bluuebunny/crossref_metadata_2025_split huggingface dataset:
Factors accounting for the ability of children with SLI to learn agreement morphemes in intervention
Authors: PAWŁOWSKA MONIKA , LEONARD LAURENCE B. , CAMARATA STEPHEN M. , BROWN BARBARA , CAMARATA MARY N. 
Published: January 2008

ABSTRACTThe aim of this study was to uncover factors accounting for the ability of children with specific language impairment (SLI) to learn agreement morphemes in intervention. Twenty-five children with SLI who participated in a six-month intervention program focused on teaching third person singular -s or auxiliary is/are/was showed a wide range of use of the target morpheme after intervention. Regression analyses showed that age and two factors expected to be related to agreement – the use of noun plural -s and subject/verb constructions prior to intervention – significantly predicted progress in the acquisition of agreement morphemes. In contrast, the pretreatment use of morphemes hypothesized to be unrelated to agreement was not a significant predictor of progress. The results indicate that the ability of children with SLI to learn agreement morphemes relies on their prior ability to use noun plural and subject/verb constructions.
The influence of discourse context on children's provision of auxiliary BE
Authors: THEAKSTON ANNA L. , LIEVEN ELENA V. M. 
Published: January 2008

ABSTRACTChildren pass through a stage in development when they produce utterances that contain auxiliary BE (he's playing) and utterances where auxiliary BE is omitted (he playing). One explanation that has been put forward to explain this phenomenon is the presence of questions in the input that model S-V word order (Theakston, Lieven & Tomasello, 2003). The current paper reports two studies that investigate the role of the input in children's use and non-use of auxiliary BE in declaratives. In Study 1, 96 children aged from 2 ; 5 to 2 ; 10 were exposed to known and novel verbs modelled in questions only or declaratives only. In Study 2, naturalistic data from a dense database from a single child between the ages of 2 ; 8 to 3 ; 2 were examined to investigate the influence of (1) declaratives and questions in the input in prior discourse, and (2) the child's immediately previous use of declaratives where auxiliary BE was produced or omitted, on his subsequent use or non-use of auxiliary BE. The results show that in both the experimental and naturalistic contexts, the presence of questions in the input resulted in lower levels of auxiliary provision in the children's speech than in utterances following declaratives in the input. In addition, the children's prior use or non-use of auxiliary BE influenced subsequent use. The findings are discussed in the context of usage-based theories of language acquisition and the role of the language children hear in their developing linguistic representations.
Perseverant responding in children's picture naming*
Authors: BOOTH JOSEPHINE , VITKOVITCH MELANIE 
Published: January 2008

ABSTRACTTwo groups of children were given pictures of animals to name as quickly as they could. The groups comprised 40 nursery aged children (mean age 3 ; 11) and 40 Year 2 children (mean age 6 ; 9) attending primary school in London. The 30 animals were presented one by one, on cards, and any errors made by the children were noted. Consistent with a similar object naming study with adults (Vitkovitch, Kirby & Tyrrell, 1996) and a study with children (Gershkoff-Stowe, 2002), picture naming errors referred to earlier named objects. However, while adults showed below-chance interference from objects that had only just been named (Lag 1), children were most susceptible to interference from very recently named objects (see also Gershkoff-Stowe, 2002). Furthermore, the proportion of younger children making Lag 1 errors was higher than the proportion of older children making Lag 1 errors. The results are discussed in relation to the activation levels of lexical representations.
Child-directed speech: relation to socioeconomic status, knowledge of child development and child vocabulary skill
Authors: ROWE MEREDITH L. 
Published: January 2008

ABSTRACTThis study sought to determine why American parents from different socioeconomic backgrounds communicate in different ways with their children. Forty-seven parent–child dyads were videotaped engaging in naturalistic interactions in the home for ninety minutes at child age 2 ; 6. Transcripts of these interactions provided measures of child-directed speech. Children's vocabulary comprehension skills were measured using the Peabody Picture Vocabulary Test at 2 ; 6 and one year later at 3 ; 6. Results indicate that: (1) child-directed speech with toddlers aged 2 ; 6 predicts child vocabulary skill one year later, controlling for earlier toddler vocabulary skill; (2) child-directed speech relates to socioeconomic status as measured by income and education; and (3) the relation between socioeconomic status and child-directed speech is mediated by parental knowledge of child development. Potential mechanisms through which parental knowledge influences communicative behavior are discussed.
THE IONIZATION OF ORGANIC MOLECULAR CRYSTALS BY NEAR U.V. LIGHT*
Authors: Kearns David R. 
Published: January 2008

