Prevention of cracking of soldered joints in electronic assemblies

Printed circuit board design allows for thermal stressing of the soldered joints during many thermal cycles. Components' leads should be cleaned, tinned, and freed of particles that prevent solder adherence, have a thin conformal coating, and have an air space between the coating and the body of the component

A study of the possible preventive effects of muscular exercises and intermittent venous occlusion on the cardiovascular deconditioning observed after 10 days bed recumbency - Experimental design

Experiment designed to study preventive effects of muscular exercises on intermittent venous occlusion on cardiovascular deconditioning observed after 10 days bed recumbenc

Magnesium levels of Tennessee soils in relation to crop growth

Within the past few years reports of magnesium deficiency in various crops have been received from several sections of the state. As early as 1946 chlorotic striping of corn had been observed on the Cumberland Plateau. In the summers of 1948 and 1949 reports of magnesium deficiencies in corn were received from the Highland Rim and the Central Basin areas of the state. Also magnesium deficiencies in cotton were reported in Lincoln County, Tennessee in the summer of 1949. Field observations in the affected areas revealed that typical deficiency symptoms were rather widespread on the Cumberland Plateau, appearing in corn, tobacco, cauliflower and some other crops grown in that area. In the other sections of the state the symptoms appeared in widely scattered fields and were noticed primarily in corn. A study of the nature and extent of the trouble was begun in the summer of 1948. This paper is a report of that study to date

Cordial Digraphs

A $(0,1)$-labeling of a set is said to be friendly if the number of elements of the set labeled 0 and the number labeled 1 differ by at most 1. Let $g$ be a labeling of the edge set of a graph that is induced by a labeling $f$ of the vertex set. If both $g$ and $f$ are friendly then $g$ is said to be a cordial labeling of the graph. We extend this concept to directed graphs and investigate the cordiality of directed graphs. We show that all directed paths and all directed cycles are cordial. We also discuss the cordiality of oriented trees and other digraphs

(0,1)-Matrices, Discrepancy and Preservers

Let m and n be positive integers, and let R = (r1, . . . , rm) and S = (s1, . . . , sn) be nonnegative integral vectors. Let A(R,S) be the set of all m × n (0, 1)-matrices with row sum vector R and column vector S. Let R and S be nonincreasing, and let F(R) be the m × n (0, 1)-matrix, where for each i, the ith row of F(R,S) consists of ri 1’s followed by (n−ri) 0’s. Let A ∈ A(R,S). The discrepancy of A, disc(A), is the number of positions in which F(R) has a 1 and A has a 0. In this paper we investigate linear operators mapping m × n matrices over the binary Boolean semiring to itself that preserve sets related to the discrepancy. In particular, we show that bijective linear preservers of Ferrers matrices are either the identity mapping or, when m = n, the transpose mapping

A note on k-primitive directed graphs

AbstractWe consider the problem of which primitive directed graphs can be k-colored to yield a k-primitive directed graph. If such a k-coloring exists, then certainly such a graph must have at least k cycles. We prove that any primitive directed graph admits a 2-coloring that is 2-primitive. By contrast, for each k⩾4, we construct examples of primitive directed graphs having k cycles for which no k-coloring is k-primitive. We also give some partial results for the case that k=3

The effect of bedrest on various parameters of physiological function. part xii- the effect of bedrest on bone mass and calcium balance

Bed rest effect on various parameters of physiological functions - bone mass and calcium balanc