This document discusses different measures of association used to quantify relationships between exposure and disease in epidemiology. It defines risk ratio, rate ratio, and odds ratio. Risk ratio compares the risk of disease between two groups. Rate ratio compares incidence rates between groups. Odds ratio is calculated from a 2x2 table and approximates the risk ratio. Examples are given to demonstrate calculating each measure using epidemiological data from published studies. The key measures - risk ratio, rate ratio, and odds ratio - are defined and formulas are provided to calculate them. Real epidemiological data is then used to demonstrate calculating these measures in practice.
Frequency Measures Used in EpidemiologyIntroductionIn e.docxMARRY7
Frequency Measures Used in Epidemiology
Introduction
In epidemiological studies, many qualitative variables have only two possible categories, such as
Alive or dead
Case or control
Exposed and unexposed
The frequency measures for dichotomous variable include:
Ratio
Proportion
Rate
( All the above 3 measure are based on the same formula: )
Ratios, Proportion, and Rates Compared
In a ratio, the values of x and y may be completely independent from each other or x is a part of y
For example , the gender of the children attending a specific program could be compared in one of the following ways:
Proportion is a ratio in which X is included in Y
For example , the gender of the children attending a specific program
Rate is a proportion that measures the occurrence of an event in a population over time
Rate = X
Ratios, Proportion, and Rates Compared
Example 1: The following table was part of an article published by Dr. Mshana and his colleagues. The title of this study is “Outbreak of a novel Enterobacter sp. carrying blaCTX-M-15 in a neonatal unit of a tertiary care hospital in Tanzania. ". Please use this table to answer the following questions.
Source: Mshana SE, Gerwing L, Minde M, Hain T, Domann E, Lyamuya E, et al. Outbreak of a novel Enterobacter sp. carrying blaCTX-M-15 in a neonatal unit of a tertiary care hospital in Tanzania. International journal of antimicrobial agents. 2011;38(3):265-9.
4
Example 1
What is the ratio of males to females? 7 : 10
What proportion of premature babies? 12/17=0.706
What proportion of patients were discharged? 11/17=0.647
What is the ratio of prematurity to birth asphyxia ? 12 : 5
Source: Mshana SE, Gerwing L, Minde M, Hain T, Domann E, Lyamuya E, et al. Outbreak of a novel Enterobacter sp. carrying blaCTX-M-15 in a neonatal unit of a tertiary care hospital in Tanzania. International journal of antimicrobial agents. 2011;38(3):265-9.
5
Example 2:
In 1989, 733,151 new cases of gonorrhea were reported among the United States civilian population. The 1989 mid-year U.S. civilian population was estimated to be 246,552,000. What is the 1989 gonorrhea incidence rate for the U.S. civilian population? (For these data we will use a value of 105 for 10n ).
Answer:
Incidence rate = X
Incidence rate = X = 297.4 per 100,000
6
Measures of association:
They are used to quantify the relationship between exposure and disease among two groups
They are used to compare the disease occurrence among one group with the disease occurrence in the another group
They include the following measures based on the study design:
Risk Ratio (RR):
It also called relative risk
It is used to compare the risk of health related events in two groups
The following formula cis used to calculate the RR:
A risk ratio of 1.0 indicates identical risk in the two groups
A risk ratio greater than 1.0 indicates an increased risk for the numerator group
A risk ratio greater than 1.0 ...
Frequency Measures Used in EpidemiologyIntroductionIn e.docxMARRY7
Frequency Measures Used in Epidemiology
Introduction
In epidemiological studies, many qualitative variables have only two possible categories, such as
Alive or dead
Case or control
Exposed and unexposed
The frequency measures for dichotomous variable include:
Ratio
Proportion
Rate
( All the above 3 measure are based on the same formula: )
Ratios, Proportion, and Rates Compared
In a ratio, the values of x and y may be completely independent from each other or x is a part of y
For example , the gender of the children attending a specific program could be compared in one of the following ways:
Proportion is a ratio in which X is included in Y
For example , the gender of the children attending a specific program
Rate is a proportion that measures the occurrence of an event in a population over time
Rate = X
Ratios, Proportion, and Rates Compared
Example 1: The following table was part of an article published by Dr. Mshana and his colleagues. The title of this study is “Outbreak of a novel Enterobacter sp. carrying blaCTX-M-15 in a neonatal unit of a tertiary care hospital in Tanzania. ". Please use this table to answer the following questions.
