bluuebunny/crossref_metadata_2025_split huggingface dataset:
On the Photographic Reciprocity Law Failure and Related Effects. I. The Low Intensity Failure
Authors: Katz E. 
Published: January 2005

(1) The order principle (o.p.) states: ``The grains of an emulsion become developable in the course of an exposure in a given sequence independent of the exposure and development variables.'' This hypothesis appears to have a wide range of applicability. It forms an ideally simple link for correlating experimental isodense exposures and theoretical single grain response predictions. Moreover, in many cases where the o.p. is not strictly applicable, corrections can be derived (Section 12) which again make quantitative comparison of theory and experimental data possible.
(2) Extending ideas of Gurney, Mott, and Webb, a quantitative theory of the low intensity reciprocity law failure (l.i.f.) is developed, by analyzing the statistics of light absorption and the survival function of the electrons. Confrontation of various theoretical possibilities with experimental data selects the following basic assumptions: (a) A monoatomic Ag speck of sub-latent image is unstable against thermal agitation, but a diatomic speck is stable for most practical purposes; finally a triatomic speck is completely stable. (b) The energy required to set free an electron from a monoatomic speck (electron trap depth) is not the same for all traps. There must be a quasi-continuous distribution of depths (e.g. as given by formula (10)).
With these assumptions the theory describes satisfactorily the principal features in the shape of experimental l.i.f. curves. It is found that the l.i.f. slope varies systematically with grain size and the theory checks qualitatively with this result. The experimental temperature dependence of l.i.f. curves agrees satisfactorily with the theory.
Vibrational Spectra of the Four Lowest Nitroparaffins
Authors: Smith Don C. , Pan Chi-Yuan , Nielsen J. Rud 
Published: January 2005

The infra-red spectra from 2 to 22μ of nitromethane, nitroethane, 1-nitropropane and 2-nitropropane have been obtained for both vapor and liquid phases. The Raman shifts have been measured for the liquids, and for nitromethane the polarizations of the bands have been determined.
A satisfactory interpretation of the spectra has been obtained for nitromethane on the basis of assigned fundamental frequencies that agree with those proposed previously by Wells and Wilson, except for the B1 methyl rocking mode. The fundamental frequencies have not been determined for the other compounds, but the positions of the nitro group absorptions have been determined empirically.
Light Scattering and Spectrophotometry of Colloidal Solutions
Authors: Doty Paul , Steiner Robert F. 
Published: January 2005

During the past several years it has been demonstrated that the light scattered from dilute solutions of macromolecules or colloidal particles is intimately related to the weight, size, and interaction of the solute species. Theoretical developments and improved techniques have made possible the determination of the molecular weight, dimension and activity coefficient of a number of polymers and proteins in solution. In these investigations the intensity of light scattered at various angles from a monochromatic beam passing through the solution has been measured by means of specially designed photometers. However, it would appear that the equivalent information could be derived from a different means of observation—that of transmission measurements at various wave-lengths. If this possibility could be exploited the common techniques of spectrophotometry could replace the more specialized ones now used. The extent to which this is feasible is explored in this paper.
As a first step it is necessary to review some aspects of the scattering from small particles and the internal interference arising in the case of larger particles. This opportunity is taken to present a compilation of the scattering factors and the quantities derived from them, that is the dissymmetry and correction factor, in a more precise and convenient form than has appeared previously, because of the use to which they are put in the following sections. The calculations relating to the case of transmittance of solutions containing larger particles are then presented and in the final sections the application of both methods of observation to the determination of the molecular weight and size of samples of polystyrene and tobacco mosaic virus is reported.
Vibrational Intensities. III. Carbon Dioxide and Nitrous Oxide
Authors: Eggers David F. , Crawford Bryce L. 
Published: January 2005

