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HandWiki is the world's largest wiki-style encyclopedia dedicated to science, technology and computing. It allows you to create and edit articles as long as you have external citations and login account. In addition, this is a content management environment that can be used for collaborative editing of original scholarly content, such as books, manuals, monographs and tutorials.

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Precipitation
In an aqueous solution, precipitation is the process of transforming a dissolved substance into an insoluble solid from a super-saturated solution. The solid formed is called the precipitate. In case of an inorganic chemical reaction leading to precipitation, the chemical reagent causing the solid to form is called the precipitant. The clear liquid remaining above the precipitated or the centrifuged solid phase is also called the 'supernate' or 'supernatant'. The notion of precipitation can also be extended to other domains of chemistry (organic chemistry and biochemistry) and even be applied to the solid phases (e.g., metallurgy and alloys) when solid impurities segregate from a solid phase.
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  • 07 Nov 2022
Topic Review
Measure of Presortedness
In computer science, a measure of presortedness of a sequence represents how much work is required to sort the sequence. If the sequence is pre-sorted, sorting the sequence entirely require little work, hence it is expected to have a small measure of presortedness. In particular, the measure of a sorted sequence is 0. Some sorting algorithms are more efficient on pre-sorted list, as they can use this pre-work into account to avoid duplicate work. The measure of presortedness allows to formalize the notion that an algorithm is optimal for a certain measure.
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  • 07 Nov 2022
Topic Review
ISO Standards for Trailer Connectors
A number of ISO standards cover trailer connectors, the electrical connectors between vehicles and the trailers they tow that provide a means of control for the trailers. These are listed below, with notes on significant deviations from them that can cause problems.
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  • 07 Nov 2022
Topic Review
OPPO R7s
OPPO R7s is a line of Android-based smartphone manufactured by Oppo that were released in October, 2015. OPPO R7 series has all-metal flashing, the fit and finish and the arcs towards its display edges. OPPO Company developed after OPPO R5s. However, the phone was discontinued with the release of more developed version like OPPO R15 and OPPO R17. The phone offers an improved screen, battery and design comparing to the pervious phones. Reviewer had a mix review. Its design and battery quality were universally praised, also, its display received the positive feedback after tests. Reviews had both positive and negative comments, with no finger print sensor or face ID like Apple system. This would result insecurity of personal privacy.
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  • 07 Nov 2022
Topic Review
Egyptian Medical Papyri
Egyptian medical papyri are ancient Egyptian texts written on papyrus which permit a glimpse at medical procedures and practices in ancient Egypt. The papyri give details on disease, diagnosis, and remedies of disease, which include herbal remedies, surgery, and magical spells. It is thought there were more medical papyri, but many have been lost due to grave robbing. The largest study of the medical papyri to date has been undertaken by Humboldt University of Berlin and was titled Medizin der alten Ägypter ("Medicine of ancient Egypt"). Early Egyptian medicine was based mostly on a mixture of magic and religious spells. Most commonly "cured" by use of amulets or magical spells, the illnesses were thought to be caused by spiteful behavior or actions. Afterwards, doctors performed various medical treatments if necessary. The instructions for these medical rituals were later inscribed on papyrus scrolls by the priests performing the actions.
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  • 07 Nov 2022
Topic Review
Loot System
In video games, a loot system is a method of distributing in-game items amongst a group of players, after having "looted" them.
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  • 07 Nov 2022
Topic Review
Compounds of Aluminium
Aluminium (or aluminum) combines characteristics of pre- and post-transition metals. Since it has few available electrons for metallic bonding, like its heavier group 13 congeners, it has the characteristic physical properties of a post-transition metal, with longer-than-expected interatomic distances. Furthermore, as Al3+ is a small and highly charged cation, it is strongly polarizing and aluminium compounds tend towards covalency; this behaviour is similar to that of beryllium (Be2+), an example of a diagonal relationship. However, unlike all other post-transition metals, the underlying core under aluminium's valence shell is that of the preceding noble gas, whereas for gallium and indium it is that of the preceding noble gas plus a filled d-subshell, and for thallium and nihonium it is that of the preceding noble gas plus filled d- and f-subshells. Hence, aluminium does not suffer the effects of incomplete shielding of valence electrons by inner electrons from the nucleus that its heavier congeners do. Aluminium's electropositive behavior, high affinity for oxygen, and highly negative standard electrode potential are all more similar to those of scandium, yttrium, lanthanum, and actinium, which have ds2 configurations of three valence electrons outside a noble gas core: aluminium is the most electropositive metal in its group. Aluminium also bears minor similarities to the metalloid boron in the same group; AlX3 compounds are valence isoelectronic to BX3 compounds (they have the same valence electronic structure), and both behave as Lewis acids and readily form adducts. Additionally, one of the main motifs of boron chemistry is regular icosahedral structures, and aluminium forms an important part of many icosahedral quasicrystal alloys, including the Al–Zn–Mg class.
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  • 07 Nov 2022
Topic Review
Face Inversion Effect
The face inversion effect is a phenomenon where identifying inverted (upside-down) faces compared to upright faces is much more difficult than doing the same for non-facial objects. A typical study examining the face inversion effect would have images of the inverted and upright object presented to participants and time how long it takes them to recognise that object as what it actually is (i.e. a picture of a face as a face). The face inversion effect occurs when, compared to other objects, it takes a disproportionately longer time to recognise faces when they are inverted as opposed to upright. Faces are normally processed in the special face-selective regions of the brain, such as the fusiform face area. However, processing inverted faces involves both face-selective regions and the scene and object recognition regions of the parahippocampal place area and lateral occipital cortex. There seems to be something different about inverted faces that requires them to also involve these scene and object processing mechanisms. The most supported explanation for why faces take longer to recognise when they are inverted is the configural information hypothesis. The configural information hypothesis states that faces are processed with the use of configural information to form a holistic (whole) representation of a face. Objects, however, are not processed in this configural way. Instead, they are processed featurally (in parts). Inverting a face disrupts configural processing, forcing it to instead be processed featurally like other objects. This causes a delay since it takes longer to form a representation of a face with only local information.
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Topic Review
Storage of Cultural Heritage Objects
The storage of cultural heritage objects typically falls to the responsibility of cultural heritage institutions, or individuals. The proper storage of these objects can help to ensure a longer lifespan for the object with minimal damage or degradation. With so many different types of artifacts, materials, and combinations of materials, keepers of these artifacts often have considerable knowledge of the best practices in storing these objects to preserve their original state.
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  • 07 Nov 2022
Topic Review
Schizotypal Personality Disorder
Schizotypal personality disorder (STPD), also known as schizotypal disorder, is a mental and behavioural disorder. DSM classification describes the disorder specifically as a personality disorder characterized by thought disorder, paranoia, a characteristic form of social anxiety, derealization, transient psychosis, and unconventional beliefs. People with this disorder feel pronounced discomfort in forming and maintaining social connections with other people, primarily due to the belief that other people harbour negative thoughts and views about them. Peculiar speech mannerisms and socially unexpected modes of dress are also characteristic. Schizotypal people may react oddly in conversations, not respond, or talk to themselves. They frequently interpret situations as being strange or having unusual meaning for them; paranormal and superstitious beliefs are common. Schizotypal people usually disagree with the suggestion their thoughts and behaviour are a 'disorder', and seek medical attention for depression or anxiety instead. Schizotypal personality disorder occurs in approximately 3% of the general population and is more common in males. The term "schizotype" was first coined by Sandor Rado in 1956 as an abbreviation of "schizophrenic phenotype". STPD is classified as a cluster A personality disorder, also known as the "odd or eccentric" cluster.
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