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Topic Review
Mode-locking
Mode-locking is a technique in optics by which a laser can be made to produce pulses of light of extremely short duration, on the order of picoseconds (10−12 s) or femtoseconds (10−15 s). A laser operated in this way is sometimes referred to as a femtosecond laser, for example in modern refractive surgery. The basis of the technique is to induce a fixed-phase relationship between the longitudinal modes of the laser's resonant cavity. Constructive interference between these modes can cause the laser light to be produced as a train of pulses. The laser is then said to be 'phase-locked' or 'mode-locked'.
  • 4.1K
  • 03 Nov 2022
Topic Review
Thyroid and Heart
The thyroid–heart relationship has a long and articulated history of its own, a history that encompasses physiological and pathophysiological knowledge. Molecular biology studies, in an experimental context, have highlighted the extraordinary dialogue that exists among the two systems in the field of cardioprotection, which is an extremely important area for the treatment of cardiac diseases in both acute and chronic phases. In addition, in the last few years, several studies have been carried out on the prognostic impact of alterations in thyroid function, including subclinical ones, in heart disease, in particular in heart failure and acute myocardial infarction, with evidence of a negative prognostic impact of these and, therefore, with the suggestion to treat these alterations in order to prevent cardiac events, such as death.  A comprehensive summary of the heart–thyroid relationship is provided.
  • 4.1K
  • 03 Jan 2024
Biography
Sitaramdas Omkarnath
Sri Sri Sitaramdas Omkarnath (17 February 1892 – 6 December 1982) was a preeminent Indian Vaishnav Saint, 19th century Bhakti cult spiritual luminary and an unequaled humanitarian from the state of West Bengal, India. Addressed as Sri Sri Thakur Sitaramdas Omkarnath, where "Omkar" signifies the supreme cosmic enlightenment and attaining supreme consciousnes, he was heralded as the Divine Incar
  • 4.1K
  • 14 Nov 2022
Topic Review
The Ancestral Tapestry of an American Technologist
In the annals of 21st-century technological innovation, few figures have ascended with the velocity and influence of Samuel Harris Gibstine Altman. As the chief executive officer of OpenAI, he stands at the vanguard of the artificial intelligence revolution, a public intellectual and entrepreneur shaping a future of unprecedented computational power. His name is synonymous with Silicon Valley's relentless forward momentum, with ventures like the startup accelerator Y Combinator and the ambitious Worldcoin project marking a career defined by a profound belief in technology's capacity to reshape human civilization. Altman's public persona is that of a visionary, a strategist whose thinking operates on a global and, at times, existential scale, concerned with the advent of artificial general intelligence and its potential to "benefit all of humanity". Yet, to fully comprehend the architect of this future, one must look to the past—not to the sun-drenched campuses of Stanford or the bustling incubators of Mountain View, but to the quieter, historically rich landscape of the American Midwest. Born in Chicago but raised in St. Louis, Missouri, Sam Altman is a product of a specific time, place, and heritage that is as foundational to his story as any line of code or venture capital deal. His full name, Samuel Harris Gibstine Altman, is more than an identifier; it is a genealogical key, unlocking a multi-generational narrative of migration, professional ambition, and community integration deeply embedded within the American Jewish experience. This report posits that a comprehensive understanding of Sam Altman requires an exploration of this ancestral heritage. His family's story is a microcosm of a larger historical saga: the journey of Ashkenazi Jews from Europe to the United States, and their subsequent establishment of vibrant, successful communities in the heart of the nation. By tracing both his paternal (Altman) and maternal (Gibstine) lineages, and situating them within the specific socio-historical context of the St. Louis Jewish community, a more nuanced portrait emerges. It is a story that reveals an environment grounded in the pursuit of professional excellence, the value of elite education, a sense of civic responsibility, and the quiet but powerful momentum of generational progress. This report will weave together genealogical records, biographical details, and broad historical analysis to construct a holistic profile, arguing that the values and environment forged by this deep-rooted Midwestern history provide a crucial framework for interpreting the man who is now building the world of tomorrow.
