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Topic Review
4D Scanning Transmission Electron Microscopy
4D scanning transmission electron microscopy (4D STEM) is a subset of scanning transmission electron microscopy (STEM) which utilizes a pixelated electron detector to capture a convergent beam electron diffraction (CBED) pattern at each scan location. This technique captures a 2 dimensional reciprocal space image associated with each scan point as the beam rasters across a 2 dimensional region in real space, hence the name 4D STEM. Its development was enabled by evolution in STEM detectors and improvements computational power. The technique has applications in visual diffraction imaging, phase orientation and strain mapping, phase contrast analysis, among others. The name 4D STEM is common in literature, however it is known by other names: 4D STEM EELS, ND STEM (N- since the number of dimensions could be higher than 4), position resolved diffraction (PRD), spatial resolved diffractometry, momentum-resolved STEM, "nanobeam precision electron diffraction", scanning electron nano diffraction, nanobeam electron diffraction, or pixelated STEM.
  • 1.2K
  • 11 Oct 2022
Topic Review
4D-Based Environmental Impact Analysis of Road Project Variants
Road construction work has a multitude of impacts on its host environment, and the effect of these impacts varies according to the areas it crosses. Taking these impacts into account from the earliest stages of project planning is the ideal approach pursued by planners to ensure that their plans not only take these impacts into account but also mitigate their effects as much as possible. Drawing up a project schedule that considers the impact of the work requires an in-depth understanding of its scale, spatial extent, and timing. 
  • 264
  • 06 Nov 2023
Topic Review
4D-Flow Imaging in Aortic Valve Disease
The development of abnormal blood flow has been demonstrated to be due to a variety of pathological causes, such as atherosclerotic plaque or valvular disease. Traditionally, cardiovascular magnetic resonance imaging (MRI) has provided high-quality imaging of the heart with its surrounding structures. 4D-flow imaging is an advanced cardiac MR imaging technique that allows fluid hemodynamics to be measured non-invasively in patients. As a growing field in radiology, its adaptation and clinical use remain underutilized. 
  • 329
  • 21 Jun 2023
Topic Review
4Th Dimension
4D (4th Dimension, or Silver Surfer, as it was known during early development) is a relational database management system and IDE developed by Laurent Ribardière. 4D was created in 1984 and had a slightly delayed public release for Macintosh in 1987 with its own programming language. The 4D product line has since expanded to an SQL back-end, integrated compiler, integration of PHP, and several productivity plug-ins and interfaces. Some of the plug-ins created by 4D include 4D Write (a word processor), 4D View (somewhat like a spreadsheet, but with extra functionality) and 4D Internet Commands (which allowed for the addition of Internet-related functionality to a database). There are also over 100 third-party plugins, free and commercial. 4D can also be used as a web server, to run compiled database applications. Today, 4D is published by the France company 4D SAS and has a sales, distribution and support presence in most major markets, with the United States, the United Kingdom, and France being the primary markets. The product is localized in more than a dozen languages.
  • 376
  • 02 Nov 2022
Topic Review
5-(Hydroxymethyl)-2-furfural (HMF)
5-(Hydroxymethyl)-2-furfural (HMF), represents a wide class of heterocycles and is formed as an intermediary product of the Maillard reaction or formed by carbohydrate dehydration in an acid medium. HMF also can be generated in significantly amounts at low temperatures during long periods of storage. The formation of HMF is affected by the concentration and type of sugar, acid, minerals, pH as well as amino acids.
  • 1.4K
  • 16 Nov 2021
Topic Review
5-10-Methylenetetrahydrofolate Reductase
The 5-10-methylenetetrahydrofolate reductase (MTHFR) enzyme is vital for cellular homeostasis due to its key functions in the one-carbon cycle, which include methionine and folate metabolism, and protein, DNA, and RNA synthesis. 
  • 587
  • 14 Feb 2022
Topic Review
5-ALA Metabolic Pathway
5-Aminolevulinic acid (5-ALA) is a natural amino acid and a precursor of heme and chlorophyll. Exogenously administered 5-ALA is metabolized into protoporphyrin IX (PpIX). PpIX accumulates in cancer cells because of the low activity of ferrochelatase, an enzyme that metabolizes PpIX to heme. High expression of 5-ALA influx transporters, such as peptide transporters 1/2, in cancer cells also enhances PpIX production. Because PpIX radiates red fluorescence when excited with blue/violet light, 5-ALA has been used for the visualization of various tumors. 
  • 696
  • 22 Jun 2022
Topic Review
5-alpha Reductase Deficiency
5-alpha reductase deficiency is a condition that affects male sexual development before birth and during puberty. People with this condition are genetically male, with one X and one Y chromosome in each cell, and they have male gonads (testes). Their bodies, however, do not produce enough of a hormone called dihydrotestosterone (DHT). DHT has a critical role in male sexual development, and a shortage of this hormone disrupts the formation of the external sex organs before birth.
  • 568
  • 23 Dec 2020
Topic Review
5-Aminolevulinic Acid in Gliomas
5-aminolevulinic acid (5-ALA) is a porphyrin precursor in the heme synthesis pathway. When supplied exogenously, certain cancers consume 5-ALA and convert it to the fluorogenic metabolite protoporphyrin IX (PpIX), causing tumor-specific tissue fluorescence. Preoperative administration of 5-ALA is used to aid neurosurgical resection of high-grade gliomas such as glioblastoma, allowing for increased extent of resection and progression free survival for these patients. Targeting the heme synthesis pathway and understanding its dysregulation in malignant tissues could aid the development of adjunct therapies to increase intraoperative fluorescence after 5-ALA treatment
  • 567
  • 14 Apr 2021
Topic Review
5-Aminolevulinic Acid in Photodynamic Therapy
5-Aminolevulinic acid (ALA) is a naturally occurring amino acid synthesized in all nucleated mammalian cells. As a porphyrin precursor, ALA is metabolized in the heme biosynthetic pathway to produce protoporphyrin IX (PpIX), a fluorophore and photosensitizing agent. ALA administered exogenously bypasses the rate-limit step in the pathway, resulting in PpIX accumulation in tumor tissues. Such tumor-selective PpIX disposition following ALA administration has been exploited for tumor fluorescence diagnosis and photodynamic therapy (PDT) with much success. Five ALA-based drugs have now received worldwide approval and are being used for managing very common human (pre)cancerous diseases such as actinic keratosis and basal cell carcinoma or guiding the surgery of bladder cancer and high-grade gliomas, making it the most successful drug discovery and development endeavor in PDT and photodiagnosis. 
  • 446
  • 04 May 2023
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