APC Science Union · Online Library

Author: Shenzhou Reviewer: Weiming   The biuret reaction of proteins is based on a simple principle and is relatively easy to perform. This article explains the reaction, and the procedure is very safe, so anyone with the necessary materials can try it at home.   First, when urea is heated to 180°C, two urea molecules condense, releasing one molecule of ammonia and forming biuret. The reaction equation is shown below:   Biuret contains the -CO-NH- group. Under alkaline conditions, it reacts with Cu2+ ions to form a purplish-red chelate. Its structure is shown below:   At this point, the basis for using this experiment to detect proteins should be clear. Proteins consist of many amino acids linked by peptide bonds, so dipeptides and larger polypeptides contain structures similar to thos ...

Author: Zi Bo (ZiBo) Reviewer: Weiming   Hello, my name is Zi Bo (ZiBo), and I graduated this year. I do not know why, but here I am writing an article for you. The last time I remember a Chinese teacher praising my writing was in sixth grade. His comment was: “If you didn’t copy this, it’s very well written!” So even if my article does not entertain you, it will not waste your time.   I am an introvert who often looks up at the sky. When classmates run into me, they sometimes ask, “Are you pondering life again?” I smile without answering. (Classmates greet me when they see me because I have never been someone who fades into the background. I may be introverted, but I do not like being unnoticed.) I enjoy thinking, and I can appreciate the meaning of both “If I learned the Way in the mor ...

Author: Shiguang Reviewer: Baiyan   Before we begin, consider a question: why compress a file? Unsure, you set the question aside and decide to download something. After opening NetEase Cloud Music, you find several songs you like in the daily recommendations and immediately try to save them. The download menu offers lossless, high, and standard quality. Wanting the best for your ears, you choose lossless, only to be asked to buy a membership. Frustrated, you… choose high quality instead.   Thinking back to the original question, you wonder whether the high-quality version is simply a compressed form of the lossless one, since its file is smaller. It is. Although the high-quality version does not sound quite as good as the lossless version, it takes up less disk space and is easier to tr ...

Author: Zikongli Reviewer: Guanfu · Juntian   In the previous installment, “Financial Crises: The Netherlands—The Temptation of Tulips,” we recounted the Dutch tulip bubble during capitalism’s infancy. From its formation and expansion to its final collapse, the episode exposed the madness and greed buried in human nature. The crisis struck down the Netherlands, once the “coachman of the seas,” in a single blow. One might think it would have made people more wary of financial alchemy. Yet, as Hegel observed, the only lesson people learn from history is that they learn nothing from history.   John Law was born into a wealthy family in Edinburgh, Scotland, in 1671. His father was a banker, and as the eldest son, Law began a three-year apprenticeship in his father’s accounting office at four ...

Author: N Reviewer: Baiyan   Alternating current and direct current are the two basic ways electricity is used in everyday life. Each has advantages the other cannot replace, so we are often interested in converting AC to DC or DC to AC. My research showed that AC is converted to DC primarily through a rectifier circuit, whose key component is the diode. Taking AC-to-DC conversion as its point of departure, this article investigates diodes and their role in rectifier circuits. The aim is to understand the principles of rectification and the connections and differences between ideal circuit models and actual circuit components and modules, while developing a deeper command of circuit theory and the Multisim simulation tool. 1. Introduction   Alternating current and direct current are the ...

Author: @cheeze molecule (translator) Credit: Mark Schiefelbein/AP/Shutterstock   Practical questions that Professor He Jiankui and other genome-editing researchers must face.   In late November, the reported birth of twin babies whose genes had been edited to make them resistant to HIV caused an uproar. It also ignited fierce debate over experiments using CRISPR, the laws governing them, and the ethical issues involved.The controversy drew opposition, neutrality, and support. At the Second International Summit on Human Genome Editing, held a few days later, the organizing committee called the event “unexpected and deeply disturbing.” Researchers in the life sciences had mixed reactions, but most believed the experiment had been conducted prematurely and questioned its legality and safe ...

Author: phy Dongxi   (A text-heavy popular-science article—lots of reading ahead)   Most of us played with springs as children: the springs in retractable pens, for example, or those in a Rubik’s Cube (yes, I somehow bring up the Rubik’s Cube every three sentences). Screw-like springs turn up everywhere:   When you roll this spring across a tabletop, you seem to see a train of waves traveling from one end to the other. Similarly, when a drill bit or the red, white, and blue pole outside a barbershop rotates, its spiral appears to keep “emerging” from one end and disappearing at the other. It looks like a wave in motion.   We can calculate this wave’s speed quite easily. Suppose the helix has radius r, rotational frequency f, and pitch h. The “wave” we observe is the helix’s projection o ...

Author: APC Editorial Department Science Outreach Group   P.S. Most of the technical content below comes from answers provided by an expert who wished to remain anonymous, with a smaller portion compiled from other experts’ chat records.   On September 19 and 20, a card began circulating wildly through all kinds of small chat groups:   That’s right: those two blue words, “Click me,” set off a full-scale science-outreach battle…   First, the short version: this card poses no danger to you. Clicking it is harmless and will not expose your information. Just do not forward it afterward, and especially do not recklessly modify things at random.   So what exactly was this science-outreach battle? Let us sort out the timeline~   On the evening of September 19, 2020, the card first appeared in ...

Author: Self-Control Reviewer: Millisecond   Financial crisis: a specter haunting every country with a market economy. Ever since humanity created financial systems, crises have ranked among the most frightening of events. Each time one appears, countless people can go from immense wealth to utter poverty overnight.   The Great Depression triggered by the financial crisis of 1929–1932 even helped bring about the Second World War indirectly. Looking closely at the crises in financial history reveals just how many tricks the financial titans of the past employed—and how irrational people could become when profits beckoned.   We will trace this frightening phenomenon gradually and in chronological order. Today, we begin with the first crisis of the modern financial system: the tulip bubble ...

Author: Qingliu Reviewer: Yuandao   Skinner may be unfamiliar to many readers, but Pavlov is likely a household name. Pavlov was a Soviet physiologist, psychologist, and physician; the founder of the theory of higher nervous activity; a pioneer in the physiology of higher nervous activity; and the architect of the theory of conditioned reflexes. He was also one of the figures outside traditional psychology who most profoundly influenced the field’s development, and he received the Nobel Prize in Physiology or Medicine. (That really is a lot of titles.) Portrait of Pavlov   Pavlov conducted a famous experiment. He noticed that dogs salivated when they saw food, so he rang a bell each time before feeding them. Eventually, the dogs salivated at the sound of the bell even when no food appea ...