Explaining all the difficult concepts with precise and accurate points, 3D models, animations and smart art graphics.
Principle
The NMR phenomenon
Theory
Precessional frequency (ν)
Chemical shift
Spin-spin interactions
Interpretation of NMR
Chemical shift (δ)
Multiplicity of the signal
Coupling constant
Instrumentation
Fourier NMR
Continuous wave NMR
Applications
Identification testing
Assay of drugs
Nuclear magnetic resonance (NMR) spectroscopyVK VIKRAM VARMA
SPECTROSCOPY
NMR SPECTROSCOPY
HISTORY
THEORY
PRINCIPLE
INSTRUMENTATION
SOLVENTS USED IN NMR(PROTON NMR)
CHEMICAL SHIFT
FACTORS AFFECTING CHEMICAL SHIFT
RELAXATION PROCESS
SPIN-SPIN COUPLING
푛+1 RULE
NMR SIGNALS IN VARIOUS COMPOUNDS
COUPLING CONSTANT
NUCLEAR MAGNETIC DOUBLE RESONANCE/ SPIN DECOUPLING
FT-NMR
ADVANTAGES & DISADVANTAGES
APPLICATIONS
REFERENCE
Nuclear magnetic resonance (NMR) spectroscopyVK VIKRAM VARMA
SPECTROSCOPY
NMR SPECTROSCOPY
HISTORY
THEORY
PRINCIPLE
INSTRUMENTATION
SOLVENTS USED IN NMR(PROTON NMR)
CHEMICAL SHIFT
FACTORS AFFECTING CHEMICAL SHIFT
RELAXATION PROCESS
SPIN-SPIN COUPLING
푛+1 RULE
NMR SIGNALS IN VARIOUS COMPOUNDS
COUPLING CONSTANT
NUCLEAR MAGNETIC DOUBLE RESONANCE/ SPIN DECOUPLING
FT-NMR
ADVANTAGES & DISADVANTAGES
APPLICATIONS
REFERENCE
PRINCIPLES of FT-NMR & 13C NMR
Fourier Transform
FOURIER TRANSFORM NMR SPECTROSCOPY
THEORY OF FT-NMR
13C NMR SPECTROSCOPY
Principle
Why C13-NMR is required though we have H1-NMR?
CHARACTERISTIC FEATURES OF 13 C NMR
Chemical Shifts
NUCLEAR OVERHAUSER ENHANCEMENT
Short-Comings of 13C-NMR Spectra
Quadrupole and Time of Flight Mass analysers.Gagangowda58
Description about important mass analysers Quadrupole and TOF: Principle, Construction and Working, Advantages and Disadvantages and their Applications.
In this slides contains principle and instrumentation of Differential Scanning Calorimeter (DSC).
Presented by: N Poojitha. (Department of pharmaceutics),
RIPER, anantapur.
This is regarding the Fourier Transform NMR helpful for the analysis in the Pharmaceutical field and this is helpful to the Masters students as this topic is in the syllabus and the presentation gives the complete and detail idea of various aspects of FT-NMR.
In this slide contains principle of IR spectroscopy and sampling techniques.
Presented by: R.Banuteja (Department of pharmaceutical analysis).
RIPER, anantpur.
NMR - Nuclear magnetic resonance (NMR).pptxmuskaangandhi1
Nuclear magnetic resonance (NMR) spectroscopy is the study of molecules by recording the interaction of radiofrequency (Rf) electromagnetic radiations with the nuclei of molecules placed in a strong magnetic field.
It is concerned with absorption of certain amount of energy
by spinning nuclei in a magnetic field when irradiated with
radiofrequency radiation (RFR) of equivalent energy.
NMR gives the information about the number and configuration of
magnetically active atoms, like positions of different types
of Hydrogen over the C- skeleton of an organic molecule.
Absorption of RFR occurs when the nucleus undergoes
transition from one alignment in the applied magnetic field
to the opposite alignment, i.e. from parallel (ground state)
orientation to anti-parallel (excited state) orientation.
When the frequency of the oscillating electric field of the
incoming RFR just matches the frequency of the electric field
generated by the precising nucleus, then the 2 fields can
couple, and the energy can be transferred from the
incoming radiation to the nucleus, thus causing a spin change
(clock-wise to anti-clock-wise).
This condition is called "resonance", and the nucleus is said to
have resonance with the incoming electromagnetic wave
(RFR).
