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They also accumulate and store various essential material, both of which allows the akinete to serve as a survival structure for up to many years. [1] [4] However, akinetes are not resistant to heat. [1] Akinetes usually develop in strings with each cell differentiating after another and this occurs next to heterocysts if they are present. [1]
In low nitrogen environments, heterocyst differentiation is triggered by the transcriptional regulator NtcA. NtcA influences heterocyst differentiation by signaling proteins involved in the process of heterocyst differentiation. For instance, NtcA controls the expression of several genes including HetR which is crucial for heterocyst ...
Magnetotactic bacteria use a process known as biomineralization to exert an incredible degree of control on the formation of the mineral crystals within the magnetosomes. [7] [8] The process of biomineralization allows the MTB to control the shape and size along with the alignment of each individual magnetite crystal. These specific magnetite ...
The human eye, showing the iris and pupil. In 1802, philosopher William Paley called it a miracle of "design."In 1859, Charles Darwin himself wrote in his Origin of Species, that the evolution of the eye by natural selection seemed at first glance "absurd in the highest possible degree". [3]
Some of the earliest ideas and mathematical descriptions on how physical processes and constraints affect biological growth, and hence natural patterns such as the spirals of phyllotaxis, were written by D'Arcy Wentworth Thompson in his 1917 book On Growth and Form [2] [3] [note 1] and Alan Turing in his The Chemical Basis of Morphogenesis (1952). [6]
Line-of-sight fire, shooting directly at a visible target on a relatively flat trajectory. The target is in the line of sight of the sighting device and the rifleman's rule applies. Line-of-sight range; Line-of-sight (missile), the straight line between the missile and the target; Radar horizon
The image at the sagittal focus is a short line, oriented in the direction of the tangential plane; images of spokes radiating from the center are sharp at this focus. In between these two foci, a round but "blurry" image is formed. This is called the medial focus or circle of least confusion. This plane often represents the best compromise ...
The visual system is the physiological basis of visual perception (the ability to detect and process light).The system detects, transduces and interprets information concerning light within the visible range to construct an image and build a mental model of the surrounding environment.