Nuclear Magnetic Resonance (NMR)

Nuclear magnetic resonance (NMR) is a technique depending on the basis that nucleus within atoms have spinning properties and this spinning properties is used to determine the absorption and emmission of energy, moreover, this property can be used to determine the electromagnetic properties of nuclei. (Resonance is the vibrational frequency of a moving or rotating object. Magnetic Resonance is a technique, where computer is used for analyzing the response of atoms of hydrogen or any other element to a generated magnetic field. So by this response the electronic images of the atoms or molecular structures of solids can be obtained).

This is used for determining the chemical structure of materials and more properly for organic materials.

Proton NMR (represented by 1H NMR) is the type of NMR spectroscopy in which protons within a molecule or hydrogen atoms are under study for determination of structure. (J Urenjak et al.) It is a non-invasive technique. It has many important uses. (J. D. Otvos et al.) One of the application of 1H NMR is for quantifying plasma lipoproteins.

Carbon NMR is the type of NMR spectroscopy in which carbon atoms are under study for determination of the structure. (L. P. Lindeman et al.) Carbon-13 form is mostly used for this purpose and this is one of the great tools for structure analysis because it is naturally abundant. For molecules with few polar functional groups, like hydrocarbons, the fully proton decoupled carbon-13 NMR spectra are usually much better resolved than the proton NMR spectra.

Zero field NMR (A. Bielecki et al.)has been used when there is no predefined direction in space. In this case, all crystallites contribute equivalently and resolved dipolar splittings can be judged by internuclear distances. The importance of this is in molecular structure determination without the need for single crystals or oriented samples.

References:
A. Bielecki, D. Zax, K. Zilm, and A. Pines, Zero-Field Nuclear Magnetic Resonance. Physical Review letters, 50, Pages 1807 - 1810 (1983).
(Physical Review Letters - 14 March 2008 - American Physical Society Periodical/Physical Review Letters October - December 1980 /Physical Review Letters July-September 20 1965 Bound Volume by American Physical Society )

J. D. Otvos, E.J. Jeyarajah, D.W. Bennett, Quantification of plasma lipoproteins by proton nuclear magnetic resonance spectroscopy. Clinical Chemistry, 1991 Mar;37(3):Pages 377-86.

J Urenjak, SR Williams, DG Gadian and M Noble, Proton nuclear magnetic resonance spectroscopy unambiguously identifies different neural cell types. Journal of Neuroscience, Vol 13, Pages 981-989.

L. P. Lindeman, J. Q. Adams, Chemical Shifts for the Paraffins through C9,
Analytical Chemistry, Volume 43, No. 10, August 1971. Page 1245.

Further Reading:
Nuclear Magnetic Resonance by P. J. Hore

Nuclear Magnetic Resonance Spectroscopy: An Introduction to Principles, Applications, and Experimental Methods by Joseph B. Lambert , Eugene P. Mazzola

Principles of Nuclear Magnetic Resonance in One and Two Dimensions by Richard R. Ernst , Geoffrey Bodenhausen and Alexander Wokaun

Nuclear Magnetic Resonance: Concepts and Methods by Daniel Canet

Encyclopedia of Nuclear Magnetic Resonance by David M. Grant and Robin Harris

Copyright (c) 2008, jeepakistan.blogspot.com

Transistor

An electronic device that can be used to control the flow of current.

Field effect transistor:
A transistor using electric field for accumulating or depleting one of the channel region, which is used for the allowing or stoping conduction.(W. Shockley et al.)The "field-effect" type of transistor is one in which the conductivity of a layer of semiconductor is modulated by a transverse electric field. A unipolar field effect transistor is one in which, the amplifying action involves currents carried pre-dominantly by one kind of carrier.

(Piet Bergveld et al.)Ion sensitive field effect transistor is a type of transistor that makes it easy to sense the ionic activities without using the reference electrodes.

References:
Piet Bergveld, Development, Operation, and Application of the Ion-Sensitive Field-Effect Transistor as a Tool for Electrophysiology. IEEE transactions on biomedical engineering Sept. 1972, Volume: BME-19, Issue: 5, Pages 342-351.

