bluuebunny/crossref_metadata_2025 huggingface dataset:
Deconvolution algorithms for instrumental applications: A comparative study
Authors: Morawski Roman Z. , Szczecinski Leszek , Barwicz Andrzej
Published: May 2005

Deconvolution algorithms for measurand reconstruction are considered. Their metrological and numerical properties are briefly characterized. Six algorithms most frequently used for instrumental applications are selected for closer analysis. Their comparative study is based on the use of spectrometric‐type synthetic data, calorimetric‐type synthetic data and spectrometric real‐world data. Conclusions concerning computational complexity and accuracy of the compared algorithms as well as their metrological applicability are drawn.
A correlation principal component regression analysis of NIR data
Authors: Sun Jianguo
Published: May 2005

The use of principal component regression (PCR) as a multivariate calibration method has been discussed by a number of authors. In most situations principal components are included in the regression model in sequence based on the variances of the components, and the principal components with small variances are rarely used in regression. As pointed out by some authors, a low variance for a component does not necessarily imply that the corresponding component is unimportant, especially when prediction is of primary interest. In this paper we investigate a different version of PCR, correlation principal component regression (CPCR). In CPCR the importance of principal components in terms of predicting the response variable is used as a basis for the inclusion of principal components in the regression model. Two typical examples arising from calibrating near‐infrared (NIR) instruments are discussed for the comparison of the two different versions of PCR along with partial least squares (PLS), a commonly used regression approach in NIR analysis. In both examples the three methods show similar optimal prediction ability, but CPCR performs better than standard PCR and PLS in terms of the number of components needed to achieve the optimal prediction ability. Similar results are also seen in other NIR examples.
Selectivity, local rank, three‐way data analysis and ambiguity in multivariate curve resolution
Authors: Tauler Romà , Smilde Age , Kowalski Bruce
Published: May 2005

A new multivariate curve resolution method is presented and tested with data of various levels of complexity. Rotational and intensity ambiguities and the effect of selectivity on resolution are the focus. Analysis of simulated data provides the general guidelines concerning the conditions for uniqueness of a solution for a given problem. Multivariate curve resolution is extended to the analysis of three‐way data matrices. The particular case of three‐way data where only one of the orders is common between slices is studied in some detail.
Distance and class space in the UNEQ class‐modeling technique
Authors: Forina M. , Lanteri S. , Sarabia L.
Published: May 2005

Different estimators of the Mahalanobis distance (such as that based on the Defrise—Gussenhoven correction) are studied and compared with respect to the bias on the distance and the characteristics (sensitivity and specificity) of the class model.

Results obtained using estimators with critical values from χ2‐statistics are compared with those obtained using estimators with critical values from β‐statistics (training set) and Hotelling statistics (evaluation set).

Tables are reported for D‐statistics (useful for simulating populations of two categories with selectable theoretical sensitivity and specificity) and for critical values of the Mahalanobis distance obtained from β‐statistics.

For objects of the training set the estimator of the Mahalanobis distance based on the estimate of the covariance matrix produces models with the optimum sensitivity. The same model has too low a sensitivity for objects of the model category in the evaluation set, but good specificity for objects of outer categories.

The estimator with the Defrise–Gussenhoven correction produces enlarged models with too high a sensitivity for objects in the training set, good sensitivity for objects of the model category in the evaluation set and low specificity for objects of outer categories.
Application of procrustean methods to mid‐and near‐infrared spectral data
Authors: Vigneau E. , Devaux M. F. , Safar M.
Published: May 2005

Procrustean methods allow the fitting of a given matrix to another given matrix observed on the same objects. In the traditional approach orthogonal constraints are imposed upon the transformation matrix, whereas in the alternative approach Procrustean analysis may be performed without such constraints. The two methods (with and without constraints) were compared on data dealing with mid‐ and near‐infrared spectra of oil. The aim was to reconstruct the mid‐infrared spectral information using data from the near‐infrared spectra. Unconstrained Procrustean analysis proved to be the more efficient for both the calibration and verification sets. Furthermore, the analysis of the transformation matrix between the two infrared ranges made it possible to indicate wavelengths and wave numbers corresponding to the same chemical groups.
Messy simulated annealing
Authors: Kvasnička V. , Pospíchal J.
Published: May 2005

The method of simulated annealing is modified so that the concept of messy chromosomes is applied. Constituent genes of messy chromosomes are specified by their respective names (indices) and values (alleles) simultaneously. Unlike simple chromosomes (binary vectors), messy chromosomes may be either under‐ or overspecified with respect to the problem being solved. The messy simulated annealing algorithm is a very robust and efficient stochastic optimization method which is able to find correct minima of deceptive or highly multimodal objective functions. This is shown by way of a number of simulations.
Univariate regression models with errors in both axes
Authors: Riu J. , Rius F. X.
Published: May 2005

Calibration is a fundamental step in the calculation of the unknown concentration of analyte in most analytical methods. It is known that for certain methodologies, if only the errors in the independent variable are taken into account, there may be considerable errors in the estimation of the value of the regression coefficients, the derived statistical parameters and in some cases the sought for response and concentration values. This paper reviews the calibration methods including some references to procedures for the detection of outliers and robust regression when there are errors in both axes. The advantages and limitations of the different approaches are discussed and a comparative study is made of the approaches of several techniques for which computer programmes have been developed based on the algorithms put forward by the different authors. Finally, some trends of future development in this field are envisaged.
Maximum sum of binary‐coded residuals (MASBR) regression as a robust procedure for treatment of spectral data
Authors: Wang Ji‐Hong , Xie Yu‐Long , Yu Ru‐Qin
Published: May 2005