Experimental intensity measurements can be combined with known harmonic and anharmonic potential constants of molecules to determine the variation of dipole moment with displacement. We have used a finite Taylor's series for both potential energy and dipole moment. The effect on intensity of frequency variation over the band is included explicitly for both parallel and perpendicular bands as in Fermi resonance between several bands. Intensities of two fundamental and four combination bands in carbon dioxide were measured. A complete second-order perturbation treatment of intensities was carried out for several bands, and the possible relation of the results to resonance structures is mentioned. The relative importance of electrical and mechanical anharmonicity is indicated.
Two cubic potential constants were determined for nitrous oxide from measured intensities, known rotational convergence, normal coordinates, and bond distances. Using these constants a first-order intensity treatment was carried out for several combination bands. The intensities of three fundamental and three combination bands were measured. Discrepancies in measured rotational convergences are mentioned, and possible lines are suggested for further work on nitrous oxide.
The Kinetics of the Forward and Reverse Reactions for the Vapor Phase Thermal Bromination of Chloroform
Authors: Sullivan John H. , Davidson Norman 
Published: January 2005

The rates of the forward and reverse reactions for the homogeneous vapor phase thermal bromination of chloroform, CHCl3+Br2=CBrCl3+HBr(A), have been measured in the range 420–455°K and are given by −d(Br2)/dt=kf(CHCl3)(Br2)12[1+k2(HBr)/k3(Br2)]−1−kr(CBrCl3)(Br2)12[1+k3(Br2)/k2(HBr)]−1; where log10kf (liter/mole)12 sec−1=(−32,030/4.575T)+11.15, log10kr=(−32,930/4.575T)+12.70. The mechanism of the reaction is, M+Br2=2Br+MCl3CH+Br=Cl3C−+HBr→(1)←(2)Cl3C−+Br2=CCl3Br+Br→(3)←(4)where log10k1=(−9300/4.575T)+9.36, log10k4=(−10,200/4.575T)+10.91, (k2/k3)=0.040. The activation energies imply that the CH bond in CHCl3 is weaker than that in CH4 by 6+E2 kcal and the Cl3C–Br bond is weaker than the H3C–Br bond by 11+E2 kcal, where E2, the activation energy of reactions (2) and (3), is estimated to be ≤7 kcal.
The directly determined equilibrium constant for (A) agrees well with the kinetic value, Ke=k1k3/k2k 4; log10Ke=(900/4.575T)−0.15. From these data, for CCl3Br, ΔH°f,298°=−9.4 kcal, S°298°=80 eu S° was calculated as 80 eu from electron diffraction and spectroscopic data.
The equation for k4 is identical with that obtained in a previous study of the exchange of radioactive bromine between Br2 and CBrCl3, thus proving this free radical mechanism for the exchange reaction.
The Parallel Vibrations of Linear Triatomic Molecules
Authors: Thomas W. J. Orville 
Published: January 2005

The possible solutions of the valence force potential constants occurring in the potential function for the stretching modes of some triatomic molecules are found; these are found as functions of a parameter p related to the coordinates describing the parallel modes of vibration.
The form of the normal modes and the potential energy distribution corresponding to a particular set of constants for each molecule is obtained.
Culicoides midge trap enhancement with animal odour baits in Scotland
Authors: Mands V. , Kline D. L. , Blackwell A. 
Published: January 2005

Abstract.  Examples of the commercial trap Mosquito Magnet® Pro™ (MMP emitting attractant 1‐octen‐3‐ol in carbon dioxide 500 mL/min generated from propane fuel), were run 24 h/day on the Isle of Skye, Scotland, during June–August 2001 and evaluated for catching Culicoides biting midges (Diptera: Ceratopogonidae). From 30 days trapping, the catch averaged 2626 ± 1358 Culicoides females/trap/day (mean ± SE, range 558 ± 139 to 6088 ± 3597, for five sets of six consecutive nights), predominantly the pest Culicoides impunctatus Goetghebuer (68% overall), plus C. vexans (Stæger) > C. delta Edwards > C. pulicaris (L.) > C. lupicaris Downs & Kettle > C. albicans (Winnertz) > other Culicoides spp.Attempts were made to enhance the odour baiting system by adding hexane‐extracts (2.1 mg/day) of hair samples from large host animals, resulting in the following effects on Culicoides collections: sheep − 53 %, red deer − 26 %, calf + 20%, pony + 40%, water buffalo + 262%, with greatest increases for C. impunctatus and C. pulicaris.Serial concentrations of these animal extracts (10−1 − 10−3 × 2.2 g/mL) were assayed on parous female C. impunctatus response in a Y‐tube olfactometer (air‐flow 150 mL/min), and by electroantennogram (EAG) on Culicoides nubeculosus Meigen laboratory‐reared parous females. Positive behavioural responses to host odours were dose‐dependent: the water buffalo extract being most active (threshold 0.22 g/mL), similar to deer, whereas other host extracts were ≥ 10‐fold less active. Correspondingly, the EAG threshold was lowest for water buffalo, 10‐fold greater for deer, calf and pony, but not detected for sheep. If the active component(s) of these host extracts can be identified and synthesized, they might be employed to improve the capture of Culicoides midges for local control by removal trapping.
Arrested succession in logging gaps: is tree seedling growth and survival limiting?
Authors: Paul John R. , Randle April M. , Chapman Colin A. , Chapman Lauren J. 
Published: January 2005

