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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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Permeability (Earth Sciences)
Permeability in fluid mechanics and the earth sciences (commonly symbolized as κ, or k) is a measure of the ability of a porous material (often, a rock or an unconsolidated material) to allow fluids to pass through it. The permeability of a medium is related to the porosity, but also to the shapes of the pores in the medium and their level of connectedness.
  • 8.8K
  • 25 Oct 2022
Topic Review
NanoPutian
NanoPutians are a series of organic molecules whose structural formulae resemble human forms. James Tour et al. (Rice University) designed and synthesized these compounds in 2003 as a part of a sequence on chemical education for young students. The compounds consist of two benzene rings connected via a few carbon atoms as the body, four acetylene units each carrying an alkyl group at their ends which represents the hands and legs, and a 1,3-dioxolane ring as the head. Tour and his team at Rice University used the NanoPutians in their NanoKids educational outreach program. The goal of this program was to educate children in the sciences in an effective and enjoyable manner. They have made several videos featuring the NanoPutians as anthropomorphic animated characters. Construction of the structures depends on Sonogashira coupling and other synthetic techniques. By replacing the 1,3-dioxolane group with an appropriate ring structure, various other types of putians have been synthesized, e.g. NanoAthlete, NanoPilgrim, and NanoGreenBeret. Placing thiol (R-SH) functional groups at the end of the legs enables them to "stand" on a gold surface. "NanoPutian" is a portmanteau of nanometer, a unit of length commonly used to measure chemical compounds, and lilliputian, a fictional race of humans in the novel Gulliver's Travels by Jonathan Swift.
  • 1.6K
  • 20 Oct 2022
Topic Review
Shibboleth (Shibboleth Consortium)
Shibboleth is a single sign-on log-in system for computer networks and the Internet. It allows people to sign in using just one identity to various systems run by federations of different organizations or institutions. The federations are often universities or public service organizations. The Shibboleth Internet2 middleware initiative created an architecture and open-source implementation for identity management and federated identity-based authentication and authorization (or access control) infrastructure based on Security Assertion Markup Language (SAML). Federated identity allows the sharing of information about users from one security domain to the other organizations in a federation. This allows for cross-domain single sign-on and removes the need for content providers to maintain user names and passwords. Identity providers (IdPs) supply user information, while service providers (SPs) consume this information and give access to secure content.
  • 912
  • 20 Oct 2022
Topic Review
Double-Blind FROG
Double-Blind FROG is a method for simultaneously measuring two unknown ultrashort laser pulses. Well established ultrafast measurement techniques like Frequency-Resolved Optical Gating (FROG) and its simplified version GRENOUILLE can only measure one unknown ultrashort laser pulse at a time. Another version of FROG, called cross-correlation FROG (XFROG), also measures only one pulse, but it involves two pulses: a known reference pulse and the unknown pulse to be measured. In modern optics experiments, ultrashort laser pulses have been used in a great variety of engineering application and scientific research, for example, biomedical engineering, material science, nonlinear spectroscopy, ultrafast chemistry, etc. Often, these experiments involve using two potentially different input laser pulses, for example, Raman spectroscopy, two-color pump-probe experiments, and non-degenerate four-wave mixing. In many situations, an output pulse is generated by a nonlinear optical process, such as harmonic generation, continuum generation, or optical parametric oscillation. In all such cases, measuring more than one pulse simultaneously is required to completely characterize the experiment and understand its results in order to eventually understand the underlying science of the process under study. Thus a measurement device capable of measuring two pulses simultaneously is highly desired.
  • 1.0K
  • 20 Oct 2022
Topic Review
Natural Rate of Interest
The natural rate of interest, sometimes called the neutral rate of interest, is the interest rate that supports the economy at full employment/maximum output while keeping inflation constant. It cannot be observed directly. Rather, policy makers and economic researchers aim to estimate the natural rate of interest as a guide to monetary policy, usually using various economic models to help them do so.
