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Project

1-Wire Weather Station

The weather station in this project is quite basic, measuring only temperature, pressure, and humidity, but it may be easily expanded to measure other weather components, such as wind speed and rainfall. The design is based on using a series of…

Project

3x3x3 LED Cube

LEDs (light-emitting diodes) are rectifying semiconductor devices that convert electrical energy into electromagnetic radiation. You can use these devices to create a 3-dimensional light display. LED cubes require some care and good soldering skills…

Project

Chatbot, an Artificially Intelligent Microcontroller

The term "Chatbot" is used for a computer or computer program that is made to emulate some form of human intelligence through conversation. In this project, you will learn how easy it is to make a specific microcontroller—an Arduino™ Uno—seem as…

Project

Heart-Rate Monitor

This project uses a sensitive light-detecting resistor to detect small changes in the light beaming through your finger as your blood pumps through tiny arteries in the finger. This device is not the same as the heart-rate monitors typically used in…

Project

Text-Controlled RGB LED

A red, green, and blue (RGB) light-emitting diode (LED) is a useful electronic component that can produce visible light in a variety of colors. This is done by varying the intensity of the light output of the three different color LED elements (red,…

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from article Moving-target indication

Diagram of radar system with moving-target indication.

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from article Amplitude-modulation radio

An example of a low-frequency broadcast antenna. This three-tower array is connected to the Beidweiler long-wave transmitter (located in Beidweiler, Luxembourg), which broadcasts at a frequency of 234 kHz. Each tower is 290 m (951 ft) tall. (Photo…

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from article Borrelia

A digitally colorized scanning electron micrograph of a grouping of numerous Borrelia burgdorferi bacteria. The B. burgdorferi pathogen is responsible for causing Lyme disease, which is transmitted to humans by way of a tick bite. Borrelia…

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from article Cognition

The internal structures and processes that constitute the basis for cognition emanate from the brain (shown here in a colorized magnetic resonance image). (Credit: Shutterstock)

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from article Cognition

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from article Cognition

Light micrograph of Purkinje neurons (light blue) in the cerebellum. Nerve cells of the brain act collectively to process information needed for proper cognitive functioning. (Credit: Steve Gschmeissner/Science Photo Library/Alamy Stock Photo)

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from article Oral glands

The three major bilateral pairs of salivary oral glands found in mammals: the parotid, submandibular, and sublingual glands. (Image from A. L. Mescher, Junqueira's Basic Histology, 13th edition, McGraw-Hill, New York, 2013)

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from article Xiphosurida

Segmentation of Limulus polyphemus. Inconclusive evidence indicates that there are 15 segments (6 in the prosoma, 9 in the opisthosoma). The telson (XV) may be a terminal spine that has become articulated and has incorporated the anus into its base.

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from article Xiphosurida

Phylogeny and representative species of the class Xiphosura, including the order Xiphosurida and its sister group, synziphosurines (a paraphyletic stem group).

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from article Xiphosurida

Paleolimulus signatus, a limuline xiphosurid from the Permian of Kansas, showing appendages and book gills. Length of specimen: 1.25 cm (0.5 in.).

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from article Xiphosurida

Carapaces of adult male Limulina. (a) Limulus polyphemus. (b) Tachypleus tridentatus. (c) Carcinoscorpius rotundicauda.

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from article Xiphosurida

Embryonic and larval development of Limulus polyphemus. (a) Early embryo, side view. (b) Late embryo. (c) Yolk-filled digestive tract of larva. Note the segmentation of yolk in the newly hatched stage and the six lobes of digestive gland. (d) First…

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from article Xiphosurida

Morphology of adult male Limulus polyphemus. (a) Dorsal view. (b) Ventral view, appendages not shown. (c) Cross section through prosoma showing internal anatomy. (d) Posterior view. (e) Lateral view.

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from article Feather

Typical flight feather. (a) Full view. (b) Detail of base. (c) Detail of vane. (After J. Van Tyne and A. J. Berger, Fundamentals of Ornithology, 2d ed., John Wiley and Sons, 1976)

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from article Feather

Parts of three barbs from a vaned feather, showing the hooking mechanism of the overlapping barbules. (After J. C. Welty, The Life of Birds, Saunders, 1962)

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from article Feather

Types of feathers, (a) Filoplume. (b) Vane or contour. (c) Down. (d) Semiplume. (After J. C. Welty, The Life of Birds, Saunders, 1962)

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from article Feather

Section through growing feather follicle. (After R. I. C. Spearman, The keratinization of epidermal scales, feathers, and hairs, Biol. Rev., 41:59–69, 1966)

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from article Tay-Sachs disease

