Four-urn catenary model for excretion

A chain-like arrangement of four urns (a catenary system) into which different color balls (white, corresponding to radio atoms, and black, corresponding to stable atoms) are being transferred is used to simulate the transport of atoms down the GI tract of man and animals. Into the first urn (stomach) are placedw _o white balls andr black balls while in the 2nd (small intestines) and 3rd (large intestines) urn, onlyr blacks are put in, with no whites. A sample of sizer is transferred from the 1st, 2nd and 3rd urns to the 2nd, 3rd and 4th (infinite universe) urns. From the random variable difference equations the first and second moments for the distribution of the number of radio atoms present in each urn are obtained. The variance of the contents of radioatoms in the excretion urn is Research sponsored by the Office of Health and Environmental Research, U.S. Department of Energy under contract W-7405-eng-26 with the Union Carbide Corporation.     

On a two urn model of Polya-type

A two urn Polya-type scheme is considered in whichr black balls (corresponding to the stable form of an element) are added to urn one at every stage and the same number of balls are removed at random at every stage from the same urn. In between these two operations, which form a stage or iteration, a fixed number of balls is exchanged at random between urns one and two. Urn one has a given initial number of white balls (corresponding to a radioactive form of the same element). The problem of interest is to study the stochastic aspect of the number of white balls remaining in urn one (and/or urn two) aftern iterations.     

A reinforcement depletion urn problem—II. Application and generalization

The urn model discussed in part is generalized so that the random depletion of balls from the urn in any cycle is not necessarily the same as the reinforcement in that cycle. This model is applied to an urn containing balls of three colors (white, red, black) for which the black balls always receive reinforcements, whereas there is only one cycle in which red balls are added. Experimental data are considered in which red balls correspond to radioactive iodine atoms, black balls to stable iodine atoms and white balls to empty space, all relating to the thyroid gland. Half-life periods for the radioactive iodine in relation to the time of uptake (ten years, fifteen years, etc.) are considered.     

A statistical model of the reproduction of aphids

1. The logistic function has been generally used to describe the reproductive process of a “population” of animal. However, this model can not give us any information about the reproductive process of “individuals” in the population. In this study a statistical model on the basis of the reproduction of individuals of barley aphid is presented to find the proportion of the mature individuals, the heterogeneity in reproductive ability of the aphids, etc.
2. The model is constructed as follows:
3. The probability that j insects are found on a plant at time t₀ is represented as Q(j).
4. The probability that h individuals of j have reproductive ability, say, mature individuals, in the period t₀ to t₁ is represented as B(h/j)=_jC_hw^h(1−w)^j−h, where w is the proportion of mature individuals.
5. In a population with a homogeneous reproductive ability, the probability that each parent lays i offspring in the period t₀ to t₁ is represented as P(i/m)=e^−mmⁱ/i!, where m is mean. And, in a population, m changes according to the gamma distribution. Hence the probability that a parent lays i offspring between t₀ and t₁ is represented as , where p and k are parameters of negative binomial distribution. The probability that h parents on a plant lays s offspring is represented as .
6. From the assumptions mentioned above, the probability that s offspring are to be found at time t₁ on a plant with the original j individuals at time t₀ is represented by
7. The experimental populations were demonstrated to fit well to the model.

     

Mate-searching behavior of the black chafer <Emphasis Type="Italic">Holotrichia kiotonensis</Emphasis> (Coleoptera: Scarabaeidae): identification of a sex pheromone,and male orientation behavior controlled by olfactory and visual cues

In the black chafer Holotrichia kiotonensis Brenske (Coleoptera: Scarabaeidae), mating behavior was observed between 1940 and 2010 hours at < 0.1 lx in both the laboratory and the field. In the laboratory, an ether extract of female abdominal glands induced a series of pre-mating behaviors such as short-distance orientation and abdominal bending. When the extract was fractionated by silica gel column chromatography, the active fraction was eluted with 50% ether in hexane and 100% ether. Gas chromatography–mass spectrometry analysis revealed that both active fractions contained anthranilic acid (2-amino-benzoic acid) as a major compound. The amount of this compound was determined to be ca. 600 ng/female by high performance liquid chromatography analysis with a fluorescence detector. In the field, male chafers were observed to land on cotton balls impregnated with 10 mg of authentic anthranilic acid. When a white ball treated with anthranilic acid was placed 2–10 cm away from an untreated black ball, males were observed to land significantly more frequently on the latter. These results suggest that males could recognize white balls below 0.1 lx and landed on black balls. When a treated black ball was placed beside an untreated black ball, more males landed on the former. The difference was significant when the distance between the two lures was 5 or 10 cm, but not significant when it was 2 cm. These observations demonstrated that anthranilic acid was the sex-attractant pheromone for the black chafer H. kiotonensis and that the males located and landed on a pheromone source by using olfaction in conjunction with visual orientation. The importance of visual orientation in this nocturnal species is discussed in comparison with the congeneric diurnal species Holotrichia loochooana loochooana.     

