186,150 research outputs found
Ecological and physiological aspects of aestivation-diapause in the larvae of two Pyralid stalk borers of maize in Kenya
No full textStalk borers are highly destructive to a large number of important graminaceous crops all over the world. Some examples of economically important stalk borers and a general description of their life-cycle are mentioned in chapter 1. In the same chapter difficulties in controlling the insects are described. The crucial role of aestivation- diapause in the life history of tropical stalk borers is elucidated and the importance of further research on this subject is demonstrated.Aestivation-diapause in two Pyralid stalk borers, Chilopartellus (Swinhoe) and Chilo orichalcociliella (Strand) was investigated under field and laboratory conditions.The relation between diapause and climate during three consecutive years is described in chapter 2. Yearly and seasonal fluctuations in the larval and pupal populations of the two stalk borers in maize appeared to be considerable. As long as the water conditions for plant growth were suitable, insects had a continuous development. Under these conditions larvae had pigmented spots and could not survive dry conditions. Soon after cessation of the rains (or irrigation) rates of pupation decreased. At that time larvae lost their cuticular pigmentation and became resistant to drought. Comparison of the incidence of aestivation in the field with the prevailing climatic conditions showed that only lack of rain could be associated with the arrested larval development. No effects of temperature, relative humidity or photoperiod could be found. These results indicate that the host plant may be involved in the induction of diapause.Chapter 3 is concerned with characteristics of pre-diapause and diapause larvae. Evidence was obtained that under natural conditions larvae do not feed during diapause as long as they are not disturbed. The physiological condition of field-collected stem borer larvae changed considerably upon entering diapause: a decreased rate of oxygen consumption, rate of heart beat and water content, an increased fat content, and arrested development of the testes were found. These changes normally occurred before larvae were turning unspotted and/or were becoming resistant to drought.The condition of the host plant in relation to diapause induction is described in chapter 4. Diapause could be induced inside maize plants of different developmental stages. It was shown that the first (physiological) signs of the diapause syndrome appear in larvae feeding in stems containing 70-80% water and very little (Marked differences were found in the consumption and utilization of stems of maize plants in different developmental stages. Its possible relevance to diapause is discussed.In chapter 5 experiments are described on the induction of aestivation-diapause by varying the food condition. Most early 5th instar larvae of C. partellus entered diapause after being introduced into aged maize stems containing 75% water, 8% sugar and 1.3% protein (fresh wt.). Pupation rate, cuticular pigmentation, QO 2 and water content of these larvae werecomparable to values obtained from field-collected aestivating larvae. Larvae which had developed beyond the early 5th instar were less sensitive to the diapause inducing factors of the aged maize stem : most of them pupated.Test of 30 different diets with varying protein, sugar and water contents, indicated that diets containing 0.9-1.1% protein and 70% water were best in inducing diapause. Early 5th instar larvae on diets with the above mentioned protein content grew slowly (but reached normal weights), moulted into the unspotted form and had a retarded rate of pupation. Larvae on diets with lower protein contents hardly developed at all, whereas on diets with higher protein contents larvae pupated normally. Larvae reared on diets in which the water content had been reduced from the normal level of 86% to 70%, resulted in areduction of the larval water content and respiratory rate, close to values normal for field-collected diapause larvae. Evidence was obtained that larvae reared on diapause inducing diets attained a certain degree of drought resistance. Early 5th instar or younger larvae were the most sensitive stages to diapause induction by diet.Many larvae on aged maize stems and artificial diets turned unspotted even though pupating soon thereafter. The relevance of the cuticular pigmentation as a criterion for aestivation-diapause is discussed. The endocrine involvement in the aestivation- diapause is described in chapter 6. From juvenile hormone titre determinations and ligation experiments evidence was obtained that the diapause is regulated by an intermediate level of JH. Application of JH to non-diapause larvae prevented pupation of these larvae but did not evoke other aspects of the diapause syndrome
Instrument for fine-mechanical or surgical applications
No full textThe invention relates to an instrument for high-precision or surgical applications of a minimally invasive nature, comprising a distally positioned directable head, a shaft upon which the head is positioned, and a proximally positioned handgrip for operating the head, wherein a ring of cables comprising longitudinally extending cables connects to the head, wherein each cable of the ring of cables is disposed such that at least a part of both sides is in direct contact with another cable of the ring of cables, and wherein the cables are fixedly secured in the radial direction.Mechanical, Maritime and Materials Engineerin
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Appropriate Similarity Measures for Author Cocitation Analysis
No full textWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
No full textWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
Dr. Edward P. Wimberly, ITC, July 2011
No full textThis video is a conversation with Dr. Edward P. Wimberly. Dr. Wimberly talks about his book, "No Shame in Wesley's Gospel: A Twenty-First Century Pastoral Gospel". Brad Ost, AUC Woodruff Library, is the interviewer
Author Rights and Scholarly Publishing
No full textOriginally posted at
http://blog.library.gsu.edu/2014/10/24/author-rights-and-scholarly-publishing/</p
Design of a Steerable Laparoscopic Aspirator-Irrigator: FlowFlex
No full textLaparoscopy is a type of minimally invasive surgery in which instruments with long, slender shafts between handle and end effector are inserted through small incisions in the abdominal wall. A laparoscopic aspirator-irrigator (LAI) has a hollow shaft used to evacuate undesirable substances using a vacuum pressure, rinse tissue using a stream of pressurized saline, and manipulate adherent tissue.Although laparoscopic instruments typically have a steerable tip to compensate for the loss of maneuverability due to the small incision, all currently available laparoscopic aspirator-irrigators lack a steerable tip. This lack is associated with sub-optimal aspiration and irrigation efficacy, mechanical trauma resulting from interference with obstructive tissue, interference with other instruments, and a lack of fine motor control of the tip. Although LAI’s with a steerable tip are known from patent literature [1]–[6], they all seem to have been abandoned, which suggests that the implementation of a steerable tip on an LAI tends to compromise performance relative to cost. Therefore, the objective of the current study is to design a new laparoscopic aspirator-irrigator (FlowFlex) with a steerable tip that mitigates the limitations of a conventionally rigid, straight tip to the extent of warranting its additional cost.To meet the objective, design requirements have been generated, tentative prototypes have been designed and evaluated, and a Final Prototype has been designed based on the superior tentative prototypes. Its steerable tip consists of an inner tube that is rigid and straight and an outer tube with an elastic, pre-curved silicone tip. Whereas the inner tube is stationary, the user can rotate, retract, or protract the outer tube by moving the tip control wheel on its proximal end using the index or middle finger, causing the tip to rotate, straighten, or deflect.The Final Prototype meets all important design requirements; it is cost-effective, due to the particularly simple and cheap steerable tip, it has ample flow rate capacity, it is unsusceptible to clogging, and it is sufficiently maneuverable. Although its main limitation is the low stiffness of its pre-curved tip, the ability of the tip to be rigidized by straightening makes it at least as capable of manipulating tissue as a conventional laparoscopic aspirator-irrigator.Mechanical Engineerin
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