Source: Mshana SE, Gerwing L, Minde M, Hain T, Domann E, Lyamuya E, et al. Outbreak of a novel Enterobacter sp. carrying blaCTX-M-15 in a neonatal unit of a tertiary care hospital in Tanzania. International journal of antimicrobial agents. 2011;38(3):265-9.
4
Example 1
What is the ratio of males to females? 7 : 10
What proportion of premature babies? 12/17=0.706
What proportion of patients were discharged? 11/17=0.647
What is the ratio of prematurity to birth asphyxia ? 12 : 5
Source: Mshana SE, Gerwing L, Minde M, Hain T, Domann E, Lyamuya E, et al. Outbreak of a novel Enterobacter sp. carrying blaCTX-M-15 in a neonatal unit of a tertiary care hospital in Tanzania. International journal of antimicrobial agents. 2011;38(3):265-9.
5
Example 2:
In 1989, 733,151 new cases of gonorrhea were reported among the United States civilian population. The 1989 mid-year U.S. civilian population was estimated to be 246,552,000. What is the 1989 gonorrhea incidence rate for the U.S. civilian population? (For these data we will use a value of 105 for 10n ).
Answer:
Incidence rate = X
Incidence rate = X = 297.4 per 100,000
6
Measures of association:
They are used to quantify the relationship between exposure and disease among two groups
They are used to compare the disease occurrence among one group with the disease occurrence in the another group
They include the following measures based on the study design:
Risk Ratio (RR):
It also called relative risk
It is used to compare the risk of health related events in two groups
The following formula cis used to calculate the RR:
A risk ratio of 1.0 indicates identical risk in the two groups
A risk ratio greater than 1.0 indicates an increased risk for the numerator group
A risk ratio greater than 1.0 ...
Periodontal disease is a widely prevalent disease worldwide which often gets unnoticed or it often ignored due to its slowly progressive nature. It is of concern since it can cause irrepairable damage to tooth supporting structures if not early diagnosed or treated.
Understanding epidemiology study in medical statisticsLaud Randy Amofah
What is an Epidemiology?
Epidemiology studies the distribution of diseases within populations of people and factors related to them. Epidemiologist analyzes what causes disease outbreaks in order to treat existing diseases and prevent future outbreaks.
You have just finished a health education in-service to the communit.docxbriancrawford30935
You have just finished a health education in-service to the community on the hazards of smoking. A representative of the tobacco industry is present at your in-service and makes the following comment regarding your presentation: "You gave a nice presentation. However, I disagree with you that smoking can cause lung cancer. There is still not enough evidence to indicate that smoking can cause cancer."
Your task is as follows:
1. Respond to his statement and indicate why there is a cause-effect relationship between smoking and lung cancer using the
five criteria for causality
.
2. What is your interpretation of the evidence on how smoking affects lung cancer?
READ: FIVE CRITERIA FOR CAUSALITY
Assignment Expectations, in order to earn full credit:
Please write your paper in your own words. That is the only way I can evaluate your level
Analytic epidemiology is defined as the study of the determinants of disease or reasons for relatively high or low frequency in specific groups. Analytic epidemiology answers questions regarding why the rate is high or low in a particular group. Observations of differences lead to formation of hypotheses.
Analytic Studies
There are basically two types of studies: experimental and observational. In an experimental study, the exposure has not occurred yet. The investigator controls the exposure in the study groups and studies the impact. For example, he may immunize one group with an experimental vaccine that has been developed for a disease and compare the frequency with which the disease develops to the control group (which had no modification). In an observational study, the exposure has already occurred. The exposures and outcomes are observed and analyzed, not created experimentally. Observational studies are often more practical and continue to provide the major contribution to our understanding of diseases. There are two main types of observational studies: cohort (prospective) and case-control (retrospective) studies.
In a cohort study, a group of people who share a common experience within a defined time period (cohort) are categorized based upon their exposure status. For example, individuals at a work place where an asbestos exposure occurred would be considered a cohort. Another example would be individuals attending a wedding where a foodborne illness occurred. Cohort studies have well-defined populations. Often, cohort studies involve following a cohort over time in order to determine the rate at which a disease develops in relation to the exposure.