In this paper, a novel robust regression method, the maximum sum of binary coded residuals (MASBR), is proposed. Instead of the sum of squared residuals used in least squares regression as the minimization criterion, MASBR regression maximizes the sum of binary coded residuals. MASBR regression is designed for cases where the conventional robust regression methods with breakdown points less than 50% fail. To circumvent the problem of being trapped in local optima, a stepwise‐varying acceptable error limit (SVAEL) algorithm is proposed. Both numerical simulation and treatment of real analytical data demonstrate the feasibility of MASBR regression in conjunction with the SVAEL algorithm.
Low pressure chemical vapor deposition of metallic films of iron, manganese, cobalt, copper, germanium and tin employing bis(trimethyl)silylamido complexes, M(N(SiMe3)2)n
Authors: Baxter David V. , Chisholm Malcolm H. , Gama Gennaro J. , Hector Andrew L. , Parkin Ivan P.
Published: May 2005

The deposition of metallic films by chemical vapor deposition, in contrast to the use of physical methods such as evaporation or sputtering, offers the potential advantage of conformal coverage and substrate selectivity in microelectronics applications. Here, the title compounds have been used to deposit high‐purity metal films and can be seen as substrate‐selective precursors.
Deposition of aluminum nitride thin films by MOCVD from the trimethylaluminum–ammonia adduct
Authors: Jones Anthony C. , Rushworth Simon A. , Houlton David J. , Roberts John S. , Roberts Victoria , Whitehouse Colin R. , Critchlow Gary W.
Published: May 2005

Growth of epitaxial AIN from a directly bonded compound in the absence of any NH3, as described here, is an important technological advance. It is reported that the use of the adduct Me3AINH3 as a single‐source precursor has allowed the epitaxial growth on sapphire of AIN films of a quality suitable for buffer layers in the growth of device layers avoiding the disadvantages of traditional MOCVD of AIN. Details are given of deposition schemes, the carbon and oxygen contamination is discussed, and a probable deposition mechanism is proposed.
Hydrogen in Cvd Diamond Films
Authors: Rutledge Karen Mcnamara , Gleason Karen K.
Published: May 2005

Understanding of the incorporation of hydrogen and its role in determining the properties of CVD diamond is critical to the successful commercial production of these films. Hydrogen is usually the most abundant impurity in solid‐state CVD diamond and has been studied extensively by a variety of techniques, including nuclear magnetic resonance, infrared spectroscopy, and several others. This article reviews the application of a number of characterization methods to the study of hydrogen in CVD diamond, with particular attention toward understanding the incorporation of this impurity and its effect on properties of commercial significance.
Aerosol‐assisted chemical vapor deposition of CeO2‐doped Y2O3‐stabilized ZrO2 films on porous ceramic supports for membrane applications
Authors: Xia Changfeng , Ward Timothy L. , Schwartz Robert W.
Published: May 2005

Dense stabilized zirconia has a number of important applications because of its oxygen ion conductivity and excellent thermal and chemical stability. Conventional multicomponent CVD has a number of problems, including low precursor delivery rates and premature decomposition. The results in this paper suggest that the novel use of aerosol‐assisted CVD can be used to overcome these problems. The Figure shows the cross section of a CeO2‐doped Y2O3‐stabilized ZrO2 film deposited by AACVD.

magnified image
The first monomeric, volatile bis‐azide single‐source precursor to Gallium nitride thin films
Authors: Miehr Alexander , Ambacher Oliver , Rieger Walter , Metzger Thomas , Born Eberhard , Fischer Roland A.
Published: May 2005

Group III nitrides are strong candidates for use in light emitting diodes and semiconductor lasers. There are, though, a number of shortcomings of currently available precursors. There is a need for less toxic and pyrophoric precursors that can be used for low temperature deposition. The single source nitrogen‐rich GaN precursor reported here, building on the concept of intramolecularly based adduct stabilization, shows considerable promise for producing high quality layers.
Trends in precursor selection for MOCVD
Authors: Maury Francis
Published: May 2005

MOCVD has many promising advantages over physical processes but industrial applications are still sparse, probably because commercial availability of suitable precursors is limited. In this Research News article the stringent requirements for metal‐organic compounds for thermal MOCVD as well as for photo‐MOCVD and MOMBE are critically reviewed. In particular, the problem of carbon incorporation in deposited films and the use of single‐source precursors for multi‐element deposits are discussed.
The synthesis and thermal evaluation of a novel cerium precursor to grow thick ceria films by metal‐organic chemical vapor deposition (MOCVD)
Authors: McAleese John , Darr Jawwad A. , Steele Brian C. H.
Published: May 2005

Ce1‐xGdxO2‐x/2 as a thick electrolyte in solid oxide fuel cells should result in high current densities and acceptable ohmic losses at 500°C. It would be interesting to be able to grow such an electrolyte by MOCVD, and in this work the synthesis and thermal evaluation of a novel, air‐stable, liquid cerium precursor [{Ce(fod)3}2(tetraglyme)] for the MOCVD of the cerium component of the electrolyte is reported. Growth of good quality, thick, crystalline ceria films from the precursor has been demonstrated for the first time.
Analysis and modeling of SIPOS deposition in a hot wall tubular reactor. Part II: Modeling of SIPOS deposition
Authors: Fayolle Francine , Couderc Jean‐Pierre , Duverneuil Patrick
Published: May 2005