In NMR technique, the frequency of the RFR is kept constant
(60MHz) and the strength of magnetic field is varied.
At certain value of the applied field strength, depending
upon the nature of proton or nucleus, the energy required to
flip the proton matches the energy of radiation.
As a result, absorption takes place and a signal is observed
in the spectrum. Such a signal or peak is called an NMR
Spectrum.
NMR spectrum is graphical plot of relative intensity
(Y axis) and the δ value (x axis).
The nucleus of a hydrogen atom (proton) behaves as a spinning bar magnet because it possesses both electric and magnetic spin.
Like any other spinning charged body, the nucleus of hydrogen atom also generates a magnetic field.
Nuclear magnetic resonance Involves the interaction between an oscillating magnetic field of electromagnetic radiation and the magnetic energy of the hydrogen nucleus or some other type of nuclei when these are placed in an external static magnetic field.
The sample absorbs electromagnetic radiations in radio wave region at different frequencies since absorption depends upon the type of protons or certain nuclei contained in the sample)
Consider a spinning top. It also performs a slower waltz like motion,
in which the spinning axis of the top moves slowly around
the vertical.
This is processional motion & the top is said to be processing around the vertical axis of earth's gravitational field.
The precession arises from the interaction of spin with earth's gravity acting vertically downwards.
It is called Gyroscopic motion.
Proton will be showing processional motion due to interaction of Spin &
Gravitational force of Earth
Nuclear magnetic resonance spectroscopy, most commonly known as NMR spectroscopy or magnetic resonance spectroscopy, is a spectroscopic technique to observe local magnetic fields around atomic nuclei.
PRINCIPLES of FT-NMR & 13C NMR
Fourier Transform
FOURIER TRANSFORM NMR SPECTROSCOPY
THEORY OF FT-NMR
13C NMR SPECTROSCOPY
Principle
Why C13-NMR is required though we have H1-NMR?
CHARACTERISTIC FEATURES OF 13 C NMR
Chemical Shifts
NUCLEAR OVERHAUSER ENHANCEMENT
Short-Comings of 13C-NMR Spectra
Quadrupole and Time of Flight Mass analysers.Gagangowda58
Description about important mass analysers Quadrupole and TOF: Principle, Construction and Working, Advantages and Disadvantages and their Applications.
In this slides contains principle and instrumentation of Differential Scanning Calorimeter (DSC).
Presented by: N Poojitha. (Department of pharmaceutics),
RIPER, anantapur.
This is regarding the Fourier Transform NMR helpful for the analysis in the Pharmaceutical field and this is helpful to the Masters students as this topic is in the syllabus and the presentation gives the complete and detail idea of various aspects of FT-NMR.
In this slide contains principle of IR spectroscopy and sampling techniques.
Presented by: R.Banuteja (Department of pharmaceutical analysis).
RIPER, anantpur.
NMR - Nuclear magnetic resonance (NMR).pptxmuskaangandhi1
Nuclear magnetic resonance (NMR) spectroscopy is the study of molecules by recording the interaction of radiofrequency (Rf) electromagnetic radiations with the nuclei of molecules placed in a strong magnetic field.
It is concerned with absorption of certain amount of energy
by spinning nuclei in a magnetic field when irradiated with
radiofrequency radiation (RFR) of equivalent energy.
NMR gives the information about the number and configuration of
magnetically active atoms, like positions of different types
of Hydrogen over the C- skeleton of an organic molecule.
Absorption of RFR occurs when the nucleus undergoes
transition from one alignment in the applied magnetic field
to the opposite alignment, i.e. from parallel (ground state)
orientation to anti-parallel (excited state) orientation.
When the frequency of the oscillating electric field of the
incoming RFR just matches the frequency of the electric field
generated by the precising nucleus, then the 2 fields can
couple, and the energy can be transferred from the
incoming radiation to the nucleus, thus causing a spin change
(clock-wise to anti-clock-wise).
This condition is called "resonance", and the nucleus is said to
have resonance with the incoming electromagnetic wave
(RFR).
In NMR technique, the frequency of the RFR is kept constant
(60MHz) and the strength of magnetic field is varied.
At certain value of the applied field strength, depending
upon the nature of proton or nucleus, the energy required to
flip the proton matches the energy of radiation.
As a result, absorption takes place and a signal is observed
in the spectrum. Such a signal or peak is called an NMR
Spectrum.