In a cohort study, relative risk is used to determine whether an association exists between an exposure and a disease. Relative risk is defined as ratio of the incidence rate among exposed individuals to the incidence rate among unexposed individuals.
To calculate the relative risk, you would use the following formula:
(a/a+b) / (c/c+d)
where:
a = the number of individuals with a disease who were exposed.
b = the number of individ.
Chapter 3Measures of Morbidity and Mortality Used in EpidemiolEstelaJeffery653
Chapter 3
Measures of Morbidity and Mortality Used in Epidemiology
Learning Objectives
Define and distinguish among ratios, proportions, and rates
Explain the term population at risk
Identify and calculate commonly used rates for morbidity, mortality, and natality
State the meanings and applications of incidence rates and prevalence
Learning Objectives (cont’d)
Discuss limitations of crude rates and alternative measures for crude rates
Apply direct and indirect methods to adjust rates
List situations where direct and indirect adjustment should be used
Overview of Epidemiologic Measures
Count
The simplest and most frequently performed quantitative measure in epidemiology.
Refers to the number of cases of a disease or other health phenomenon being studied.
Examples of Counts
Cases of influenza reported in Westchester County, New York, during January of a particular year.
Traffic fatalities in Manhattan in a 24-hour time period
College dorm students who had mono
Foreign-born stomach cancer patients
Ratio
The value obtained by dividing one quantity by another.
Consists of a numerator and a denominator.
The most general form has no specified relationship between numerator and denominator.
Rates, proportions, and percentages are also ratios.
Example of a
Simple Sex Ratio Calculation
A ratio may be expressed at = X/Y
Simple sex ratio (data from textbook)
Of 1,000 motorcycle fatalities, 950 victims are men and 50 are women.
Number of male cases 950
Number of female cases 50
19:1 male to female
=
=
Example of a
Demographic Sex Ratio Calculation
This ratio refers to the number of males per 100 females. In the U.S., the sex ratio in 2010 for the entire population was 96.7, indicating more females than males.
Number of male cases 151,781,326
Number of female cases 156,964,212
96.7
X 100 =
=
X 100
Example of a
Sex Ratio at Birth Calculation
The sex ratio at birth is defined as: (the number of male births divided by the number of female births) multiplied by 1,000.
Number of male births
Number of female births
X 1,000
Definition of Proportion
A measure that states a count relative to the size of the group.
A ratio in which the numerator is part of the denominator.
May be expressed as a percentage.
Uses of Proportions
Can demonstrate the magnitude of a problem.
Example: 10 dormitory students develop hepatitis. How important is this problem?
If only 20 students live in the dorm, 50% are ill.
If 500 students live in the dorm, 2% are ill.
Example of a Proportion
Calculate the proportion of African-American male deaths among African-American and white boys aged 5 to 14 years.
Rate
Definition: a ratio that consists of a numerator and a denominator and in which time forms part of the denominator.
Contains the following elements:
disease frequency
unit size of population
time period during which an event occurs
Crude death rate =
Number of deaths in a given y ...
Analytic StudiesThere are basically two types of studies experi.docxrossskuddershamus
Analytic Studies
There are basically two types of studies: experimental and observational. In an experimental study, the exposure has not occurred yet. The investigator controls the exposure in the study groups and studies the impact. For example, he may immunize one group with an experimental vaccine that has been developed for a disease and compare the frequency with which the disease develops to the control group (which had no modification). In an observational study, the exposure has already occurred. The exposures and outcomes are observed and analyzed, not created experimentally. Observational studies are often more practical and continue to provide the major contribution to our understanding of diseases. There are two main types of observational studies: cohort (prospective) and case-control (retrospective) studies.
In a cohort study, a group of people who share a common experience within a defined time period (cohort) are categorized based upon their exposure status. For example, individuals at a work place where an asbestos exposure occurred would be considered a cohort. Another example would be individuals attending a wedding where a foodborne illness occurred. Cohort studies have well-defined populations. Often, cohort studies involve following a cohort over time in order to determine the rate at which a disease develops in relation to the exposure.
In a cohort study, relative risk is used to determine whether an association exists between an exposure and a disease. Relative risk is defined as ratio of the incidence rate among exposed individuals to the incidence rate among unexposed individuals.
