scholarly journals The Spread of Bacterial Infection Some Characteristics of Long-continued Epidemics

1921 ◽  
Vol 19 (4) ◽  
pp. 350-379 ◽  
Author(s):  
W. W. C. Topley
Keyword(s):  
Considerable Proportion ◽  
Epidemic Disease ◽  
Susceptible Population ◽  
Infected Population ◽  
Average Survival ◽  
Constant Rate ◽  
Cage Population ◽  
Direct Experiment ◽  
The One ◽  
Spread Of Infection

The results so far obtained have raised many questions and answered few of them. The important rôle played in the spread of epidemic disease by the re-accumulation of a susceptible population is clearly indicated. It seems not unreasonable to hope that valuable information as to the effect produced by variations in the rate of such re-accumulation, and on other matters, may be obtained by the satisfying method of direct experiment. The bearing of such information on the well-known fluctuations in the incidence of epidemic diseases, and especially perhaps of those which fall most heavily on children, are too obvious to need emphasising.The following conclusions seem permissible at the present stage:(1) If susceptible mice be continuously added to an infected population the spread of infection will continue over a long period of time. There is no evidence that this period has a limit.(2) When susceptible mice are added continuously and at a constant rate to an infected population, the spread of infection, as judged by a mortality curve, is propagated in regularly recurring waves. These waves are most easily observed by noting the fluctutations in the total cage-population. It seems probable that the period of these fluctuations will be found to depend on the rate of addition of susceptible individuals, but this point has still to be determined.(3) The actual deaths may occur in large groups, with intervals during which deaths are few and far between, or they may fall in a succession of smaller groups, increasing and diminishing in size to form the larger waves. In all cases there is this tendency for the occurrence of such small groups of deaths with definite maximal points. There would seem to be two fluctuating processes, the one superimposed upon the other.(4) The average survival-time of mice added to the cage, and their chance of ultimate survival if no more susceptible mice are introduced, vary according to the phase at which they are added. If they gain entrance to the cage during the rise of a wave they are unlikely to live for long. If they are introduced during the fall of a wave their chances of survival are greatly increased, and they will usually outlive mice which are added at a later date but at a time before the commencement of the next wave.(5) The rate of extinction of a population, among which infection is actively spreading, will be far less rapid if they are kept isolated, than if further susceptible individuals continuously gain access to them. A proportion of the infected population, which would have survived indefinitely under the former circumstances, will die under the latter.(6) The ultimate survivors among such a population have not escaped infection, but have successfully resisted it. A considerable proportion of them are harbouring the causative parasite in their tissues.My sincere thanks are due to my colleagues, Dr H. B. Weir and Dr G. S. Wilson, for their constant help, and to Mrs Phyllis Worthington whose assistance in this work I have been able to obtain by the aid of the Medical Research Council.

scholarly journals Efficient Cryopreservation of Populus tremula by In Vitro-Grown Axillary Buds and Genetic Stability of Recovered Plants

Plants ◽  
2021 ◽  
Vol 10 (1) ◽  
pp. 77
Author(s):  
Elena O. Vidyagina ◽  
Nikolay N. Kharchenko ◽  
Konstantin A. Shestibratov
Keyword(s):  
Survival Rate ◽  
Axillary Buds ◽  
Long Term Storage ◽  
Average Survival ◽  
Transgenic Lines ◽  
Ssr Loci ◽  
One Step ◽  
The One

Axillary buds of in vitro microshoots were successfully frozen at –196 °C by the one-step freezing method using the protective vitrification solution 2 (PVS2). Microshoots were taken from 11 transgenic lines and three wild type lines. Influence of different explant pretreatments were analyzed from the point of their influence towards recovery after cryopreservation. It was found out that the use of axillary buds as explants after removal of the apical one increases recovery on average by 8%. The cultivation on growth medium of higher density insignificantly raises the regenerants survival rate. Pretreatment of the osmotic fluid (OF) shows the greatest influence on the survival rate. It leads to the increase in survival rate by 20%. The cryopreservation technology providing regenerants average survival rate of 83% was developed. It was based on the experimental results obtained with explant pretreatment. Incubation time in liquid nitrogen did not affect the explants survival rate after thawing. After six months cryostorage of samples their genetic variability was analyzed. Six variable simple sequence repeat (SSR) loci were used to analyze genotype variability after the freezing-thawing procedure. The microsatellite analysis showed the genetic status identity of plants after cryopreservation and of the original genotypes. The presence of the recombinant gene in the transgenic lines after cryostorage were confirmed so as the interclonal variation in the growth rate under greenhouse conditions. The developed technique is recommended for long-term storage of various breeding and genetically modified lines of aspen plants, as it provides a high percentage of explants survival with no changes in genotype.

