APC Science Union · Online Library

Author: 未名 Reviewer: 未名 Introduction   In 1886, Karl Benz built the world’s first three-wheeled automobile powered by an internal-combustion engine. What chiefly distinguished it from a horse-drawn carriage was its powertrain; the basic form of the modern four-wheeled car came from Daimler. Over the next century and more, vehicle bodies evolved along with the demand for greater mobility and changing aesthetic tastes. From the Beetle to the ponton body and then the wedge shape, designers have pursued forms that reduce drag without sacrificing visual appeal. This article briefly examines the relationship between automotive styling and aerodynamics. Automotive Styling and Aerodynamic Drag   At constant speed on a level road under normal atmospheric pressure, a car's aerodynamic ...

The Philosophy and Theology of Saint Augustine Author: Михaїл-А-Булгáкoв☦️ Reviewed by: 观复·钧天   Saint Augustine was an extraordinarily prolific writer whose works dealt mainly with questions of theology. His polemical writings addressed the issues of his day and, once they had served their purpose, generally lost all significance. Some of them, however, especially those concerning the Pelagians, have continued to exert a real influence into modern times. I do not intend to cover everything he wrote. Instead, I will examine the works and arguments that seem to me important in themselves or in their historical influence: First, his pure philosophy, especially his theory of time Second, the philosophy of history presented in The City of God Third, the theory of salvation develop ...

Author: Shiguang Reviewed by: Dongda   Many readers probably first encountered “procedural art” in an elementary-school information technology class, when a textbook introduced the fascinating program Turtle Graphics. Think back: how did we make the little turtle move? The answer was code. In 1996, Seymour Papert and Wally Feurzeig invented Logo, a language designed to teach children programming, and we used it to direct a turtle around the screen as it drew. As technology has evolved, however, Logo has gradually faded from view, and mainstream approaches to drawing have changed as well.   This article shows how to use a shader language—called simply Shader below—to draw a 3*3 checkerboard. I use UE4 for the demonstration. If you are interested, try the algorithm pres ...

Fluorescent Proteins: A Brief History and How They Work Author: Polar Glacier Reviewed by: Weiming Abstract   Green fluorescent protein (GFP), discovered and isolated from the jellyfish Aequorea victoria in 1962, and the red fluorescent protein drFP583, discovered in 1999 in corals of the genus Discosoma, have become widely used tools throughout biological research. They are nontoxic, emit strong fluorescence when excited by specific wavelengths of light, have low molecular weights, are easy to incorporate into vectors, and can be expressed in many organisms. These properties have made fluorescent proteins useful across a broad range of fields, and researchers now have many varieties to choose from. History of Fluorescent-Protein Research   Green fluorescent protei ...

The Phases of Earth as Seen from the Moon Author: Congyu Reviewed by: Yuandao and Shiguang   What does Earth look like from the Moon? If you know a little about the Earth–Moon system and lunar phases, you may already sense that something is wrong with this image. It comes from Horizon Lunar Colony, a map in the game Overwatch. Setting artistic license aside, the screenshot gives us a useful starting point for exploring the phases of celestial bodies. Figure 1: Screenshot from Overwatch. The image greatly exaggerates Earth's apparent size. From the Moon, Earth has an apparent diameter of about 1.9 degrees, only 3.6 times that of the Sun.   A celestial body's phase depends on the relative positions of the Sun, the body, and the observer. It tells us how much of the su ...

Early Greek Philosophy Author: Михaїл-А-Булгáкoв☦️ Reviewer: Nancy   Early Greek philosophy belonged to Greek culture as a whole, not just to city-states such as Athens and Sparta. Its thinkers used ancient Greek to think, write, and debate. Together, they helped shift explanations of the world away from the gods who had dominated earlier civilizations and toward a human-centered outlook concerned with education and cultivation. In doing so, they challenged divine authority whether it came from Babylon, Assyria, Egypt, or Greece's own Olympus.   The Stoics received early Greek philosophy through the selective interpretations of Socrates, Plato, and especially Aristotle. Greek and Latin Church Fathers later intertwined it with Neoplatonism and incorporated it into Ch ...

Basic Mineral Descriptions: How to Read a Rock Author: 约翰史密斯   Hello, everyone. This article introduces some common terms for describing mineral properties.   Why learn to describe minerals in the first place? The Earth contains an enormous variety of mineral deposits. Specimens that look completely different may be the same mineral, while specimens that look almost identical may have entirely different compositions.   Judging a specimen by appearance alone can easily lead us astray. Take the famous “fool’s gold,” for example:   It may glitter like gold, but it is simply pyrite and has nothing to do with gold itself. Even the broad category of iron ore includes hematite, magnetite, limonite, and many other minerals. Describing a specimen systemat ...

How to Get Color Right Author: Shiguang   How do you get color right? Did that question send your mind somewhere naughty? No—this is a perfectly respectable science article. So let me show you a picture with some color in it. Entirely innocent, see? The cute little object below is a color wheel. It will be the star of this article, so take a moment to remember its shape.   We will cover the basics of color, followed by several common approaches to building a palette. Color Theory and Color Schemes How Do Humans See Color?   In nature, light leaves a source and strikes an object's surface. Most objects absorb some of that light and reflect the rest into our eyes; the reflected portion is the color we see. An object that absorbs none of the light falling o ...

The Degeneracy of the Genetic Code Author: Shenzhou Reviewed by: Shenzhou   During translation, the genetic code maps a nucleotide sequence to an amino acid sequence, while tRNAs physically carry out that mapping. The code is therefore the essential link between nucleic acids and proteins.   Early mathematical analyses led scientists to conclude that codons had to contain three bases to encode all 20 amino acids. Crick later inserted or deleted different numbers of bases in bacteriophages and compared the resulting phenotypes. His experiments supported the hypothesis that the genetic code is read in nucleotide triplets.   At about the same time, Nirenberg and Matthaei used synthetic mRNA and an in vitro translation system to match several simple codons, in ...

The Cambrian Explosion and Early Life Author: John Smith Reviewed by: Dongda Before we begin   Paleontology, as its name suggests, studies life from its earliest origins to the recent past. Geologists divide Earth's history into units based on the sequence of rock layers and the fossils found in them. Just as biology classifies organisms by kingdom, phylum, class, order, family, genus, and species, the geologic time scale is divided into eons, eras, periods, epochs, ages, and chrons. Each smaller unit belongs to a larger one. The relationship resembles that of the Zhìdé era name (583–587), which belongs to the Chen dynasty, itself part of the Northern and Southern Dynasties. Units larger than a period cover too much time for our purposes, while smaller units are more detailed ...