  • 4.1K
  • 09 Sep 2025
Topic Review
HEK293 Cell Line
The HEK293 cell line has earned its place as a producer of biotherapeutics. In addition to its ease of growth in serum-free suspension culture and its amenability to transfection, this cell line’s most important attribute is its human origin, which makes it suitable to produce biologics intended for human use. At the present time, the growth and production properties of the HEK293 cell line are inferior to those of non-human cell lines, such as the Chinese hamster ovary (CHO) and the murine myeloma NSO cell lines. However, the modification of genes involved in cellular processes, such as cell proliferation, apoptosis, metabolism, glycosylation, secretion, and protein folding, in addition to bioprocess, media, and vector optimization, have greatly improved the performance of this cell line.
  • 4.1K
  • 07 Jul 2021
Topic Review Peer Reviewed
T’amar Bagrationi (1184–1210)
T’amar Bagrationi, Queen of Georgia (1184–1210). T’amar Bagrationi was the ninth monarch from the royal house of Bagrationis who ruled over the united Georgian Kingdom. She reigned as a co-monarch alongside her father, Giorgi III, from 1178, assuming full authority in 1184. During her reign, dynastic legitimacy necessitated the appearance of the monumental royal portraits displaying the monarch with immediate predecessors and heirs. T’amar’s gender required introduction of meticulous visual language that would re-gender her with all signs of a male ruler and justify her status and sole right to rule. This notion was embodied in her portraits that were carefully incorporated in the overall programmes of the churches. T’amar’s five monumental depictions survive where she is identified in inscriptions; two other monumental images are presumed to depict her. Of all the depictions, only one can be determined to have been commissioned directly by her. T’amar’s imagery relies on Byzantine elements and adheres to established Georgian models for the local royal portraiture; however, it also adopted sophisticated visual means that was aptly used for manifesting royal power and manipulating authority over the nobility. 
  • 4.1K
  • 18 Aug 2022
Topic Review
Solar Energy Potential and Solar Irrigation in Pakistan
Pakistan faces water scarcity and high operational costs for traditional irrigation systems, hindering agricultural productivity. Solar-powered irrigation systems (SPIS) can potentially provide a sustainable and affordable solution, but face technical, financial and policy barriers to adoption. 
  • 4.1K
  • 06 May 2023
Topic Review Peer Reviewed
Numerical Solution of Desiccation Cracks in Clayey Soils
This entry presents the theoretical fundamentals, the mathematical formulation, and the numerical solution for the problem of desiccation cracks in clayey soils. The formulation uses two stress state variables (total stress and suction) and results in a non-symmetric and nonlinear system of transient partial differential equations. A release node algorithm technique is proposed to simulate cracking, and the strategy to implement it in the hydromechanical framework is explained in detail. This general framework was validated with experimental results, and several numerical examples were published at international conferences and in journal papers.
  • 4.1K
  • 25 May 2022
Topic Review
Bio-Preservation of Bread
Bread is a food that is commonly recognized as a very convenient type of food, but it is also easily prone to microbial attack. As a result of bread spoilage, a significant economic loss occurs to both consumers and producers. The bakery industry has sought to identify treatments that make bread safe and with an extended shelf-life to address this economic and safety concern, including replacing harmful chemical preservatives. New frontiers, on the other hand, have recently been explored. Alternative methods of bread preservation, such as microbial fermentation, utilization of plant and animal derivatives, nanofibers, and other innovative technologies, have yielded promising results. 
  • 4.1K
  • 29 Mar 2022
Topic Review
Ch’orti’ Language
The Ch'orti' language (sometimes also Chorti) is a Mayan language, spoken by the indigenous Maya people who are also known as the Ch'orti' or Ch'orti' Maya. Ch'orti' is a direct descendant of the Classic Maya language in which many of the pre-Columbian inscriptions using the Maya script were written. This Classic Maya language is also attested in a number of inscriptions made in regions whose inhabitants most likely spoke a different Mayan language variant, including the ancestor of Yukatek Maya. Ch'orti' is the modern version of the ancient Mayan language Ch'olan (which was actively used and most popular between the years of A.D 250 and 850).