Numerical assessment on the performance of variable area single- and two-stage ejectors: A comparative study

2021 ◽  
pp. 095440892110331
Author(s):  
Anil Kumar ◽  
Virendra Kumar ◽  
PMV Subbarao ◽  
Surendra K Yadav ◽  
Gaurav Singhal
Keyword(s):  
Change Theory ◽  
Single Stage ◽  
Two Stage ◽  
Entrainment Ratio ◽  
Ansys Fluent ◽  
One Dimensional ◽  
Flow Parameters ◽  
Constant Rate ◽  
Numerical Assessment ◽  
The One

The two-stage ejector has been suggested to replace the single-stage ejector geometrical configuration better to utilize the discharge flow’s redundant momentum to induce secondary flow. In this study, the one-dimensional gas dynamic constant rate of momentum change theory has been utilized to model a two-stage ejector along with a single-stage ejector. The proposed theory has been utilized in the computation of geometry and flow parameters of both the ejectors. The commercial computational fluid dynamics tool ANSYS-Fluent 14.0 has been utilized to predict performance and visualize the flow. The performance in terms of entrainment ratio has been compared under on- design and off-design conditions. The result shows that the two-stage ejector configuration has improved (≈57%) entrainment capacity than the single-stage ejector under the on-design condition.

e-Democracy and Community Networks

2011 ◽  
pp. 249-266 ◽  
Author(s):  
Tom Gross
Keyword(s):  
Technological Progress ◽  
Virtual Communities ◽  
Technological Development ◽  
The Other ◽  
Community Networks ◽  
Considerable Proportion ◽  
Political Systems ◽  
Political Leaders ◽  
Electronic Democracy ◽  
The One

Political systems and technology are interdependent and influence each other. On the one hand, political systems and political leaders aim at influencing technological development and benefiting from technological progress; on the other, technological development has a considerable proportion of its own dynamics and potential to influence society and political systems. This chapter particularly focuses on electronic democracy and virtual communities and accordingly discusses recent ideas and plans of political leaders, derives requirements for technology, presents systems and prototypes, and reports cases demonstrating how and what technology is really used.

Deterministic and stochastic epidemics with several kinds of susceptibles

1985 ◽  
Vol 17 (01) ◽  
pp. 1-22 ◽  
Author(s):  
Frank Ball
Keyword(s):  
Epidemic Model ◽  
Susceptible Population ◽  
Basic Model ◽  
Spread Of Infection

We consider the spread of a general epidemic amongst a population consisting of invididuals with differing susceptibilities to the disease. Deterministic and stochastic versions of the basic model are described and analysed. For both versions of the model we show that assuming a uniform susceptible population, with average susceptibility, leads to an increased spread of infection. We also show how our results can be extended to the carrier-borne epidemic model of Weiss (1965).

scholarly journals SYNERGY AMONG LYMPHOID CELLS MEDIATING THE GRAFT-VERSUS-HOST RESPONSE

1972 ◽  
Vol 135 (5) ◽  
pp. 1059-1070 ◽  
Author(s):  
Robert E. Tigelaar ◽  
Richard Asofsky
Keyword(s):  
Lymph Node ◽  
Lymphoid Cells ◽  
Spleen Cells ◽  
Blood Leukocytes ◽  
Graft Versus Host ◽  
Average Survival ◽  
Lymph Node Cells ◽  
The One ◽  
Kinetics Of ◽  
Cell Inoculum

A mortality assay was used to quantitate graft-versus-host (GVH) reactions in sublethally irradiated (400 R) neonatal (C57BL/6 x BALB/c)F1 recipients of BALB/c lymphoid cells from various tissues. The probit of the 35 day cumulative per cent of mortality was a linear function of the logarithm of the cell inoculum for any tissue; reactivities of different tissues fell on a series of parallel lines. Peripheral blood leukocytes (PBL), the most active cells, were about 30 times as active as thymocytes, the least active cells studied; femoral lymph node cells and spleen cells were about 23 and 8 times as reactive as thymocytes, respectively. The average survival time of recipients of thymocytes who eventually died was nearly a week longer than that of recipients of comparably lethal numbers of PBL, lymph node, or spleen cells. Mixtures of PBL and thymocytes gave levels of 35 day mortality significantly greater than those expected if the reactivities of the mixture had been merely the sum of the reactivities of the components measured separately, thereby confirming in any assay independent of host splenomegaly the synergistic interaction of thymocytes and PBL in the GVH reaction. Both populations of cells in the mixture had to be allogeneic to the host in order to observe this synergy. The kinetics of cumulative mortality observed for mixtures of PBL and thymocytes were indistinguishable from those seen with thymocytes alone, indicating activation of the latter cell type. Finally, comparison of the relative abilities of different cell populations to cause splenomegaly on the one hand and lethal runting on the other has raised the possibility that expression of different effector functions of cell-mediated immune reactions may in fact be initiated by distinct cells.