AbstractThirty years after selective timber harvest in the Kibale National Park, Uganda, many abandoned logging gaps are dominated by Acanthus pubescens, and show little forest recovery. To examine if this arrested successional state was caused by limited tree seedling growth and survival, we planted seedlings of four forest tree species (Albizia grandibracteata, Mimusops bagshawei, Prunus africana and Uvariopsis congensis) in A. pubescens‐dominated logging gaps and in control areas of adjacent forest. To assess if clearing A. pubescens facilitates forest regeneration, we planted seedlings of two species (A. grandibracteata and U. congensis) in small clearings cut within the logging gaps. We examined mortality, growth, herbivory and site characteristics among the treatments. Finally, we described the physical attributes of the A. pubescens‐dominated gaps. Seedlings of all the four species survived and grew equally well in A. pubescens and forest treatments, and most site characteristics were also similar. Seedlings planted in clearings grew more than in either forest or A. pubescens sites. Very few established trees were found in A. pubescens sites, and most of these were near the forest edges. We also discussed the role of elephants (Loxodonta africana) and collapsing A. pubescens canopies in the maintenance of an arrested successional state in these logging gaps.
The use of structural species size classes in the description of the woody vegetation of a nature reserve
Authors: Brown L. R. , Bredenkamp G. J. 
Published: January 2005

AbstractThe need for a scientifically based wildlife management plan and more knowledge on the vegetation ecology of the Borakalalo Nature Reserve prompted an ecological investigation of the Reserve. One of the aims was to develop a structural classification of the woody component using species size (SPIZE) classes. A further aim was to compare the various structural classes identified with the recognized floristically derived plant communities of the Reserve. The frequency, density, percentage crown cover and importance value for each woody species were calculated. A classification of the woody component was done using a TWINSPAN classification algorithm on this structural density data. Fifteen structural SPIZE classes were identified, described and compared with the described plant communities. The results of this study indicate that structural SPIZE classes could also be used to explain the spatial distribution of woody species within and between various plant communities.
Influence of anthropogenic activities on water quality of a tropical stream ecosystem
Authors: Mokaya Sophia K. , Mathooko Jude M. , Leichtfried Maria 
Published: January 2005

AbstractWater samples were collected from three sites located in the middle reach of the Njoro River, Kenya, and analysed for total phosphorus (TP), orthophosphate, ammonia‐nitrogen, and nitrate‐nitrogen to evaluate stressor sources (e.g. factories and wastewater ponds) and the general stream water quality. The stream surface water was also analysed for biochemical oxygen demand (BOD5) to provide an overview of organic matter loading. Mugo, Egerton Bridge and the canning factory sites of the Njoro River had low water quality which is likely to be due to poor farming, partially treated effluents and poor provision of sanitation facilities to the riparian communities. The concentrations of the selected nutrients did not differ significantly among the three sites, presumably due to pollution of the whole stream reach by the catchment nutrient sources. High phosphate concentrations (i.e. ∼0.76 mgPO4 l−1 and ∼0.87 mgTP l−1) at Canning Factory were recorded during the low flow dry season. Nitrate‐nitrogen concentrations varied significantly with water discharge which explained between 63 and 87% of the nutrient variability in the three sites. BOD5 differed significantly among the three sites, with historical effects of wastewater and factory effluent discharge being reflected in the results of Egerton Bridge and Canning Factory. The concentrations of ammonia‐nitrogen, TP and orthophosphate were higher in the wastewater than in the river water whereas nitrate‐nitrogen was lower. This study indicates that the Njoro River is stressed by nutrients from the activities within its catchment. With the increasing population, the nutrient load to the river will continue to increase and the water quality will continue to deteriorate. Reductions of nutrient loads into the river as well as provision of sanitation facilities to the riparian communities are needed to control further water degradation.
Management of the Nile perch, Lates niloticus fishery in Lake Victoria in light of the changes in its life history characteristics
Authors: Ogutu‐Ohwayo Richard 
Published: January 2005

