bluuebunny/crossref_metadata_2025 huggingface dataset:
Mouse Inbred Strain Sequence Information and Yin-Yang Crosses for Quantitative Trait Locus Fine Mapping
Authors: Shifman Sagiv , Darvasi Ariel
Published: November 2004

The shared ancestry of mouse inbred strains, together with the availability of sequence and phenotype information, is a resource that can be used to map quantitative trait loci (QTL). The difficulty in using only sequence information lies in the fact that in most instances the allelic state of the QTL cannot be unambiguously determined in a given strain. To overcome this difficulty, the performance of multiple crosses between various inbred strains has been proposed. Here we suggest and evaluate a general approach, which consists of crossing the two strains used initially to map the QTL and any new strain. We have termed these crosses “yin-yang,” because they are complementary in nature as shown by the fact that the QTL will necessarily segregate in only one of the crosses. We used the publicly available SNP database of chromosome 16 to evaluate the mapping resolution achievable through this approach. Although on average the improvement of mapping resolution using only four inbred strains was relatively small (i.e., reduction of the QTL-containing interval by half at most), we found a great degree of variability among different regions of chromosome 16 with regard to mapping resolution. This suggests that with a large number of strains in hand, selecting a small number of strains may provide a significant contribution to the fine mapping of QTL.
A Spatial Statistical Model for Landscape Genetics
Authors: Guillot Gilles , Estoup Arnaud , Mortier Frédéric , Cosson Jean François
Published: November 2004

Landscape genetics is a new discipline that aims to provide information on how landscape and environmental features influence population genetic structure. The first key step of landscape genetics is the spatial detection and location of genetic discontinuities between populations. However, efficient methods for achieving this task are lacking. In this article, we first clarify what is conceptually involved in the spatial modeling of genetic data. Then we describe a Bayesian model implemented in a Markov chain Monte Carlo scheme that allows inference of the location of such genetic discontinuities from individual geo-referenced multilocus genotypes, without a priori knowledge on populational units and limits. In this method, the global set of sampled individuals is modeled as a spatial mixture of panmictic populations, and the spatial organization of populations is modeled through the colored Voronoi tessellation. In addition to spatially locating genetic discontinuities, the method quantifies the amount of spatial dependence in the data set, estimates the number of populations in the studied area, assigns individuals to their population of origin, and detects individual migrants between populations, while taking into account uncertainty on the location of sampled individuals. The performance of the method is evaluated through the analysis of simulated data sets. Results show good performances for standard data sets (e.g., 100 individuals genotyped at 10 loci with 10 alleles per locus), with high but also low levels of population differentiation (e.g., FST < 0.05). The method is then applied to a set of 88 individuals of wolverines (Gulo gulo) sampled in the northwestern United States and genotyped at 10 microsatellites.
Naturally Segregating Quantitative Trait Loci Affecting Wing Shape of Drosophila melanogaster
Authors: Mezey Jason G , Houle David , Nuzhdin Sergey V
Published: November 2004

Variation in vein position and wing shape of Drosophila melanogaster depends on many genes. In the following, we report the results of a QTL analysis of wing shape in D. melanogaster. We identified QTL responsible for natural variation for wing shape and analyzed their interactions with developmental genetic signaling pathways important for vein positioning. The QTL analysis indicated that the total number of QTL segregating in this population is likely to be very large. The locations of putative QTL identified in this study were compared to those identified in previous studies and, while there is more correspondence across studies than expected by chance on the third chromosome, the studies appear to have identified different QTL. Using a complementation design, we tested for interactions among these QTL with the Hedgehog and Decapentaplegic signaling pathways, which are important for the development and position of vein pairs L3-L4 and L2-L5. Three QTL showed strong interactions with these two pathways, supporting the hypothesis that these QTL are involved in these pathways. Naturally segregating variation can therefore act through known signaling pathways to produce variation in vein position.
How well does the finite Fourier transform approximate the Fourier transform?
Authors: Epstein Charles L.
Published: November 2004

We show that the answer to the question in the title is “very well indeed.” In particular, we prove that, throughout the maximum possible range, the finite Fourier coefficients provide a good approximation to the Fourier coefficients of a piecewise continuous function. For a continuous periodic function, the size of the error is estimated in terms of the modulus of continuity of the function. The estimates improve commensurately as the functions become smoother. We also show that the partial sums of the finite Fourier transform provide essentially as good an approximation to the function and its derivatives as the partial sums of the ordinary Fourier series. Along the way we establish analogues of the Riemann‐Lebesgue lemma and the localization principle. © 2004 Wiley Periodicals, Inc.
A pilot study of behavioural and psychological signs and symptoms of dementia in patients of Indian sub‐continent origin admitted to a dementia day hospital in the United Kingdom
Authors: Haider Imran , Shah Ajit
Published: November 2004

Background

There is a paucity of cross‐cultural studies of behavioural and psychological symptoms of dementia (BPSD).

Method

BPSD were examined in a consecutive series of Indian sub‐continent origin and white indigenous elders admitted to a dementia day hospital using the BEHAVE‐AD. The correlates of individual BPSD in each of the two ethnic groups and the differences between the two ethnic groups were examined.

