformations and constant coefficient linear equations to finite and infinite intervals, along with conformal mappings and the perturbation method. Comprised of 180 chapters, this book begins with an introduction to transformations as well as general ideas about differential equations and how they are solved, together with the techniques needed to determine if a partial differential equation is well-posed or what the "natural" boundary conditions are. Subsequent sections focus on exact and approximate analytical solution techniques for differential equations, along with numerical methods for ordinary and partial differential equations. This monograph is intended for students taking courses in differential equations at either the undergraduate or graduate level, and should also be useful for practicing engineers or scientists who solve differential equations on an occasional basis.
Publisher: Academic Press
ISBN: 1483220966
Category : Mathematics
Languages : en
Pages : 694
Book Description
Handbook of Differential Equations is a handy reference to many popular techniques for solving and approximating differential equations, including exact analytical methods, approximate analytical methods, and numerical methods. Topics covered range from transformations and constant coefficient linear equations to finite and infinite intervals, along with conformal mappings and the perturbation method. Comprised of 180 chapters, this book begins with an introduction to transformations as well as general ideas about differential equations and how they are solved, together with the techniques needed to determine if a partial differential equation is well-posed or what the "natural" boundary conditions are. Subsequent sections focus on exact and approximate analytical solution techniques for differential equations, along with numerical methods for ordinary and partial differential equations. This monograph is intended for students taking courses in differential equations at either the undergraduate or graduate level, and should also be useful for practicing engineers or scientists who solve differential equations on an occasional basis.
Quantities, Units and Symbols in Physical Chemistry
Author: International Union of Pure and Applied Chemistry. Physical and Biophysical Chemistry Division
Publisher: Royal Society of Chemistry
ISBN: 0854044337
Category : Reference
Languages : en
Pages : 240
Book Description
Prepared by the IUPAC Physical Chemistry Division this definitive manual, now in its third edition, is designed to improve the exchange of scientific information among the readers in different disciplines and across different nations. This book has been systematically brought up to date and new sections added to reflect the increasing volume of scientific literature and terminology and expressions being used. The Third Edition reflects the experience of the contributors with the previous editions and the comments and feedback have been integrated into this essential resource. This edition has been compiled in machine-readable form and will be available online.
Publisher: Royal Society of Chemistry
ISBN: 0854044337
Category : Reference
Languages : en
Pages : 240
Book Description
Prepared by the IUPAC Physical Chemistry Division this definitive manual, now in its third edition, is designed to improve the exchange of scientific information among the readers in different disciplines and across different nations. This book has been systematically brought up to date and new sections added to reflect the increasing volume of scientific literature and terminology and expressions being used. The Third Edition reflects the experience of the contributors with the previous editions and the comments and feedback have been integrated into this essential resource. This edition has been compiled in machine-readable form and will be available online.
Introduction to Radiometry and Photometry, Second Edition
Author: William Ross McCluney
Publisher: Artech House
ISBN: 1608078345
Category : Technology & Engineering
Languages : en
Pages : 485
Book Description
This second edition of an Artech House classic title describes in detail the relationship between radiometry and photometry. It covers information needed to solve problems in radiation transfer and detection, detectors, measuring instruments, and concepts in colorimetry. This revised second edition presents an updated treatment of modern radiometry and photometry, including brand new sections on applications and developments in light sources and scientific instruments for measuring radiation and light. Engineers are also provided with an exciting new chapter on the use of computerized optical ray tracing for “virtual” experiments on optical systems.
Publisher: Artech House
ISBN: 1608078345
Category : Technology & Engineering
Languages : en
Pages : 485
Book Description
This second edition of an Artech House classic title describes in detail the relationship between radiometry and photometry. It covers information needed to solve problems in radiation transfer and detection, detectors, measuring instruments, and concepts in colorimetry. This revised second edition presents an updated treatment of modern radiometry and photometry, including brand new sections on applications and developments in light sources and scientific instruments for measuring radiation and light. Engineers are also provided with an exciting new chapter on the use of computerized optical ray tracing for “virtual” experiments on optical systems.
