bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Study of the Magnetic Structure of LaMn2O5 from Neutron Powder Diffraction Data
Authors: Muñoz Angel , Alonso Jose A. , Casais María T. , Martínez‐Lope María J. , Martínez Jose L. , Fernández‐Díaz María T. 
Published: February 2005

AbstractPolycrystalline LaMn2O5 has been studied by neutron powder diffraction in conjunction with magnetization data. The crystal structure of this oxide contains infinite chains of edge‐sharing Mn4+O6 octahedra, interconnected by Mn3+O5 pyramids and LaO8 units. Susceptibility measurements show that LaMn2O5 presents an antiferromagnetic order below a TN value of about 31 K. Neutron diffraction experiments confirm the long‐range ordering below this temperature in a magnetic structure characterized by the propagation vector k = (0,0,1/2). The magnetic arrangement is defined by the basis vectors (Gx,Ay,0) and (0,0,C′z) for the Mn4+ and Mn3+ ions, respectively. At 3.5 K, the magnetic moments are 2.59(4) and 1.61(7) μB for the Mn3+ (4h site) and Mn4+ ions (4f site), respectively. Superexchange interactions between the Mn4+ ions through Mn4+–O–Mn4+ paths are considered in order to explain the commensurate character of the magnetic structure in comparison with the incommensurate structures observed for most of the RMn2O5 (R = rare earth metal) compounds. A spin‐glass‐type behaviour, which probably involves the short‐range order in the Mn3+ sublattice, is observed above TN. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)
New Complexes of Divalent Thulium with Substituted Phospholyl and Cyclopentadienyl Ligands
Authors: Nief François , de Borms Brice Tayart , Ricard Louis , Carmichael Duncan 
Published: February 2005

AbstractIn order to try to stabilise the TmII ion with phospholyl ligands lacking methyl groups at the 3 and 4 positions, the following ligand precursors were prepared: sodium 2,5‐di‐tert‐butylphospholyl [Na(Htp)] (3) and sodium 2,5‐bis(trimethylsilyl)phospholyl [Na(Hsp)] (8). Because of its similar steric bulk, we also decided to use sodium di‐tert‐butylcyclopentadienyl [NaCptt] (9) as a ligand precursor. Compound 3 was obtained by sodium cleavage of the P–P bond of 2,5,2′,5′‐tetra‐tert‐butyl‐1,1′‐diphosphole (2). Halogen‐lithium exchange in 1,4‐diiodo‐1,4‐bis(trimethylsilyl)buta‐1,3‐diene (4) followed by reaction with PhPCl2 afforded 1‐phenyl‐2,5‐bis(trimethylsilyl)phosphole (5). Treatment of 5 with lithium metal followed by oxidative treatment with iodine gave 2,5,2′,5′‐tetrakis(trimethylsilyl)‐1,1′‐diphosphole (7) which could be transformed into 8 by treatment with sodium. Treatment of 3, 8 and 9 with [TmI2(THF)3] in diethylether yielded three new organothulium(II) complexes [Tm(Htp)2(THF)] (10), [Tm(Hsp)2(THF)] (11) and [Tm(Cptt)2(THF)] (12), respectively, which could be isolated pure as crystalline solids in low to moderate yields. Complexes 10, 11 and 12 were studied by X‐ray crystallography and their structures compared with those of two previously described complexes, [Tm(Cp′′)2(THF)] 1 [Cp = 1,3‐bis(trimethylsilyl)cyclopentadienyl] and [Tm(Dtp)2(THF)] (13) (Dtp = 3,4‐dimethyl‐2,5‐di‐tert‐butylphospholyl). Although the phospholyl ligands may be slightly more bulky than their cyclopentadienyl counterparts, the structures of 1, 10, 11 and 12 are remarkably similar and are substantially different from that of the more bulky 13. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)
Posterior evaluation of odour intensity in gas chromatography–olfactometry: comparison of methods for calculation of panel intensity and their consequences
Authors: Pet'ka Ján , Ferreira Vicente , Cacho Juan 
Published: February 2005

