All articles starting with H

Hemant Taneja

Hemant Taneja is a venture capital investor who joined General Catalyst in 2001 and has been its CEO since 2021, backing companies including Stripe, Snap, and Anthropic.

Sep 21, 2026

Hemantha Wickramasinghe, known as H. Kumar Wickramasinghe, is an electrical engineer who invented several scanning probe microscopes, became an IBM Fellow, and is a distinguished professor at UC Irvine.

Hematemesis

Hematemesis, vomiting of blood, signals upper GI bleeding from peptic ulcers, varices, or Mallory-Weiss tears; distinguished from hemoptysis by acidic, coffee-ground vomit and managed with endoscopy.

Hematene

Hematene is a two-dimensional material of iron oxide, Fe₂O₃, first reported in 2018 by Rice University researchers who exfoliated atomic-scale sheets from natural hematite ore; it founded a family of non-van der Waals 2D materials.

Hematidrosis

Hematidrosis, also called hematohidrosis or bloody sweat, is a rare eccrine sweat disorder in which blood-tinged fluid oozes from intact skin, typically under extreme stress; ICD-10 L74.8, treated with beta-blockers such as propranolol.

Oct 15, 2026

Hematin

Hematin is an iron-containing porphyrin, the hydroxide-ligated form of protoporphyrin IX related to hemin, whose crystallization into hemozoin in malaria parasites is targeted by quinoline antimalarials.

Hematite

Hematite is an iron oxide mineral, Fe₂O₃, and the most important ore of iron; most formed in Precambrian banded iron formations, and it also occurs on Mars.

Hematite photoanodes

Hematite photoanodes are photoelectrodes made of hematite (α-Fe₂O₃), a stable, low-cost, n-type iron oxide semiconductor that absorbs sunlight and oxidizes water in photoelectrochemical water-splitting cells.

Hematochezia

Hematochezia, or bright red blood per rectum, is passage of fresh red or maroon blood from the rectum, usually from lower GI bleeding (diverticula, angiodysplasia, neoplasms, colitis, hemorrhoids) but occasionally a brisk upper GI bleed with hemodynamic instability.

Hematocrit

Hematocrit (HCT, packed cell volume, PCV) is the percentage of blood volume made up of red blood cells, measured by centrifugation or calculated by automated Coulter-principle analyzers; typical adult ranges are 41–50% for men and 36–47% for women, used to assess anemia, polycythemia, and dehydration.

Hematodinium

Hematodinium (type species H. perezi) is a genus of parasitic dinoflagellates in the order Syndiniales that infects the hemolymph of marine crabs, lobsters, and shrimp, causing Bitter Crab Disease and major aquaculture losses in China.

Hematology

Hematology is the branch of internal medicine concerned with blood, blood-forming organs, and blood diseases, including anemias, clotting disorders, and blood cancers such as leukemia and lymphoma.

Hematoma

Hematoma: a localized collection of clotted blood outside blood vessels in an organ, tissue, or body space; also called a bruise (contusion) when superficial. Types include subdural, epidural, subungual, and auricular hematomas.

Hematophagy

Hematophagy, also called sanguivory, is the feeding habit of animals that ingest the blood of other animals, best known in mosquitoes, ticks, and vampire bats.

Hematopoietic cell

Hematopoietic cell: any blood-forming cell, from self-renewing hematopoietic stem cells through progenitors to mature erythrocytes, leukocytes, and platelets; hierarchy, niches, epigenetics, and transplantation.

Hematopoietic cell signal transducer

HCST (DAP10, KAP10, PIK3AP) is a human chromosome 19 gene encoding a 93-aa transmembrane immune adaptor that pairs with NKG2D, recruits PI3K and Grb2-Vav1 via its YINM motif, and drives NK and CD8 T cell cytotoxicity.

Hematopoietic multipotent progenitor cell

Hematopoietic multipotent progenitor (MPP) cells are short-term, self-renewal-limited descendants of hematopoietic stem cells that generate multiple blood lineages; subtypes include FLT3+ LMPPs, myeloid- and erythroid-biased human MPPs, and HSC-independent embryonic eMPPs.

Hematopoietic stem cell

The hematopoietic stem cell, or blood stem cell, is a bone marrow cell that renews itself for life and gives rise to all blood cell types, including white cells, red cells, and platelets.

Hematopoietic Stem Cell Mobilization

Hematopoietic stem cell mobilization moves HSCs from bone marrow to blood for apheresis before transplantation, using G-CSF, CXCR4 inhibitors like plerixafor, or cyclophosphamide chemo-mobilization; about 15% of patients mobilize poorly.

Oct 15, 2026

Hematoporphyrin

Hematoporphyrin, also known as hematoporphyrin IX, is a porphyrin first isolated from blood in 1841 that acts as a photosensitizer and parent compound of the photodynamic therapy drug Photofrin.

Hematoporphyrin Photoradiation

Hematoporphyrin photoradiation, or photodynamic therapy (PDT), is a form of photochemotherapy using visible light applied locally or topically to destroy diseased tissue. Its initial application was described in 1903.

Oct 15, 2026

Hematoxylin

Hematoxylin is a natural compound extracted from the heartwood of the logwood tree, used worldwide as the nuclear stain in histology and, with eosin, in the routine H&E stain of diagnostic pathology.

Sep 29, 2026

Hematoxylin and eosin staining

Hematoxylin and eosin (H&E) staining is a histological method that turns cell nuclei blue-purple and cytoplasm pink, and is the most widely used stain for cancer diagnosis.

Hematuria

Hematuria, blood in the urine, is gross (visible) or microscopic (≥3 RBC/HPF on urinalysis). Causes range from infection, stones, and BPH to urinary tract cancer; AUA/SUFU guidelines stratify evaluation by malignancy risk.

Hemavati Mound

Hemavati Mound: protected archaeological site at Hemavati (ancient Henjeru), Sri Sathya Sai district, Andhra Pradesh; Nolamba dynasty capital 8th-11th century, with protected group of old temples, Nolamba sculptures, and about 20 inscriptions under ASI Amaravati Circle.

Hemba ancestor figures

Hemba ancestor figures, called singiti, are carved wooden statues made by the Hemba people of the Democratic Republic of the Congo to honor male ancestors, mainly chiefs and lineage founders.

Hembury

Hembury (Hembury Fort, Hembury Hillfort) is a multivallate Iron Age hillfort near Payhembury, Devon, over a Neolithic causewayed enclosure dated about 3700 BC, briefly occupied by the Roman army in the mid-first century AD, and owned since 2023 by the Devon Archaeological Society.