NMR spectrum is graphical plot of relative intensity
(Y axis) and the δ value (x axis).
The nucleus of a hydrogen atom (proton) behaves as a spinning bar magnet because it possesses both electric and magnetic spin.
Like any other spinning charged body, the nucleus of hydrogen atom also generates a magnetic field.
Nuclear magnetic resonance Involves the interaction between an oscillating magnetic field of electromagnetic radiation and the magnetic energy of the hydrogen nucleus or some other type of nuclei when these are placed in an external static magnetic field.
The sample absorbs electromagnetic radiations in radio wave region at different frequencies since absorption depends upon the type of protons or certain nuclei contained in the sample)
Consider a spinning top. It also performs a slower waltz like motion,
in which the spinning axis of the top moves slowly around
the vertical.
This is processional motion & the top is said to be processing around the vertical axis of earth's gravitational field.
The precession arises from the interaction of spin with earth's gravity acting vertically downwards.
It is called Gyroscopic motion.
Proton will be showing processional motion due to interaction of Spin &
Gravitational force of Earth
Nuclear magnetic resonance spectroscopy, most commonly known as NMR spectroscopy or magnetic resonance spectroscopy, is a spectroscopic technique to observe local magnetic fields around atomic nuclei.
Theory of NMR, nuclear magnetic resonance, instrumentation, solvents, chemical shift, photon NMR, spin coupling, coupling constant and applications.
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NMR, principle, chemical shift , valu,13 C, applicationTripura University
Nuclear magnetic resonance (NMR) is a physical phenomenon in which nuclei in a strong, constant magnetic field are perturbed by a weak oscillating magnetic field (in the near field [1]) and respond by producing an electromagnetic signal with a frequency characteristic of the magnetic field at the nucleus. This process occurs near resonance, when the oscillation frequency matches the intrinsic frequency of the nuclei, which depends on the strength of the static magnetic field, the chemical environment, and the magnetic properties of the isotope involved; in practical applications with static magnetic fields up to ca. 20 tesla, the frequency is similar to VHF and UHF television broadcasts (60–1000 MHz). NMR results from the specific magnetic properties of certain atomic nuclei. Nuclear magnetic resonance spectroscopy is widely used to determine the structure of organic molecules in solution and study molecular physics and crystals as well as non-crystalline materials. NMR is also routinely used in advanced medical imaging techniques, such as magnetic resonance imaging (MRI). The original application of NMR to condensed matter physics is nowadays mostly devoted to strongly correlated electron systems. It reveals large many-body couplings by fast broadband detection, and it should not be confused with solid-state NMR, which aims at removing the effect of the same couplings by magic angle spinning techniques.
1. contents - NMR SPECTROMETER
INTRUMENTATION OF NMR
COMPONENTS OF NMR SPECTROMETER
REFERENCES
2. NMR Spectrometer is an instrument which is used to obtain NMR Spectra.
A high resolution spectrometer contains a complex collection of electronic equipments.
NMR spectrometers are referred to as 300 MHz instruments (or) 500 MHz instruments, depending upon the frequency of the RF radiation used for resonance.
These spectrometers use very powerful magnets to create a small but measurable energy difference between two possible spin states.
3. COMPONENTS OF NMR SPECTROMETER
Magnet
Field Lock
Shim Coils
Probe Unit
- Sample Holder
- RF Oscillator
- Sweep Generator
- RF Receiver
Detector
Read out Device
4. magnets ;-
The heart of both continuous-wave and Fourier form NMR instruments is the magnet.
Magnets produces the magnetic field, which determines the frequency of any nucleus.
Sensitivity and resolution are critically dependent on quality of magnet.
It should give homogenous magnetic field, i.e. the strength of the magnetic field should not change from point to point.
The magnet must be capable of producing a very strong magnetic field with strength at least 10,000 gauss
5. Types of Magnets
Permanent Magnet:
Permanent magnets with field strengths of 0.7, 1.4, and 2.1 T are mostly used.
Permanent magnets are highly temperature-sensitive and require extensive thermostating and shielding as a consequence.
It is inexpensive and simple to operate.
They are operated up to 30 – 60 MHz
They provide field of good homogeneity.
Disadvantage:- Field variation is not possible, as required, because different nuclei resonate at different magnetic field.
6. Electro Magnets:
They require power supply to produce magnetic field
Cooling system is required to counter the heat generated from the electric power.