Results

There were no differences between the two groups on most of the demographic and clinical variables examined, except that Indian sub‐continent elders had a greater number of children. There were no differences between the two groups on the MMSE scores, BEHAVE‐AD total scores and BEHAVE‐AD subscale scores (with one exception). Indian sub‐ continent origin patients had lower scores on the anxiety and phobias subscale. Within the Indian sub‐continent origin group, Alzheimer's disease (AD) was associated with activity disturbance and vascular dementia with affective disturbance. Within the indigenous group, aggressivity was associated with males and prescription of neuroleptics, and affective disturbance with prescription of antidepressants.

Conclusion

There is a need to develop and evaluate translated versions of instruments that measure BPSD. After development of these instruments there is a need for cross‐cultural population‐based epidemiological studies of BPSD. Copyright © 2004 John Wiley & Sons, Ltd.
Predicting absolute contact numbers of native protein structure from amino acid sequence
Authors: Kinjo Akira R. , Horimoto Katsuhisa , Nishikawa Ken
Published: November 2004

The contact number of an amino acid residue in a protein structure is defined by the number of Cβ atoms around the Cβ atom of the given residue, a quantity similar to, but different from, solvent accessible surface area. We present a method to predict the contact numbers of a protein from its amino acid sequence. The method is based on a simple linear regression scheme and predicts the absolute values of contact numbers. When single sequences are used for both parameter estimation and cross‐validation, the present method predicts the contact numbers with a correlation coefficient of 0.555 on average. When multiple sequence alignments are used, the correlation increases to 0.627, which is a significant improvement over previous methods. In terms of discrete states prediction, the accuracies for 2‐, 3‐, and 10‐state predictions are, respectively, 71.4%, 54.1%, and 18.9% with residue type‐dependent unbiased thresholds, and 76.3%, 59.2%, and 21.8% with residue type‐independent unbiased thresholds. The difference between accessible surface area and contact number from a prediction viewpoint and the application of contact number prediction to three‐dimensional structure prediction are discussed. Proteins 2005. © 2004 Wiley‐Liss, Inc.
Early events in protein aggregation: Molecular flexibility and hydrophobicity/charge interaction in amyloid peptides as studied by molecular dynamics simulations
Authors: Valerio Mariacristina , Colosimo Alfredo , Conti Filippo , Giuliani Alessandro , Grottesi Alessandro , Manetti Cesare , Zbilut Joseph P.
Published: November 2004

In a previous article (Zbilut et al., Biophys J 2003;85:3544–3557), we demonstrated how an aggregation versus folding choice could be approached considering hydrophobicity distribution and charge. In this work, our aim is highlighting the mutual interaction of charge and hydrophobicity distribution in the aggregation process. Use was made of two different peptides, both derived from a transmembrane protein (amyloid precursor protein; APP), namely, Aβ(1‐28) and Aβ(1‐40). Aβ(1‐28) has a much lower aggregation propensity than Aβ(1‐40). The results obtained by means of molecular dynamics simulations show that, when submitted to the most “aggregation‐prone” environment, corresponding to the isoelectric point and consequently to zero net charge, both peptides acquire their maximum flexibility, but Aβ(1‐40) has a definitely higher conformational mobility than Aβ(1‐28). The absence of a hydrophobic “tail,” which is the most mobile part of the molecule in Aβ(1‐40), is the element lacking in Aβ(1‐28) for obtaining a “fully aggregating” phenotype. Our results suggest that conformational flexibility, determined by both hydrophobicity and charge effect, is the main mechanistic determinant of aggregation propensity. Proteins 2005. © 2004 Wiley‐Liss, Inc.
Quaternary structure is critical for protein display on capsid‐like particles (CLPs): Efficient generation of hepatitis B virus CLPs presenting monomeric but not dimeric and tetrameric fluorescent proteins
Authors: Vogel Maren , Vorreiter Jolanta , Nassal Michael
Published: November 2004

Self‐organizing assemblies such as viral capsids may be used as symmetrical molecular platforms for the display of heterologous sequences, with applications ranging from vaccines to structural studies. The 183‐amino‐acid hepatitis B virus (HBV) core protein assembles spontaneously into icosahedral capsid‐like particles (CLPs). The most exposed, and most immunogenic, substructure on the CLPs is a small loop that connects two long antiparallel α‐helices which act as dimerization interface. Ninety (90) or 120 dimers multimerize into the capsid; the four‐helix bundles formed by the dimers protrude as spikes from the surface. We recently demonstrated that the entire enhanced green fluorescent protein (eGFP) can be inserted into this loop, yielding CLPs that natively displayed eGFP on their surface. The central location of the insertion site requires that any insert be fixed to the carrier via both termini, with corresponding restrictions regarding insert size and structure. eGFP obviously satisfied these criteria but, surprisingly, all attempts to produce CLPs with the isostructural red fluorescent proteins DsRed1, DsRed2, and HcRed failed. Suspecting their oligomerization tendency to be responsible, we generated fusions containing instead monomeric yellow, cyan, and red fluorescent proteins (mYFP, mCFP and mRFP1). This strongly increased the yields of YFP and CFP‐CLPs, and it allowed for the first time to efficiently generate red fluorescent CLPs. Hence insert quaternary structure is a highly critical factor for CLP assembly. These data have important implications for the rational design of self‐assembling fusion proteins. Proteins 2005. © 2004 Wiley‐Liss, Inc.
Tobacco use in schizophrenia: a study of cotinine concentrations in the saliva of patients and controls
Authors: Strand Jan-Erik , Nybäck Henrik
Published: November 2004