  • 720
  • 20 Oct 2022
Topic Review
Cholera Outbreaks and Pandemics
Seven cholera pandemics have occurred in the past 200 years, with the first pandemic originating in India in 1817. Additionally, there have been many documented cholera outbreaks, such as a 1991–1994 outbreak in South America and, more recently, the 2016–2021 Yemen cholera outbreak. Although much is known about the mechanisms behind the spread of cholera, this has not led to a full understanding of what makes cholera outbreaks happen in some places and not others. Lack of treatment of human feces and lack of treatment of drinking water greatly facilitate its spread. Bodies of water have been found to serve as a reservoir, and seafood shipped long distances can spread the disease. Between 1816 and 1923, the first six cholera pandemics occurred consecutively and continuously over time. Increased commerce, migration, and pilgrimage are credited for its transmission. Late in this period (particularly 1879–1883), major scientific breakthroughs toward the treatment of cholera develop: the first immunization by Pasteur, the development of the first cholera vaccine, and identification of the bacterium Vibrio cholerae by Filippo Pacini and Robert Koch. After a long hiatus, a seventh cholera pandemic spread in 1961. The pandemic subsided in the 1970s, but continued on a smaller scale. Outbreaks occur across the developing world to the current day. Epidemics occurred after wars, civil unrest, or natural disasters, when water and food supplies had become contaminated with Vibrio cholerae, and also due to crowded living conditions and poor sanitation. Deaths in India between 1817 and 1860 in the first three pandemics of the nineteenth century, are estimated to have exceeded 15 million people. Another 23 million died between 1865 and 1917, during the next three pandemics. Cholera deaths in the Russian Empire during a similar time period exceeded 2 million.
  • 10.2K
  • 20 Oct 2022
Topic Review
Spousal Privilege
In the common law, spousal privilege (also called marital privilege or husband-wife privilege) is a term used in the law of evidence to describe two separate privileges that apply to spouses: the spousal communications privilege and the spousal testimonial privilege. Both types of privilege are based on the policy of encouraging spousal harmony and preventing spouses from having to condemn, or be condemned by, their spouses: the spousal communications privilege or confidences privilege is a form of privileged communication that protects the contents of confidential communications between spouses during their marriage from testimonial disclosure, while spousal testimonial privilege (also called spousal incompetency and spousal immunity) protects the individual holding the privilege from being called to testify in proceedings relating to his/her spouse. However, the spousal privileges have their roots in the legal fiction that a husband and wife were one person.
  • 2.8K
  • 20 Oct 2022
Topic Review
Svabhava
Svabhava (Sanskrit: svabhāva; Pali: sabhāva; Chinese: 自性; pinyin: zìxìng; Tibetan: རང་བཞིན, Wylie: rang-bzhin) literally means "own-being" or "own-becoming". It is the intrinsic nature, essential nature or essence of beings. The corresponding concept in Western philosophy is substance theory. The concept and term svabhāva are frequently encountered in Hindu and Buddhist traditions such as Advaita Vedanta (e.g. in the Avadhūta Gītā), Mahayana Buddhism (e.g. in the Ratnagotravibhāga), Vaishnavism (e.g., the writings of Ramanuja) and Dzogchen (e.g. in the seventeen tantras). In the nondual Advaita Vedānta yoga text, Avadhūta Gītā, Brahman (in the Upanishadic denotation) is the svabhāva. In the Mahāyāna Buddhadharma tradition(s) it is one of a suite of terms employed to denote the Buddha-nature, such as "gotra".
  • 1.7K
  • 20 Oct 2022
Topic Review
Widow
A widow is a woman whose spouse has died and a widower is a man whose spouse has died. The treatment of widows and widowers around the world varies.
  • 4.5K
  • 25 Oct 2022
Topic Review
Thaumarchaeota
The Thaumarchaeota or Thaumarchaea (from the Ancient Greek:) are a phylum of the Archaea proposed in 2008 after the genome of Cenarchaeum symbiosum was sequenced and found to differ significantly from other members of the hyperthermophilic phylum Crenarchaeota. Three described species in addition to C. symbiosum are Nitrosopumilus maritimus, Nitrososphaera viennensis, and Nitrososphaera gargensis. The phylum was proposed in 2008 based on phylogenetic data, such as the sequences of these organisms' ribosomal RNA genes, and the presence of a form of type I topoisomerase that was previously thought to be unique to the eukaryotes. This assignment was confirmed by further analysis published in 2010 that examined the genomes of the ammonia-oxidizing archaea Nitrosopumilus maritimus and Nitrososphaera gargensis, concluding that these species form a distinct lineage that includes Cenarchaeum symbiosum. The lipid crenarchaeol has been found only in Thaumarchaea, making it a potential biomarker for the phylum. Most organisms of this lineage thus far identified are chemolithoautotrophic ammonia-oxidizers and may play important roles in biogeochemical cycles, such as the nitrogen cycle and the carbon cycle. Metagenomic sequencing indicates that they constitute ~1% of the sea surface metagenome across many sites. Thaumarchaeota-derived GDGT lipids from marine sediments can be used to reconstruct past temperatures via the TEX86 paleotemperature proxy, as these lipids vary in structure according to temperature. Because most Thaumarchaea seem to be autotrophs that fix CO2, their GDGTs can act as a record for past Carbon-13 ratios in the dissolved inorganic carbon pool, and thus have the potential to be used for reconstructions of the carbon cycle in the past.
  • 2.7K
  • 20 Oct 2022
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