They are more effective than the permanent magnet because of possibility of field variation
They are operated up to 60 - 90 MHz
7. 3. Super conducting magnet:
A super conducting magnet has an electromagnet made up of superconducting wire.
These magnets attain fields large as 21 T.
Superconducting wire has a resistance approximately equal to zero by immersing it in liquid helium (at 0° c).
Superconducting magnet systems be filled with liquid nitrogen every 10 days
The length of superconducting wire in the magnet is typically several miles.
They are operated up to 470 MHz
8. field lock
In order to produce a high resolution NMR spectrum of a sample there is need of homogeneous magnetic field.
The field strength might vary due to aging of the magnet, movement of metal object near the magnet, and temperature fluctuations.
9. shim coils
Shim coils are pairs of wire loops.
By using these coils Current is adjusted until the magnetic field has required homogeneity.
Magnetic field produced by the Shim coils cancels the small residual inhomogeneities in the magnetic field.
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Acute scrotum is a general term referring to an emergency condition affecting the contents or the wall of the scrotum.
There are a number of conditions that present acutely, predominantly with pain and/or swelling
A careful and detailed history and examination, and in some cases, investigations allow differentiation between these diagnoses. A prompt diagnosis is essential as the patient may require urgent surgical intervention
Testicular torsion refers to twisting of the spermatic cord, causing ischaemia of the testicle.
Testicular torsion results from inadequate fixation of the testis to the tunica vaginalis producing ischemia from reduced arterial inflow and venous outflow obstruction.
The prevalence of testicular torsion in adult patients hospitalized with acute scrotal pain is approximately 25 to 50 percent
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Lung Cancer: Artificial Intelligence, Synergetics, Complex System Analysis, S...Oleg Kshivets
RESULTS: Overall life span (LS) was 2252.1±1742.5 days and cumulative 5-year survival (5YS) reached 73.2%, 10 years – 64.8%, 20 years – 42.5%. 513 LCP lived more than 5 years (LS=3124.6±1525.6 days), 148 LCP – more than 10 years (LS=5054.4±1504.1 days).199 LCP died because of LC (LS=562.7±374.5 days). 5YS of LCP after bi/lobectomies was significantly superior in comparison with LCP after pneumonectomies (78.1% vs.63.7%, P=0.00001 by log-rank test). AT significantly improved 5YS (66.3% vs. 34.8%) (P=0.00000 by log-rank test) only for LCP with N1-2. Cox modeling displayed that 5YS of LCP significantly depended on: phase transition (PT) early-invasive LC in terms of synergetics, PT N0—N12, cell ratio factors (ratio between cancer cells- CC and blood cells subpopulations), G1-3, histology, glucose, AT, blood cell circuit, prothrombin index, heparin tolerance, recalcification time (P=0.000-0.038). Neural networks, genetic algorithm selection and bootstrap simulation revealed relationships between 5YS and PT early-invasive LC (rank=1), PT N0—N12 (rank=2), thrombocytes/CC (3), erythrocytes/CC (4), eosinophils/CC (5), healthy cells/CC (6), lymphocytes/CC (7), segmented neutrophils/CC (8), stick neutrophils/CC (9), monocytes/CC (10); leucocytes/CC (11). Correct prediction of 5YS was 100% by neural networks computing (area under ROC curve=1.0; error=0.0).
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Tom Selleck, an enduring figure in Hollywood. has captivated audiences for decades with his rugged charm, iconic moustache. and memorable roles in television and film. From his breakout role as Thomas Magnum in Magnum P.I. to his current portrayal of Frank Reagan in Blue Bloods. Selleck's career has spanned over 50 years. But beyond his professional achievements. fans have often been curious about Tom Selleck Health. especially as he has aged in the public eye.
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Introduction
Many have been interested in Tom Selleck health. not only because of his enduring presence on screen but also because of the challenges. and lifestyle choices he has faced and made over the years. This article delves into the various aspects of Tom Selleck health. exploring his fitness regimen, diet, mental health. and the challenges he has encountered as he ages. We'll look at how he maintains his well-being. the health issues he has faced, and his approach to ageing .
Early Life and Career
Childhood and Athletic Beginnings
Tom Selleck was born on January 29, 1945, in Detroit, Michigan, and grew up in Sherman Oaks, California. From an early age, he was involved in sports, particularly basketball. which played a significant role in his physical development. His athletic pursuits continued into college. where he attended the University of Southern California (USC) on a basketball scholarship. This early involvement in sports laid a strong foundation for his physical health and disciplined lifestyle.