Nicotine has been proposed to provide anxiety relief, oral gratification and self-medication of psychotic symptoms in psychiatric patients. In order to investigate the relations between psychopathology and tobacco use we measured the concentration of cotinine, the major metabolite of nicotine, in the saliva of psychiatric patients and healthy volunteers. In a sample of 42 schizophrenic patients we correlated smoking status, cotinine levels, symptom profiles (PANSS), and neuroleptic side effects (Simpson–Angus). Despite reporting the same amount of cigarettes consumed per day the saliva concentration of cotinine was significantly higher in patients with schizophrenia than in the controls. There were no significant differences in clinical characteristics between smoking and non-smoking schizophrenic patients, but smokers tended to be on higher drug doses. High cotinine concentrations correlated significantly with the negative symptoms Passive withdrawal and Social avoidance. The results indicate that the schizophrenic patients smoke cigarettes more intensely than other patients and healthy subjects. The correlation between high cotinine levels and negative symptomatology may reflect an attempt by schizophrenic patients to overcome the emotional withdrawal and thus the results may lend support to a self-medication hypothesis.
The labor–machine dyad and its influence on mix flexibility
Authors: Karuppan Corinne M. , Ganster Daniel C.
Published: November 2004

The joint, mediating, and interactive effects of three elements of labor and machine flexibility on mix flexibility were tested empirically in a PCB assembly plant. Both subjective and objective data were collected. Some elements of labor and machine flexibility mediated the relationship between an emphasis on competitive priorities and mix flexibility. The interactive effects of machine and labor flexibility on mix flexibility confirmed prior findings that the pursuit of total flexibility is not desirable. For low levels of labor flexibility, increasing machine flexibility yields at the most a very moderate improvement in mix flexibility. When labor flexibility is high, increasing machine flexibility proves to be counter‐productive. These results may suggest that the traditional forms of labor flexibility need to evolve when technological capabilities are more fully exploited.
Developing countries and market access: the bitter-sweet taste of the European Union's sugar policy in southern Africa
Authors: Gibb Richard
Published: November 2004

The European Union's Common Agricultural Policy (CAP) has long been criticised for its price-distorting impact on world markets. Pressure to reform the CAP emanated previously from domestic European concerns over the costs, efficacy and efficiency of the policy and, internationally, from countries whose competitive advantage was undermined. More recently developing countries, NGOs, multilateral institutions and development agencies have orchestrated a campaign to liberalise European agriculture, in the expectation that developing countries will benefit from a shift in production away from high-cost European producers. But it would be naïve to think of liberalisation as bringing universal benefits to the developing world. Inevitably, under any system of regulation, market or intervention, there will be a complex pattern of winners and losers. This paper examines the impacts of Europe's sugar policy on southern Africa and finds, somewhat surprisingly, that the region stands to benefit more from a preservation of the status quo than from liberalisation.
Biogenesis of the Reservosomes ofTrypanosoma cruzi
Authors: Sant'Anna Celso , de Souza Wanderley , Cunha-e-Silva Narcisa
Published: November 2004

Reservosomes are endocytic compartments found in the posterior region of epimastigotes of Trypanosoma cruzi. In the differentiation from trypomastigotes to epimastigotes (reverse metacyclogenesisin vitro), one has the rare opportunity of following the biogenesis of an endocytic compartment. Metacyclic trypomastigotes incubated in LIT medium highly enriched with fetal calf serum differentiated directly to epimastigotes. In recently differentiated epimastigotes, acidic organelles were found in round compartments spread along the cell body, whereas in control epimastigotes they were found in reservosomes located in the posterior region. Ultrastructural analysis of intermediate forms showed that the cytostome and reservosomes appeared before differentiation to epimastigotes was completed. Many polymorphic reservosomes, with or without lipid inclusions, were observed from the anterior portion of the cell body, in close relationship with the Golgi complex, to the posterior region. Endocytic tracers were observed in the cytostome, flagellar pocket, vesicles, and newly formed reservosomes. Cruzipain, the main protease ofT. cruzi, was localized in newly formed reservosomes and in vesicles budding from thetrans-Golgi network that seem to fuse with reservosomes. Ingested gold-labeled albumin and cruzipain colocalized in recently formed reservosomes. Endocytosis and immunocytochemical analysis suggested that the endocytic and the secretory pathways may contribute to reservosome formation.
Polyphosphate Content and Fine Structure of Acidocalcisomes ofPlasmodium falciparum
Authors: Ruiz Felix A. , Luo Shuhong , Moreno Silvia N.J. , Docampo Roberto
Published: November 2004