To calculate the relative risk, you would use the following formula: (a/a+b) / (c/c+d) where:
a = the number of individuals with a disease who were exposed.
b = the number of individuals without a disease who were exposed.
c = the number of individuals with a disease who were NOT exposed.
d = the number of individuals without a disease who were NOT exposed.
In a case-control study, the sample is based upon illness status, rather than exposure status. The researcher identifies a group of people who meet the case definition and a group of people who do not have the illness (controls). The objective is to determine if the two groups differ in the rate of exposure to a specific factor or factors.
In contrast to a cohort study, the total number of people exposed in a case-control study is unknown. Therefore, relative risk cannot be used. Instead, an odds ratio or risk ratio is used. An odds ratio measures the odds that an exposed individual will develop a disease in comparison to an unexposed individual. Please click the button below to learn how to calculate an odds ratio.
To calculate an odds ratio, you would use the following formula: ad/bc
where:
a = the number of individuals with a disease who were exposed.
b = the number of individuals without a disease who were exposed.
c = the number of individu.
Morbidity (from Latin morbidus: sick, unhealthy) refers to having a disease or a symptom of disease, or to the amount of disease within a population.
Any departure, subjective or objective from a state of physiological well being.
Morbidity also refers to medical problems caused by a treatment.
It is usually represented or estimated using prevalence or incidence.
Cohort, case control & survival studies-2014Ramnath Takiar
The presentation discusses about Cohort, Case-control and Survival studies. The concept of Cohort and Case-control studies is explained with the help of diagrams as perceived by me. Some discussion is also there about survival and relative survival. Appropriate data is also provided to explain about survival and relative survival.
Periodontal disease is a widely prevalent disease worldwide which often gets unnoticed or it often ignored due to its slowly progressive nature. It is of concern since it can cause irrepairable damage to tooth supporting structures if not early diagnosed or treated.
Understanding epidemiology study in medical statisticsLaud Randy Amofah
What is an Epidemiology?
Epidemiology studies the distribution of diseases within populations of people and factors related to them. Epidemiologist analyzes what causes disease outbreaks in order to treat existing diseases and prevent future outbreaks.
You have just finished a health education in-service to the communit.docxbriancrawford30935
You have just finished a health education in-service to the community on the hazards of smoking. A representative of the tobacco industry is present at your in-service and makes the following comment regarding your presentation: "You gave a nice presentation. However, I disagree with you that smoking can cause lung cancer. There is still not enough evidence to indicate that smoking can cause cancer."
Your task is as follows:
1. Respond to his statement and indicate why there is a cause-effect relationship between smoking and lung cancer using the
five criteria for causality
.
2. What is your interpretation of the evidence on how smoking affects lung cancer?
READ: FIVE CRITERIA FOR CAUSALITY
Assignment Expectations, in order to earn full credit:
Please write your paper in your own words. That is the only way I can evaluate your level
Analytic epidemiology is defined as the study of the determinants of disease or reasons for relatively high or low frequency in specific groups. Analytic epidemiology answers questions regarding why the rate is high or low in a particular group. Observations of differences lead to formation of hypotheses.
Analytic Studies
There are basically two types of studies: experimental and observational. In an experimental study, the exposure has not occurred yet. The investigator controls the exposure in the study groups and studies the impact. For example, he may immunize one group with an experimental vaccine that has been developed for a disease and compare the frequency with which the disease develops to the control group (which had no modification). In an observational study, the exposure has already occurred. The exposures and outcomes are observed and analyzed, not created experimentally. Observational studies are often more practical and continue to provide the major contribution to our understanding of diseases. There are two main types of observational studies: cohort (prospective) and case-control (retrospective) studies.
In a cohort study, a group of people who share a common experience within a defined time period (cohort) are categorized based upon their exposure status. For example, individuals at a work place where an asbestos exposure occurred would be considered a cohort. Another example would be individuals attending a wedding where a foodborne illness occurred. Cohort studies have well-defined populations. Often, cohort studies involve following a cohort over time in order to determine the rate at which a disease develops in relation to the exposure.
In a cohort study, relative risk is used to determine whether an association exists between an exposure and a disease. Relative risk is defined as ratio of the incidence rate among exposed individuals to the incidence rate among unexposed individuals.
