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Katherine Johnson’s mathematical calculations helped guide some of America’s most important early space missions while she confronted the racial and gender barriers faced by Black women in twentieth-century America.
MORE →Reflects the personal views, recollections, and perspective of the author, Mike Davis.
This is a personal recollection on the Move fire on May 13, 1985
| Sclerocactus sileri | |
|---|---|
| |
Scientific classification 
| |
| Kingdom: | Plantae |
| Clade: | Tracheophytes |
| Clade: | Angiosperms |
| Clade: | Eudicots |
| Order: | Caryophyllales |
| Family: | Cactaceae |
| Subfamily: | Cactoideae |
| Genus: | Sclerocactus |
| Species: | S. sileri
|
| Binomial name | |
| Sclerocactus sileri (L.D.Benson) K.D.Heil & J.M.Porter
| |
Sclerocactus sileri, the Siler fishhook cactus, is a rare and very small cactus found mostly in mineral-rich desert areas of intermediate elevations, notably in the American states of Utah, Nevada, and northern Arizona.
Sclerocactus sileri grows to about 25 cm tall and 12 cm wide. The cactus also shows a flower of diameter about 20 mm (1 in), with whitish or yellowish petals that show venation in a purple color. Flowering occurs in the spring season.
Sclerocactus sileri has both central and radial spines. Central spines have length up to about 15 to 30 mm (1 to 1 in) and are brownish-black in color. There are four central spines (4-5 per areole),[2] where the lower central spine is white, abaxial central spines are tinged, is gray-purplish, angled, and strongly hooked and slightly contorted. Central spines are 1.2–3 cm long and 0.5–1 mm wide, curving towards the ground. The two lateral spines are flattened and thicker. The upper central spine is white to tan and is curved and strongly flattened.
Radial spines have length up to about 10 to 20 mm (0 to 1 in) and are white in color. There are about 6-8 radial spines per areole which are acicular.[3]
Seeds are black to light brown in color, and are 2.2-2.5 mm wide, with a rounded papillae.[2]
Flowers and fruits of Sclerocactus sileri are very similar to others of the same family, such as S. whipplei or S. pubispinus. The phenology of the flowers from Sclerocactus sileri bloom during the months of April and May, while the fruits during the months of May and June.[3] Flowers are 2.5–3 cm (1-1.2 in) long and 2.5–3 cm in diameter, with a glabrous exterior floral tube. The outer tepals have brownish and yellowish margins, the larger oblanceolate, 10–15 mm long, mucronate, marginally membranous and crisped or minutely toothed. The inner tepals are yellow, sometimes suffused with brown, the largest lanceolate, 15–25 mm long and mucronate. The filaments are white or greenish white, 7–10 mm long, anthers yellow, about 1 mm long; style yellowish-green, 14–20 mm long; stigma lobes 5-8 and about 1.2-2.5 mm long; ovary 3–7 mm long at anthesis; scales few, membranous, scarious-margined, minutely toothed or fringed. The fruit is green, turning red, ovoid, dry, and 0.8-2.2 cm long. Fruits extend longitudinally, along two to four ventral slits. Black seeds are 2.75–3 mm in diameter and 2.25- 2.5 mm long.[3]
The names Sclerocactus sileri and Pediocactus sileri have a confused relationship in the literature. (Sclerocactus was included in Pediocactus by Arp in 1972, but this was not accepted by authorities well conversant in the Cactaceae.)[4] According to the treatment in the Flora of North America,[2] the taxon described here was first named by L.D. Benson (in 1969) as the variety sileri of Sclerocactus pubispinus. It was raised to a full species under the name Sclerocactus sileri by K.D. Heil and J.M. Porter in 1994.[5] Quite separately, Echinocactus sileri was first described in 1896 and transferred to Pediocactus sileri by L.D. Benson in 1961.[6][7] The two taxa are treated as two separate species in the Flora of North America, which has entries for:
Mistakenly, Anderson (2001) describes only one species, under the name Sclerocactus sileri, treating Pediocactus sileri as a synonym.[8] His description largely matches the description of Pediocactus sileri in the Flora of North America, and he uses the same common names (gypsum cactus, Siler's pincushion cactus) although the distribution he gives ("a very restricted area in Coconino County, Arizona") corresponds to that of Sclerocactus sileri in the Flora of North America ("restricted to northeast Coconino County, Arizona").[2]
Sclerocactus sileri is narrowly distributed. It has been seen in only Arizona, U.S.A, in Coconino County, although it is very close to the Utah border. See Sclerocactus sileri (L. D. Benson) K. D. Heil & J. M. Porter, Haseltonia. 2: 39. 1994.