Although acidocalcisomes have been well characterized morphologically in other apicomplexan parasites, no such characterization has been done in Plasmodium spp. Here, we report thatPlasmodium falciparummerozoites possess electron-dense organelles rich in phosphorus and calcium, as detected by X-ray microanalysis of intact cells, which are similar to the acidocalcisomes of other apicomplexans, but of more irregular form. In agreement with these results malaria parasites possess large amounts of short- and long-chain polyphosphate (polyP), which are associated with acidocalcisomes in other organisms. PolyP levels were highest in the trophozoite stage of the parasite. Treatment of isolated trophozoites with chloroquine resulted in a significant hydrolysis of polyP. Taken together, these results provide evidence that acidocalcisomes fromPlasmodium falciparumdo not differ significantly from acidocalcisomes of other apicomplexan parasites.
Studying the Cell Biology of Apicomplexan Parasites Using Fluorescent Proteins
Authors: Gubbels Marc-Jan , Striepen Boris
Published: November 2004

The ability to transfect Apicomplexan parasites has revolutionized the study of this important group of pathogens. The function of specific genes can be explored by disruption of the locus or more subtly by introduction of altered or tagged versions. Using the transgenic reporter gene green fluorescent protein (GFP), cell biological processes can now be studied in living parasites and in real time. We review recent advances made using GFP-based experiments in the understanding of protein trafficking, organelle biogenesis, and cell division inToxoplasma gondiiandPlasmodium falciparum. A technical section provides a collection of basic experimental protocols for fluorescent protein expression inT. gondii. The combination of thein vivomarker GFP with an increasingly diverse genetic toolbox forT. gondiiopens many exciting experimental opportunities, and emerging applications of GFP in genetic and pharmacological screens are discussed.
Structural Analysis ofCryptosporidium parvum
Authors: Petry Franz
Published: November 2004

Cryptosporidium parvum(Apicomplexa, formerly Sporozoa) is the causative agent of cryptosporidiosis, an enteric disease of substantial medical and veterinary importance.C. parvumshows a number of unique features that differ from the rest of the class of coccidea in which it is currently grouped taxonomically. Differences occur in the overall structure of the transmission form and the invasive stages of the parasite, its intracellular location, the presence of recently described additional extracellular stages, the host range and target cell tropism, the ability to autoinfection, the nonresponsiveness to anticoccidial drugs, the immune response of the host, and immunochemical and genetic characteristics. These differences have an important impact on the infectivity, the epidemiology, the therapy, and the taxonomy of the parasite. The present article describes the structural analysis of the parasite using light and electron microscopy with an emphasis on structural details unique toC. parvum.
New Approaches to the Microscopic Imaging ofTrypanosoma brucei
Authors: Field Mark C. , Allen Clare L. , Dhir Vivek , Goulding David , Hall Belinda S. , Morgan Gareth W. , Veazey Paul , Engstler Markus
Published: November 2004

Protozoan parasites are fearsome pathogens responsible for a substantial proportion of human mortality, morbidity, and economic hardship. The principal disease agents are members of the orders Apicomplexa (Plasmodium, Toxoplasma, Eimeria) and Kinetoplastida (Trypanosomes, Leishmania). The majority of humans are at risk from infection from one or more of these organisms, with profound effects on the economy, social structure and quality of life in endemic areas; Plasmodium itself accounts for over one million deaths per annum, and an estimated 4 × 107disability-adjusted life years (DALYs), whereas the Kinetoplastida are responsible for over 100,000 deaths per annum and 4 × 106DALYs. Current control strategies are failing due to drug resistance and inadequate implementation of existing public health strategies.Trypanosoma brucei, the African Trypanosome, has emerged as a favored model system for the study of basic cell biology in Kinetoplastida, because of several recent technical advances (transfection, inducible expression systems, and RNA interference), and these advantages, together with genome sequencing efforts are widely anticipated to provide new strategies of therapeutic intervention. Here we describe a suite of methods that have been developed for the microscopic analysis ofT. bruceiat the light and ultrastructural levels, an essential component of analysis of gene function and hence identification of therapeutic targets.
Calendar of Meetings and Courses
Authors: Hudson JoAn , Zaluzec Nestor
Published: November 2004

Following is a list of microscopy-related meetings and courses. The
editors would greatly appreciate input to this list via the electronic
submission form found in the MSA World-Wide Web page at
http://www.msa.microscopy.com. We will gladly add hypertext
links to the notice on the web and insert a listing of the meeting in
the next issue of the Journal. Send comments and questions to JoAn
Hudson, hudson@uoneuro.uoregon.edu or Nestor Zaluzec,
zaluzec@aaem.amc.anl.gov.
On determining the nature and orientation of magnetic directional discontinuities: Problems with the minimum variance method
Authors: Hausman B. A. , Michel F. C. , Espley J. R. , Cloutier P. A.
Published: November 2004

The minimum variance method (MVA) has been used for over 3 decades to analyze directional discontinuities in solar wind magnetic field data. We recount how MVA was formulated and show that it does not do what many expect. We demonstrate a robust alternative for distinguishing tangential discontinuities from rotational discontinuities (RDs). We also stress that averaging magnetic field data to time resolutions of a minute or more (common with National Space Science Data Center data sets) obliterates RDs.
Modeling water mass formation in the Mertz Glacier Polynya and Adélie Depression, East Antarctica
Authors: Marsland S. J. , Bindoff N. L. , Williams G. D. , Budd W. F.
Published: November 2004

