This document provides instructions for a science experiment to measure the force needed to bend drinking straws of different lengths. Students will collect straws of full length, half length, and quarter length. They will then measure the length of each straw and record the force required to bend it using a spring balance. By comparing the results, students can determine whether longer or shorter straws require more force to bend, relating this to whether long or short bones break more easily in the human skeleton. The purpose is to use straws as a model for bones to safely conduct the experiment and observe the effects of length on structural strength.
Summary
Definition
Friction is a catchall word that refers to any force that resists relative tangential motion (or intended motion).
"Relative tangential motion" is a fancy way to say "slipping" or "sliding".
Its direction is opposite the relative velocity (or intended velocity).
Types
Dry friction
The resistive force between solid surfaces in contact that resists their relative tangential motion.
"Friction" is often synonymous with "dry friction".
Viscous friction-
for more.......... go to this link :)
http://physics.info/friction/summary.shtml
Summary
Definition
Friction is a catchall word that refers to any force that resists relative tangential motion (or intended motion).
"Relative tangential motion" is a fancy way to say "slipping" or "sliding".
Its direction is opposite the relative velocity (or intended velocity).
Types
Dry friction
The resistive force between solid surfaces in contact that resists their relative tangential motion.
"Friction" is often synonymous with "dry friction".
Viscous friction-
for more.......... go to this link :)
http://physics.info/friction/summary.shtml
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 .
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Multi-source connectivity as the driver of solar wind variability in the heli...Sérgio Sacani
The ambient solar wind that flls the heliosphere originates from multiple
sources in the solar corona and is highly structured. It is often described
as high-speed, relatively homogeneous, plasma streams from coronal
holes and slow-speed, highly variable, streams whose source regions are
under debate. A key goal of ESA/NASA’s Solar Orbiter mission is to identify
solar wind sources and understand what drives the complexity seen in the
heliosphere. By combining magnetic feld modelling and spectroscopic
techniques with high-resolution observations and measurements, we show
that the solar wind variability detected in situ by Solar Orbiter in March
2022 is driven by spatio-temporal changes in the magnetic connectivity to
multiple sources in the solar atmosphere. The magnetic feld footpoints
connected to the spacecraft moved from the boundaries of a coronal hole
to one active region (12961) and then across to another region (12957). This
is refected in the in situ measurements, which show the transition from fast
to highly Alfvénic then to slow solar wind that is disrupted by the arrival of
a coronal mass ejection. Our results describe solar wind variability at 0.5 au
but are applicable to near-Earth observatories.
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z = 11.5 − 15. These objects show compact half-light radii of R1/2 ∼ 50 − 200pc, stellar masses of
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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
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Since the loophole-free Bell experiments of 2020 and the Nobel prizes in physics of 2022, critics of Bell's work have retreated to the fortress of super-determinism. Now, super-determinism is a derogatory word - it just means "determinism". Palmer, Hance and Hossenfelder argue that quantum mechanics and determinism are not incompatible, using a sophisticated mathematical construction based on a subtle thinning of allowed states and measurements in quantum mechanics, such that what is left appears to make Bell's argument fail, without altering the empirical predictions of quantum mechanics. I think however that it is a smoke screen, and the slogan "lost in math" comes to my mind. I will discuss some other recent disproofs of Bell's theorem using the language of causality based on causal graphs. Causal thinking is also central to law and justice. I will mention surprising connections to my work on serial killer nurse cases, in particular the Dutch case of Lucia de Berk and the current UK case of Lucy Letby.
Laboratory activity do long bones break more easily than short bones
1. MENTARI INTERCULTURAL SCHOOL
IB MIDDLE YEARS PROGRAM
Assessment Objectives:
• Identify the parts and function of human skeleton system.
• Compare bones of the human skeleton system.
• Measure the force needed to make the straw bend.
Introduction: In this experiment, you will use drinking straws instead of real bones. You will measure the force
needed to make the straw bend, rather than break. The diagram shows how you will find the force needed to bend
the straw. You will use a spring balance. It’s easiest to do this in pairs. One of you pulls the spring balance. The other
one notes the reading on the spring balance when the straw collapses.
Data Table [Level 5-6]
QUESTION:
What conclusion can you make from your results? [Level7-8]
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Reference:
Jones, M., Fellowes-Freeman, D., & Sang, D. (2013). Cambridge Checkpoint Science Coursebook 7. United
Kingdom: Cambridge University Press 2013.
Student Name: CN 2nd
Term SY 2018 - 2019
Grade Level: 8 Date: Parent’s Signature
Section: Teacher: Armand Anthony L. Galicia
Formative Assessment – Laboratory Activity
Unit/Topic: Do Long Bones Break More Easily Than Short
Bones?
The Differences of the Forces Needed to Bend the Straw
Length of Straw in [cm]
Force Needed to Bend the
Straw [N]
Procedures:
1. Collect two identical straws. Keep one full length. Cut one
in half. Cut one of the halves into half again.
2. Measure the length of a full-length straw, in cm. Fill in your
measurement in the first row of your results table.
3. Find the force needed to make a full length straw bend.
Write your result in your results table.
4. Now repeat steps 3 and 4 with the half-length straw and the
one-quarter length straw.