A full theoretical model of SIPOS deposition is presented, building on the preceding article. A code previously developed to treat the deposition of undoped and doped polysilicon has been extended to the more complex case of SIPOS deposition from SiH4 and N2O. The model is in good agreement with experiment at the center of a wafer, but is only qualitatively correct at the wafer periphery. Even with these limitations the code gives a satisfactory simulation of the influence of temperature and pressure on the deposition process and provides a deeper insight into the deposition mechanism.
Conversion of tetraethoxysilane (TEOS) to silica film‐forming precursors in atomic oxygen‐induced chemical vapor deposition
Authors: Wróbel Aleksander M. , Walkiewicz‐Pietrzykowska Agnieszka , Stasiak Marek , Kulpiúski Józef
Published: May 2005

The gas phase reactions of tetraethoxysilane in atomic oxygen‐induced chemical vapor deposition were investigated. A high‐resolution gas chromatography/mass spectrometry examination of the reaction products, collected in a cold trap, revealed the presence of linear and cyclic siloxane oligomers containing the ‐(EtO)2SiO‐ repeating unit. The structure of the identified oligomers and mechanisms of TEOS reactions with atomic oxygen suggest that diethoxysilanone plays a predominant role in the silica film growth process.
Palladium Thin Films Grown by CVD from (1,1,1,5,5,5‐Hexafluoro‐2,4‐pentanedionato) Palladium(II)
Authors: Bhaskaran Vijay , Hampden‐Smith Mark J. , Kodas Toivo T.
Published: May 2005

The precursor (1,1,1,5,5,5‐hexafluoro‐2,4‐pentanedionato) palladium(II) [Pd(hfac)2] was used to deposit high‐purity, polycrystalline palladium films under low‐pressure CVD conditions at high growth rates (1000–4000 Å/min) over a substrate temperature range of 80–200°C in the presence of H2. Mixing of the precursor and H2 streams near the substrate was required to avoid reactions of the precursor with H2 at locations other than the substrate surface. Auger electron spectroscopy (AES) showed that the films were impurity free when sufficient H2 was used. Resistivity values of 20 μΩcm were obtained at the higher deposition temperatures (∼200 °C) while high values of 50 μΩ cm were observed at the lower deposition temperatures (∼ 90 °C). The deposition rate was feed‐rate limited even at the lowest deposition temperatures and highest precursor delivery rates, suggesting that even higher deposition rates could be obtained with higher feed rates. A high precursor conversion of 50–60 % was observed. The high surface reaction probability of Pd(hfac)2 in the presence of H2 was reflected qualitatively by trench fill studies which showed a greater film thickness on the top of sub‐micrometer trenches than in the bottom.
Microwave Plasma CVD in the System Si‐C‐H‐Ar: Effect of Process Parameters
Authors: Scordo Stephane , Ducarroir Michel , Berjoan René , Jauberteau Jean Louis
Published: May 2005

Si‐C films were prepared on steel by the microwave (2.45 GHz) decomposition of tetramethylsilane (TMS) diluted in argon. The device used decouples the plasma power and the substrate temperature. The effects of various parameters (substrate position, temperature, gas flow rate, power, pressure) on composition and deposition rate were investigated. They are discussed in relation to electrostatic probe measurements. For all conditions, deposition rates are high (3–60 μm h−1). By using only TMS, the Si/C ratio in the films is restricted to values between 0.3 and 0.7. The variations in the process parameters do not induce significant changes in film compositions, however, they significantly change the deposition rates and the film hardness. In this field, the TMS dissociation process seems quite invariant with the conditions. With the introduction of SiH4 to the input gas phase (i.e., mixture SiH4 + TMS + Ar), silicon‐rich films were obtained. The composition range was extended to Si/C = 1.7 but the mechanical properties are strongly changed.
Recollections of CVD Conferences
Authors: Blocher John M.
Published: May 2005

The “father” of CVD, Dr. John Blocher, takes us on a nostalgic trip down memory lane with some personal recollections about the beginning of CVD and about the International CVD and EUROCVD conferences he has attended over the last 30 years. There are some delightful professional and social cameos, illustrating the scientific stimulation and sense of community the meetings have provided. The younger members of the international CVD community will indeed see that we have a substantial and rich heritage.
Quantum Modeling of the CVD of transition metal materials
Authors: Cundari Thomas R. , Sommerer Shaun O.
Published: May 2005