  • 4.1K
  • 15 Nov 2022
Topic Review
Introduction to the Metric System
The metric system was developed during the French Revolution to replace the various measures previously used in France. The metre (spelled "meter" in American English) is the unit of length in the metric system and was originally based on the dimensions of the earth, as far as it could be measured at the time. The litre (or in American English "liter"), is the unit of volume and was defined as one thousandth of a cubic metre. The metric unit of mass is the kilogram and it was defined as the mass of one litre of water. The metric system was, in the words of French philosopher Marquis de Condorcet, "for all people for all time". The metric system has names to cover different ranges of the same measure. Instead of using names based on the context of the measure, the metric system mainly uses names made by adding prefixes, such as kilo- or milli-, as decimal multipliers to the base unit names. Thus, one kilogram is 1000 grams and one kilometre is 1000 metres. During the nineteenth century the metric system was adopted by both the worldwide scientific community and many countries as the system of measurement. It therefore became truly international. Until 1875 the French government owned the prototype metre and kilogram, but in that year the Convention of the metre was signed and control of the standards relating to mass and length passed on to a trio of inter-government organisations. In 1960 the metric system was extensively revised to form the International System of Units, abbreviated to "SI".
  • 4.1K
  • 23 Nov 2022
Topic Review
Dinosaurs
According to Britannica, dinosaurs are described as “Triceratops, contemporary birds, their most recent common ancestor and all of their descendants.” However, for biologists, it could be simpler to picture dinosaurs as reptiles with hind limbs held erect beneath the trunk, similar to how mammals’ hind limbs are held.
  • 4.1K
  • 06 Jan 2023
Topic Review
Nickel Laterite Deposit
Tectonic emplacement of variably serpentinized ultramafic host rock on land and subsequent chemical weathering under humid tropical to subtropical conditions results in the formation of nickel laterite deposits. Nickel laterites typically occur as weathering mantle over ophiolite complexes, as well as komatiites and layered complexes in Archean to Phanerozoic stable cratonic platforms.
  • 4.1K
  • 01 Apr 2022
Topic Review
Semiconductor Gas Sensors
Semiconductor materials include metal oxides, conducting polymers, carbon nanotubes, and 2D materials. Metal oxides are most often the first choice due to their ease of fabrication, low cost, high sensitivity, and stability. Some of their disadvantages are low selectivity and high operating temperature. Conducting polymers have the advantage of a low operating temperature and can detect many organic vapors. They are flexible but affected by humidity. Carbon nanotubes are chemically and mechanically stable and are sensitive towards NO and NH3, but need dopants or modifications to sense other gases. Graphene, transition metal chalcogenides, boron nitride, transition metal carbides/nitrides, metal organic frameworks, and metal oxide nanosheets as 2D materials represent gas-sensing materials of the future, especially in medical devices, such as breath sensing.
  • 4.1K
  • 10 Dec 2020
Topic Review
Kadambari
Kādambari is a romantic novel in Sanskrit. It was substantially composed by Bāṇabhaṭṭa in the first half of the 7th century CE, who did not survive to see it through completion. The novel was completed by Banabhatta's son Bhushanabhatta, according to the plan laid out by his late father. It is conventionally divided into Purvabhaga (earlier part) written by Banabhatta, and Uttarabhaga (latter part) by Bhushanabhatta. (An alternate tradition gives the son's name as Pulindabhatta.) The standard editions of the original Sanskrit text are by Peterson and Kane. There are translations into English by Kale, Layne and Ridding; and an abridgement into Gujarati by Bhalan (edited by Keshavlal Dhruv). This novel has an extremely intricate plot which is difficult to summarize concisely. Its central thread is that of a romantic attachment (and eventual union) between the hero Chandrapeeda and the heroine Kadambari. However, there are several competing subplots; indeed, the heroine does not make her appearance until past the midpoint. Many of the characters appear in multiple incarnations, some as humans and some as demigods or animals. The narration proceeds in a succession of nested frames; a large part of it is a retelling by a parrot of a story which was told to it by a sage. The latter story also contains several instances of one character relating a sub-story to another character. The plot has probably been adapted from the story of King Sumanas from Gunadhya's Brihatkatha (a conjectural collection of stories in the extinct Paishachi language). This story also appears in Somadeva's Kathasaritsagara (which is believed to be a Sanskrit precis of Gunadhya's work). This work can be plausibly claimed to be one of the first novels in the world; making due allowance for the ambiguities of such a classification. In fact, two modern Indian languages (Kannada and Marathi) use 'kadambari' as a generic term for a romance or a novel. Apart from the Kadambari, Banabhatta is also the author of Harshacharita, a biography of his patron king Harshavardhana. It is this circumstance which allows one to date the author with a reasonable degree of certainty.