The Estimation of a Multivariate Fitness Function from Several Samples Taken from a Population

The situation is considered where the multivariate distribution of certain variables X₁, X₂, …, X_p is changing with time in a population because natural selection related to the X's is taking place. It is assumed that random samples taken from the population at times t₁, t₂, …, t_s are available and it is desirable to estimate the fitness function w_t(x₁, x₂,…,x_p) which shows how the number of individuals with X_i = x_i, i = 1, 2, …, p at time t is related to the number of individuals with the same X values at time zero. Tests for population changes are discussed and indices of the selection on the population dispersion and the population mean are proposed. The situation with a multivariate normal distribution is considered as a special case. A maximum likelihood method that can be applied with any form of population distribution is proposed for estimating w_t. The methods discussed in the paper are illustrated with data on four dimensions of male Egyptian skulls covering a time span from about 4500 B.C. to about 300 A.D. In this case there seems to have been very little selection on the population dispersion but considerable selection on means.     

A Note on the Characterization of the Normal Distribution

Suppose X₁, X₂,…, X_n are independent and identically distributed random variables with absolutely continuous distribution function F. It is known that if F is standard normal distribution then (i)∑X²_i is a chi-square with n degrees of freedom and (ii)nX¯² is a chi-square with 1 degrees of freedom where X¯=1/n ∑X_i. Here the above two properties are utilized to characterize the normal distribution.     

Factors determining the microflora of stored barley grain

Colonisation of barley grain has been studied during storage at different water contents and with and without restriction of the air supply to simulate conditions in unsealed silos. Grain stored with a water activity >0·9 a_w (20% water content) heated spontaneously when aeration was unrestricted, the maximum temperature attained increasing with a_w to 58 °C at 1·0 a_w (39% water content). The presence of many unripe grains increased the tendency to heat at a given mean water content. Although heating was prevented by sheeting to restrict the air supply, it could occur subsequently when the sheeting was removed. Both heating and restriction of the air supply were associated with increased carbon dioxide (to >25%) and decreased oxygen concentrations (to <5%). Germination of grain after 6·9 months storage was correlated with a_w; germination levels approaching 100% were retained only at about 0·7 a_w (13·5% water content). Colonisation by Aspergillus species was correlated with a_w and temperature and similar correlations with Penicillium species were also found, with P. verrucosum var. cyclopium abundant at 0·85-0·90 a_w (17·20% water content) and P. piceum, P. funiculosum and P. capsulatum at 0·90-0·95 a_w (20–25% water content). In sealed containers P. roquefortii occurred at 1·00 a_w (39% water content) and P. hordei at 0·90-0·92 a_w (20–22% water content). Spores of fungi and actinomycetes formed during spontaneous heating of grain survived 6 months sealed storage although Absidia corymbifera and Micropolyspora faeni may have declined in numbers. Fungicides applied to the ripening grain had only limited effect on the colonisation of the grain during storage.     

Effects of reduction in beef surface water activity on the survival of Salmonella Typhimurium DT104 during heating

Aim: To investigate the influence of reducing beef surface water activity (a_w) on the survival of Salmonella Typhimurium DT104 during heating. Methods and Results: Beef discs were surface inoculated with S. Typhimurium DT104 and either untreated or dried to achieve surface a_w values of 0·95, 0·85 and 0·70. The samples were vacuum packed, heat‐treated at 60°C and removed at predetermined times. The inactivation curves were influenced by a_w and treatment time. Biphasic inactivation curves were observed for S. Typhimurium DT104 heat‐treated on beef samples with altered a_w values, which were characterized by an initial decline in cell numbers at commencement of heating followed by a much slower rate of inactivation during the remaining treatment period. Point estimates of the heating time required to achieve a 1 log reduction on beef surfaces with a_w of 0·99, 0·95, 0·85 and 0·70 were 0·5, 1·55, 11·25 and 17·79 min, respectively. Conclusions: A decrease in beef surface a_w can substantially enhance the survival of S. Typhimurium DT104 after heating. Significance and Impact of the Study: Caution needs to be taken using dry air as a decontamination method as this may rapidly decrease product surface and pathogen a_w values resulting in enhanced survival.     