High rates of sea ice growth and brine rejection in the Mertz Glacier Polynya drive the production of dense continental shelf waters in the Adélie Depression. We consider the rate of outflow of waters having sufficient density to sink into the neighboring abyssal ocean and form Adélie Land Bottom Water (ALBW). Along with Weddell and Ross Sea Bottom Waters, the ALBW is an important source of Antarctic Bottom Water. The relevant processes are modeled using a variant of the Max Planck Institute Ocean Model (MPIOM) under daily NCEP‐NCAR reanalysis forcing for the period 1991–2000. The orthogonal curvilinear horizontal grid allows for the construction of a global domain with high resolution in our region of interest. The modeled Mertz Glacier Polynya is realistic in location and extent, exhibiting low ice thickness (<0.4 m) and low ice fraction (<50%). The net surface ocean to atmosphere heat flux exceeds 200 W m2 and is dominated by sensible heat exchange. In wintertime (May through September inclusive), 7.5 m of sea ice forms over the Adélie Depression at a rate of 4.9 cm d−1: this results in annual average volumetric production of 99 km3 of sea ice. The associated brine release drives dense shelf water formation. The off‐shelf flow of dense water exhibits strong interannual variability in response to variability in both atmospheric forcing and ocean preconditioning. Averaged over the period 1991–2000 the off shelf flow of dense water is 0.15 Sv: for a period of strong outflow (1993–1997), this increases to 0.24 Sv. Most of the outflow occurs during July through October, at a rate of 0.40 (0.63) Sv over the period 1991–2000 (1993–1997). The peak mean monthly outflow can exceed 1 Sv.
Influence of the Amazon River on the surface optical properties of the western tropical North Atlantic Ocean
Authors: Del Vecchio Rossana , Subramaniam Ajit
Published: November 2004

The distribution of chromophoric‐dissolved‐organic‐matter (CDOM) was investigated in the western tropical North Atlantic Ocean (WTNA) during the low and high flow periods of the Amazon River. A strong correlation was observed between in situ CDOM absorption at 490 nm and in situ diffuse attenuation coefficient at 490 nm (K490) during the high flow period (ratio of 0.7). SeaWiFS monthly composites of K490 showed (1) very low values over most of the WTNA, with higher values restricted to the continental shelf during the low flow season and (2) higher K490 over much of the WTNA extending offshore to >1000 km from the river mouth during the high flow season. The relative contribution to light absorption by particulate (phytoplankton and detritus) and dissolved (CDOM) materials was investigated at selected wavelengths. At 440 nm during the high flow period (1) CDOM dominated (∼70%) total light absorption closer to the river mouth; (2) phytoplankton and detritus dominated (∼40% each) absorption farther offshore but still within the Amazon plume; and (3) CDOM contributed ∼20%, phytoplankton >60%, and detritus ∼10% outside the plume. In situ data suggests a terrestrial source for the CDOM off the coast of South America during the high flow period with possible offshore local sinks (photodegradation) as well as sources (in situ production). The Amazon River strongly influences the optical properties of the WTNA at distances over 1000 km from the river mouth. Retrievals of phytoplankton biomass based on satellite ocean color data can be largely overestimated in the WTNA, if the contribution to light absorption by CDOM and detritus is not taken into account.
Characterization and evolution of tropospheric plumes from Lascar and Villarrica volcanoes, Chile
Authors: Mather T. A. , Tsanev V. I. , Pyle D. M. , McGonigle A. J. S. , Oppenheimer C. , Allen A. G.
Published: November 2004

Direct sampling (filter pack and impactor) and remote sensing (ultraviolet spectroscopy and Sun photometry) of the plumes of Lascar and Villarrica volcanoes, Chile, reveal that both are significant and sustained emitters of SO2 (28 and 3.7 kg s−1, respectively), HCl (9.6 and 1.3 kg s−1, respectively), HF (4.5 and 0.3 kg s−1, respectively) and near‐source sulfate aerosol (0.5 and 0.1 kg s−1, respectively). Aerosol plumes are characterized by particle number fluxes (0.08–4.0 μm radius) of ∼1017 s−1 (Lascar) and ∼1016 s−1 (Villarrica), the majority of which will act as cloud condensation nuclei at supersaturations >0.1%. Impactor studies suggest that the majority of these particles contain soluble SO42−. Most aerosol size distributions were bimodal with maxima at radii of 0.1–0.2 μm and 0.7–1.5 μm. The mean particle effective radius (Reff) ranged from 0.1 to 1.5 μm, and particle size evolution during transport appears to be controlled by particle water uptake (Villarrica) or loss (Lascar) rather than sulfate production.
An X-Ray Study of the Wüstite (FeO) Solid Solutions
Authors: Jette Eric R. , Foote Frank
Published: November 2004

A series of iron oxides with compositions between 76.08 and 76.72 percent Fe, all of them lying within the single phase solid solution area known as Wüstite has been prepared and the lattice constants and densities of the individual members determined. The NaCl structure found by earlier investigators and considered by them to be the structure of FeO has been found throughout this series. Contrary to the earlier results the size of the unit cell decreases as the iron content decreases. The solid solution is of a complex type; an oxygen ion replaces an FeO group with an accompanying increase in valence of 2 Fe++ to 2 Fe+++. The results are discussed from the chemical and structural points of view.
Chemical Aspects of the Infrared Absorption Spectra of the Ethyl Halides
Authors: Cross Paul C. , Daniels Farrington
Published: November 2004