Quantum mechanical studies of the decomposition pathways of model OMCVD precursors are analyzed, in particular kinetic trends as a function of OMCVD precursors components‐metal (M), element (E), ancillary ligands (Ln), element substituents (Z), transfer group (At) and leaving group (X), 1. Based on geometric and energetic effects it is possible to further subdivide these components into three groups: active site (M, E), participants (At, X), and spectators (Ln, Z). Considerable progress has been made over the past several years, although many challenges remain in quantum modeling of transition metal materials and reactions pertinent to their CVD from volatile organometallics. Computational improvements in methods and technology are briefly discussed in relation to quantum modeling of OMCVD precursor structure and reactivity. Future directions are considered in which to more closely integrate the results of quantum modeling of OMCVD reactions with other aspects in this diverse research area.
Metal‐containing poly (p‐xylylene) films by CVD: Poly (p‐xylylene) with germanium crystals
Authors: Hopf Henning , Gerasimov Genrikh N. , Chavalun Sergei N. , Rozenberg Valerial I. , Popova Elena L. , Nikolaeva Elena V. , Grogoriev Evgenii I. , Zavjalov Sergei A. , Trakhtenberg Leonid I.
Published: May 2005

Metal‐containing polymer films are of interest for sensor, magnetic, nonlinear optical, and catalytic applications. This communication describes the preparation of poly(p‐xylylene) coatings incorporating Ge crystals from Ge‐containing paracyclophane monomer. Vapor pyrolysis of the monomer gives copolymer films with Ge fragments, which are thermally decomposed to Ge crystals. This leads to an increase in film conductivity and there is the potential for an application as a humidity sensor.
The Growth of Indium Selenide Thin Films from a Novel Asymmetric Dialkyldiselenocarbamate of Indium
Authors: O'Brien Paul , Otway David J. , Walsh John R.
Published: May 2005

Thin films of cubic In2Se3 have been grown by low‐pressure metal‐organic chemical vapor deposition (LP‐MOCVD) using the novel precursor In(Se2CNMe n‐hexyl)3. The precursor was prepared from carbon diselenide and a modified experimental procedure for the synthesis of CSe2 is described. Films were grown on glass and InP(111) between 450 and 500°C, and characterized by X‐ray diffraction and scanning electron microscopy.
Structural and Electrical Changes in Polycrystalline Silicon Thin Films That Are Heavily In Situ Boron‐Doped and Thermally Oxidized with Dry Oxygen
Authors: Boukezzata Messaoud , Birouk Boubekeur , Mansour Farida , Bielle‐Daspet Daniéle
Published: May 2005

In this paper, we investigate some particular aspects of changes in the thermal behavior polycrystalline silicon films deposited by low pressure CHEMICAL VAPOR DEPOSITION (LPCVD). The results will concern changes in both the structural and electrical properties of heavily (2 × 1020 cm−3) in situ boron‐doped thin films before and after thermal‐oxidation treatments. Secondary ion mass spectrometry (SIMS), transmission electron microscopy (TEM), and four‐point‐probe resistivity (FPPR) measurements were carried out on submicrometer layers (≈ 300 nm) deposited at two interesting temperatures Td = 520 °C and Td = 605 °C. The termal‐oxidation experiments are performed under dry O2 at three oxidation temperatures Tox = 840, 945, and 1050 °C for several durations. Remarkable changes in the behavior of doping profile, grain growth, and electrical conductivity were observed. While the kinetic‐oxidation analyses reveal the presence of a “differential oxidation rate (DOR)” between the two layers, recrystallization effects show a similar behavior, called “diferential growth mechanism (DGM)”, between the same layers. These observations seem to be characteristic of the in situ heavily boron‐doped films, consistent with results of a previous study.
The production of chimeric rats and their use in the analysis of the hooded pigmentation pattern
Authors: Yamamura Ken‐ichi , Markert Clement L.
Published: May 2005

New, improved media and procedures for making rat chimeric embryos and culturing them in vitro have been developed. We have produced 27 rat chimeras: 20 males and 7 females. This ratio of males to females is consistent with that seen in mouse chimeras, suggesting that rat sex chimeras develop as phenotypic males. By aggregating embryos containing appropriate genetic markers for pigment cell differentiation, it is possible to produce chimeras that elucidate the site of action of the hooded gene. The coat color patterns of black ↔ black hooded chimeras display a white belly spot. In black ↔ albino hooded chimeras, small patches of white hair appear on the head and a large white spot occurs on the belly. Black ↔ agouti hooded chimeras display both agouti and nonagouti pigmentation over the entire surface of the chimera. These animals are fully pigmented with no white spots. In black ↔ albino non‐hooded chimeras, rather small irregular patches of black and white hairs are distributed throughout the pelage. Histological examination of sections of hair follicles obtained from the white areas in the head of black ↔ albino hooded chimeras revealed amelanotic melanocytes. On the other hand, hair bulbs from the white belly spots do not contain any such melanocytes. Thus the white hairs of the head are due to the presence of albino melanocytes, but the white hairs of the belly are due to the total absence of melanocytes. All these observations are consistent with the conclusion that the hooded gene acts within melanoblasts, probably to retard their migration from the neural crest and/or to prevent their entrance into the hair follicles of the white areas of hooded rats.
Studies of fs(1)1621, a mutation producing ovarian tumors in Drosophila melanogaster
Authors: Gollin Susanne M. , King Robert C.
Published: May 2005

