Standing waves are created on a string fixed at both ends when waves traveling in opposite directions interfere and superimpose. Nodes occur where the amplitude is zero, while antinodes have maximum amplitude. For a string of length L fixed at both ends, standing waves can only occur at wavelengths of λ=2L/m, where m is a positive integer. The fundamental frequency corresponds to the longest wavelength of λ=2L and higher harmonics have shorter wavelengths and higher frequencies that are integer multiples of the fundamental.
Working through the concepts of constructive and destructive interference patterns of two waves, these slides include questions that serve to clarify interference conceptually and mathematically.
A learning object that explains the concept of how constructive and destructive interference between two sound waves with varying frequncies produces beats. Practice problems with answers are included to improve understanding.
This Presentation is useful to study Advanced Engineering Mathematics about Fourier Series and Fourier Integral. This Presentation is also useful make PPT on this topic.
A clicker style question that gives the wavelength of a standing wave and asks the learner to identify the corresponding envelope from five choices. Solution explores two methods to identify the correct envelope--one discusses the wavelength and the length of the string, while the second explores an approach incorporating antinodes.
In this presentation, I explain what a standing wave on a string is, the difference between a standing wave and a travelling wave, and go over some practice problems.
Working through the concepts of constructive and destructive interference patterns of two waves, these slides include questions that serve to clarify interference conceptually and mathematically.
A learning object that explains the concept of how constructive and destructive interference between two sound waves with varying frequncies produces beats. Practice problems with answers are included to improve understanding.
This Presentation is useful to study Advanced Engineering Mathematics about Fourier Series and Fourier Integral. This Presentation is also useful make PPT on this topic.
A clicker style question that gives the wavelength of a standing wave and asks the learner to identify the corresponding envelope from five choices. Solution explores two methods to identify the correct envelope--one discusses the wavelength and the length of the string, while the second explores an approach incorporating antinodes.
In this presentation, I explain what a standing wave on a string is, the difference between a standing wave and a travelling wave, and go over some practice problems.
This LO gives you a simple easy to understand explanation of what a standing wave is (video included) and how it is different from a travelling wave. Afterwards a few sample questions are given to apply knowledge.
CBSE Physics/ Lakshmikanta Satapathy/ Wave Motion Theory/ Reflection of waves/ Traveling and stationary waves/ Nodes and anti-nodes/ Stationary waves in strings/ Laws of transverse vibration of stretched strings
Introduction:
RNA interference (RNAi) or Post-Transcriptional Gene Silencing (PTGS) is an important biological process for modulating eukaryotic gene expression.
It is highly conserved process of posttranscriptional gene silencing by which double stranded RNA (dsRNA) causes sequence-specific degradation of mRNA sequences.
dsRNA-induced gene silencing (RNAi) is reported in a wide range of eukaryotes ranging from worms, insects, mammals and plants.
This process mediates resistance to both endogenous parasitic and exogenous pathogenic nucleic acids, and regulates the expression of protein-coding genes.
What are small ncRNAs?
micro RNA (miRNA)
short interfering RNA (siRNA)
Properties of small non-coding RNA:
Involved in silencing mRNA transcripts.
Called “small” because they are usually only about 21-24 nucleotides long.
Synthesized by first cutting up longer precursor sequences (like the 61nt one that Lee discovered).
Silence an mRNA by base pairing with some sequence on the mRNA.
Discovery of siRNA?
The first small RNA:
In 1993 Rosalind Lee (Victor Ambros lab) was studying a non- coding gene in C. elegans, lin-4, that was involved in silencing of another gene, lin-14, at the appropriate time in the
development of the worm C. elegans.
Two small transcripts of lin-4 (22nt and 61nt) were found to be complementary to a sequence in the 3' UTR of lin-14.
Because lin-4 encoded no protein, she deduced that it must be these transcripts that are causing the silencing by RNA-RNA interactions.
Types of RNAi ( non coding RNA)
MiRNA
Length (23-25 nt)
Trans acting
Binds with target MRNA in mismatch
Translation inhibition
Si RNA
Length 21 nt.
Cis acting
Bind with target Mrna in perfect complementary sequence
Piwi-RNA
Length ; 25 to 36 nt.
Expressed in Germ Cells
Regulates trnasposomes activity
MECHANISM OF RNAI:
First the double-stranded RNA teams up with a protein complex named Dicer, which cuts the long RNA into short pieces.
Then another protein complex called RISC (RNA-induced silencing complex) discards one of the two RNA strands.
The RISC-docked, single-stranded RNA then pairs with the homologous mRNA and destroys it.
THE RISC COMPLEX:
RISC is large(>500kD) RNA multi- protein Binding complex which triggers MRNA degradation in response to MRNA
Unwinding of double stranded Si RNA by ATP independent Helicase
Active component of RISC is Ago proteins( ENDONUCLEASE) which cleave target MRNA.