Transition to Acting
Selleck's transition from an athlete to an actor came with its physical demands. His first significant role in "Magnum P.I." required him to perform various stunts and maintain a fit appearance. This role, which he played from 1980 to 1988. necessitated a rigorous fitness routine to meet the show's demands. setting the stage for his long-term commitment to health and wellness.
Fitness Regimen
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Tom Selleck health and fitness regimen has evolved. adapting to his changing roles and age. During his "Magnum, P.I." days. Selleck's workouts were intense and focused on building and maintaining muscle mass. His routine included weightlifting, cardiovascular exercises. and specific training for the stunts he performed on the show.
Selleck adjusted his fitness routine as he aged to suit his body's needs. Today, his workouts focus on maintaining flexibility, strength, and cardiovascular health. He incorporates low-impact exercises such as swimming, walking, and light weightlifting. This balanced approach helps him stay fit without putting undue strain on his joints and muscles.
Importance of Flexibility and Mobility
In recent years, Selleck has emphasized the importance of flexibility and mobility in his fitness regimen. Understanding the natural decline in muscle mass and joint flexibility with age. he includes stretching and yoga in his routine. These practices help prevent injuries, improve posture, and maintain mobilit
ARTIFICIAL INTELLIGENCE IN HEALTHCARE.pdfAnujkumaranit
Artificial intelligence (AI) refers to the simulation of human intelligence processes by machines, especially computer systems. It encompasses tasks such as learning, reasoning, problem-solving, perception, and language understanding. AI technologies are revolutionizing various fields, from healthcare to finance, by enabling machines to perform tasks that typically require human intelligence.
3. • The NMR phenomenon
Principle
• Precessional frequency (ν)
• Chemical shift
• Spin-spin interactionsTheory
•Chemical shift (δ)
•Multiplicity of the signal
• Coupling constant
Interpretation of
NMR
• Fourier NMR
• Continuous wave NMR
Instrumentation
• Identification testing
• Assay of drugs
Applications
4. • Defined as a condition when the frequency of the applied
magnetic field becomes equal to the frequency of magnetic field
produced by the nucleus.
• Process whereby energy from an external source is absorbed and
brings about a change or resonance to an ‘excited’ or high energy
state
Nuclear Magnetic
Resonance
• An analytical chemistry technique used in quality control and
research for determining the content and purity of a sample as
well as its molecular structure
• The energy required for NMR lies in the low energy or long
wavelength radio-frequency end of the electromagnetic spectrum.
NMR
spectroscopy
5. The nucleus of the hydrogen
atom, i.e., the proton, just
behaves as if it is a small
spinning bar magnet.
It does so because it evidently
possesses an electrical charge
as well as a mechanical spin.
Consequently, a spinning
charged body will generate a
magnetic field.
8. A gyroscope (from Greek gûros, "circle" and
skopéō, "to look") is a spinning wheel or disc in
which the axis of rotation is free to assume any
orientation.
Precession is a change in the orientation of the
rotational axis of a rotating body.
Torque-induced precession (gyroscopic precession) is
the phenomenon in which the axis of a spinning object
(e.g., a gyroscope) describes a cone in space when an
external torque is applied to it
9.
10.
11. HOW
•Whenever a proton is precessing in the aligned orientation (low
energy) it can absorb energy and pass into the orientation (high
energy) ; and subsequently it can lose this extra energy and
relax back into the aligned state
WHEN
•Interestingly, the precessing proton can only absorb energy from
the radio frequency source if the precessing frequency is exactly
the same as that of the radio frequency beam ; and when this
particular situation arises, the nucleus and the radio frequency
beam are said to be in resonance, thereby justifying the term
‘nuclear magnetic resonance’.
HENCE
•In NMR spectroscopy, the precessing protons of an organic
molecule, after being duly exposed to a powerful external
magnetic field (ranging between 60-400 MHz), are irradiated
with radio frequency energy of the appropriate frequencies,
thereby promoting protons from the low-energy (aligned state)
to the highenergy (opposed state).
12. The Spin Quantum
Number (ms)
describes the angular
momentum of an
electron.
An electron spins around
an axis and has both
angular momentum and
orbital angular
momentum.
Because angular
momentum is a vector,
the Spin Quantum
Number (s) has both a
magnitude (1/2) and
direction (+ or -)
Each orbital can only hold two
electrons. One electron will
have a +1/2 spin and the
other will have a -1/2 spin.