The ethyl methane sulfonate‐induced mutation, fs(1)1621, resides at 11.7 on the genetic map and within segment 4F1‐5A1 of the cytological map of the X chromosome. When homozygous, fs(1)1621 renders females semisterile but has no effect on their viability; nor does it affect the viability or fertility of hemizygous males. Heterozygous females are fertile and have cytologically normal ovaries. The ovaries of homozygous females first produce normal oocytes, which, if fertilized, can develop into adult males or females. After this period, ovarian chambers containing only pseudonurse cells are formed, and finally mutant germaria produce only tumors. These contain hundreds to thousands of cells that appear to be derived from germarial cystocytes, because they occasionally form clones of interconnected cells and also can differentiate into endopolyploid pseudonurse cells. Raising the temperature speeds the rate at which tumors form; lowering it increases the probability of pseudonurse cell differentiation. Df(1)C159 includes fs(1)1621. The pattern of ovarian chamber production is more temperature sensitive in hemizygous females than in homozygous ones. The morphology of hemizygous tumors and the number of dividing cells within them also differ from homozygotes. These observations support the hypothesis that fs(1)1621 is producing a product, that less is produced by one gene than by two, and that the product plays a role in the mitosis and cytokinesis of ovarian cystocytes.
Mating type differentiation in Tetrahymena thermophila: Strong influence of delayed refeeding of conjugating pairs
Authors: Orias Eduardo , Baum Mary P.
Published: May 2005

Mating type differentiation in Tetrahymena thermophila is known to regularly involve stable hereditary alterations at a single chromosomal locus in the somatic (macro)nucleus. This differentiation is directionally affected by the temperature at which new macronuclei develop after fertilization. We now report large and predictable effects of delayed refeeding of conjugating pairs upon mating type differentiation, particularly among mat‐2 homozygotes. The mating types whose frequency is affected the most are IV, VI, and VII, a set different from that most affected by temperature. We interpret our observations to reveal the existence of a second system which can participate in mating type differentiation, with different specificity from the system influenced by temperature under conditions of early refeeding of conjugating pairs. These observations enrich the phenomenology surrounding mating type differentiation in T thermophila and provide additional, easily controllable experimental conditions for the manipulation of mating type frequencies.
Age‐dependent behavior loss in adult Drosophila melanogaster
Authors: Leffelaar David , Grigliatti Thomas
Published: May 2005

The use of Drosophila as an organism in which to study aging has been limited by the fact that few biomarkers of aging exist in the adult. In this paper we examine behavior loss relative to longevity in wild‐type populations maintained at 22°C and 29°C to determine whether behavior loss—that is, loss of ability to perform certain innate behavioral responses within a defined test interval—can be used as biomarkers of aging. We find that under controlled conditions behavior loss can be used as a landmark of aging in populations maintained at either 22°C or 29°C. The ability to perform normal geotactic and phototactic responses is lost during the reproductive phase of the adult populations, whereas motor activity is not lost until well into the death phase. We feel that the use of behavior loss, together with other parameters of longevity in Drosophila, will allow comparisons to be made between different strains or between different environmental conditions to test their effect on aging. In the companion paper we demonstrate the use of behavior loss to identify a mutation which may accelerate the aging process.
Genetic control of cell interactions in chimeras
Authors: Markert Clement L.
Published: May 2005

The manufacture of mammalian chimeras by aggregating embryos of different genetic constitutions makes possible the study of the genetic control of cellular interactions during embryonic development. Several different chimeric combinations have been made to study the role of the sex‐reversed mutation in gonadogenesis and in gametogenesis. Sex reversed directs the gonad to become a testis and thus renders a SxrXX mouse sterile since gonocytes with two X chromosomes cannot complete gametogenesis in a testis. However, SxrXX gonocytes in the ovary of a female chimera become normal oocytes. The competitive interactions of genetically different melanoblasts in populating hair follicles and of primordial germ cells in populating the gonad have been revealed in chimeras. Chimeras have also been used to rescue inviable teraploid embryos and to permit teteraploid cells to display their differentiative capacities in normal tissue environments. We conclude that the genotype affects the capacity of cells to elaborate and to respond to inductive stimuli at each step in differentiation. The fine tuning of cellular interactions becomes apparent in chimeras made from embryos of different genotype.
Opportunities for natural selection on DNA and protein at the Adh locus in Drosophila melanogaster
Authors: Clarke Bryan , Whitehead Diane L.
Published: May 2005

A study was made of environmental and genetic factors affecting the quantity and disposition of the alcohol dehydrogenase (ADH) protein in Drosophila melanogaster. It was found that the amount of enzyme per fly is greatly influenced by the environmental conditions in which it develops. A critical factor is the concentration of yeast in the medium. A high concentration of yeast can double the quantity of ADH. The yeast appears to act through the provision of protein, and the protein to act through the provision of threonine, which is already known to induce ADH in fungi.

Various genetic factors affect the quantity of enzyme. Males have more ADH than females. Files homozygous for the Fast allele have more ADH than those homozygous for the slow allele, and the difference is greater in females than in males. One particular line (ve), homozygous for Slow, has approximately half the normal quantity of enzyme, and the quantity segregates with the electrophoretic allele. Lines differ in the relative amounts of ADH in the gut (including Malpighian tubules) and the fat body. In general it seems that slow lines have relatively more enzyme in the fat body. In a cross between ve and a line homozygous to Fast, the difference in tissue distribution segregated with the electrophoretic allele. It is argued, but not demonstrated, that the differences in quantity and tissue distribution are due to nucleotide substitutions in noncoding regions close to, or within, the structural gene.