scholarly journals Relationship of Paratyphoid Fever to Food Poisoning Outbreaks

1925 ◽  
Vol 24 (1) ◽  
pp. 37-44 ◽  
Author(s):  
William G. Savage ◽  
P. Bruce White
Keyword(s):  
Food Poisoning ◽  
The Other ◽  
Considerable Proportion ◽  
Common Cause ◽  
Clinical Type ◽  
The Common ◽  
The One ◽  
Paratyphoid Fever ◽  
Relationship Of

Owing, in our opinion, to faulty classification and terminology of bacterial types, it is very common, especially on the Continent and, to a lesser extent, in U.S.A., to ascribe outbreaks of food poisoning to B. paratyphosus B, the common cause of paratyphoid fever. If such a conception is true, it is obvious that B. paratyphosus B can at one time cause paratyhpoid fever, at another an outbreak of food poisoning. Further, one would expect in outbreaks of either condition that some cases would be of the one clinical type while others would exhibit the other. In particular in outbreaks of paratyphoid fever in which the vehicle of infection was some form of food, it is to be anticipated, on this view, that a considerable proportion of the cases would be of acute food poisoning type.

Some Experiments on the Flow of Miscible Fluids of Unequal Density Through Porous Media

1963 ◽  
Vol 3 (04) ◽  
pp. 277-280 ◽  
Author(s):  
F.E. Crane ◽  
H.A. Kendall ◽  
G.H.F. Gardner
Keyword(s):  
Extreme Case ◽  
The Other ◽  
Gravity Force ◽  
Mobility Ratio ◽  
Transition Range ◽  
Gravity Forces ◽  
Single Finger ◽  
Constant Rate ◽  
Production History ◽  
The One

Introduction Craig, et al investigated the effect of gravity on frontal displacements for circumstances in which the gravity forces were significant. Blackwell, et al, dealt with the other extreme in which gravity forces were negligible. The considerable difference between their results is illustrated in Fig. 1 where the breakthrough recoveries are plotted against the mobility ratio. The experiments described in the present paper were conducted to examine how the transition from the one extreme case to the other occurs when the gravity forces are gradually reduced.The transition is well illustrated by the production history after breakthrough. Fig. 2 shows how the number of pore volumes which must be injected at a constant rate to displace 98 per cent of the original fluid depends on the gravity force. For each mobility ratio there is a transition range, and a very significant change in the number of pore volumes occurs when this range is transversed. This range of the gravity force is physically linked withtheformationofviscousfingers.A single finger is predominant for larger gravity forces; a multiplicity of fingers is formed for smaller gravity forces. Improved recovery and the occurrence of multiple fingers is concomitant with a large increase in the amount by which the fluids are mixed within the porous medium.The transition range depends on all the dimensionless groups which characterize the problem; but this dependence has not been exhaustively studied as yet and only fragmentary results are discussed in this paper. SPEJ P. 277^

VEGETATIVE PROPAGATION OF WILD OATS, AVENA FATUA, AND OTHER ECONOMICALLY IMPORTANT SPECIES OF AVENEAE AND HORDEAE

1932 ◽  
Vol 7 (2) ◽  
pp. 204-220 ◽  
Author(s):  
L. E. Kirk ◽  
T. K. Pavlychenko
Keyword(s):  
Vegetative Propagation ◽  
Ground Level ◽  
The Other ◽  
Considerable Proportion ◽  
Important Species ◽  
Wild Oats ◽  
The Difference ◽  
The One ◽  
Favorable Conditions ◽  
Nodal Tissue

Following the discovery that small sections of wild oats seedlings could become rerooted and develop into normal plants, a study was undertaken to determine from what part or parts of the seedlings new growth can originate, and whether cultivated oats, wheat, barley and spring rye, would behave in a similar manner. Special attention was given to the problem of vegetative propagation in wild oats as a factor in the control of this weed.Small sections of wild oats seedlings, one inch in length and containing the coleoptile node, became rerooted under favorable conditions and produced fully developed plants. Cultivated oats behaved in a similar manner to wild oats in this respect, but the latter produced the more vigorous growth.When land is infested with wild oats and is plowed shallow, or cultivated shortly after the seedlings have emerged from the soil, a considerable proportion of them, under certain conditions, may produce new plants by vegetative regrowth. The extent to which this may occur in the field depends largely on the soil moisture as well as on other conditions which facilitate rerooting, such as shallow plowing, and packing when conditions for plant growth are favorable.With young seedlings of wild oats at time of emergence, regrowth occurred mostly from a small area located between ground level and one inch below the surface. The same was found to be true of cultivated oats. With seedlings of wheat, barley and spring rye, at time of emergence, regrowth originated only from nodal tissue close to the seed. The difference in this respect, between oats, Aveneae, on the one hand, and wheat, barley and rye, Hordeae, on the other, is due to the fact that the area of elongation in oats is the mesocotyl, whereas in other cereals it is the first internode.At later stages in seedling development of both oats and the other cereals, nodes which were capable of regrowth developed immediately below and above the ground level. With older seedlings in the first-, second-, and third-leaf stage, the youngest node above ground, which is the one nearest the soil, had the greatest power of regrowth.