W. Shockley, A Unipolar "Field-Effect" Transistor. Proceedings of the IRE, Nov. 1952 Volume: 40, Issue: 11, Pages 1365-1376.

Further Reading:
Transistor Circuit Techniques: Discrete and integrated, 3rd Edition by Gordon J. Ritchie

Copyright (c), 2008, jeepakistan.blogspot.com

Calorimetry

Calorimetry is the study of heat reading in chemical changes or physical changes. It is a thermoanalytical method that measure changes in enthalpy or heat during when the reaction is in progress. [1]

Types of Calorimetry:
There are two main types related to calorimetry:

1. Constant pressure calorimetry.
This measures heat at constant pressure, and represented by "qp" or delta H.

2. Constant Volume calorimetry.
This measures heat at constant volume and represented by "qv" or delta E. [2]

Other types are as follows:

Scanning calorimetry:
(Julian M. Sturtevant) In this calorimeter, there is the measurement of the specific heat of the system as the function of the temperature. Differential scanning Calorimetry is the measurement of the change of the difference in the heat flow rate to the sample and to a reference sample while they are subjected to a controlled temperature program. [3]

Indirect calorimetry:
(D. C. Simonson et al.)Indirect calorimetry is the net rate of disappearence of a substrate (It is not importantly the metabolic changings that the substrate may undergo before its removal from its metabolic pool.)

References:
[1] Handbook of Thermal Analysis and Calorimetry by Michael E. Brown, Patrick K. Gallagher. Elsevier Publishing, 2003.

[2] Chemistry and Chemical Reactivity by John C. Kotz, Paul M. Treichel, Gabriela C. Weaver
Published by Thomson Brooks/Cole, 2005.

[3] Differential Scanning Calorimetry By G.W.H. Höhne, W.F. Hemminger, H.-J. Flammersheim, Published by Springer, 2003

D. C. Simonson, R. A. DeFronzo , Indirect calorimetry: methodological and interpretative problems. American journal of Physiology, Endocrinology and Metabolism 258: Pages E399-E412, 1990.

Julian M. Sturtevant, Biochemical applications of differential scanning calorimetry. Annual Review of Physical ChemistryVol. 38: 463-488. 1987.

Further Reading:
Principles of Thermal Analysis and Calorimetry by P.J. Haines

Comprehensive Handbook of Calorimetry and Thermal Analysis by The Japan Society of Calorimetry and Thermal Analysis

Journal of Thermal Analysis and Calorimetry

Calorimetry and Thermal Analysis

Copyright (c), 2008, jeepakistan.blogspot.com

Conductors

Conductors can cause electricity to pass through it easily.

Transmission of electrons:
(Abraham Nitzan) Electron transmission through molecules and molecular interfaces has been a subject of intensive research due to recent interest in electron transfer phenomena underlying the operation of the scanning tunneling microscope (STM) on one hand, and in the transmission properties of molecular bridges between conducting leads on the other.
In these processes the traditional molecular view of electron transfer between donor and acceptor species give rise to a novel view of the molecule as a current carrying conductor, and observables such as electron transfer rates and yields are replaced by the conductivities, or more generally by current-voltage relationships, in molecular junctions.

(Noriaki Hamada et al.) There are variations in electronic transport in Carbon microtubules ( either they are metallic or semiconductors with narrow and moderate band gaps) depending on the diameter of the tubule and on the degree of helical arrangement of the carbon hexagons. This drastic variation in the band structure can be explained by the 2-dimensional band structure of graphite.

(Albert E. Seaver) Ohm's law (equation) is often used for the study of charge transport. When Ohm's law is combined with Gauss's law and the equation of continuity, a differential equation of volume charge density relaxation can be formed. The solution for this equation is material's permitivity divided by electrical conductivity that shows charge decays exponentially with a relaxation time.

Experiments show that good conductors follow a exponential decay and poor conductors show a decay which is more hyperbolic than exponential.

Following equation has been developed which can be used for both good conductors and poor insulators:

where

Pp is inserted charge

Pp0 is initial charge density

Tm is relaxation time constant

Tp is perturbation time constant.