It seems likely that the observed environmental and genetic differences in the quantity and disposition of ADH will influence the relative selective values of the electrophoretic genotypes.
Allelic isozyme variants in the mexican axolotl (Ambystoma mexicanum) as potential markers for developmental experiments
Authors: Cooper Gillian M. , Armstrong John B. , Gottlob‐McHugh Sylvia
Published: May 2005

Four isozyme systems were surveyed in our laboratory‐bred colony of axolotls (Ambystoma mexicanum) to determine whether there were elecrophoretic variants that could be used as markers in developmental experiments. For malate dehydrogenase (MDH), lactate dehydrogenase (LDH), and phosphoglucomutase (PGM), the best separations were obtained by isoelectric focussing on polyacrylamide slab gels, whereas for soluble esterases (Est), conventional polyacrylamide gel electrophoresis was used. The patterns for both MDH and LDH were consistent with two‐locus models, but no variation was obtained. The results for PGM support a single‐locus model with two alleles that are expressed codominantly in heterozygotes. There is also evidence for a third, null allele. The pgm gene maps approximately 24 map units from its centromere. The majority of the animals tested produced four esterase bands. We propose that each is controlled by a separate locus. One of the bands, Est‐3, is absent in some animals. The results of various crosses support the proposition that these animals are homozygous for a null allele. The est‐3 gene is distant from its centromere.
The role of cell death in the induction of pattern abnormalities in a cell‐lethal mutation of drosophila
Authors: Girton Jack R. , Kumor Anne L.
Published: May 2005

The effects of 48‐hr 29°C temperature treatments on the imaginal leg discs of Drosophila hemizygous for a temperature‐sensitive cell‐lethal mutation were examined to determine whether the induction of patches of cell death in the imaginal discs is a prerequisite for the induction of pattern triplications. In a statistical analysis, the frequency of induction of cell death was found to be highly correlated with the frequency of induction of triplications. In addition, individual discs in which cell death had been induced were cultured and found to triplicate at frequencies significantly greater than discs with no visible cell death, or unselected discs from the same larvae.
Stage specific embryonic defects following heat shock in Drosophila
Authors: Eberlein Susan
Published: May 2005

Heat shock of pre‐adult Drosophila disrupts development and causes phenotypic abnormalities. Type of abnormality depends on developmental stage at time of shock. Defects probably result from disruption of stage specific processes by the heat shock response (which includes reduction of normal mRNA and protein production). This study uses heat shock to study stage specific processes in early development. Short, intense shocks (2–3 min, 42–43°C) are administered to carefully staged embryos within the first 5 h of development. Stage specific defects occur following shock at syncitial blastoderm or later. Abnormal segmentation follows shock at syncitial or cellular blastoderm. Segmentation is also disrupted by shocks 1 h after the onset of gastrulation, but not by shocks at the onset of gastrulation. Segmentation defects include phenocopies of pair rule mutants, which lack parts of alternate segments. Defective shortening of the germ band is common following shock at the onset of gastrulation. Germ band shortening normally occurs several hours after the time of shock; thus heat shock specifically affects control of a later developmental process. Development does not simply cease at the time of the distrupted process; rather a specific step in the developmental sequence is omitted or altered. Stage specific defects do not occur following pre‐blastoderm shock. Pre‐blastoderm eggs have few or no normal processes controlled by transcription, and poor ability to induce the heat shock response. This suggests that stage specific defects require disruption of transcription controlled processes. Pre‐blastoderm eggs survive a 3‐min shock less well than older eggs. The ability of older eggs to induce the heat shock response probably enhances survival. The mutant hairy was also investigated. Extreme alleles show a striking pair rule phenotype, while a weak allele does not. Heat shock of animals heterozygous or homozygous for the weak allele at blastoderm specifically increases the frequency of the extreme hairy phenotype. Thus heat shock may disrupt the same developmental process as is altered by the mutation.
Differential expression of histone sequences in Drosophila following heat shock
Authors: Spadoro Joanne P. , Copertino Donald W. , Strausbaugh Linda D.
Published: May 2005

The expression of the sequences encoding the four nucleosomal histone proteins was examined following heat shock of a variety of Drosophila cells and was found to be highly differential. In Drosophila melanogaster KC‐O cells grown in suspension culture, there is a continuation of the synthesis of all four of the nucleosomal histone proteins following heat shock. Analysis of RNA from these cells confirms that histone messengers are transcribed and located on polysomes. This exact same pattern of histone protein synthesis occurs in KC‐O cells grown to low density on plates. In contrast, KC‐O cells grown to high density on plates exhibit a dramatic elevation of H2b protein synthesis relative to the synthesis of the other core histones. Organs from D melanogaster third instar larvae were examined to ascertain whether histone protein synthesis continues following heat shock in the organism. Different tissue types exhibited differential histone synthesis. Imaginal disks excised from heat‐shocked larvae continue to synthesize nucleosomal histones in a variable fashion. In contrast, neither fat bodies, brains, nor salivary glands continues to synthesize core histone proteins at a significant level. D hydei plated cell cultures and larval tissues fail to synthesize histones at any detectable level following a heat shock. Based on these observations, we propose that there is a differential synthesis of nucleosomal proteins in Drosophila that is highly dependent on the state of the cells prior to the heat shock.
Histochemical analysis of the ecdysterone‐regulated expression of the Drosophila genes P1 and LSP‐2
Authors: Paco‐Larson M. Luisa , Nakanishi Yoshinobu , Levine Michael , Garen Alan
Published: May 2005