Summary The niechanisms by which near u.v. light cause internal ionization in organic molecular crystals are examined theoretically for the anthracene crystal. Theoretical predictions of the quantum yield for photoionization by the various mechanisms are presented and compared with values recently obtained from studies of photoconduction in anthracene. From this comparison we conclude that:(i) Good agreement between calculated and observed quantum yields suggests that the method used for the calculations is essentially valid.(ii) Provided the energy requirements can be met, quantum yields for photoionization may approach unity.(iii) The lifetimes of excited singlet and triplet states and the rate of intersystem crossing materially influence the quantum yields for photoionization.(iv) An aggregated, but not necessarily ordered, molecular system should be capable of exhibiting quantum yields for photoionization which are as large as those which can be obtained with single crystals. The possible relevance of these results for biological systems is discussed briefly.
ORGANIC PHOTOCHEMISTRY OF NUCLEIC ACIDS*
Authors: Wacker A. , Dellweg H. , Träger L. , Kornhauser A. , Lodemann E. , Türck G. , Selzer R. , Chandra P. , Ishimoto M. 
Published: January 2008

Summary Starting with the isolation of thymine dimer derived from DNA of u.v.‐irradiated bacteria, a systematic investigation was begun from which it was concluded that the basis for the action of u.v.‐light is a photochemical dimerization. Depending on the dose of u.v.‐light and the conditions for hydrolysis of DNA and isolation procedures, other photoproducts of thymine were isolated. Experimental data for the conversion of cytosine to uracil are presented. By use of monochromatic u.v.‐light we could demonstrate that only intrastrand dimerization occurs. The radiation chemical behavior of uracil and cytosine was investigated with tritium labeled compounds.The mechanism for the various kinds of sensitization with 5‐halogen‐uracils, with dyes (thiopyronin, methylene blue, and pyronin) with carcinogenic hydrocarbons and with furocoumarins, which parallels partly the photochemical degradation of guanine is discussed.U.V.‐inactivated bacteria and polyuridylic acid are reactivated better by irradiation with visible light when hydrogen peroxide or uranyl acetate are present. The mechanism of this reaction is discussed.The absence of the α, β‐unsaturated double bond could be expected to protect the thymine molecule from dimerization; after incorporation of azathymine into the DNA, bacteria do indeed exhibit u.v.‐resistance. Moreover, after treatment of bacteria with hydrogen peroxide and visible light, by which the 5,6 double bond in the thymine and cytosine molecules is also attacked, bacteria become u.v.‐resistant.The specific alteration of uracil and cytosine by u.v.‐irradiation and of guanine through photodynamic action can be used as a simple method for sequence analysis of protein codons. It is also of use in determining the interaction between messenger‐RNA, transfer‐RNA and ribosomes during protein synthesis.
A METHOD OF ASSAYING IN VIVO THE SURVIVAL OF ULTRA VIOLET‐IRRADIATED TUMOUR CELLS
Authors: Stevens G. H. , Roe E. M. F. 
Published: January 2008

Abstract— The growth of ultraviolet‐irradiated ascites tumour cells in adult animals which have received a total‐body dose of x‐radiation appears to be a suitable method to obtain data on the survival of the treated tumour cells, if the dose of total‐body radiation and its time before tumour cell inoculation are chosen correctly.In assessing tumour cell survival, the analysis of the time of appearance of the resulting solid tumours, using the linear relationship between the reciprocal of this time and the logarithm of the number of cells injected is preferred to probit or to Reed‐Muench analysis of the number of tumour‐takes. The 1/T method of analysis yields more precise estimates of the survival ratios and greater economy in the use of host animals without a disproportionate increase in the labour involved in obtaining the data.An application of this method to the determination of survival‐ratios of u.v.‐irradiated Landschütz ascites tumour cells is described.
THE EFFECTS OF ULTRAVIOLET AND VISIBLE RADIATION ON MOUSE ASCITES TUMOUR CELLS
Authors: Roe E. M. F. , Stevens G. H. 
Published: January 2008