Die genetische Grundlage der Monogenie bei der Schmei?fliege Chrysomya rufifacies (Calliphoridae, Diptera)

Summary Recently in our wild stock of the monogenic blowfly Chrysomya rufifacies a recessive mutation white (w) causing white instead of red-brown eyes spontaneously appeared (Fig. 1). This marker gene enabled us to clarify the genetic basis of monogeny in this species. F₁ offspring produced by reciprocal crossings between normal (+/+) and white-eyed (w/w) flies were phenotypically wildtype (Table 1). In F₂ offspring of female-producing (thelygenic) and male-producing (arrhenogenic) F₁ females wildtype and white-eyed flies appeared in the expected 3:1 ratio; in several crossings a slight deviation of this ratio indicated a reduced viability of the w/w individuals (Table 2). Examination of F₂ progeny of thelygenic F₁+/w females, which had received the w allele from their father, showed that most of the F₂+/+ females were thelygenic, whereas most of the F₂ w/w females were arrhenogenic; among F₂+/w females thelygenic and arrhenogenic individuals occurred in almost equal numbers (Table 3). On the other hand, when F₂ offspring of thelygenic F₁+/w females which had inherited the w allele from their mother were tested, most of the F₂+/+ females turned out to be arrhenogenic and most of the F₂ w/w females thelygenic; among F₂+/w females thelygenic and arrhenogenic flies also were found in almost equal frequencies (Table 4). the sex-linked inheritance of the factor w following from these results was also confirmed by an analysis of the progeny of thelygenic F₁+/w females backcrossed with w/w males. Among the R₁ offspring of F₁+/w females, which had received the w allele from their father, the +/w females were predominantly thelygenic compared to their predominantly arrhenogenic w/w sisters (Table 5). Analysis of R₁ progeny of F₁+/w females, which had inherited the w allele from their mother, yielded reciprocal results (Table 6).This mode of incomplete sex-linkage of the mutation white observed in C. rufifacies (Figs. 2–5) supports the hypothesis that thelygenic females are heterozygous for a dominant female sex realizer (F') with predetermined sex-determining properties, and that arrhenogenic females as well as the males are homozygous for the recessive allele f (Fig. 6). The recombination frequency between F'/f and the w-Locus was calculated to be 12.72±0.72 per cent.

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Mit Unterstützung durch die Deutsche forschungsgemeinschaft.     

Experimental warming disrupts reproduction and dung burial by a ball‐rolling dung beetle

1. Insects are sensitive to climate change. Consequently, insect‐mediated ecosystem functions and services may be altered by changing climates. 2. Dung beetles provide multiple services by burying manure. Using climate‐controlled chambers, the effects of warming on dung burial and reproduction by the dung beetle Sisyphus rubrus Paschalidis, 1974 were investigated. Sisyphus rubrus break up dung by forming and rolling away balls of manure for burial and egg deposition. 3. To simulate warming in the chambers, 0, 2 or 4 °C offsets were added to field‐recorded, diurnally fluctuating temperatures. We measured dung ball production and burial, egg laying, survival and residence times of beetles. 4. Temperature did not affect the size or number of dung balls produced; however warming reduced dung ball burial by S. rubrus. Because buried balls were more likely to contain eggs, warming could reduce egg laying via a reduction in ball burial. Warming reduced the humidity inside the chambers, and a positive relationship was found between the number of dung balls produced and humidity in two temperature treatments. Temperature did not affect survival, or whether or not a beetle left a chamber. Beetles that did leave the chambers took longer to do so in the warmest treatment. 5. This study demonstrates that climate warming could reduce reproduction and dung burial by S. rubrus, and is an important first step to understanding warming effects on burial services. Future studies should assess warming effects in field situations, both on individual dung beetle species and on aggregate dung burial services.     

Monte carlo computation of the supercoiling energy,the sedimentation constant,and the radius of gyration of unknotted and knotted circular DNA

Closed random Gaussian polygonal chains of N (6 < N < 150) bonds of equal length b and thickness d have been generated on a computer. The knot type, the writhing number w, the radius of gyration, and the average of the inverse of the distance between two apices have been determined for each chain. For all the studied knot types—0, 3₁, 4₁, 5₁, and 5₂—the probability density of finding a given w is Gaussian. The Gaussian is centered about 0 for the amphichiral knots. Therefore, for long circular DNAs, the contribution to the supercoiling energy, which depends on w only, may be considered as purely entropic and may be expressed as ARTw²/N, in agreement with previous semiempirical considerations. The parameter A increases with chain thickness, it decreases as N gets larger but rapidly reaches a plateau. Comparison with experimental data from the literature would suggest that the ratio of the writhing to the constraint increases with ionic strength. The ratio of sedimentation constant of the supercoiled DNA to the sedimentation constant of the nicked DNA varies as N^1/4 (w/N)², and therefore depends on the writhing density and on the length of the DNA.     