Introduction to Reference Sources in the Health Sciences, Sixth Edition
Author: Jeffrey T. Huber
Publisher: American Library Association
ISBN: 0838911846
Category : Language Arts & Disciplines
Languages : en
Pages : 489
Book Description
Prepared in collaboration with the Medical Library Association, this completely updated, revised, and expanded edition lists classic and up-to-the-minute print and electronic resources in the health sciences, helping librarians find the answers that library users seek. Included are electronic versions of traditionally print reference sources, trustworthy electronic-only resources, and resources that library users can access from home or on the go through freely available websites or via library licenses. In this benchmark guide, the authors Include new chapters on health information seeking, point-of-care sources, and global health sources Focus on works that can be considered foundational or essential, in both print and electronic formats Address questions librarians need to consider in developing and maintaining their reference collections When it comes to questions involving the health sciences, this valuable resource will point both library staff and the users they serve in the right direction.
Publisher: American Library Association
ISBN: 0838911846
Category : Language Arts & Disciplines
Languages : en
Pages : 489
Book Description
Prepared in collaboration with the Medical Library Association, this completely updated, revised, and expanded edition lists classic and up-to-the-minute print and electronic resources in the health sciences, helping librarians find the answers that library users seek. Included are electronic versions of traditionally print reference sources, trustworthy electronic-only resources, and resources that library users can access from home or on the go through freely available websites or via library licenses. In this benchmark guide, the authors Include new chapters on health information seeking, point-of-care sources, and global health sources Focus on works that can be considered foundational or essential, in both print and electronic formats Address questions librarians need to consider in developing and maintaining their reference collections When it comes to questions involving the health sciences, this valuable resource will point both library staff and the users they serve in the right direction.
Advances in Atomic, Molecular, and Optical Physics
Author: Susanne Yelin
Publisher: Academic Press
ISBN: 0128209887
Category : Science
Languages : en
Pages : 316
Book Description
Advances in Atomic, Molecular, and Optical Physics, Volume 69, the latest release in this ongoing series, provides a comprehensive compilation of recent developments in a field that is in a state of rapid growth, as new experimental and theoretical techniques are used on many problems, both old and new. Topics covered in this new release include Strong-field ion spectroscopy, Configurable microscopic optical potentials, Polaritons, Rydberg excitation of trapped cold ions - a new platform for quantum technologies, High intensity QED, Recollision imaging, and more. - Presents the work of international experts in the field - Contains comprehensive articles that compile recent developments in a field that is experiencing rapid growth, with new experimental and theoretical techniques emerging - Ideal for users interested in optics, excitons, plasmas and thermodynamics - Covers atmospheric science, astrophysics, and surface and laser physics, amongst other topics
Publisher: Academic Press
ISBN: 0128209887
Category : Science
Languages : en
Pages : 316
Book Description
Advances in Atomic, Molecular, and Optical Physics, Volume 69, the latest release in this ongoing series, provides a comprehensive compilation of recent developments in a field that is in a state of rapid growth, as new experimental and theoretical techniques are used on many problems, both old and new. Topics covered in this new release include Strong-field ion spectroscopy, Configurable microscopic optical potentials, Polaritons, Rydberg excitation of trapped cold ions - a new platform for quantum technologies, High intensity QED, Recollision imaging, and more. - Presents the work of international experts in the field - Contains comprehensive articles that compile recent developments in a field that is experiencing rapid growth, with new experimental and theoretical techniques emerging - Ideal for users interested in optics, excitons, plasmas and thermodynamics - Covers atmospheric science, astrophysics, and surface and laser physics, amongst other topics
Handbook on the Physics and Chemistry of Rare Earths
Author:
Publisher: Elsevier
ISBN: 0444633308
Category : Science
Languages : en
Pages : 373
Book Description