3H‐labeled DNA probes for the ecdysterone‐inducible Drosophila genes P1 and LSP‐2 were hybridized in situ to RNA in sections of embryos and larvae. Intense hybridization was detected specifically in fat body cells of third‐instar larvae and not in other cells of third‐instar larvae nor in any cells at earlier stages. These results confirm the stringent tissue‐ and stage‐specificity of P1 and LSP‐2 expression. Hybridization of both probes occurred to virtually all the cells in the fat bodies, indicating that both genes are expressed in the same cells. Since P1 expression begins several hours later than LSP‐2 expression, and appears to be induced directly by ecdysterone, this finding implies that one or more of the fat body components mediating the response to ecdysterone is gene‐specific.
Ovarian teratocarcinomas in LT/Sv mice carrying t‐mutations
Authors: Artzt Karen , Calo Catherine , Pinheiro Elizabeth Neuner , Dimeo‐Talento Althea , Tyson Frederick L.
Published: May 2005

Ovarian teratomas that result from parthenogenetic activation of oocytes provide a double tool for developmental geneties. First, they provide a way of measuring recombination between a gene and its centromere. Second, in the absence of crossing over there is the potential of producing tumors that are homozygous for genes that would be lethal in the course of in utero embryonic development. We have applied both aspects to several t‐ haplotypes containing different early acting t‐lethal genes. In a study of 26 tumors, genotyped by Southern blot analysis of the major histocompatibility complex (MHC), we measured the distance between the centromere and the start of the t‐complex as 5.6 ± 2.3 cM. We found a marked deficiency of t‐homozygous genotypes among the tumors we studied, although T/T genotypes formed teratomas at levels comparable to controls. None of the lethal t‐haplotypes we studied permit homozygous embryos to develop to the primitive streak stage, while T/T embryos do develop essentially normally through that stage. Thus, although the total number of tumors observed from t‐bearing mice was small, the great difference in the incidence of t/t tumors versus the incidence of T/T tumors suggests strongly that the parthenogeretic embryos that convert to teratocarcinomas must first pass through some of the stages of normal early development, including the formation of three germ layers and the primitive streak.
Locus determining the human sperm‐specific lactate dehydrogenase, LDHC, is syntenic with LDHC
Authors: Edwards Yvonne H. , Povey Sue , Levan Kay M. , Driscoll Catherine E. , Millan Jose Luis , Goldberg Erwin
Published: May 2005

From the data presented in this report, the human LDHC gene locus is assigned to chromosome 11. Three genes determine lactate dehydrogenase (LDH) in man. LDHA and LDHB are expressed in most somatic tissues, while expression of LDHC is confined to the germinal epithelium of the testes. A human LDHC cDNA clone was used as a probe to analyze genomic DNA from rodent/human somatic cell hybrids. The pattern of bands with LDHC hybridization is easily distinguished from the pattern detected by LDHA hybridization, and the LDHC probe is specific for testis mRNA.

The structural gene LDHA has been previously assigned to human chromosome 11, while LDHB maps to chromosome 12. Studies of pigeon LDH have shown tight linkage between LDHB and LDHC leading to the expectation that these genes would be syntenic in man. However, the data presented in this paper show conclusively that LDHC is syntenic with LDHA on human chromosome 11.

The terminology for LDH genes LDHA, LDHB, and LDHC is equivalent to Ldhl, Ldh2, and Ldh3, respectively.
Comparative gene mapping: A valuable new tool for mammalian developmental studies
Authors: Womack James E.
Published: May 2005

Technological advances in the 1970s encouraged the mapping of homologous gene loci in different mammalian species, including mouse and man. One hundred eighty‐five homologous loci have now been mapped in these two species. Conservation of linkage is sufficient to identify substantial segments of the two genomes that have been left intact since their divergence from a common ancestor. The recognition of these conserved segments allows experimental manipulation of mouse chromosomes or chromosomal regions to produce models of human chromosomal anomalies of medical importance.

Comparative gene mapping has been extended beyond mouse and man and the genomes of some species, including domestic cattle, appear to be more highly conserved relative to humans than the mouse. Such species may be particularly useful in providing models of human chromosomal anomalies that cannot be duplicated in laboratory mice.
DNA methylation in plants
Authors: Hepburn Angus G. , Belanger Faith C. , Mattheis James R.
Published: May 2005

Higher plant DNA is extensively methylated, but the two methylated sequences (CpG and CpNpG) show different characteristics. Using sequence analysis techniques, we demonstrate that while CpG methylation follows the existing models for cytosine methylation in animals, CpNpG methylation does not. Although there is evidence to support the suggestion that the low CpG frequency has arisen from deaminational conversion of 5‐methylcytosine to thymidine, there appears to be no comparable conversion of 5‐methylcytosine in the CpNpG configuration. It therefore appears that between the evolution of CpG and CpNpG cytosine methylation systems, a mechanism evolved for the correction of C→T conversion, probably using the methylated strand to direct the repair in the correct direction.
G‐proteins in the signal‐transduction pathways of Dictyostelium discoideum
Authors: Ewa Snaar‐Jagalska B. , Kesbeke Fanja , Van Haastert Peter J. M.
Published: May 2005