AbstractNile perch was introduced into lakes Victoria and Kyoga in the 1950s and 1960s from Lake Albert. The changes in prey eaten and the life history characteristics of Nile perch in lakes Victoria and Kyoga from the 1960s to 1990s were examined and compared with Lake Albert. The dominant prey eaten changed from haplochromines, Caridina nilotica, Rastrineobola argentea, and Nile perch juveniles. The condition factor deteriorated from 1.4 in 1960s to 1.2 in 1990s, compared with 1.3 in Lake Albert suggesting a reduction in food supply. Therefore, exploitation of Nile perch prey should be controlled. The size at first maturity increased from 30–40 to 40–50 cm and 50–59 to 80–100 cm for males and females, which is similar to Lake Albert. Sex ratios decreased from 85–100 to 20–65 females for every 100 males suggesting that Nile perch had less capacity to replenish its stocks such that breeding females should be protected. As males mature at 50–55 cm and females at 80–100 cm, immature males of <50 cm and breeding females of >100 cm could be protected through size selective exploitation of fish of 50–100 cm using gillnets of 127–254 mm.
Microhabitat choice and diet of rodents in Maynugus irrigation field, northern Ethiopia
Authors: Gebresilassie Workneh , Bekele Afework , Belay Gurja , Balakrishnan M. 
Published: January 2005

AbstractAn ecological study on the choice of microhabitat and diet of small mammals was carried out in Maynugus irrigation field of the Tigray region in northern Ethiopia. Abundance of rodents was high during the reproductive phase of the agricultural plants. Mastomys erythroleucus occurred more frequently in vegetable fields, whereas Arvicanthis dembeensis was more frequent in habitats with monocot plants. Scrotal males and reproductive females consumed more food by weight than abdominal males and quiescent females. Arvicanthis dembeensis consumed more food than M. erythroleucus. Both the species consumed more food during the main rainy season. All the cultivated plants were attacked by these rodents with a degree of difference in relation to season, species, sex, age and sexual condition. As rodent attack was more intense during the fruiting phase of the plants, rodent control management should be carried out during the flowering phase.
Seasonal variation of feeding patterns and food selection by crop‐raiding elephants in Zimbabwe
Authors: Osborn F. V. 
Published: January 2005

AbstractElephants and humans are increasingly coming into conflict because of the conversion of elephant habitat into agricultural areas. In order to identify trends that influence raiding behaviour, the nutritional makeup of food items consumed by crop‐raiding elephants over a 2‐year period were analysed and a trigger for crop raiding was identified. The point at which the quality of wild grasses declines below the quality of crop species corresponded to the movement of bull elephants out of a protected area and into fields. This finding may have wider implications for developing predictive models of elephant/human interactions.
Fire effects on mycorrhizal symbiosis and root system architecture in southern African savanna grasses
Authors: Hartnett David C. , Potgieter Andre F. , Wilson Gail W. T. 
Published: January 2005

AbstractMycorrhizal symbiosis is a key factor influencing aspects of grassland and savanna structure and functioning including plant growth, competition, population and community dynamics, and responses to fire and herbivory. This study assessed the effects of fire on mycorrhizal symbiosis and root system architecture (RSA) in South African savanna grasses. Eighteen grass species were sampled across contrasting fire frequency treatments in the Kruger National Park experimental burn plots. All eighteen species studied were highly colonized by arbuscular mycorrhizal fungi (AMF). Both mycorrhizal symbiosis and RSA were strongly affected by fire, with an increase in AMF colonization and a decrease in root branching and fine root development with decreasing fire frequency. Greater water limitation in frequently burned savanna may result in greater fine root development, thus reducing plant dependency on AMF for acquisition of soil resources. Reduced mycorrhizal colonization in frequently burned savanna may also be driven by higher phosphorus : nitrogen ratios, or indirect effects related to higher grazing intensities in frequently burned sites.
Biology of the marbled lungfish, Protopterus aethiopicus Heckel, in Lake Baringo, Kenya
Authors: Mlewa Chrisestom Mwatete , Green John M. 
Published: January 2005