To calculate the relative risk, you would use the following formula:
(a/a+b) / (c/c+d)
where:
a = the number of individuals with a disease who were exposed.
b = the number of individ.
Chapter 3Measures of Morbidity and Mortality Used in EpidemiolEstelaJeffery653
Chapter 3
Measures of Morbidity and Mortality Used in Epidemiology
Learning Objectives
Define and distinguish among ratios, proportions, and rates
Explain the term population at risk
Identify and calculate commonly used rates for morbidity, mortality, and natality
State the meanings and applications of incidence rates and prevalence
Learning Objectives (cont’d)
Discuss limitations of crude rates and alternative measures for crude rates
Apply direct and indirect methods to adjust rates
List situations where direct and indirect adjustment should be used
Overview of Epidemiologic Measures
Count
The simplest and most frequently performed quantitative measure in epidemiology.
Refers to the number of cases of a disease or other health phenomenon being studied.
Examples of Counts
Cases of influenza reported in Westchester County, New York, during January of a particular year.
Traffic fatalities in Manhattan in a 24-hour time period
College dorm students who had mono
Foreign-born stomach cancer patients
Ratio
The value obtained by dividing one quantity by another.
Consists of a numerator and a denominator.
The most general form has no specified relationship between numerator and denominator.
Rates, proportions, and percentages are also ratios.
Example of a
Simple Sex Ratio Calculation
A ratio may be expressed at = X/Y
Simple sex ratio (data from textbook)
Of 1,000 motorcycle fatalities, 950 victims are men and 50 are women.
Number of male cases 950
Number of female cases 50
19:1 male to female
=
=
Example of a
Demographic Sex Ratio Calculation
This ratio refers to the number of males per 100 females. In the U.S., the sex ratio in 2010 for the entire population was 96.7, indicating more females than males.
Number of male cases 151,781,326
Number of female cases 156,964,212
96.7
X 100 =
=
X 100
Example of a
Sex Ratio at Birth Calculation
The sex ratio at birth is defined as: (the number of male births divided by the number of female births) multiplied by 1,000.
Number of male births
Number of female births
X 1,000
Definition of Proportion
A measure that states a count relative to the size of the group.
A ratio in which the numerator is part of the denominator.
May be expressed as a percentage.
Uses of Proportions
Can demonstrate the magnitude of a problem.
Example: 10 dormitory students develop hepatitis. How important is this problem?
If only 20 students live in the dorm, 50% are ill.
If 500 students live in the dorm, 2% are ill.
Example of a Proportion
Calculate the proportion of African-American male deaths among African-American and white boys aged 5 to 14 years.
Rate
Definition: a ratio that consists of a numerator and a denominator and in which time forms part of the denominator.
Contains the following elements:
disease frequency
unit size of population
time period during which an event occurs
Crude death rate =
Number of deaths in a given y ...
Analytic StudiesThere are basically two types of studies experi.docxrossskuddershamus
Analytic Studies
There are basically two types of studies: experimental and observational. In an experimental study, the exposure has not occurred yet. The investigator controls the exposure in the study groups and studies the impact. For example, he may immunize one group with an experimental vaccine that has been developed for a disease and compare the frequency with which the disease develops to the control group (which had no modification). In an observational study, the exposure has already occurred. The exposures and outcomes are observed and analyzed, not created experimentally. Observational studies are often more practical and continue to provide the major contribution to our understanding of diseases. There are two main types of observational studies: cohort (prospective) and case-control (retrospective) studies.
In a cohort study, a group of people who share a common experience within a defined time period (cohort) are categorized based upon their exposure status. For example, individuals at a work place where an asbestos exposure occurred would be considered a cohort. Another example would be individuals attending a wedding where a foodborne illness occurred. Cohort studies have well-defined populations. Often, cohort studies involve following a cohort over time in order to determine the rate at which a disease develops in relation to the exposure.
In a cohort study, relative risk is used to determine whether an association exists between an exposure and a disease. Relative risk is defined as ratio of the incidence rate among exposed individuals to the incidence rate among unexposed individuals.
To calculate the relative risk, you would use the following formula: (a/a+b) / (c/c+d) where:
a = the number of individuals with a disease who were exposed.
b = the number of individuals without a disease who were exposed.
c = the number of individuals with a disease who were NOT exposed.
d = the number of individuals without a disease who were NOT exposed.
