Gravity is a fundamental force that causes objects with mass to accelerate towards each other. Kepler determined that planetary orbits are elliptical rather than circular, and that planets move faster when closer to the sun. Newton realized that the force causing apples and the moon to move was gravity. His law of universal gravitation stated that the gravitational force between objects is directly proportional to their masses and inversely proportional to the square of the distance between them. Gravity creates gravitational fields around massive objects that other objects interact with. Tides are caused by differences in the moon's gravitational pull on the near and far sides of Earth.
Earliest Galaxies in the JADES Origins Field: Luminosity Function and Cosmic ...Sérgio Sacani
We characterize the earliest galaxy population in the JADES Origins Field (JOF), the deepest
imaging field observed with JWST. We make use of the ancillary Hubble optical images (5 filters
spanning 0.4−0.9µm) and novel JWST images with 14 filters spanning 0.8−5µm, including 7 mediumband filters, and reaching total exposure times of up to 46 hours per filter. We combine all our data
at > 2.3µm to construct an ultradeep image, reaching as deep as ≈ 31.4 AB mag in the stack and
30.3-31.0 AB mag (5σ, r = 0.1” circular aperture) in individual filters. We measure photometric
redshifts and use robust selection criteria to identify a sample of eight galaxy candidates at redshifts
z = 11.5 − 15. These objects show compact half-light radii of R1/2 ∼ 50 − 200pc, stellar masses of
M⋆ ∼ 107−108M⊙, and star-formation rates of SFR ∼ 0.1−1 M⊙ yr−1
. Our search finds no candidates
at 15 < z < 20, placing upper limits at these redshifts. We develop a forward modeling approach to
infer the properties of the evolving luminosity function without binning in redshift or luminosity that
marginalizes over the photometric redshift uncertainty of our candidate galaxies and incorporates the
impact of non-detections. We find a z = 12 luminosity function in good agreement with prior results,
and that the luminosity function normalization and UV luminosity density decline by a factor of ∼ 2.5
from z = 12 to z = 14. We discuss the possible implications of our results in the context of theoretical
models for evolution of the dark matter halo mass function.
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.
Seminar of U.V. Spectroscopy by SAMIR PANDASAMIR PANDA
Spectroscopy is a branch of science dealing the study of interaction of electromagnetic radiation with matter.
Ultraviolet-visible spectroscopy refers to absorption spectroscopy or reflect spectroscopy in the UV-VIS spectral region.
Ultraviolet-visible spectroscopy is an analytical method that can measure the amount of light received by the analyte.
Comparing Evolved Extractive Text Summary Scores of Bidirectional Encoder Rep...University of Maribor
Slides from:
11th International Conference on Electrical, Electronics and Computer Engineering (IcETRAN), Niš, 3-6 June 2024
Track: Artificial Intelligence
https://www.etran.rs/2024/en/home-english/
THE IMPORTANCE OF MARTIAN ATMOSPHERE SAMPLE RETURN.Sérgio Sacani
The return of a sample of near-surface atmosphere from Mars would facilitate answers to several first-order science questions surrounding the formation and evolution of the planet. One of the important aspects of terrestrial planet formation in general is the role that primary atmospheres played in influencing the chemistry and structure of the planets and their antecedents. Studies of the martian atmosphere can be used to investigate the role of a primary atmosphere in its history. Atmosphere samples would also inform our understanding of the near-surface chemistry of the planet, and ultimately the prospects for life. High-precision isotopic analyses of constituent gases are needed to address these questions, requiring that the analyses are made on returned samples rather than in situ.
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 .
2. Gravity is the tendency of objects with
mass to accelerate towards each other.
Gravity is one of the four fundametal
forces in nature.
What is gravity?
3. Mass is a physical property of matter
that explains how much matter is in an
object.
Weight is a force which is calculated by
multipying the acceleration of gravity
times mass.
Mass does not change while weight
changes when gravity changes.
Mass and Weight
4. Kepler’s Laws
Kepler determined that the orbits of the
planets were not perfect circles, but
ellipses, with the Sun at one focus.
Sun
Planet
5. Kepler’s Second Law
Kepler determined that a planet moves
faster when near the Sun, and slower
when far from the Sun.
Sun
Planet
Faster
Slower
6. The Apple & the Moon
Isaac Newton realized that the motion of
a falling apple and the motion of the
Moon were both actually the same
motion, caused by the same force -
the gravitational force.
8. At the Earth’s Surface
Newton knew that the gravitational
force on the apple equals the apple’s
weight, mg, where g = 9.8 m/s2.
W = mg
9. Weight of the Moon
Newton reasoned that the centripetal
force on the moon was also supplied by
the Earth’s gravitational force.
Fc = mg
?
10. Universal Gravitation
From this, Newton reasoned that the
strength of the gravitational force is not
constant, in fact, the magnitude of the
force is inversely proportional to the
square of the distance between the
objects.
11. Universal Gravitation
Newton concluded that the gravitational
force is:
Directly proportional to the masses of
both objects.
Inversely proportional to the distance
between the objects.
12. Law of Universal Gravitation
In symbols, Newton’s Law of
Universal Gravitation is:
Fgrav = G
Where G is a constant of proportionality.
G = 6.67 x 10-11 N m2/kg2
m1m2
r 2
13. Inverse Square Law
Newton’s Law of Universal Gravitation
is often called an inverse square law,
since the force is inversely proportional
to the square of the distance.
14. The Gravitational Field
During the 19th century, the notion of
the “field” entered physics (via Michael
Faraday).
Objects with mass create an invisible
disturbance in the space around
them that is felt by other massive
objects - this is a gravitational field.
15. The Gravitational Field
So, since the Sun is very massive, it
creates an intense gravitational field
around it, and the Earth responds to
the field. No more “action at a
distance.”
16. Gravitational Field Strength
To measure the strength of the
gravitational field at any point, measure
the gravitational force, F, exerted on
any “test mass”, m.
Gravitational Field Strength, g = F/m
17. Gravitational Field Strength
Near the surface of the Earth, g = F/m =
9.8 N/kg = 9.8 m/s2.
In general, g = GM/r2, where M is the
mass of the object creating the field, r is
the distance from the object’s center,
and G = 6.67 x10-11 Nm2/kg2.
18. Gravitational Force
If g is the strength of the gravitational
field at some point, then the
gravitational force on an object of mass
m at that point is Fgrav = mg.
If g is the gravitational field strength at
some point (in N/kg), then the free fall
acceleration at that point is also g (in
m/s2).
19. Earth’s Tides
There are 2 high tides and 2 low tides
per day.
The tides follow the Moon.
20. Why Two Tides?
Tides are caused by the stretching of a
planet.
Stretching is caused by a difference in forces
on the two sides of an object.
Since gravitational force depends on
distance, there is more gravitational force on
the side of Earth closest to the Moon and less
gravitational force on the side of Earth farther
from the Moon.
22. Why the Moon?
The Sun’s gravitational pull on Earth is
much larger than the Moon’s
gravitational pull on Earth. So why do
the tides follow the Moon and not the
Sun?
23. Why the Moon?
Since the Sun is much farther from
Earth than the Moon, the difference in
distance across Earth is much less
significant for the Sun than the Moon,
therefore the difference in gravitational
force on the two sides of Earth is less
for the Sun than for the Moon (even
though the Sun’s force on Earth is
more).
24. Why the Moon?
The Sun does have a small effect on
Earth’s tides, but the major effect is due
to the Moon.