(For further studies see references)

Properties of Conductors:
(J.B. Pendry et al.)Some microstructures, which are built from nonmagnetic conducting sheets, exhibit an effective magnetic permeability indicated by μeff, which can be tuned to values not accessible in naturally occurring materials, including large imaginary components of μeff.

Super conductors:
Extremely good conductors at low heat which produce no heat and causes no resistance. (Clovis Jacinto de Matos)There is a strong attractive gravitational forces between two electrons in superconductors which is concluded from the Eddington–Dirac large number relation, together with Beck and Mackey electromagnetic model of vacuum energy in superconductors.

Semi-Conductors:
Semi-conductors can pass electricity but not to that extent as conductors and they have the ability to pass electricity only at high temperatures.

Optical conductors:
Conductors which have the ability to pass light.

Transparent conductors:
(K. L. Chopra et al.) Studies are in process for the refinement and progress of transparent conductors. Non-stoichiometric, doped films of oxides of tin, indium, cadmium, zinc and their various alloys, deposited by numerous techniques, exhibit nearly metallic conductivity.

References:
Abraham Nitzan, Electron transmission through molecules and molecular interfaces. Condensed Matter

Albert E. Seaver, An Equation For Charge Decay Valid in Both Conductors
and Insulators. Proceedings ESA-IEJ Joint Meeting 2002, Pages pp. 349-360.

Clovis Jacinto de Matos, Gravitational force between two electrons in superconductors. Physica C: Superconductivity, Volume 468, Issue 3, 1 February 2008, Pages 229-232.

J. B. Pendry, A. J. Holden, D. J. Robbins, W. J. Stewart, Magnetism from conductors and enhanced nonlinear phenomena. Ieee Transactions on Microwave Theory & Techniques , 1999Volume: 47, Issue: 11, Pages 2075-2084.

K. L. Chopra, S. Major, D. K. Pandya, Transparent conductors -- a status review. THIN SOL. FILMS. Vol. 102, no. 1, Pages, 1-46. 1983.

Noriaki Hamada, Shin-ichi Sawada, and Atsushi Oshiyama , New one-dimensional conductors: Graphitic microtubules. Physical review letters, 68, Pages 1579 - 1581 (1992)

Further Reading:
High Conductivity Solid Ionic Conductors: Recent Trends and Applications by International Conference on Solid State Ionics 1987 Garmisch-partenki

The Physics of Organic Superconductors and Conductors (Springer Series in Materials Science) by A. G. Lebed

Transparent Conductive Zinc Oxide: Basics and Applications in Thin Film Solar Cells by Klaus Ellmer, Andreas Klein, Bernd Rech

Copyright (c), 2008, jeepakistan.blogspot.com

Internet

Internet is most revolutionizing thing in the present word. It makes this world a global village more properly it makes this world a home. Internet is used to get and send information. Previously, it was used only for textual informations. But nowadays work is in much more progress for MIME (Multipurpose internet mail extensions). This can be used for non-textual information protocol.


References:


Further Reading:
How internet works by Preston Gralla

Computer

Copyright (c), 2008, jeepakistan.blogspot.com

Microwave

Introduction:
[1] Microwaves are electromegnetic waves in the frequency spectrum ranging approximately from 1 GigaHertz to 30 GigaHertz. This corresponds to wavelengths from 30 cm to 1 cm.

Application of Microwaves:
(Yunfeng Zhao et al.)Microwave energy has great potential to improve the nuclear fuel process in terms of reduction in required processing time and temperature and increased recovery of elements. Microwave energy has significant advantages that are waiting to be explored.

References:
[1] Microwaves by K. C. Gupta

Yunfeng Zhao, Jing Chen. Applications of microwaves in nuclear chemistry and engineering. Progress in Nuclear Energy, Volume 50, Issue 1, January 2008, Pages 1-6

Further Reading:
Microwave Engineering by David M. Pozar

Microwave Radio Links: From Theory to Design (Wiley Series in Telecommunications and Signal Processing) by Carlos Salema


Copyright (c), 2008, jeepakistan.blogspot.com