In a case-control study, the sample is based upon illness status, rather than exposure status. The researcher identifies a group of people who meet the case definition and a group of people who do not have the illness (controls). The objective is to determine if the two groups differ in the rate of exposure to a specific factor or factors.
In contrast to a cohort study, the total number of people exposed in a case-control study is unknown. Therefore, relative risk cannot be used. Instead, an odds ratio or risk ratio is used. An odds ratio measures the odds that an exposed individual will develop a disease in comparison to an unexposed individual. Please click the button below to learn how to calculate an odds ratio.
To calculate an odds ratio, you would use the following formula: ad/bc
where:
a = the number of individuals with a disease who were exposed.
b = the number of individuals without a disease who were exposed.
c = the number of individu.
Morbidity (from Latin morbidus: sick, unhealthy) refers to having a disease or a symptom of disease, or to the amount of disease within a population.
Any departure, subjective or objective from a state of physiological well being.
Morbidity also refers to medical problems caused by a treatment.
It is usually represented or estimated using prevalence or incidence.
Cohort, case control & survival studies-2014Ramnath Takiar
The presentation discusses about Cohort, Case-control and Survival studies. The concept of Cohort and Case-control studies is explained with the help of diagrams as perceived by me. Some discussion is also there about survival and relative survival. Appropriate data is also provided to explain about survival and relative survival.
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.
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.
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.
This pdf is about the Schizophrenia.
For more details visit on YouTube; @SELF-EXPLANATORY;
https://www.youtube.com/channel/UCAiarMZDNhe1A3Rnpr_WkzA/videos
Thanks...!
(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.
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 .
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.
1. Measures of Association
The key to epidemiologic analysis is comparison. Occasionally you might observe an
incidence rate among a population that seems high and wonder whether it is actually
higher than what should be expected based on, say, the incidence rates in other
communities. Or, you might observe that, among a group of case-patients in an outbreak,
several report having eaten at a particular restaurant. Is the restaurant just a popular one,
or have more case-patients eaten there than would be expected? The way to address that
concern is by comparing the observed group with another group that represents the
expected level.
A measure of association quantifies the relationship between exposure and disease among
the two groups. Exposure is used loosely to mean not only exposure to foods,
mosquitoes, a partner with a sexually transmissible disease, or a toxic waste dump, but
also inherent characteristics of persons (for example, age, race, sex), biologic
characteristics (immune status), acquired characteristics (marital status), activities
(occupation, leisure activities), or conditions under which they live (socioeconomic status
or access to medical care).
The measures of association described in the following section compare disease
occurrence among one group with disease occurrence in another group. Examples of
measures of association include risk ratio (relative risk), rate ratio, odds ratio, and
proportionate mortality ratio.
Risk ratio
Definition of risk ratio
A risk ratio (RR), also called relative risk, compares the risk of a health event (disease,
injury, risk factor, or death) among one group with the risk among another group. It does
so by dividing the risk (incidence proportion, attack rate) in group 1 by the risk
(incidence proportion, attack rate) in group 2. The two groups are typically differentiated
by such demographic factors as sex (e.g., males versus females) or by exposure to a
suspected risk factor (e.g., did or did not eat potato salad). Often, the group of primary
interest is labeled the exposed group, and the comparison group is labeled the unexposed
group.
Method for Calculating risk ratio
The formula for risk ratio (RR) is:
Risk of disease (incidence proportion, attack rate) in group of primary
interest
2. Risk of disease (incidence proportion, attack rate) in comparison group
A risk ratio of 1.0 indicates identical risk among the two groups. A risk ratio greater than
1.0 indicates an increased risk for the group in the numerator, usually the exposed group.
A risk ratio less than 1.0 indicates a decreased risk for the exposed group, indicating that
perhaps exposure actually protects against disease occurrence.
EXAMPLES: Calculating Risk Ratios
Example A: In an outbreak of tuberculosis among prison inmates in South Carolina in
1999, 28 of 157 inmates residing on the East wing of the dormitory developed
tuberculosis, compared with 4 of 137 inmates residing on the West wing.(11) These data
are summarized in the two-by-two table so called because it has two rows for the
exposure and two columns for the outcome. Here is the general format and notation.