Abstract— Effects of ultraviolet and visible radiation on the viability of Landschutz ascites tumour cells have been tested by growing control and treated tumour samples in adult mice. The tumour cells were irradiated as a dilute suspension in isotonic buffered salt solution, and were equilibrated at 0°C with oxygen or with nitrogen before irradiation.Tumour cell proliferation was measured by a variety of techniques. The preferred assay‐method was the growth of solid tumours in the axillae and groins of mice after sub‐cutaneous inoculation of varying dilutions of treated or control ascites tumour cells. The immune response of the mice to the injected cells was reduced by whole body irradiation with a 300r dose of x‐rays two days before inoculation. Results were calculated from parallel line assays using the reciprocal of the delay in appearance of the solid tumours up to 30 days post‐innoculation. This reciprocal (1/T) was linearly related to the logarithm of the number of cells inoculated.Photoreactivation has been demonstrated for this system, in which both U.V. and visible radiations were absorbed by the same cells. Light delivered alone in oxygen or in nitrogen was without effect on cell‐viability, but it increased cell‐survival after u.v.‐irradiation in nitrogen and decreased survival after u.v.‐irradiation in oxygen. Ultraviolet radiation alone was not significantly more lethal in oxygen than in nitrogen. A further observation in this work was an interaction between irradiated and control tumour cells injected into the same animal.It is suggested that the radiation used may affect the antigenic character of the tumour cells as well as their reproductive capadity.
A STUDY OF CHLOROPHYLL FLUORESCENCE IN VIVO BY A FLOW METHOD
Authors: Lavorel Jean 
Published: January 2008

Abstract— A flow method has been devised for the study of fluorescence transients during the induction period of photosynthetic systems. The principle of transformation of time‐transients into space‐transients is quantitatively worked out and the characteristics and mode of operation of the apparatus is described and illustrated with experimental results.With this method spectroscopic and kinetic investigation of in vivo chlorophyll fluorescence have been undertaken. The fluorescence emission can be split into two componmts—a variable part and a constant part—with different spectral distributions. The excitation spectrum of the light induced fluorescence changes shows that the variable part is sensitized by system 11, whereas the constant part mainly sensitized by system II has a small component originating from system I. The light‐induced fluorescence change decays in darkness with half‐time of about 10‐2s; this decay is highly sensitive to the action of inhibitors of oxygen evolution.The flow method can be extended to measurements of oxygen, luminescence, absorption differences. It permits using high‐intensity analytic beams with no actinic action; it is well suited for the integration of low level signals.
ON PHYTOCHROME AND CYTOCHROMES IN PHOTOPERIODIC PHENOMENA: A BIOCHEMICAL APPROACH
Authors: Greef J. A. De 
Published: January 2008

Réumé— Pour les plantes vertes nous présentons une hypothèse alternative en ce qui concerne l'action de rayons de longueur d'onde donnée sur la morphogénèse. Sur la base de données analytiques le chloroplaste peut être considéré comme similaire à la mitochondrie, avec la réserve importante que des composés photoactifs participent aux oxydations chimiques terminales dans le chloroplaste. Dans les plantes vertes deux cytochromes sont connus: un du type c, le cytochrome f, et un autre de type b6 le cytochrome b6. On a proposé que le cytochrome b6 est réduit et que l'eau est oxydée simultanément. L'électron libéré est transféré sur le cytochrome f qui, ensuite, est oxydé tandis que le NADP est réduit. De plus, la lumière rouge foncé paraît convertir le cytochrome b6 dans la forme oxydée. Celle‐ci peut passer à nouveau dans la forme reduite après élairement sous rayons de longueur d'onde plus courte. Le cytochrome b6 pourrait donc occuper une position de commutateur entre les systèmes oxydés et réduits dans la cellule. Déterminant pour la position de ce commutateur sont d'une part la longueur d'onde de la lumière et d'autre part la cwantité totale d'énérgie.Le fait aue le cvtochrome b6 est maintenu uar la lumière rouge‐foncé dans la forme oxvdée. empêherait la réduction de NADP. Ainsi ia voie métaboliGe normale serait modifiée ce qui trouverait son expression dans un changement de l'aspect morphologique de la plante.L'analogie est très remarquable entre le spectre d'action de la forme oxydée du cytochrome b6 et celui de la forme P660 du phytochrome qui se forme également suite à un éclairement rouge‐foncé et qui est considerée comme physiologiquement inactive. Plusiers données expérimentales soutiennent ce point de vue.
SOME QUALITATIVE DIFFERENCES BETWEEN GROUND AND EXCITED STATES
Authors: MALRIEU J. P. 
Published: January 2008