The Handbook on the Physics and Chemistry of Rare Earths is an ongoing series covering all aspects of rare earth science—chemistry, life sciences, materials science, and physics. The main emphasis of the Handbook is on rare earth elements [Sc, Y and the lanthanides (La through Lu)] but information is also included, whenever relevant, on the closely related actinide elements. The individual chapters are comprehensive, broad, up-to-date critical reviews written by highly experienced invited experts. The series, which was started in 1978 by Professor Karl A. Gschneidner Jr., combines and integrates both the fundamentals and applications of these elements and now publishes two volumes a year. - Individual chapters are comprehensive, broad, critical reviews - Contributions are written by highly experienced, invited experts - Up-to-date overviews of developments in the field
Publisher: Elsevier
ISBN: 0444633308
Category : Science
Languages : en
Pages : 373
Book Description
The Handbook on the Physics and Chemistry of Rare Earths is an ongoing series covering all aspects of rare earth science—chemistry, life sciences, materials science, and physics. The main emphasis of the Handbook is on rare earth elements [Sc, Y and the lanthanides (La through Lu)] but information is also included, whenever relevant, on the closely related actinide elements. The individual chapters are comprehensive, broad, up-to-date critical reviews written by highly experienced invited experts. The series, which was started in 1978 by Professor Karl A. Gschneidner Jr., combines and integrates both the fundamentals and applications of these elements and now publishes two volumes a year. - Individual chapters are comprehensive, broad, critical reviews - Contributions are written by highly experienced, invited experts - Up-to-date overviews of developments in the field
MOLECULAR STRUCTURE AND SPECTROSCOPY, Second Edition
Author: ARULDHAS, G.
Publisher: PHI Learning Pvt. Ltd.
ISBN: 9788120332157
Category : Science
Languages : en
Pages : 448
Book Description
Designed to serve as a textbook for postgraduate students of physics and chemistry, this second edition improves the clarity of treatment, extends the range of topics, and includes more worked examples with a view to providing all the material needed for a course in molecular spectroscopy—from first principles to the very useful spectral data that comprise figures, charts and tables. To improve the conceptual appreciation and to help students develop more positive and realistic impressions of spectroscopy, there are two new chapters—one on the spectra of atoms and the other on laser spectroscopy. The chapter on the spectra of atoms is a detailed account of the basic principles involved in molecular spectroscopy. The chapter on laser spectroscopy covers some new experimental techniques for the investigation of the structure of atoms and molecules. Additional sections on interstellar molecules, inversion vibration of ammonia molecule, fibre-coupled Raman spectrometer, Raman microscope, supersonic beams and jet-cooling have also been included. Besides worked-out examples, an abundance of review questions, and end-of-chapter problems with answers are included to aid students in testing their knowledge of the material contained in each chapter. Solutions manual containing the complete worked-out solutions to chapter-end problems is available for instructors.
Publisher: PHI Learning Pvt. Ltd.
ISBN: 9788120332157
Category : Science
Languages : en
Pages : 448
Book Description
Designed to serve as a textbook for postgraduate students of physics and chemistry, this second edition improves the clarity of treatment, extends the range of topics, and includes more worked examples with a view to providing all the material needed for a course in molecular spectroscopy—from first principles to the very useful spectral data that comprise figures, charts and tables. To improve the conceptual appreciation and to help students develop more positive and realistic impressions of spectroscopy, there are two new chapters—one on the spectra of atoms and the other on laser spectroscopy. The chapter on the spectra of atoms is a detailed account of the basic principles involved in molecular spectroscopy. The chapter on laser spectroscopy covers some new experimental techniques for the investigation of the structure of atoms and molecules. Additional sections on interstellar molecules, inversion vibration of ammonia molecule, fibre-coupled Raman spectrometer, Raman microscope, supersonic beams and jet-cooling have also been included. Besides worked-out examples, an abundance of review questions, and end-of-chapter problems with answers are included to aid students in testing their knowledge of the material contained in each chapter. Solutions manual containing the complete worked-out solutions to chapter-end problems is available for instructors.