Healthy neuron (top) and neuron affected by Tay-Sachs disease (bottom). Defective hexosaminidase A enzyme activities in the case of Tay-Sachs disease allow lipid substrates to be stored in lysosomal compartments. This abnormal storage becomes toxic,…

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from article Tay-Sachs disease

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from article Tay-Sachs disease

Tay-Sachs disease results from mutations of a gene known as the HEX A gene, which encodes the α-subunit of the hexosaminidase A enzyme. When both partners are mutation carriers, each pregnancy has a 25% chance of being affected. (Copyright ©…

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from article Chromatophore

Chromatophores in the skin of the cephalopod squid Loligo (Doryteuthis) plei. Large brownish chromatophores are encircled by medium-sized red chromatophores, and small yellow chromatophores are interspersed throughout the skin. Each chromatophore…

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from article Chromatophore

Skin of the common prawn Palaemon (Leander) serratus, with red and white chromatophores showing a twofold effect upon injecting the prawn with a sinus-gland extract. Red pigment becomes less dispersed and some is converted into a blue color diffused…

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from article Chromatophore

Skin of a squirrelfish (Holocentrus adscensionis) with chromatophores as seen by transmitted light. Note the few large finely branched melanophores and many small erythrophores (seen as balls of concentrated red) over a screen of larger oval…

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from article Chromatophore

A squirrel tree frog (Hyla squirella) hanging on a branch. This frog is capable of displaying a variety of different colors, especially shades of green, yellow, and brown. Its coloration is an adaptive feature resulting from chromatophore changes…

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from article Pseudomonas

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from article Cell walls (plant)

Stylized model of the plant primary cell wall, showing layers of semicrystalline cellulose microfibrils associating with cross-linking hemicellulose polymers, embedded in a pectin matrix.

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from article Cell walls (plant)

Light microscopy image of the outer cell layers and cuticle of a tomato fruit. The cuticle in this organ, shown here with a red stain, forms an exceptionally thick lipid coating on the outer epidermal cell and also permeates into the underlying cell…

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from article Cell walls (plant)

Model showing the multiple layers that can be observed in some secondary cell walls, which vary in the direction that the constituent cellulose microfibrils are deposited.

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from article Cell walls (plant)

Cell expansion. (a) Two cells (left) of similar size, but different orientations of microfibril deposition show contrasting directions of cell expansion (right). (b) Model of the deposition of cellulose microfibrils by cellulose synthase complexes,…

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from article Throat

Sagittal section of a human head showing the structure of the pharynx and associated structures. (After J. C. B. Grant, A Method of Anatomy, Williams and Wilkins, 1952)

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from article Plant breeding

Utilizing a variety of selection techniques, plant breeders can modify plant species with respect to one or more phenotypic traits, thereby producing new and improved types of farm crops or decorative plants. (Copyright © McGraw-Hill Education)

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from article Plant breeding

Plant breeders have developed superior cultivars of a number of important crops. For example, traditional varieties of rice typically have many thin stalks, which can support relatively few seeds. Through selection techniques, rice yields can be…

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from article Plant breeding

Sequence of steps in crossing inbred plants and using the resulting single-crossed seed to produce double-crossed hybrid seed. (Credit: Crops Research Division, Agricultural Research Service, United States Department of Agriculture)

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from article Pseudoscorpionida

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from article Pseudoscorpionida

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from article Pseudoscorpionida

Pseudoscorpion morphology. (a) Adult, in two views. (b) Chelicera of a male pseudoscorpion. (Illustration based on an original by H. S. Pratt)

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from article Orthida

Orthida: (a) dorsal, (b) ventral, (c) posterior, and (d) anterior views of Platystrophia, Ordovician; (e) diversity history of orthid families. (a–d after R. C. Moore, C. G. Lalicker, and A. G. Fischer, Invertebrate Fossils, McGraw-Hill, New York,…

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from article Eumalacostraca

Phylogeny of the Eumalacostraca. (a) Based on the caridoid facies concept (after F. Schram, ed., Crustacean Phylogeny, Crustacean Issues, A. A. Balkema NE, vol. 1, 1983). (b) Based on general morphological characters (after F. R. Schram, Crustacea,…

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from article Zebra

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from article Optical microscope

Microscope objectives: (a) 16-mm (0.63-in.) dry achromat; (b) typical high-power dry achromat; (c) 2-mm (0.08-in.), NA 1.40, oil-immersion apochromat. (Photographic Service Department, Kodak Research Laboratory)

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from article Optical microscope

Two types of catadioptric objective. (a) Maksutov type. (b) 53X, NA 0.72, ultraviolet objective, designed by Gray. Glass elements in the latter serve purely as reflectors. (Photographic Service Department, Kodak Research Laboratory)

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from article Optical microscope