AbstractIn this paper we provide life history characteristics for an introduced marbled lungfish (Protopterus aethiopicus) population in Lake Baringo, Kenya, including their length–weight relationship, body condition, fecundity, sex ratio, reproduction and food. These data are compared with those of other populations. Samples were obtained from the commercial fishery between January and October 2001. The lungfish exhibited positive allometric growth, with the length–weight relationship described by the equation: logW = −6.41 + 3.52 logTL. The mean relative condition factor was close to unity, did not vary much between months and was not significantly different between sexes. The overall sex ratio was skewed in favour of females. The size of fish at first maturity was 70–76 cm total length (TL) for females and 82–88 cm TL for males. Fish in maturity stages III–IV occurred in all monthly samples suggesting year round spawning. The marbled lungfish in Lake Baringo is largely piscivorous and its impact on other fishes certainly warrants further research.
The regeneration of soil micro‐arthropod assemblages in a rehabilitating coastal dune forest at Richards Bay, South Africa
Authors: Kumssa Diriba B. , van Aarde Rudi J. , Wassenaar Theo D. 
Published: January 2005

AbstractThe structure and composition of the soil micro‐arthropod communities of five postmining rehabilitating sites (between 1 and 24 years after rehabilitation) are compared with that of an undisturbed dune forest benchmark. We extracted soil micro‐arthropods (Acari and insects) with a modified Berlese–Tullgren funnel and used soil carbon, calcium, potassium, magnesium, nitrogen, sodium, phosphorous and acidity (pH) as explanatory variables of micro‐arthropod community composition.Acari accounted for the majority of all the micro‐arthropods (between 65 and 97% of the sample) at the different sites. Density, richness, diversity and composition showed significant differences between the unmined benchmark site and the rehabilitating sites for both insects and Acari, with weak habitat‐age related patterns. Canonical Correspondence Analysis suggests that differences between samples from regenerating sites and those from the benchmark sites slowly decrease with increasing regeneration age, but that community composition is only weakly related to soil properties. Our results suggest that coastal dune forest rehabilitation could give rise to the regeneration of micro‐arthropod assemblages, but it may take a long time. Therefore, potential limiting factors for community regeneration need to be identified to improve the chances for successful restoration.
A comparative study between intermittent microwave and infrared drying of bioproducts
Authors: Chua Kian Jon , Chou Siaw Kiang 
Published: January 2005

SummaryA systematic experimental study of both intermittent microwave (MW) and infrared (IR) drying was used to compare the efficacy of the two methods when batch drying two bioproducts, namely potato and carrot. The controllable parameters examined in this study were MW power and IR intensity level, MW and IR intermittencies and the transition period from convective to MW drying. A comparison of the drying kinetics showed intermittent MW drying to be an effective method for shortening the drying time that was required to reach a certain moisture content when it was compared with intermittent IR drying and convective‐MW drying. A comparison of the colour degradation of the product showed that step variation of the IR intensity during intermittent drying reduced the colour change of the product less than constant radiative intermittent IR drying.
Power and temperature distribution during microwave thawing, simulated by using Maxwell's equations and Lambert's law
Authors: Liu Chang Min , Wang Qi Zhi , Sakai Noboru 
Published: January 2005

SummaryThe microwave thawing of frozen food was simulated by using an equation to describe heat conduction. This was based on the fact that the thermal and dielectric properties of food vary with temperature. The microwave power absorbed was modelled by using Maxwell's equations and Lambert's law. The power and temperature distributions calculated using both models were compared. Although Lambert's law is theoretically less applicable for simulating the transmitted microwave power, it provided an effective numerical approach for calculating temperature distribution during microwave thawing, which proved compatible with experimental results.