Differential interference contrast microscopy

Climate of Chicago

The Climate of Chicago is classified as humid continental (Köppen climate classification Dfa), characterized by four distinct seasons and significant variations in temperature and precipitation between seasons. Chicago, located in the United States in the state of Illinois, experiences cold, snowy winters and warm, humid summers. The city's location near Lake Michigan significantly influences its weather patterns, contributing to the so-called "lake effect" that can amplify snowfall and moderate temperature extremes.

Temperature

Chicago's winters are cold, with average January temperatures hovering around 23°F (-5°C). Snowfall is common, with the city receiving an average of 36 inches (91 cm) per year. The coldest temperature ever recorded in Chicago was -27°F (-33°C) on January 20, 1985.

Summers in Chicago are warm and humid, with average July temperatures around 75°F (24°C). However, heatwaves can push temperatures above 90°F (32°C) on several days. The highest temperature ever recorded in Chicago was 105°F (41°C) on July 24, 1934.

Precipitation

Chicago receives an average annual precipitation of about 36 inches (914 mm), distributed fairly evenly throughout the year. Spring and summer are the wettest seasons, often featuring thunderstorms. Winter precipitation typically falls as snow, with significant variability in snowfall from year to year.

Wind

Chicago is famously known as the "Windy City," though this nickname originally referred to its political climate rather than its physical one. Nevertheless, Chicago does experience a significant amount of wind, partly due to its flat, open landscape. The average wind speed in the city is 10.3 mph (16.6 km/h).

Lake Effect

Lake Michigan has a profound impact on the climate of Chicago, especially in the winter. The lake effect can cause sudden snowstorms on the leeward side of the lake, including Chicago. This phenomenon occurs when cold air moves over the relatively warmer waters of Lake Michigan, picking up moisture and heat before depositing it as snow onshore. The lake also helps to moderate temperature extremes, keeping Chicago slightly warmer in the winter and cooler in the summer compared to areas further inland.

Climate Change

The climate of Chicago is expected to change in the coming decades, with predictions indicating warmer temperatures, more extreme weather events, and changes in precipitation patterns. These changes could have significant impacts on the city's infrastructure, ecosystems, and residents' health.

See Also

• Geography of Chicago
• Environment of Chicago
• Urban heat island

Differential Interference Contrast Microscopy

Differential Interference Contrast Microscopy (DIC) is a microscopy technique used to enhance the contrast in unstained, transparent samples. DIC microscopy works by utilizing polarized light to produce high-contrast images of specimens with slight differences in refractive indices. This technique is particularly useful in biological and medical research, allowing for the detailed observation of live cells and tissues without the need for dyes or stains.

Principles

DIC microscopy involves splitting a beam of light into two beams that travel slightly different paths through the specimen. These beams, when recombined, interfere with each other in such a way that differences in the optical path length of the specimen are converted into variations in intensity in the image. This process creates a pseudo-3D effect, giving the illusion of depth and making fine details within the specimen more visible.

Applications

DIC microscopy is widely used in various fields of biological and medical research. It is particularly valuable for examining cellular structures, such as the nucleus, organelles, and the cytoskeleton, as well as for observing processes like cell division, motility, and intracellular transport. Its ability to image live cells without staining is a significant advantage, as it allows researchers to observe biological processes in their natural state.

Advantages and Limitations

One of the main advantages of DIC microscopy is its ability to produce high-contrast, detailed images of transparent specimens without the need for staining. However, it is important to note that DIC images are not true representations of specimen structure but rather visualizations of differences in optical path length. Additionally, DIC microscopy requires specialized equipment and can be more complex to set up and interpret than other microscopy techniques.

See Also

• Microscopy
• Polarized Light Microscopy
• Phase Contrast Microscopy