Discussion of "Riverbed degradation below large capacity reservoirs"

CER58-9.Includes bibliographical references.Proc. paper 788

Artificial roughness standard for open channels

Reprint from Transactions, American Geophysical Union, V. 33, no.6, December 1952.Includes bibliographical references.In the formulas in present use the resistance coefficient has been considered constant for a particular type of material in a particular state of upkeep. The resistance coefficient, however, is not a constant for a given channel but varies with both velocity and depth. From the nature of these formulas in present use, it may be seen that the variable influence of viscosity is not taken into consideration. Because of the need for more accurately determining the discharges in open channels a standard for roughness for open channels such as that which exists for pipes is desirable. The problem of developing a reproducible standard for roughness in open channels has previously received very little systematic study. Although several investigations have been made, each was made with a different type of roughness. This study was conducted for the purpose of determining whether an artificial roughness standard could be established for a channel with a boundary so rough that the viscous effects were negligible. The equation C = 26 .65 log10 (1.891 d/a) was established and is applicable over at least a fourfold variation in d/a and nearly a twofold variation in the resistance coefficient

Flume studies using medium sand (0.45mm)

CER58DBS2.Includes bibliographical references.The results pertaining to the progress during the first year of a comprehensive study of fluvial hydraulics, specifically roughness in alluvial channels, are presented. The report is based on the data collected by using a recirculating rectangular flume of adjustable slope, 8 feet wide, 2 feet deep, and 150 feet long with an alluvial bed of sand approximately 0. 7 foot deep. A typical river sand has been utilized. Its median diameter, d, is 0.45 mm and its relative standard deviation, σ, is 1.60. A total of 45 runs have been completed over a range of bed roughness forms extending from the plane bed with no movement to antidunes. In order to achieve this range, the discharge was varied from 2 to 21 cubic feet per second, the average velocity was varied from 0.5 to 7 feet per second, the average depth of flow was varied from 0.3 to 1.0 foot, and the slope of water surface was varied from 0.00014 to 0.01. Other variables measured included: water temperature, bed roughness, suspended sediment load, and total sediment load. Terms describing channel roughness were formulated and tested based on the data collected. The results indicate, as one possibility, that the Chezy coefficient of discharge in dimensionless form C/√g is a function of parameters involving the Froude number, viscosity of fluid, fall velocity, specific weight of the sediment, median diameter of the sediment particles and slope of the water surface. The various expressions presented were formulated on the fundamental concepts of fluid mechanics, dimensional analysis, and a detailed study of the variations of the variables measured. In the two regimes of flow the following forms of bed roughness were observed. For tranquil flow regime: plane bed without movement, ripples, dunes and transition from dunes to rapid flow forms. For rapid flow regime: plane bed with movement, standing sand waves, and antidunes. These forms of bed roughness are discussed and defined in various relationships. Other data of both a laboratory and a field nature were combined with the flume data to develop a graphical relationship in which the form of bed roughness is related to size of bed material

Process evaluation of the Newham Y2A Hub: evaluating the implementation of a specialist youth to adulthood transitions service in probation

Young adults aged 18-25 years old in the criminal justice system face age-specific maturity needs, which relate to their rehabilitation. The Youth2Adulthood (Y2A) transitions Hub was developed to address these needs, alongside additional needs such as neurodiversity. The hub used a co-located probation and commissioned services model. This process evaluation sought to gather evidence on the implementation of this bespoke hub model. Analysis of interviews with 60 members of staff and 35 young adults suggested that the Hub was implemented well. Participants were positive about the Hub and identified benefits and challenges related to its implementation

Holocentric Chromosomes of Luzula elegans Are Characterized by a Longitudinal Centromere Groove, Chromosome Bending, and a Terminal Nucleolus Organizer Region

The structure of holocentric chromosomes was analyzed in mitotic cells of Luzula elegans. Light and scanning electron microscopy observations provided evidence for the existence of a longitudinal groove along each sister chromatid. The centromere-specific histone H3 variant, CENH3, colocalized with this groove and with microtubule attachment sites. The terminal chromosomal regions were CENH3-negative. During metaphase to anaphase transition, L. elegans chromosomes typically curved to a sickle-like shape, a process that is likely to be influenced by the pulling forces of microtubules along the holocentric axis towards the corresponding microtubule organizing regions. A single pair of 45S rDNA sites, situated distal to Arabidopsis-telomere repeats, was observed at the terminal region of one chromosome pair. We suggest that the 45S rDNA position in distal centromere-free regions could be required to ensure chromosome stability. Copyright (C) 2011 S. Karger AG, Base