Sclerocactus sileri is a vascular plant, found in habitats including scrubs, forests, grasslands, and especially desert shrubs. It grows in drier soils that are rich in minerals such as gypsum and salt, and typically in sandy soils derived from Moenkopi Formation. Sclerocactus sileri grow in grama grass. The following plants are usually associated with the Sclerocactus sileri: drop seed (Sporobolus), yucca (Yucca), hedgehog cactus (Echinocereus), sagebrush (Artemisia), snakeweed (Gutierrezia), pinyon (Pinus edulis), and juniper (Juniperus).[3] Sclerocactus sileri grows in the form of perennial succulent.
Sclerocactus sileri is native to the western United States, and habitat elevations typically range from 850 to 1,650 meters.[9]
Sclerocactus sileri has no known uses for humans.
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Parallel SCSI (formally, SCSI Parallel Interface, or SPI) is the earliest of the interface implementations in the SCSI family. SPI is a parallel bus; there is one set of electrical connections stretching from one end of the SCSI bus to the other. A SCSI device attaches to the bus but does not interrupt it. Both ends of the bus must be terminated. SCSI is a peer-to-peer peripheral interface. Every device attaches to the SCSI bus in a similar manner. Depending on the version, up to 8 or 16 devices can be attached to a single bus. There can be multiple hosts and multiple peripheral devices but there should be at least one host. The SCSI protocol defines communication from host to host, host to a peripheral device, and peripheral device to a peripheral device. The Symbios Logic 53C810 chip is an example of a PCI host interface that can act as a SCSI target. SCSI-1 and SCSI-2 have the option of parity bit error checking. Starting with SCSI-U160 (part of SCSI-3), all commands and data are error checked by a cyclic redundancy check.
Fencing is the process of isolating a node of a computer cluster or protecting shared resources when a node appears to be malfunctioning. As the number of nodes in a cluster increases, so does the likelihood that one of them may fail at some point. The failed node may have control over shared resources that need to be reclaimed and if the node is acting erratically, the rest of the system needs to be protected. Fencing may thus either disable the node, or disallow shared storage access, thus ensuring data integrity.
A computer cluster is a group of autonomous computers that work together so that they can be viewed as a single system. Unlike grid computers, computer clusters have each node set to perform the same task, controlled and scheduled by software. The newest manifestation of cluster computing is cloud computing. The components of a cluster are usually connected to each other through fast local area networks, with each node (computer used as a server) running its own instance of an operating system. In most circumstances, all of the nodes use the same hardware and the same operating system, although in some setups (e.g. using Open Source Cluster Application Resources (OSCAR)), different operating systems can be used on each computer, or different hardware. Clusters are usually deployed to improve performance and availability over that of a single computer, while typically being much more cost-effective than single computers of comparable speed or availability. Computer clusters emerged as a result of the convergence of a number of computing trends including the availability of low-cost microprocessors, high-speed networks, and software for high-performance distributed computing. They have a wide range of applicability and deployment, ranging from small business clusters with a handful of nodes to some of the fastest supercomputers in the world such as IBM's Sequoia. Prior to the advent of clusters, single-unit fault tolerant mainframes with modular redundancy were employed; but the lower upfront cost of clusters, and increased speed of network fabric has favoured the adoption of clusters. In contrast to high-reliability mainframes, clusters are cheaper to scale out, but also have increased complexity in error handling, as in clusters error modes are not opaque to running programs.
Sclerocactus sileri, the Siler fishhook cactus, is a rare and very small cactus found mostly in mineral-rich desert areas of intermediate elevations, notably in the American states of Utah, Nevada, and northern Arizona.
Before the 1921 destruction of Tulsa’s Greenwood District, Black residents had created a remarkable center of business and community life. The district included stores, professional offices, entertainment venues and homes owned by Black citizens. Understanding Greenwood means learning what was built—not only what was burned.
MORE →The Greenwood District.
