Lateral Failure of Spars

It was concluded that after the critical span or depth-breadth ratio has been reached, the modulus of rupture varies approximately inversely as the first power of the span and of the depth-breadth ratio. The direction of the lateral deflection is alternate between successive supports. For this reason, we believe that rib spacing along the spar is more important in reducing lateral deflection than the distance between supports at the strut points. Furthermore, we believe that, within the limits of modern design, any increase in distance between strut points can well be compensated for by spacing the ribs closer together, providing the ribs do furnish lateral support

Millipeds (Arthropoda: Diplopoda) of the Ark - La - Tex. VI. New Geographic Distributional Records from Select Counties of Arkansas

We continue to report, in the sixth of a series of papers, new geographic records for millipeds of the state, including noteworthy records for some taxa collected from Crowley’s Ridge in eastern Arkansas. This contribution documents 47 new co. records and includes records for 19 species within 9 families and 5 orders. More uncommon millipeds found included Okliulus carpenteri (Parajulidae), Eurymerodesmus newtonus (Eurymerodesmidae), Pseudopolydesmus minor (Polydesmidae) and undescribed species of Ethojulus (Parajulidae) and Nannaria (Xystodesmidae). Undoubtedly, additional records will be reported in the future as several gaps in the distribution of Arkansas millipeds remain

Geographic Distribution and Life History Aspects of the Freshwater Shrimps, Macrobranchium ohione and Palaemonetes kadiakensis (Decapoda: Palaemonidae), in Arkansas

Two species of shrimps occur in Arkansas; they include the Ohio shrimp, Macrobrachium ohione (Smith) and the Mississippi grass shrimp, Palaemonetes kadiakensis Rathbun. The present survey is based on collections made between 1974 and 2008 with additional supplemental data from museum specimens to document the overall distribution of the 2 species. Our survey found a total of only 42 specimens of M. ohione from 6 localities (2 counties) in Arkansas, all taken from the Mississippi River. Specimens were seined over sandy substrates in 0.6-0.9 m of water without vegetation. A 1914 museum collection of 5 individual M. ohione is the only known occurrence of M. ohione from Phillips County. All other specimens were taken between 1974-1975 near the US 82 bridge (Chicot County). It appears that M. ohione is a relatively rare shrimp in Arkansas. Since specimens were documented from a single drainage system (Mississippi River) in only 2 counties, we recommend a “threatened” conservation status of M. ohione in Arkansas because of this restricted distributional range. However, P. kadiakensis is relatively abundant in Arkansas. This shrimp had previously been reported from 10 counties of the state. Over 3,400 specimens of P. kadiakensis were documented during this study from various sites in 49 counties and most were released upon capture. Grass shrimp were commonly found in sluggish backwater regions of streams especially preferring heavily vegetated lentic areas of pool regions. Mississippi grass shrimp have remained abundant and widespread in occurrence for the past 35 years. The Nature Conservancy lists populations of P. kadiakensis as secure (G5) in rounded global status. Indeed, Mississippi grass shrimp populations in Arkansas are also secure and in no need of special protection

Arkansas Endemic Flora and Fauna An Update with 13 Additional Species

Arkansas supports a diverse variety of endemic biota with most found in the Interior Highlands (Ozarks and Ouachitas) of the state. Since 1988, several compilations have updated the number of endemics known while some former endemic species have been found in other states and subsequently removed from the state list. Here, update to the list by adding 13 taxa, several of which are fish parasites, making a grand total of 139 current endemic species in Arkansas