The infrared absorption spectra of ethyl chloride, ethyl bromide and ethyl iodide have been determined with a prism spectrometer between 1.5μ and 15μ. Eight experimentally observed fundamental frequencies have been selected which, together with their first harmonics and simple combinations, are shown to account for the entire spectrum. A type of vibration between atom pairs believed to represent the important feature of the motion of the atoms is suggested for each of these fundamentals. The shifts in the absorption maxima produced by the substitution of the different halogens together with absorption and Raman data of related compounds are used in selecting these types of vibration. The bearing of these hypotheses on problems in chemical kinetics is discussed.
The Nature of the Chemical Bond. VII. The Calculation of Resonance Energy in Conjugated Systems
Authors: Pauling Linus , Sherman J.
Published: November 2004

The quantum-mechanical treatment previously applied to benzene, naphthalene, and the hydrocarbon free radicals is used in the calculation of extra resonance energy of conjugation in systems of double bonds, the dihydronaphthalenes and dihydroanthracenes, phenylethylene, stilbene, isostilbene, triphenylethylene, tetraphenylethylene, biphenyl, o, m, and p-diphenylbenzene, and 1,3,5-triphenylbenzene. The calculated values, which are in approximate agreement with empirical values from thermochemical data, are used in the discussion of chemical properties and in the formulation of rules regarding conjugation in overlapping systems.
The Virial and Molecular Structure
Authors: Slater J. C.
Published: November 2004

The virial theorem can be applied to a molecule, assuming that external forces are applied to keep the nuclei fixed. The mean electronic kinetic energy is then the negative of the mean total internal energy, plus a term arising from the virial of the external force. Since the external force is derivable from the knowledge of the total internal energy as function of nuclear position, this theorem gives a means of finding kinetic and potential energy separately for all configurations of the nuclei, as soon as the total energy is known, from experiment or theory. By using simple forms of curve for total energy, for the diatomic molecule, the kinetic and potential energy are derived and discussed. The curves give direct indication of the formation of the covalent bond, in cases where this occurs, by describing the removal of charge from the atoms to the region between the atoms, with resulting decrease of kinetic energy, increase of potential energy.
The Reactions of the Hydroxyl Radical in the Electrodeless Discharge in Water Vapor
Authors: Rodebush W. H. , Wahl M. H.
Published: November 2004

In a study of the reactions occurring in the electrodeless discharge in water vapor consistently high yields of hydrogen peroxide were obtained. A number of reactions have been studied and by a process of elimination a mechanism for the formation of hydrogen peroxide from hydroxyl has been suggested. In the course of some spectrographic investigations of the electrodeless discharge in water vapor some new bands, with heads at 3564 and 3328A, were observed which are probably due to an ionized hydroxyl. These bands were not present in the uncondensed electrode discharge but appeared in the condensed electrode discharge at low pressures.
Complex Formation due to Polarization. I. The System Krypton and Hydrogen Chloride
Authors: Glockler George , Roe Charles P. , Fuller Donald L.
Published: November 2004

Rare gases form compounds of a loose complex nature such as hydrates, solvates or mercury complexes. Such molecular aggregates contain a molecule of permanent dipole moment or an excited atom or molecule of dipole character as the other reaction partner besides the rare gas. The forces holding the complex molecule are the attraction between the permanent dipole and the dipole induced in the rare gas molecule due to its polarizability. Five lines of evidence are cited which indicate the formation of such complex molecules: (1) Band spectra of complex HgA and HgKr are known. (2) Rare gas hydrates have been described. (3) Isoelectronic systems similar to the rare gases have proton affinity. (4) Rare gas hydride ions have been found in the mass-spectrograph. (5) The P-V-T relation of gaseous mixtures show that interaction between the unlike molecules exists. The second Virial coefficient is determined experimentally for Kr–HCl mixtures as a function of composition and it is shown that interaction exists between the rare gas atom Kr and the permanent dipole HCl.
Oil Lenses on Water and the Nature of Monomolecular Expanded Films
Authors: Langmuir Irving
Published: November 2004

A higher hydrocarbon, such as tetradecane, on the surface of water forms a circular lens. The condition for the formation of such stable lenses is that the spreading coefficient FS = γ1 — γ2 — γ12 shall be negative. As the volume of the oil lens is increased, the thickness t at the center slowly approaches a limiting value given by t∞2 = —2Fsρ1/gρ2(ρ1 — ρ2). Equations are given by which FS can be accurately determined from measurements of the radii of large lenses of known volume. The magnitude of the linear tension at the lens boundary is also calculated. Experiments with tetradecane on water at 25°C give FS = —6.2 dynes cm—1 and γ = 26.9. When hydrophilic molecules are introduced into the interface between the lens and the water, they give a spreading force F12 which causes a decrease in — FS and in t. When t<0.1 mm gravitational effects are negligible and the lens degenerates into a duplex film. If such a film is confined by a movable barrier (piston), the force per unit length F exerted on the barrier is equal to FS. If the adsorbed molecules at the interface give a force F12 in accord with the gas laws, then (F — F0)(a — a0) = kT gives the equation of state of the duplex film, where F0 is the value of FS in the absence of hydrophilic substances. It is shown that this equation applies to expanded oil films on water and that these are properly regarded as duplex films although they are monomolecular. The presence of a kink in the observed F — a curves is attributed to the sudden appearance of micelles, each containing β-molecules when F12 rises to a critical value. For the fatty acids on dilute HCl, β = 13. This small value is due to the crowding apart of the heads because of hydration. The esters show little or no hydration and β = 60. The heat of formation of the micelles in the fatty acids is found to be 5.5+0.24n kg cal. per mole where n is the number of carbon atoms. The values of F0 and a0 for various substances are determined from data given by Adam.
Molecular Symmetry and the Reduction of the Secular Equation
Authors: Eyring Henry , Frost Arthur A. , Turkevich John
Published: November 2004