Abstract— Electronic excitation is deiocalized, particularly in conjugated systems: the language of molecular orbitals (MO), already very useful for ground‐state properties, is absolutely necessary to explain excited‐state properties. But the theoretical representation of excited states has special difficulties. Approximations used to represent excited states are: (1) Single determinant wave‐functions, built with the ground‐state MO (Hückel or SCF) or with special MO (restricted or unrestricted Hartree–Fock). (2) A configuration interaction: studied by perturbation development. (3) The excitonic treatment, i.e. interaction of localized excitations. The theory is applied to saturated molecules.The stable geometry of the excited state is different from that of the ground state and plays a role in many physical observables (dipole moment, vibrational structure of the band, lifetime) and in chemical processes.RESUMENLa excitación electrónica está deslocalizada particularmente en sistemas conjugados. El lenguaje de los orbitales moleculares (MO) que ha sido muy util para aclarar las propiedades del estado fundamental es absolumente necesario para explicar las propiedades del estado excitado. Pero la representación teórica de los estados excitados presenta algunas dificultades. Las aproximaciones usadas para representar los estados excitados son: (1) funciones de onda con un solo determinante construidas con el orbital molecular del estado fundamental (Hückel o SCF) o con el orbital molecular particular (restringido o no restringido Hartree‐Fock), (2) una configuration de la interacción estudiada por métodos de perturbación, (3) el tratami‐miento “excitonic”, es decir interaction de las excitaciones localizadas. La teoría se aplica a moleculas saturadas. La geometría estable del estado excitado es diferente a la del estado fundamental y tiene un rol importante en muchas de las propiedades fisicas observables, (momento dipolar, estructura vibrational y vida media) y en los procesos quimicos.
LUMINESCENCE SPECTRA OF TRANSITION METAL COMPLEXES*
Authors: ZULOAGA F. , KASHA M. 
Published: January 2008

Abstract— A systematic quantum mechanical and spectroscopic study has been made for transition metal ions containing d6 atomic configurations. Ligand field parameters and spectral data are summarized. For suitable chelates of Co(III), Rh(III), Ir(III), and Pt(IV), the lowest transition is characterized as being of d–d characteristics, with weak and broad structureless bands. For suitable chelates of Ru(II) and Os(II), the lowest transition is characterized as being of d–aπ characteristics (involving an antibonding orbital of π‐origin in the ligand), with strong bands showing pure ligand vibrational structure. The competitive nature of d–d vs. d–aπ transitions is interpreted for pyridyl chelate of Ir(III) showing d–d lowest transitions and an o‐phenanthroline chelate of Ir(III) reported in the literature as showing d‐aπ transitions. A general quantum‐theoretical rule for chelates of transition metal ions is given, and the application of the results to photochemistry and radiation chemistry is indicated.RESUMENSe ha efectuado un estudio mecánico cuántico y espectroscópico para la transición de iones metálicos que contienen una configuración atómica d6. Para quelatos apropiados de Co(III). Rh(III), Ir(III) y Pt(IV) la transición más baja está representada como una caracteróstica d–d con bandas débiles y poco estructuradas. Para quelatos apropiados de Ru(III) y Os(II) la transición mas baja está representada como una característica d–aπ (involucrando un orbital de antiunión de origen π en el ligante). con bandas fuertes mostrando la estructura vibracional del ligante. La naturaleza competitiva de las transiciones d–d vs. d–dπ es interpretada para quelatos de piridilo de Ir(III) mostrando la más baja transición d–d, y para un quelato de o‐fenentrolina de Ir(III) que tiene transiciones d–aπ segun ha sido comunicado en la literatura. Se da una regla general teorético—cuántica para quelatos de transición de iones metálicos, y se indica la aplicación de los resultados afotoquímica y radiación química.
HEAVY ATOM PERTURBATION IN MOLECULES RELATED TO THYROXINE
Authors: CILENTO G. , SANIOTO D. L. , ZINNER K. , BERENHOLC M. 
Published: January 2008