Mycoflora and mycotoxins in Brazilian black pepper,white pepper and Brazil nuts

A wide range of field and storage fungi were isolated from black pepper, white pepper and Brazil nut kernels from Amazonia. A total of 42 species were isolated from both peppers. Aspergillus flavus and A. niger were isolated more frequently from black than from white pepper. Other potential mycotoxigenic species isolated included: A. ochraceus, A. tamarii, A. versicolor, Emericella nidulans and Chaetomium globosum, Penicillium brevicompactum, P. citrinum, P. islandicum and P. glabrum. Species isolated from pepper for the first time were Acrogenospora sphaerocephala, Cylindrocarpon lichenicola, Lacellinopsis sacchari, Microascus cinereus, Petriella setifera and Sporormiella minima. Seventeen species were isolated from Brazil nut kernels. A. flavus was the dominant species followed by A. niger. P. citrinum and P. glabrum were the only penicillia isolated. Species isolated for the first time included Acremonium curvulum, Cunninghamella elegans, Exophiala sp., Fusarium oxysporum, Pseudoallescheria boydii, Rhizopusoryzae, Scopulariopsis sp., Thielavia terricola and Trichoderma citrinoviride. Considerably more metabolites were detected from black than white pepper in qualitative analyses. Chaetocin, penitrem A, and xanthocillin were identified only from black pepper, and tenuazonic acid was identified from both black and white pepper. Aflatoxin G₂, chaetoglobosin C, and spinulosin were identified from poor quality brazil nuts. Aflatoxin B₁ and B₂ were also only detected in poor quality brazil nuts at concentrations of 27.1 g kg^–1 and 2.1 g kg^–1 respectively (total 29.2 g kg^–1).This revised version was published online in October 2005 with corrections to the Cover Date.     

Besetzungsmodelle

Starting with the classical occupancy with boxes, balls and probabilities for occupying boxes, we employ new models: a ball, which met a box, occupies this box with a probability depending on the size of box content, and - using several kinds of balls - by the composition of the content too. For that purpose several models are constructed with distinctive forms of the conditions. Dealing with these models - they are special MARKO vian chains - we pay attention mainly to the so called first passage time T_z for defined events Z; in particular for certain events Z we have to prove that T_z is a random variable, and have to set up the appropriate probability generating function.     

Visual edge fixation and negative phototaxis in the mealworm beetle Tenebrio molitor

The visual fixation response of the mealworm beetle Tenebrio molitor, elicited by black stripes upon a bright background is studied in an arena and by means of the Y-maze technique. In the arena the distribution n() of the beetle's angular position is measured at different distances from the centre, which is also the starting point. If the black stripe is narrow, the maximum of n() coincides with the centre of the stripe (centre-fixation Figure 1a). If one half of the panorama is black, the distribution n() has two maxima, which are near the borders between the black and white regions (edge-fixation Figure 1b). In the Y-maze experiments the beetle is tethered, but its head is free to move. The black stripes elicit turning tendencies F(), the strength of which depends upon the angular distance between the centre of the stripe and the animal's body axis. If the black stripe is narrow, the stable zero crossing of F() lies at =0, in agreement with the centre fixation in the arena (Fig. 3). If the stripe is 180° wide, two stable zero crossings are obtained near the border lines between the black and white regions, provided that the panorama is rotated around the animal with an angular velocity w larger than about 0.08°/s (Fig. 4). Below this value of w only one stable zero crossing at =0 exists (Fig. 6). Thus the tethered beetle's response underlies a transition between centre resp. edge fixation at a critical angular velocity of the drum. Some implications of this surprising phenomenon with respect to the mechanism of fixation and negative phototaxis are discussed but at present it is considered primarily a challenge for further investigation.Supported in part by Deutsche Forschungsgemeinschaft     

Further evidence and biological significance for non-random localization of the centromere on mammalian chromosomes