A method is given for expressing a bond eigenfunction of any multiplicity in terms of a linear independent set. The independent sets for the multiplicities corresponding to one bond and to two bonds for an arbitrary number of electrons are given. A method recently given for obtaining matrix components for singlet bond eigenfunctions is generalized to include all multiplicities. Group theory is applied to the bond eigenfunctions for symmetrical molecules to reduce the secular equation and examples are worked out for all multiplicities. The possible reasons for the approximate additivity of bond energies for molecules is examined in connection with the chemist's custom of ignoring all but the strongest bonds.
The Derivation of Equations for Regular Solutions
Authors: Hildebrand J. H. , Wood S. E.
Published: November 2004

The probability function of Menke has been used as a basis for a statistical treatment of the intermolecular potentials in solutions of symmetrical molecules for which the entropy of mixing is the same as for an ideal solution of the same composition. The resulting expressions enable calculations to be made of the departure of iodine solutions from the ideal solution laws which agree satisfactorily with the observed departures.
Some Thermodynamic Properties of the H1H2, H2H2 Molecules and Compounds Containing the H2 Atom
Authors: Urey Harold C. , Rittenberg D.
Published: November 2004

The summations of state and free energies of the molecules H21, H22 and H1H2 have been calculated at temperatures from 20.4 to 700°K and their dependence on the spin and statistics of H2 discussed and illustrated. The equilibrium constants of the reaction H21+H22 = 2 H1H2 are found to deviate markedly from the value 4 expected from simple probability considerations. The equilibrium constants of the reactions H21+2 H2Cl⇄H22+2 H1Cl and H21+2 H2I→H22+2 H1I have been calculated and found to be appreciably different from unity, showing that appreciable differences in equilibrium constants of chemical reactions may be expected depending on which isotope of hydrogen enters into the reaction. Small differences in the electrode potentials of the two hydrogen isotopes may be expected but no exact estimates have been made.
On the Theory of the Structure of CH4 and Related Molecules. Part I1
Authors: Van Vleck J. H.
Published: November 2004

The primary purpose of the present series of papers is to give more explicit mathematical form to the theory of Mulliken and Hund, and in some instances to the alternative theories of Pauling and Slater and of Heitler and Rumer, for valence in carbon compounds. A critical comparison is given of the Slater-Pauling and Hund-Mulliken concepts of CH4, which are based respectively on localized bonds (``electron pairs'') with the Heitler-London method, and on one-electron wave functions (Mulliken's ``orbitals'') for a self-consistent field with tetrahedral symmetry. The H-M procedure avoids hybridization of the carbon 2s and 2p wave functions, but allows two (though never three or more) electrons to accumulate on one H atom, as well as up to eight on a C atom. Inadequate cognizance is thus taken of the tendency of inter-electronic Coulomb forces to keep two electrons apart. The S-P procedure avoids this excessive accumulation, but at the expense of not letting an individual wave function be of a symmetry type (irreducible group representation) appropriate to a tetrahedral field. In particular, its s-p hybridization ``undiagonalizes'' the internal energy of the C atom. These points are illustrated by explicit exhibition of the secular determinant, which is the main new feature. Because inter-electronic repulsions make the dynamical problem more complicated than a one-electron one, the tetrahedral symmetry need only be preserved in the properties of the total wave function of the entire system rather than that of one electron, but the departures from individual tetrahedral symmetry should be less than in the Slater-Pauling theory if the Hartree self-consistent field is really a good approximation. Thus both the H-M and S-P methods, though qualitatively exceedingly illuminating, have their own characteristic drawbacks from a quantitative standpoint unless refined by inclusion of higher approximations which ultimately merge the two methods but which practically are very difficult to make.
Induction Between Bond Moments in Some Halogenated Methanes
Authors: Smyth C. P. , McAlpine K. B.
Published: November 2004

The dipole moments of four fluorochloromethanes are measured in the vapor state. The inductive effects of carbon-halogen bond moments are calculated and, through these, the moments of methyl fluoride and methyl chloride are used to calculate approximate values for CH2Cl2, CHCl3, and CFCl3, which are in satisfactory agreement with the observed values. The moments of these molecules are then used to calculate values for other substituted methanes which are in excellent agreement with the observed values. The value of a bond moment is treated as a function of its environment.
The Quantum Mechanics of Seven and Eight Electrons with Spin Degeneracy
Authors: Eyring Henry , Kimball George E.
Published: November 2004