13. Mass Number Atomic Number Spin Quantum no.
odd Odd or even I=1/2
even even 0
even odd I=1,2,3….
14. The chemical shift in absolute terms is defined by the frequency of the
resonance expressed with reference to a standard compound which
is defined to be at 0 ppm. The scale is made more manageable by
expressing it in parts per million (ppm) and is indepedent of the
spectrometer frequency.
downfield or
deshielded
upfield or
shielded
15. Coupling constant
J is the separation (in Hertz ; Hz = sec–1) between the peaks of regular multiplets. The coupling
constants help in the identification of the coupled nuclei because Jab = Jba : and are therefore,
useful in characterizing the relative orientations of interacting protons.
Equivalent and Non-Equivalent protons
Depends on value of chemical shift
Multiplicity of Absorption signal
Depends on neighboring non-equivalent protons(2nI+1)
Singlet----Doublet----Triplet----Quartet
DEFINITON
Effect of spin of one proton on adjacent magnetically non-equivalent proton that
results in splitting of its absorption signal.
16.
17.
18. •For any system at equilibrium, in the absence of a magnetic field, all the nuclear spin states
are equally populated and hence there is no net polarization due to the nuclear spins.
Therefore, it is necessary to introduce an external magnetic field which leads to preferential
population of the lower energy nuclear spin states.
•The energy differences between the different nuclear spin states are proportional to the
strength of the magnetic field. Therefore, higher magnetic fields lead to greater separation
between the energy levels and greater polarization at equilibrium. The required magnetic
field is usually provided by an external magnet.
•For high resolution NMR spectroscopy the magnetic field homogeneity has to be better than
1 ppb (part per billion) over the volume of interest. The homogeneity requirements are
usually lower for MRI and NMR relaxometry. The homogeneity of the magnetic field created
by the primary magnet is improved by using a set of shims.
•High magnetic fields (1 Tesla to 17 Tesla) are generally preferred for high resolution, high
sensitivity NMR spectroscopic experiments. In general, higher magnetic fields provide higher
signal to noise ratio as well as higher resolution. Most high resolution NMR spectrometers
used by chemists and biologists use superconducting magnets.
19. •The probe in an NMR spectrometer is responsible for coupling the radio
frequency electromagnetic field generated by the RF transmitter to the
sample. It is also responsible for detecting the NMR signal (through
induction) and passing it to the receiver for amplification and
digitization.
•In the earliest NMR spectrometers, the probe consisted of a pair of
orthogonal coils. One coil was coupled to the RF transmitter and was
used to generate a homogeneous RF electromagnetic field over the
sample area of interest. Continuous RF or pulses of coherent RF
radiation were used to create transverse magnetization in the sample.
•The precession of this transverse magnetization would cause induction
in a second coil known as the receiver coil. The receiver coil was
orthogonal to the transmission coil. However, at present, most NMR
spectrometers and MRI instruments use a single coil for both
transmission and reception.
20. MR electronics consists of a subsystems for
controlling the MR transceiver, magnetic field
gradients, field frequency lock, spinner
speed, temperature of the sample (VT), and
an interface to a computer for receiving
controlling instructions and to transmit the
digitized data.
21. Magnetic field gradients are controlled by an
independent subsystem. Magnetic field
gradients are generated by passing current
through coils of appropriate geometry. Static
magnetic field gradients are used for
shimming. In addition pulsed magnetic field
gradients can be produced based on the
instructions in the pulse program.
22. The MR transceiver contains two major subsystems: The
transmitter and the receiver subsystems
Transmitter subsystem: It consists of the RF synthesizers and
amplifiers. This subsystem is responsible for generating pulse
sequences containing RF pulses of specified frequency,
amplitude, phase, shape and duration at specified times.
Multiple RF synthesizers are required because many MR
experiments require simultaneous application of RF pulses of
different frequencies.
RF switch is responsible for coupling either the Transmitter or the
Receiver subsystem to the probe. This ensures that the sensitive
receiver subsystem is not overloaded with the high powered RF
signal generated by the transmitter system. Also, the receiver is
'blanked' during the transmission and for a short duration
afterward.
Receiver subsystem: This consists of the components:
Preamplifier, Amplifier, Mixer and the Analog-to-Digital converter
(ADC). The Mixer is used to subtract a reference frequency of
specified phase from the observed signal, resulting a signal of
lower frequency that can be easily digitized.