scholarly journals INSURANCE RISK WITH VARIABLE NUMBER OF POLICIES

2008 ◽  
Vol 22 (2) ◽  
pp. 213-219
Author(s):  
Ivo Adan ◽  
Vidyadhar Kulkarni
Keyword(s):  
Life Insurance ◽  
Poisson Model ◽  
Variable Number ◽  
Insurance Fund ◽  
Insurance Company ◽  
Insurance Risk ◽  
Constant Rate ◽  
Remarkable Result ◽  
New Policies ◽  
The One

In this article we consider an insurance company selling life insurance policies. New policies are sold at random points in time, and each policy stays active for an exponential amount of time with rate μ, during which the policyholder pays premiums continuously at rate r. When the policy expires, the insurance company pays a claim of random size. The aim is to compute the probability of eventual ruin starting with a given number of policies and a given level of insurance fund. We establish the remarkable result that the ruin probability is identical to the one in the standard compound Poisson model where the insurance fund increases at constant rate r and claims occur according to a Poisson process with rate μ.

scholarly journals Considerations on General Methodological Assumptions of the Sciences of Sport

2012 ◽  
Vol 56 (1) ◽  
pp. 65-101 ◽  
Author(s):  
Jerzy Kosiewicz
Keyword(s):  
Ad Hoc ◽  
A Priori ◽  
Research Work ◽  
Scientific Work ◽  
Research Problem ◽  
Considerable Proportion ◽  
General Methodology ◽  
The People ◽  
The Subject ◽  
The One

Abstract The considerations included in the article are the result of several years of teaching general methodology for doctoral studies at Josef Pilsudski University of Physical Education in Warsaw.The presented text consists of two basic parts. The first includes reminiscences and associated methodological resentment. The second presents a wide panorama of standpoints concerning functions and kinds of hypotheses, their role and significance in contemporary research programs of formal, empirical (connected with natural sciences and biology), and humanities nature. Sketchy and encyclopaedic interpretations, presented in the context of commentaries by the author of this paper, thereby dominate.The aim of the first part is to draw attention to some methodological mistakes which often appear and which have become common in some academic milieus to such a degree that some intervention and postulatory correction, referring to Polish and Western methodological literature, is advisable. These shortcomings are connected, among other things, with the structure of the scientific work, with the formulation and application of hypotheses, with relations taking place between the general methodology and specialized methodologies, kinds and types of research work, with reliability of information on sources of creative information, as well with the category of verification in its relation, on the one hand, to confirmation and corroboration, and on the other hand, to testing, checking, falsification, and terms close in meaning to the last one.The abovementioned resentment results, first of all, from the fact that the authors discussed in the first part usually insist on erroneous solutions, negating a priori, without becoming acquainted with the literature on the subject or making attempts to explain or initiate a methodological argument referring to sources and studies.That resentment is significant, among other things, in the causal sense - that is, because of the fact that, firstly, it justifies and substantiates the need for a statement presenting controversial questions in a content-related and formal way. Secondly, because thanks to such (that is, cognitive-emotional) introduction, the whole argument - not only in the first, but also in the second part - is much more interesting. It is saturated with authenticity. Many readers know the figures mentioned and are familiar with their - sometimes too insouciant (sometimes not very reliable) - attitudes to important issues from the field of research methods. It is also interesting why the people cited make mistakes. Hence, it is also advisable to look at a wider methodological context of justification (included in the much longer second part) dedicated to perhaps the most thorough characteristics of the hypothesis in the literature on the subject, which is available to the author. Without presentation of the controversial issues in the first part, the second part, more important from the methodological viewpoint, might be omitted by a considerable proportion of readers. In that part attention is paid mainly to issues concerning working, initial, zero, primary, introductory, directing, gradual, auxiliary, ad hoc auxiliary, bridge, futile and true, dangerous and safe, quite natural and neutral, individual and general, complete and incomplete, deep, strong, probabilistic and non-probabilistic (that is, deterministic), related, falsifying, basic, psychological, metaphysical and materialist hypotheses, as well as those concluding ones - that is, those constituting the final effect of definite (concluded here and now) research; hence, those which have undergone verification, confirmation, corroboration or modification as those which predict and explain a given research problem in the best possible way.

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