Epidemic of illicit drug use, mechanisms of action/addiction and stroke as a health hazard

Drug abuse robs individuals of their jobs, their families, and their free will as they succumb to addiction; but may cost even more: a life of disability or even life lost due to stroke. Many illicit drugs have been linked to major cardiovascular events and other comorbidities, including cocaine, amphetamines, ecstasy, heroin, phencyclidine, lysergic acid diethylamide, and marijuana. This review focuses on available epidemiological data, mechanisms of action, particularly those leading to cerebrovascular events, and it is based on papers published in English in PubMed during 1950 through February 2011. Each drug's unique interactions with the brain and vasculature predispose even young, healthy people to ischemic or hemorrhagic stroke. Cocaine and amphetamines have the strongest association with stroke. However, the level of evidence firmly linking other drugs to stroke pathogenesis is weak. Large epidemiological studies and systematic evaluation of each drug's action on the brain and cardiovascular system are needed to reveal the full impact of drug use on the population

Planar Graph Coloring with Forbidden Subgraphs: Why Trees and Paths Are Dangerous

We consider the problem of coloring a planar graph with the minimum number of colors such that each color class avoids one or more forbidden graphs as subgraphs. We perform a detailed study of the computational complexity of this problem. We present a complete picture for the case with a single forbidden connected (induced or non-induced) subgraph. The 2-coloring problem is NP-hard if the forbidden subgraph is a tree with at least two edges, and it is polynomially solvable in all other cases. The 3-coloring problem is NP-hard if the forbidden subgraph is a path, and it is polynomially solvable in all other cases. We also derive results for several forbidden sets of cycles

Measurement of the Omega_c Lifetime

We present the measurement of the lifetime of the Omega_c we have performed using three independent data samples from two different decay modes. Using a Sigma- beam of 340 GeV/c we have obtained clean signals for the Omega_c decaying into Xi- K- pi+ pi+ and Omega- pi+ pi- pi+, avoiding topological cuts normally used in charm analysis. The short but measurable lifetime of the Omega_c is demonstrated by a clear enhancement of the signals at short but finite decay lengths. Using a continuous maximum likelihood method we determined the lifetime to be tau(Omega_c) = 55 +13-11(stat) +18-23(syst) fs. This makes the Omega_c the shortest living weakly decaying particle observed so far. The short value of the lifetime confirms the predicted pattern of the charmed baryon lifetimes and demonstrates that the strong interaction plays a vital role in the lifetimes of charmed hadrons.Comment: 15 pages, including 7 figures; gzipped, uuencoded postscrip

Between proper and strong edge-colorings of subcubic graphs

In a proper edge-coloring the edges of every color form a matching. A matching is induced if the end-vertices of its edges induce a matching. A strong edge-coloring is an edge-coloring in which the edges of every color form an induced matching. We consider intermediate types of edge-colorings, where edges of some colors are allowed to form matchings, and the remaining form induced matchings. Our research is motivated by the conjecture proposed in a recent paper of Gastineau and Togni on S-packing edge-colorings (On S-packing edge-colorings of cubic graphs, Discrete Appl. Math. 259 (2019), 63-75) asserting that by allowing three additional induced matchings, one is able to save one matching color. We prove that every graph with maximum degree 3 can be decomposed into one matching and at most 8 induced matchings, and two matchings and at most 5 induced matchings. We also show that if a graph is in class I, the number of induced matchings can be decreased by one, hence confirming the above-mentioned conjecture for class I graphs

Revisiting the Local Scaling Hypothesis in Stably Stratified Atmospheric Boundary Layer Turbulence: an Integration of Field and Laboratory Measurements with Large-eddy Simulations

The `local scaling' hypothesis, first introduced by Nieuwstadt two decades ago, describes the turbulence structure of stable boundary layers in a very succinct way and is an integral part of numerous local closure-based numerical weather prediction models. However, the validity of this hypothesis under very stable conditions is a subject of on-going debate. In this work, we attempt to address this controversial issue by performing extensive analyses of turbulence data from several field campaigns, wind-tunnel experiments and large-eddy simulations. Wide range of stabilities, diverse field conditions and a comprehensive set of turbulence statistics make this study distinct