ResumenEn conección con la perturbación producida en las hormonas tiroideas y moléculas asociadas, por el átomo pesado iodo; se ha investigado el espectro de absorción singulete‐triplete de la p—benzoquinona (max = 539 nm) cuando se la sustituye en la posicién 2–6 con el dihalógeno. En oposición a los resultados reportados por Kuboyama, no se observaun cambio en la intensidad cuando se sustituyen dos átomos de cloro. La ausencia de acomplamiento spin‐órbita se ve confirmada por la peque&#x006e;̂a intensificación de la absorción cuando los átomos sustituidos son bromo o iodo, y probablemente está conectada con el caracter n→π* de la transición. Algo sorpresivamente. la sustitución de dos átomos de iodo produce un marcado efecto batocromico cerca de donde esta localizada la transición singulete‐ triplete, aproximadamente encima de los 600 nm.
PHOTOCHEMISTRY OF POLYNUCLEOTIDES: A SUMMARY OF TEMPERATURE EFFECTS*
Authors: RAHN R. O. , HOSSZU J. L. 
Published: January 2008

Abstract— The photochemistry of polynucleotides is strongly dependent upon the temperature at which the irradiation is done. At 77°K only a limited number of pyrimidines undergo dimerization. Hydration and interstrand cross‐linking is completely prevented at this temperature. Irradiation at low temperatures leads to the formación in DNA of the spore‐type photoproduct. At elevated temperatures destacking of the bases, which occurs upon melting, leads to lower dimer yields. Variation of the irradiation temperature has proven to be of great value in determining the biological effectiveness of photoproducts that differ in their temperature dependence.RESUMENLa fotoquímica de los polinucleótidos observa una marcada dependencia con la temperatura a la que se efectua la radiación. A 77°K solo un numero limitado de pirimidinas sufre dimerización. La hidratación se puede prevenir completamente a esta temperatura. Bajas temperaturas conducen a la formación de un foto‐producto similar al de las esporas, fenómeno que no ocurre a 298°K. A elevadas temperaturas por encima del punto de fusión, se obtienen rendimientos bajos en dímeros. La variación de la temperatura de irradiación se ha probado que es de gran valor en la determinación de la efectividad biológica de los fotoproductos que difieren en su dependencia con la temperatura.
RADIOLYSIS OF PEPTIDES AND PROTEINS
Authors: WHEELER OWEN H. 
Published: January 2008

Abstract— A considerable amount of research has been published on the effect of ionizing radiation on amino acids. In aqueous solution the products are formed from an intermediate radical resulting from the abstraction of a hydrogen atom from the α‐carbon atom. Aromatic amino acids are predominately hydroxylated in the ring, phenylalanine forming tyrosine and tyrosine affording dihydroxylphenylalanine. The data on proteins are largely concerned with denaturation and the effect of radiation protecting compounds. The few studies on peptides have indicated that the mechanism of their radiolysis is similar to that of amino acids. Recent work indicates that the nature of the amino acid affects the resistance of the peptide linkage. Aromatic rings are also hydroxylated in preference to attack on the peptide group. The products were identified and analyzed using carbon‐14‐labeled peptides. The radiation protection effects of a series of organic compounds have been determined by competition for hydroxyl radicals with the labeled peptide. Comparison is made between the radiolysis and photolysis of peptides.RESUMENUna considerable cantidad de datos ha sido publicados sobre el efecto de radiación ionizante en amino‐ácidos. En solución acuosa los productos se forman a partir de un radical intermedio que resulta de la pérdida de un hidrógeno unido al carbono α. Los aminoácidos aromáticos sufren procesos de hidroxilación en el anillo, la fenilalanina formando tirosina y la tirosina formando dihidroxifenilalanina. Los datos sobre proteinas se refieren principalmente a la desnaturalización y al efecto de compuestos que protegen de la radiación. Algunos estudios en péptidos indican que el mecanismo de radiolisis es similar al de los amino‐ácidos. Trabajos recientes indican que la estabilidad de la unión peptidica depende de la naturaleza del aminoácido. Los anillos aromáticos son hidroxilados para luego ser atacada la unión peptídica. Los productos fueron analizados usando péptidos marcados con carbono‐14. Los efectos de protección a la radiación de una serie de compuestos orgánicos nan sido determinados por competencia con radicales OH· usando peptidos marcados. Se efectuan comparaciones entre la radiólisis y lafotólisis de péptidos.