DICER: endonuclease (RNase Family III)
Argonaute: Central Component of the RNA-Induced Silencing Complex (RISC)
One strand of the dsRNA produced by Dicer is retained in the RISC complex in association with Argonaute
ARGONAUTE PROTEIN :
1.PAZ(PIWI/Argonaute/ Zwille)- Recognition of target MRNA
2.PIWI (p-element induced wimpy Testis)- breaks Phosphodiester bond of mRNA.)RNAse H activity.
MiRNA:
The Double-stranded RNAs are naturally produced in eukaryotic cells during development, and they have a key role in regulating gene expression .
(May 29th, 2024) Advancements in Intravital Microscopy- Insights for Preclini...Scintica Instrumentation
Intravital microscopy (IVM) is a powerful tool utilized to study cellular behavior over time and space in vivo. Much of our understanding of cell biology has been accomplished using various in vitro and ex vivo methods; however, these studies do not necessarily reflect the natural dynamics of biological processes. Unlike traditional cell culture or fixed tissue imaging, IVM allows for the ultra-fast high-resolution imaging of cellular processes over time and space and were studied in its natural environment. Real-time visualization of biological processes in the context of an intact organism helps maintain physiological relevance and provide insights into the progression of disease, response to treatments or developmental processes.
In this webinar we give an overview of advanced applications of the IVM system in preclinical research. IVIM technology is a provider of all-in-one intravital microscopy systems and solutions optimized for in vivo imaging of live animal models at sub-micron resolution. The system’s unique features and user-friendly software enables researchers to probe fast dynamic biological processes such as immune cell tracking, cell-cell interaction as well as vascularization and tumor metastasis with exceptional detail. This webinar will also give an overview of IVM being utilized in drug development, offering a view into the intricate interaction between drugs/nanoparticles and tissues in vivo and allows for the evaluation of therapeutic intervention in a variety of tissues and organs. This interdisciplinary collaboration continues to drive the advancements of novel therapeutic strategies.
Observation of Io’s Resurfacing via Plume Deposition Using Ground-based Adapt...Sérgio Sacani
Since volcanic activity was first discovered on Io from Voyager images in 1979, changes
on Io’s surface have been monitored from both spacecraft and ground-based telescopes.
Here, we present the highest spatial resolution images of Io ever obtained from a groundbased telescope. These images, acquired by the SHARK-VIS instrument on the Large
Binocular Telescope, show evidence of a major resurfacing event on Io’s trailing hemisphere. When compared to the most recent spacecraft images, the SHARK-VIS images
show that a plume deposit from a powerful eruption at Pillan Patera has covered part
of the long-lived Pele plume deposit. Although this type of resurfacing event may be common on Io, few have been detected due to the rarity of spacecraft visits and the previously low spatial resolution available from Earth-based telescopes. The SHARK-VIS instrument ushers in a new era of high resolution imaging of Io’s surface using adaptive
optics at visible wavelengths.
Cancer cell metabolism: special Reference to Lactate PathwayAADYARAJPANDEY1
Normal Cell Metabolism:
Cellular respiration describes the series of steps that cells use to break down sugar and other chemicals to get the energy we need to function.
Energy is stored in the bonds of glucose and when glucose is broken down, much of that energy is released.
Cell utilize energy in the form of ATP.
The first step of respiration is called glycolysis. In a series of steps, glycolysis breaks glucose into two smaller molecules - a chemical called pyruvate. A small amount of ATP is formed during this process.
Most healthy cells continue the breakdown in a second process, called the Kreb's cycle. The Kreb's cycle allows cells to “burn” the pyruvates made in glycolysis to get more ATP.
The last step in the breakdown of glucose is called oxidative phosphorylation (Ox-Phos).
It takes place in specialized cell structures called mitochondria. This process produces a large amount of ATP. Importantly, cells need oxygen to complete oxidative phosphorylation.
If a cell completes only glycolysis, only 2 molecules of ATP are made per glucose. However, if the cell completes the entire respiration process (glycolysis - Kreb's - oxidative phosphorylation), about 36 molecules of ATP are created, giving it much more energy to use.
IN CANCER CELL:
Unlike healthy cells that "burn" the entire molecule of sugar to capture a large amount of energy as ATP, cancer cells are wasteful.
Cancer cells only partially break down sugar molecules. They overuse the first step of respiration, glycolysis. They frequently do not complete the second step, oxidative phosphorylation.
This results in only 2 molecules of ATP per each glucose molecule instead of the 36 or so ATPs healthy cells gain. As a result, cancer cells need to use a lot more sugar molecules to get enough energy to survive.
Unlike healthy cells that "burn" the entire molecule of sugar to capture a large amount of energy as ATP, cancer cells are wasteful.