Table 3.12A General Format and Notation for a Two-by-Two Table
Ill Well Total
Total a + c = V1 b + d = V0 T
Exposed A b a + b = H1
Unexposed C d c + d = H0
In this example, the exposure is the dormitory wing and the outcome is tuberculosis)
illustrated in Table 3.12B. Calculate the risk ratio.
Table 3.12B Incidence of Mycobacterium Tuberculosis Infection Among
Congregated, HIV-Infected Prison Inmates by Dormitory Wing — South Carolina,
1999
Developed tuberculosis?
Yes No Total
Total 32 262 T = 294
East wing a = 28 b = 129 H1 = 157
West wing c = 4 d = 133 H0 = 137
Data Source: McLaughlin SI, Spradling P, Drociuk D, Ridzon R, Pozsik CJ, Onorato I. Extensive transmission of Mycobacterium tuberculosis among
congregated, HIV-infected prison inmates in South Carolina, United States. Int J Tuberc Lung Dis 2003;7:665–672.
To calculate the risk ratio, first calculate the risk or attack rate for each group. Here are
the formulas:
Attack Rate (Risk)
Attack rate for exposed = a ⁄ a+b
Attack rate for unexposed = c ⁄ c+d
For this example:
3. Risk of tuberculosis among East wing residents = 28 ⁄ 157 = 0.178 = 17.8%
Risk of tuberculosis among West wing residents = 4 ⁄ 137 = 0.029 = 2.9%
The risk ratio is simply the ratio of these two risks:
Risk ratio = 17.8 ⁄ 2.9 = 6.1
Thus, inmates who resided in the East wing of the dormitory were 6.1 times as likely to
develop tuberculosis as those who resided in the West wing.
EXAMPLES: Calculating Risk Ratios (Continued)
Example B: In an outbreak of varicella (chickenpox) in Oregon in 2002, varicella was
diagnosed in 18 of 152 vaccinated children compared with 3 of 7 unvaccinated children.
Calculate the risk ratio.
Table 3.13 Incidence of Varicella among Schoolchildren in 9 Affected Classrooms —
Oregon, 2002
Varicella Non-case Total
Total 21 138 159
Vaccinated a = 18 b = 134 152
Unvaccinated c = 3 d = 4 7
Data Source: Tugwell BD, Lee LE, Gillette H, Lorber EM, Hedberg K, Cieslak PR. Chickenpox outbreak in a highly vaccinated school population.
Pediatrics 2004 Mar;113(3 Pt 1):455–459.
Risk of varicella among vaccinated children = 18 ⁄ 152 = 0.118 = 11.8%
Risk of varicella among unvaccinated children = 3 ⁄ 7 = 0.429 = 42.9%
Risk ratio = 0.118 ⁄ 0.429 = 0.28
The risk ratio is less than 1.0, indicating a decreased risk or protective effect for the
exposed (vaccinated) children. The risk ratio of 0.28 indicates that vaccinated children
were only approximately one-fourth as likely (28%, actually) to develop varicella as were
unvaccinated children.
Rate ratio
A rate ratio compares the incidence rates, person-time rates, or mortality rates of two
groups. As with the risk ratio, the two groups are typically differentiated by demographic
factors or by exposure to a suspected causative agent. The rate for the group of primary
interest is divided by the rate for the comparison group.
4. Rate ratio =
Rate for group of primary
interest
Rate for comparison group
The interpretation of the value of a rate ratio is similar to that of the risk ratio. That is, a
rate ratio of 1.0 indicates equal rates in the two groups, a rate ratio greater than 1.0
indicates an increased risk for the group in the numerator, and a rate ratio less than 1.0
indicates a decreased risk for the group in the numerator.
EXAMPLE: Calculating Rate Ratios (Continued)
Public health officials were called to investigate a perceived increase in visits to ships’
infirmaries for acute respiratory illness (ARI) by passengers of cruise ships in Alaska in
1998.(13) The officials compared passenger visits to ship infirmaries for ARI during
May–August 1998 with the same period in 1997. They recorded 11.6 visits for ARI per
1,000 tourists per week in 1998, compared with 5.3 visits per 1,000 tourists per week in
1997. Calculate the rate ratio.
Rate ratio = 11.6 ⁄ 5.3 = 2.2
Passengers on cruise ships in Alaska during May–August 1998 were more than twice as
likely to visit their ships’ infirmaries for ARI than were passengers in 1997. (Note: Of 58
viral isolates identified from nasal cultures from passengers, most were influenza A,
making this the largest summertime influenza outbreak in North America.)