23. Field frequency lock
The field frequency lock consists of a negative
feedback loop that keeps the magnetic field
constant. The superconducting magnets that are
commonly used in high resolution NMR spectrometers
usually have a drift of a few ppb per day (ppb = parts
per billion of the total magnetic field). Many high
resolution multidimensional NMR experiments often
require more than 1 day of measurement. In order to
the ensure that the magnetic field at the sample
stays constant, during this time, an additional small
magnetic field is created by passing current through a
loop of appropriate shape to compensate for the
change in magnetic field due to the main
(superconducting) magnet.
24. • In its first few decades, nuclear magnetic resonance spectrometers used
a technique known as continuous-wave spectroscopy (CW spectroscopy).
This more typically involved using a fixed frequency source and varying
the current (and hence magnetic field) in an electromagnet to observe
the resonant absorption signals. Require only water-cooled
electromagnets instead of the liquid-He-cooled superconducting magnets
found in higher-field FT-NMR spectrometers.
A cw-NMR spectrometer consists of a control console, magnet, and two
orthogonal coils of wire that serve as antennas for radiofrequency (RF)
radiation. One coil is attached to an RF generator and serves as a
transmitter. The other coil is the RF pick-up coil and is attached to the
detection electronics. Since the two coils are orthogonal, the pick-up coil
cannot directly recieve any radiation from the generator coil. When a
nucleus absorbs RF radiation, it can become reoriented due to its normal
movement in solution and re-emit the RF radiation is a direction that can
be recieved by the pick-up coil. This orthogonal coil arrangement greatly
increases the sensitivity of NMR spectroscopy, similar to optical
fluorescence.
Spectra are obtained by scanning the magnet and recording the pick-up
coil signal on paper at the control console.
25. Most applications of NMR involve full NMR spectra, that is, the intensity of the NMR
signal as a function of frequency. Early attempts to acquire the NMR spectrum more
efficiently than simple CW methods involved illuminating the target simultaneously
with more than one frequency. A revolution in NMR occurred when short pulses of
radio-frequency radiation began to be used—centered at the middle of the NMR
spectrum. In simple terms, a short pulse of a given "carrier" frequency "contains" a
range of frequencies centered about the carrier frequency, with the range of
excitation (bandwidth) being inversely proportional to the pulse duration, i.e.
the Fourier transform of a short pulse contains contributions from all the
frequencies in the neighborhood of the principal frequency. X
VVVVVVVVVVVVVVThe restricted range of the NMR frequencies made it relatively
easy to use short (millisecond to microsecond) radio frequency pulses to excite the
entire NMR spectrum.[citation needed]
Applying such a pulse to a set of nuclear spins simultaneously excites all the single-
quantum NMR transitions. In terms of the net magnetization vector, this corresponds
to tilting the magnetization vector away from its equilibrium position (aligned along
the external magnetic field). The out-of-equilibrium magnetization vector precesses
about the external magnetic field vector at the NMR frequency of the spins. This
oscillating magnetization vector induces a current in a nearby pickup coil, creating
an electrical signal oscillating at the NMR frequency. This signal is known as the free
induction decay (FID), and it contains the vector sum of the NMR responses from all
the excited spins
26. 1:Medicine
Medical MRI
Proton NMR and carbon-13 NMR
Biochemical information can also be obtained
from living tissue (e.g. human brain tumors) with
the technique known as in vivo magnetic
resonance spectroscopy or chemical shift NMR
Microscopy.
As one of the two major spectroscopic
techniques used in metabolomics, NMR is used to
generate metabolic fingerprints from biological
fluids to obtain information about disease states
or toxic insults.
27. 2:Chemistry
Structure of compounds: It can be a very selective
technique, distinguishing among many atoms within a
molecule or collection of molecules of the same type but
which differ only in terms of their local chemical
environment.
Identify known and novel compounds: is usually required
by scientific journals for identity confirmation of
synthesized new compounds.
NMR), since its natural abundance is nearly 100%; isotope
enrichment is required for most other elements.
Structural dynamics: such as ring-flipping in cyclohexane;
At low enough temperatures, a distinction can be made
between the axial and equatorial hydrogens in
cyclohexane.
Purity determination (w/w NMR)
28. Non-destructive testing
Data acquisition in the petroleum industry
Quantum computing
Process control