Cancer cells only partially break down sugar molecules. They overuse the first step of respiration, glycolysis. They frequently do not complete the second step, oxidative phosphorylation.
This results in only 2 molecules of ATP per each glucose molecule instead of the 36 or so ATPs healthy cells gain. As a result, cancer cells need to use a lot more sugar molecules to get enough energy to survive.
introduction to WARBERG PHENOMENA:
WARBURG EFFECT Usually, cancer cells are highly glycolytic (glucose addiction) and take up more glucose than do normal cells from outside.
Otto Heinrich Warburg (; 8 October 1883 – 1 August 1970) In 1931 was awarded the Nobel Prize in Physiology for his "discovery of the nature and mode of action of the respiratory enzyme.
WARNBURG EFFECT : cancer cells under aerobic (well-oxygenated) conditions to metabolize glucose to lactate (aerobic glycolysis) is known as the Warburg effect. Warburg made the observation that tumor slices consume glucose and secrete lactate at a higher rate than normal tissues.
A brief information about the SCOP protein database used in bioinformatics.
The Structural Classification of Proteins (SCOP) database is a comprehensive and authoritative resource for the structural and evolutionary relationships of proteins. It provides a detailed and curated classification of protein structures, grouping them into families, superfamilies, and folds based on their structural and sequence similarities.
2. How is standing wave created?
When you pluck a string with both ends
fixed:
waves travel back and forth along it
waves get reflected by the fixed end
creating wave travelling in opposite
direction
Results in the superposition of two waves
both having the same wavelength,
frequency, and amplitude but travelling
in opposite direction
3. Refresher: Nodes and Antinodes
Node:
where amplitude = 0
Antinode:
where amplitude is maximum
6. Standing Wave & String
If we have a string of length L, starting at x= 0
and ends at x=L, with both ends fixed:
Only certain wavelengths will be able to fit
on the string in order to produce standing
wave
Which wavelengths???
Let’s do some math to find out.
7. Standing Wave & String (cont’d)
The following equation describes the
amplitude of standing wave:
For our string fixed at both ends x= 0 and x
=L:
Amplitude = 0 at the two ends
The argument of sin must 0
8. Standing Wave & String (cont’d)
Sin(2pi/λ*L) = 0
2pi/λ*L = m*pi m = a positive non-zero
integer
Rearrange the equation for wavelength:
λ=2L/m, m=1,2,3,4…
λ=2L, L,2L/3,L/2….
These are the wavelengths that a string with
both ends fixed can oscillate with in a
standing wave patternnormal modes of
9. Standing Wave & String (cont’d)
Frequencies corresponding to normal modes
of vibration:
v=λf rearrange
f=v/λ =v/(2L/m) = m/2L *v
substitute v = (T / μ)^1/2
10. Standing Wave & String (cont’d)
Fundamental frequency / first harmonic:
Lowest frequency & longest wavelength
λ=2L
Higher frequencies have higher m values and
are integer multiples of first harmonic
fm=mf1
11. A conceptual question
How many nodes are present between the
fixed ends of a string vibrating in at sixth
harmonic?
12. A conceptual question (cont’d)
Hint:
Find its frequency
Find its number of antinodes
Think about the relationship between
antinodes and nodes
13. A conceptual question (cont’d)
Solution:
A string at sixth harmonic:
fm = mf1 f6=6*f1
m=6 there are six antinodes
# of nodes = # of antinodes – 1
= m-1
=5
14. Another conceptual question
When the string player puts a finger down
tightly on the string:
1.How has the part of the string that vibrates
changed?
2.How does this change the sound waves
that the string makes?
3.How does this change the sound that is
heard?
16. Another conceptual question (cont’d)
Solution:
1.The part of the string that can vibrate
becomes shorter as the finger becomes the
new fixed end of the string.
2.The new sound wave is shorter, so its
frequency is higher.
3. It sounds higher / it has a higher pitch.
(because of the higher frequency)
17. A practical question
We have a stretched string of length 10m
with both ends fixed. Its frequency at its
fourth harmonic is 240Hz.
1)What is the longest wavelength standing
wave possible on this string?
2)What is its fundamental frequency?
18. A practical question(cont’d)
Hint:
We are given value of L:
Wavelength = 2L/m
At longest wavelength, how many
antinodes do we have?
We are given frequency at fourth harmonic:
fm=m*f1
How many antinodes do we have at fourth
harmonic?
19. A practical question (cont’d)
Solution:
1)Wavelength = 2L/m
at longest wavelength, there is 1 antinode, so m=1
L=10m
Wavelength = 2*(10m) / 1 = 20m = longest wavelength
2)fm=m*f1
at fourth harmonic, there are four antinodes, so m =4
f4=240Hz
f4=4*f1
f1=f4/4=240Hz/4=60Hz = fundamental frequency