Exercise 3.7
Table 3.14 illustrates lung cancer mortality rates for persons who continued to smoke and
for smokers who had quit at the time of follow-up in one of the classic studies of smoking
and lung cancer conducted in Great Britain.
Using the data in Table 3.14, calculate the following:
1. Rate ratio comparing current smokers with nonsmokers
2. Rate ratio comparing ex-smokers who quit at least 20 years ago with nonsmokers
3. What are the public health implications of these findings?
Cigarette smoking status Lung cancer deaths Rate per 1000 person-years Rate Ratio
Current smokers 133 1.30
5. Table 3.14 Number and Rate (Per 1,000 Person-years) of Lung Cancer Deaths for
Current Smokers and Ex-smokers by Years Since Quitting, Physician Cohort Study
— Great Britain, 1951–1961
Data Source: Doll R, Hill AB. Mortality in relation to smoking: 10 years’ observation of British doctors. Brit Med J 1964; 1:1399–1410, 1460–1467.
Odds ratio
An odds ratio (OR) is another measure of association that quantifies the relationship
between an exposure with two categories and health outcome. Referring to the four cells
in Table 3.15, the odds ratio is calculated as
Odds ratio = (
a
b
)(
c
d
) = ad ⁄ bc
where
a = number of persons exposed and with disease
b = number of persons exposed but without disease
c = number of persons unexposed but with disease
d = number of persons unexposed: and without disease
a+c = total number of persons with disease (case-patients)
b+d = total number of persons without disease (controls)
The odds ratio is sometimes called the cross-product ratio because the numerator is
based on multiplying the value in cell “a” times the value in cell “d,” whereas the
denominator is the product of cell “b” and cell “c.” A line from cell “a” to cell “d” (for
the numerator) and another from cell “b” to cell “c” (for the denominator) creates an x or
cross on the two-by-two table.
For ex-smokers, years since quitting:
<5 years 5 0.67 9.6
5–9 years 7 0.49 7.0
10–19 years 3 0.18 2.6
20+ years 2 0.19
Nonsmokers 3 0.07 1.0 (reference group)
6. Table 3.15 Exposure and Disease in a Hypothetical Population of 10,000 Persons
Disease No Disease Total Risk
Total 180 9,820 10,000
Exposed a = 100 b = 1,900 2,000 5.0%
Not Exposed c = 80 d = 7,920 8,000 1.0%
EXAMPLE: Calculating Odds Ratios
Use the data in Table 3.15 to calculate the risk and odds ratios.
1. Risk ratio
5.0 ⁄ 1.0 = 5.0
2. Odds ratio
(100 × 7,920) ⁄ (1,900 × 80) = 5.2
Notice that the odds ratio of 5.2 is close to the risk ratio of 5.0. That is one of the
attractive features of the odds ratio — when the health outcome is uncommon, the odds
ratio provides a reasonable approximation of the risk ratio. Another attractive feature is
that the odds ratio can be calculated with data from a case-control study, whereas neither
a risk ratio nor a rate ratio can be calculated.
In a case-control study, investigators enroll a group of case-patients (distributed in cells a
and c of the two-by-two table), and a group of non-cases or controls (distributed in cells b
and d).
The odds ratio is the measure of choice in a case-control study (see Lesson 1). A case-
control study is based on enrolling a group of persons with disease (“case-patients”) and a
comparable group without disease (“controls”). The number of persons in the control
group is usually decided by the investigator. Often, the size of the population from which
the case-patients came is not known. As a result, risks, rates, risk ratios or rate ratios
cannot be calculated from the typical case-control study. However, you can calculate an
odds ratio and interpret it as an approximation of the risk ratio, particularly when the
disease is uncommon in the population.
Exercise 3.8
Calculate the odds ratio for the tuberculosis data in Table 3.12. Would you say that your
odds ratio is an accurate approximation of the risk ratio? (Hint: The more common the
disease, the further the odds ratio is from the risk ratio.)