A further quantitative analysis of the localization of the centromere on chromosomes was made using 16,817 individual chromosomes obtained from 723 mammalian species. Centromeric position was expressed quantitatively by the size of short arms as per cent weight (S_w) relative to the X-containing haploid set. When the class interval of S_w was 0·1 instead of the previous 0·2 (Imai, 1975), the frequency distribution of S_w showed an uneven (W-shaped) pattern with two distinct antimodes lying at S_w 0·6 (reconfirmation) and 0·1 (new finding). Two hypotheses, that are not mutually exclusive, are proposed to explain the non-random distribution of centromere position. One is that there are three structurally different short arms consisting of (1) centromere, (2) constitutive heterochromatin (as determined by C-banding), and (3) euchromatin, each arm-type being approximately characterized by the size of short arms (S_w) as S_w < 0·1, 0·1 ? S_w ? 0·6 and S_w > 0·6. The other possibility is concerned with an “orthogenetical” change of chromosome morphologies. When the chromosomes with S_w < 0·1, 0·1 ? S_w ? 0·6 and S_w > 0·6 are denoted as telocentric (T), acrocentric (A), and meta-, submeta- and subtelocentric (M, SM & ST), it was suggested that the chromosome morphologies tend to change orthogenetically (in a statistical sense) from T to M, SM & ST via A-chromosomes by rearrangements such as tandem growth of constitutive heterochromatic, pericentric inversions, and centric fusions.     

The effect of environmental colour on the growth,metabolism, physiology and skin pigmentation of the carnivorous freshwater catfish Lophiosilurus alexandri

The growth, physiology and skin pigmentation of pacamã Lophiosilurus alexandri juveniles were evaluated in an experiment using different tank colours (white, yellow, green, blue, brown and black) over an 80 day period. The tank colours did not cause significant differences to final body mass, total length, survival rate, carcass composition (moisture, crude protein, ash, ether extract, calcium, phosphorus, energy), or to plasma protein, triglyceride and cholesterol values. Haematocrit values, however, were highest for fish kept in white tanks (ANOVA P < 0·05), while the greatest haemoglobin levels were recorded for fish kept in blue and brown tanks (P < 0·01). The concentrations of cortisol (P < 0·001) and glucose (P < 0·01) were the most in fish in the black tanks. Tank colour affected skin pigmentation significantly, with fish in white tanks having the highest values of L* (brightness) and the lowest values in blue and black tanks. L*, however, decreased in all treatments throughout the experiment. C*_ab increased significantly over the course of the experiment in fish kept in white tanks. Similar increases of C*_ab were recorded in the other treatments but to a lesser extent. The use of black tanks during the cultivation of L. alexandri caused stress and should be avoided. Cultivation in white and yellow tanks produced individuals with a pale skin colour, while cultivation in blue and black tanks resulted in juveniles with a darker and more pigmented skin.     

Occurrence and genetics of black‐eyed migratory locusts,Locusta migratoria (Orthoptera: Acrididae)

Black‐eyed Locusta migratoria appeared in albino locusts as a result of crossing between a short‐winged strain originating from Tsushima Island, Japan, and an albino strain originating from Okinawa Island. The black eye trait was recessive to the white eye trait because the crosses between black‐ and white‐eyed albino locusts produced only individuals with white eyes in the F₁ generation. In the F₂ generation, black‐ and white‐eyed individuals appeared in a ratio of 1:3, indicating that the black eye trait was controlled by a simple Mendelian unit. The black eye trait showed no genetic association with other traits including wing morph, adult body dimensions and classical morphometric ratios such as hind femur length / head width and forewing length / hind femur length.     

Genes determining leucine aminopeptidase and mildew resistance from the ornamental apple, ‘White Angel’

Mildew resistance in the ornamental apple White Angel was found to be determined by complementary genes. The gene R _w was found to be necessary for the expression of resistance controlled by the resistance gene Pl _w . The close linkage between the isoenzyme gene, Lap-2, for leucine aminopeptidase and P1 _w was confirmed. The efficiency of Lap-2 as a marker in screening for mildew resistance is limited, as it cannot account for susceptible plants with the r _w r _w P1 _w p1 _w genotype. It has, however, an important role to play in combining resistance genes from different sources. The genotypes of White Angel (R _w r _w , Pl _w pl _w , Lap-2an), Jester (R _w r _w , p1 _w p _w , Lap-2an) Katja (R _w r _w ,p1 _w p1 _w , Lap-2an) and Gloster 69 (r _w r _w , p1 _w p1 _w , Lap-2an) were determined. It also appeared that R _w might influence Lap-2 activity in young seedlings.