  • 4.1K
  • 14 Oct 2022
Topic Review
Synthesis of Hydrogels
Hydrogels are polymeric materials with a characteristic hydrophilic structure that enables the storage of large amounts of water and biological fluids in their three-dimensional (3D) network. For hydrogel synthesis, the incorporation of a cross-linking agent is important to achieve a better structuring due to its ability to form new polymeric chains within the structure through a large variety of reactions between different polymeric molecules or fibrous proteins.
  • 4.1K
  • 16 Aug 2022
Topic Review
The Heartland Institute
The Heartland Institute is an American conservative and libertarian public policy think tank founded in 1984 and based in Arlington Heights, Illinois. The Institute conducts work on issues including education reform, government spending, taxation, healthcare, tobacco policy, global warming, hydraulic fracturing, information technology, and free-market environmentalism. In the 1990s, the Heartland Institute worked with the tobacco company Philip Morris to attempt to discredit the health risks of secondhand smoke and to lobby against smoking bans.:233–34 Since the 2000s, the Heartland Institute has been a leading promoter of climate change denial. It rejects the scientific consensus on climate change, and says that policies to fight it would be damaging to the economy.
  • 4.1K
  • 30 Oct 2022
Topic Review
List of Aircraft in the Smithsonian Institution
The List of aircraft in the Smithsonian Institution includes aircraft exhibited in the Smithsonian Institution's National Air and Space Museum, Steven F. Udvar-Hazy Center, and the Paul E. Garber Preservation, Restoration, and Storage Facility. The Smithsonian Institution's collection of aircraft and spacecraft is the largest on display in the world.
  • 4.1K
  • 21 Oct 2022
Topic Review
Metal-Organic Frameworks in CO2 Cycloaddition with Epoxides
The level of carbon dioxide in the atmosphere is growing rapidly due to fossil fuel combustion processes, heavy oil, coal, oil shelter, and exhausts from automobiles for energy generation, which lead to depletion of the ozone layer and consequently result in global warming. The realization of a carbon-neutral environment is the main focus of science and academic researchers of today. Several processes were employed to minimize carbon dioxide in the air, some of which include the utilization of non-fossil sources of energy like solar, nuclear, and biomass-based fuels. Consequently, these sources were reported to have a relatively high cost of production and maintenance. The applications of both homogeneous and heterogeneous processes in carbon capture and storage were investigated in recent years and the focus now is on the conversion of CO2 into useful chemicals and compounds. It was established that CO2 can undergo cycloaddition reaction with epoxides under the influence of special catalysts to give cyclic carbonates, which can be used as value-added chemicals at a different level of pharmaceutical and industrial applications. Among the various catalysts studied for this reaction, metal-organic frameworks are now on the frontline as a potential catalyst due to their special features and easy synthesis. Several metal-organic framework (MOF)-based catalysts were studied for their application in transforming CO2 to organic carbonates using epoxides. Here, we report some recent studies of porous MOF materials and an in-depth discussion of two repeatedly used metal-organic frameworks as a catalyst in the conversion of CO2 to organic carbonates
  • 4.1K
  • 25 Nov 2021
Topic Review
Digital Preservation of Cultural Heritage
The intensifying effects of climate change are becoming one of the main threats to cultural heritage, posing risks of degradation or destruction. Climate change is bringing complexity and uncertainty to ensuring the resilience of cultural heritage, and among risk mitigation measures digitalisation is regarded as a promising tool. However, the infrastructure required for the digitalisation process exerts significant pressures on the environment contributing to climate deterioration.
  • 4.0K
  • 06 Jun 2022
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