The eigenfunctions corresponding to the fourteen singlet states of a system of seven or eight electrons are given and the corresponding matrix elements tabulated in a form convenient for computation, neglecting multiple interchange integrals. Proof is given that the general method described in earlier work for writing bond eigenfunctions suffices to separate the multiplets. A method for calculating matrix components between bond eigenfunctions directly from the bond systems is also described.
Dispersion and Polarizability and the van der Waals Potential in the Alkali Halides
Authors: Mayer Joseph E.
Published: November 2004

It is shown that the ultraviolet absorption of NaCl, KCl and KI, which one may estimate from recent experimental work, is in agreement with the dispersion of these salts. With these assumed absorption curves, the dipole-dipole potential constant for the van der Waals attraction between negative ions can be calculated with considerable accuracy. The constants can be estimated for the other alkali halides. The quadrupole-dipole constant is also approximated for all alkali halides. The resulting van der Waals potential is much greater than that previously calculated and accounts for the stability of CsCl type lattice for CsCl, CsBr and CsI. The polarizability of a given ion depends on the crystal. It is here assumed that the polarizability varies inversely as the ``main frequency'' in the crystal. This is shown to be in approximate agreement with experiment.
Evaluation of the Series Which Arise in the Calculation of Thermodynamic Quantities From Spectroscopic Data
Authors: Gordon A. R. , Barnes Colin
Published: November 2004

In cases where knowledge of the molecular spectrum of a gas is sufficiently detailed to include the ``stretching'' and ``interaction'' terms in the expression for the rotational-vibrational energy states, calculation of the free energy, entropy and heat capacity for high temperatures becomes very laborious when the usual approximations are employed. In this paper, methods are developed which reduce many such calculations to a matter of interpolation in appended tables; for cases which lie outside the range of the tables, approximations are given which materially reduce the labor of computation. The procedure is illustrated by calculations for chlorine, bromine, hydrogen chloride, carbon monoxide, oxygen and nitric oxide.
Diffusion and Electrolytic Conduction in Crystals (Ionic Semiconductors)
Authors: Jost W.
Published: November 2004

In the present paper a mechanism of diffusion and electrolytic conduction in solids is discussed, which is based on a formal treatment given by Frenkel. It is assumed that in a crystal in thermal equilibrium some of the atoms or ions are removed from their normal positions in the lattice to irregular ones in the interlattice space. Then diffusion and electrolytic conduction is possible by two processes; first by migration of the ions in the interlattice space, second by migration of the vacant places. The number of ions in the interlattice space can be calculated. If one considers the influence of polarization the result agrees in the order of magnitude with the observed data. It is also shown that the activation energy connected with the processes of movement is of the correct order of magnitude. Thus a satisfactory explanation of the exponential factor occuring in the empirical conductivity (or diffusion) formula is obtained. The constant factor multiplying the exponential can be explained at once for one group of cases; for the other group, where the constants apparently are too high, a tentative explanation is proposed.
X-Ray and Electron Diffraction of Iodine and the Diiodobenzenes
Authors: Hendricks S. B. , Maxwell Louis R. , Mosley V. L. , Jefferson M. E.
Published: November 2004

The crystal structures of 1,3 and 1,4 diiodobenzene were determined from the x-ray diffraction patterns of single crystals. The separations of the iodine atoms in the molecules were found to be 6.85 and 5.92A, respectively. These values are in agreement with results obtained by analysis of the electron diffraction patterns given by the vapors of these compounds. The most satisfactory explanation of the electron diffraction results for 1,2 diiodobenzene requires the I–C valence directions to be bent by about 10° from symmetrical positions in the plane of the benzene ring. In this molecule the I–I distance was found to be 4.00A, which is approximately the same as the minimum intermolecular iodine distances in crystals of the other isomeric diiodobenzenes. Electron diffraction was obtained from vapors of carbon tetrachloride and iodine. The separation of the iodine atoms in the latter molecule was found to be 2.64A; a value in agreement with band spectra data and with previous crystal structure analysis.
Interatomic Distances in Crystals of the Alkali Halides
Authors: Huggins Maurice L. , Mayer Joseph E.
Published: November 2004

The constants of the empirical repulsion potential assumed by Born and Mayer between two ions, which may be termed the ionic ``radii,'' are calculated for the alkali and halide ions from the lattice constants of the alkali halides. By using 9 such radii the 20 lattice constants can be recalculated nearly within the probable experimental error of their determination. The good agreement is regarded as support for the assumptions involved in the calculations.
A New Method of Studying the Electrical Properties of Monomolecular Films on Liquids
Authors: Yamins H. G. , Zisman W. A.
Published: November 2004

A new method of studying the electrical properties of monomolecular films floating upon a liquid has been described. Measurements on the potential jump, dV, because of the presence of monomolecular films of oleic acid, palmitic acid, tricaprylin, and trimyristin on water have been made in order to furnish a comparison with the work of Guyot. Excellent agreement was found in all cases. In addition, Guyot's conclusion was verified that dV for fatty acids depends greatly upon the presence of a trace of sulphuric acid in the water while dV for substances like tricaprylin and trimyristin is but slightly affected by the presence of acid.