The functional interaction of surface cAMP receptors with effector enzymes via G‐proteins was investigated in Dictyostelium discoideum. Several experimental conditions were used to investigate signal transduction, such as reduced temperatures, use of down‐regulated cells and of mutants. The results are presented as a model describing the complex interaction between multiple forms of the surface cAMP receptor and different G‐proteins that are responsible for the generation of the second messengers, cAMP, cGMP, InsP3 and Ca2+.
Glycogen phosphorylase in Dictyostelium discoideum: Demonstration of two developmentally regulated forms, purification to homogeneity, immunochemical analysis, cAMP induction, in vitro translation, and molecular cloning
Authors: Rutherford C. L. , Naranan V. , Brickey D. A. , Sucic J. F. , Rogers P. V. , Selmin O.
Published: May 2005

A key step in the cellular differentiation of Dictyostelium is the degradation of glycogen to provide the precursors for synthesis of the structural end products of development. We have found that the enzyme that initiates this degradative pathway, glycogen phosphorylase (1,4‐α‐D‐glucan:orthophosphate α‐glucosyltransferase; EC 2.4.1.1), is developmentally regulated and exists as two forms. During the time course of development, a previously undescribed activity, the “b” form, decreases, while that of the “a” form increases. The “b” form is inactive unless 5′AMP is included in the reaction mixture. The two forms differ in their elution from DE52 cellulose, affinity constants, thermal stability, affinity for 5′AMP Sepharose, subunit molecular weight, and peptide maps. In crude extracts, anti‐a antiserum stains a 104‐kD protein that is associated with phosphorylase “a” activity and appears late in development, while anti‐b antiserum stains a 92‐kD protein that is associated with phosphorylase “b” activity and is present throughout development. We have also demonstrated in vitro phosphorylation of the “b” form by an endogenous protein kinase and a corresponding loss of 5′AMP dependence. If intact cells were exposed to exogenous cAMP, “b” activity decreased and was replaced by “a” activity, as well as the 104‐kD protein band on SDS‐PAGE. In order to determine if the two forms of the enzyme are different gene products, we screened lambda gt11 expression libraries with antibodies against the purified “a” and “b” forms. Three clones were found to be overlapping by Southern analysis. A yeast glycogen phosphorylase cDNA clone (gpy) and a human muscle glycogen phosphorylase clone (HM‐11) cross‐hybridized with the Dictyostelium inserts, and gpy shared a few common restriction fragments with the Dictyostelium clones on genomic blots. Northern analysis of Dictyostelium total RNA showed that the Dictyostelium inserts and gpy recognize an mRNA of 3.2 kb, while on poly A‐enriched RNA, the yeast clone detects preferentially a 3.6‐kb message.
Stalk cell formation in monolayers of Dictyostelium discoideum V12‐M2
Authors: Sobolewski Andre , Kwong Linda , Weeks Gerald
Published: May 2005

Stalk cell formation in low‐cell‐density monolayers of Dictyostelium discoideum, strain V12‐M2, occurs following the sequential addition of cyclic AMP and the differentiation‐inducing factor (DIF). Both cyclic AMP and DIF are essential for the appearance of the prestalk‐specific isozyme alkaline phosphatase‐II, which suggests that both factors are necessary for prestalk cell formation. The available evidence suggests that the cyclic AMP requirement for stalk cell formation is mediated through the cell surface cyclic AMP receptor. However, stalk cell formation is inhibited by caffeine and this inhibition is reversed by the cell‐permeable analogue 8‐Br‐cyclic AMP, which suggests in addition a possible involvement for elevated intracellular cyclic AMP concentrations in stalk cell formation.

During in vivo development ceils first become independent of cyclic AMP at the tipped aggregate stage, but the acquisition of cyclic AMP independence is advanced by several hours when cells are incubated in the presence of cyclic AMP for 2 hours. Cells do not become independent of DIF until the culmination stage of development, which suggests the possibility that DIF is required for the conversion of prestalk cells to stalk cells.

There is an absolute requirement for DIF for stalk cell formation in low‐density monolayers of prestalk cells but only part of population exhibits a requirement for cyclic AMP, which suggests that the prestalk cell population consists of two distinct cell types. Stalk cell formation from prespore cells is totally dependent on both cyclic AMP and DIF.

When isolated prestalk and prespore cells are plated in high‐density monolayers, the former cells accumulate more DIF. which suggests the possibility that DIF is preferentially synthesized by prestalk cells.
A comparison of high frequency switching in the yeast Candida albicans and the slime mold Dictyostelium discoideum
Authors: Soll David R. , Kraft Bernard
Published: May 2005

Recently, high frequency switching systems have been identified in the infectious yeast Candida albicans and the cellular slime mold Dictyostelium discoideum. In C. albicans, cells can switch at spontaneous frequencies as high as 10−2 between seven general colony morphologies in the case of strain 3153A or between two major phenotypes in the white‐opaque transition in strain WO‐1. In the latter system, dramatic changes occur in cellular phenotype as well. In D. discoideum, cells can switch at spontaneous frequencies of roughly 10−2 between a number of colony phenotypes which include alterations in developmental timing, blocks at particular morphogenetic stages, morphological aberrations, and aggregation‐minus. In the C. albicans and D. discoideum switching systems, the following characteristics are shared: (l) a limited number of switch phenotypes; (2) heritability; (3) high frequency reversibility; (4) low and high frequency modes of switching; and (5) ultraviolet (UV) stimulation of switching of cells in a low frequency mode of switching.