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Related Concept Videos

Sampling Methods: Overview01:06

Sampling Methods: Overview

3.7K
A sample refers to a smaller subset representative of a larger population. In analytical chemistry, studying or analyzing an entire population is often impractical or impossible. Therefore, samples are used to draw inferences and generalize the whole population. The sampling method selects individuals or items from a population to create a sample. Standard sampling methods include random, judgemental, systematic, stratified, and cluster sampling. 
In analytical chemistry, the choice of...
3.7K
Sampling Plans01:23

Sampling Plans

1.4K
Sampling is a crucial step in analytical chemistry, allowing researchers to collect representative data from a large population. Common sampling methods include random, judgmental, systematic, stratified, and cluster sampling.
Random sampling is a method where each member of the population has an equal chance of being selected for the sample. It involves selecting individuals randomly, often using random number generators or lottery-type methods. For example, when analyzing the properties of a...
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Sampling Methods: Sample Types01:18

Sampling Methods: Sample Types

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Sampling materials are classified into three main types: solid, liquid, and gas.
Solid samples include a variety of substances, such as sediments from water bodies, soil, metals, and biological tissues. Two standard methods for extracting sediments from water bodies are grab sampling and piston coring. Grab sampling involves using a device to collect a discrete sediment sample from the bottom of a water body with minimal disturbance. Grab samples do not always represent the entire area due to...
3.3K
Sampling Theorem01:15

Sampling Theorem

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In signal processing, the analysis of continuous-time signals, denoted as x(t), often involves sampling techniques to convert these signals into discrete-time signals. This process is essential for digital representation and manipulation. A critical component in sampling is the train of impulses, characterized by the sampling interval and the sampling frequency. The relationship between these parameters and the original signal's properties dictates the success of the sampling process.
1.7K
Sampling Continuous Time Signal01:11

Sampling Continuous Time Signal

917
In signal processing, a continuous-time signal can be sampled using an impulse-train sampling technique, followed by the zero-order hold method. Impulse-train sampling involves the use of a periodic impulse train, which consists of a series of delta functions spaced at regular intervals determined by the sampling period. When a continuous-time signal is multiplied by this impulse train, it generates impulses with amplitudes corresponding to the signal's values at the sampling points.
In the...
917
Stratified Sampling Method01:16

Stratified Sampling Method

11.7K
Sampling is a technique to select a portion (or subset) of the larger population and study that portion (the sample) to gain information about the population. The sampling method ensures that samples are drawn without bias and accurately represent the population. Because measuring the entire population in a study is not practical, researchers use samples to represent the population of interest.
To choose a stratified sample, divide the population into groups called strata and then take a...
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Methods of Soil Resampling to Monitor Changes in the Chemical Concentrations of Forest Soils
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Are stone analysis results different with repeated sampling?

Terence T N Lee1, Mohamed A Elkoushy1, Sero Andonian1

  • 1Division of Urology, Department of Surgery, McGill University Health Centre, Montreal, QC.

Canadian Urological Association Journal = Journal De L'Association Des Urologues Du Canada
|June 19, 2014
PubMed
Summary
This summary is machine-generated.

Subsequent kidney stone analyses revealed different compositions in 21.2% of patients. This highlights the importance of repeat stone analysis for accurate diagnosis and treatment planning.

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Area of Science:

  • Nephrology
  • Urology
  • Biochemistry

Background:

  • Kidney stone composition analysis is crucial for understanding underlying metabolic causes.
  • Variability in stone composition may impact treatment strategies.

Purpose of the Study:

  • To assess the frequency and types of changes in kidney stone composition upon repeat analysis.
  • To evaluate the clinical significance of differing stone compositions over time.

Main Methods:

  • Retrospective review of 303 patients with kidney stone analyses from 2006-2012.
  • Infrared spectroscopy used for centralized stone analysis.
  • Patients categorized by predominant stone type (≥60% component).

Main Results:

  • 118 patients (38.9%) had multiple stone analyses.
  • 21.2% of patients showed different stone compositions on subsequent analysis.
  • Common initial types included calcium oxalate (CaOx), calcium phosphate (CaP), and uric acid (UA).

Conclusions:

  • A significant proportion of patients exhibit changes in kidney stone composition over time.
  • Repeat stone analysis is valuable for refining diagnosis and management of nephrolithiasis.