AbstractFour methods of panel intensity calculation were compared for 13 compounds, studied on five concentration levels using gas chromatography–olfactometry. All the methods produced sigmoidal dose–response functions or fractions of sigmoid, when the missing observations were replaced with zero. In contrast, panel intensities calculated only from the reported percepts provided predominantly linear plots. The linearity of such calibration curves can be additionally improved, either by employing a panel of similar dynamic range or by replacing missing observations with predicted (censored) values. Strong scale differences were observed. The panel intensity of methyl benzoate changed rapidly over a very small range of concentrations. Conversely, a very small change of panel intensity was observed for sotolon in a concentration range of three orders of magnitude. Such differences relate closely to the Stevens' slope, in the form of exponential growth function. A systematic decrease of panel intensity was observed for some volatiles at the highest concentration levels. Some of these observations could be explained with the help of current neurobiological knowledge. Copyright © 2005 John Wiley & Sons, Ltd.
Mass law effects of adenosine triphosphate on Na, K, Mg and Ca binding by rat liver microsomes
Authors: Sanui Hisashi , Pace Nello 
Published: February 2005

AbstractThe effect of ATP on the binding of Na, K, Mg and Ca ions by rat liver microsomes was investigated. Addition of increasing amounts of ATP to a suspension of microsomes in an ionic medium containing these cations caused a marked decrease in divalent cation binding and a concomitant increase in monovalent cation binding by the microsomes. The strong nonbiological complexing agent EDTA produced qualitatively similar but quantitatively greater changes in binding. Although ATP‐dependent binding of monovalent cations has been interpreted by other investigators in terms of an ATPase system and the formation of a hypothetical monovalent cation binding intermediate, the present data demonstrate that the role of ATP may also be reasonably explained in terms of mass law interactions of the various known solute species and fixed membrane binding sites involved.
A study of the crustacean axon repetitive response: II. The effect of cations, sodium, calcium (magnesium), potassium and hydrogen (pH) in the external medium
Authors: Wright Ernest B. , Tomita Tadao 
Published: February 2005

AbstractThe effects of sodium, calcium, potassium (magnesium), potassium, and hydrogen (pH) ion concentration in the external medium on the repetitive response and the transmembrane electrical parameters of the crustacean axon have been investigated. (1) The action potential is reduced with decrease in sodium ion concentration, the relationship is linear if the spike voltage is plotted against the log (Na0). The action potential amplitude does not increase significantly, above 135 mv, attained at Na0 = 452 mM, if Na0 is increased. (2) The repetitive response and oscillatory activity in general disappears as the sodium concentration is reduced to less than 150 mM. (3) The critical firing level increases with decrease in sodium, the relationship linear with respect to log (Nao). (4) The positive after potential amplitude is not affected by the sodium concentration. (5) The membrane resistance is not affected by sodium concentration. (6) Calcium lack results in decreased critical firing level and spontaneous firing, followed by a total and irreversible loss of excitability. The membrane resistance is markedly decreased. Polarizing current, if applied early after the onset of the calcium lack effect, may restore, at least partially, the excitability phenomenon. (7) Calcium excess increases membrane resistance, depresses excitability. Calcium concentration of 150 mM abolishes the repetitive response. (8) There is a 3.3+: 1 ratio Na:Ca for threshold level of repetitive response. Lower ratio figures, by reducing Na or increasing Ca or both, eliminates repetition. Increasing the ratio figure by increasing sodium or decreasing calcium or both augments oscillatory activity. This ratio is constant between the limits 400 mM Na:125, Ca to 90 mM Na:25 mM Ca. (9) Magnesium may substitute for calcium, the Na:Mg ratio for repetitive response threshold is 3.3:2. (10) Repetitive firing may be elicited over a wide range of pH values 4.2–10.5; membrane potential and resistance values decline invariably at pH values above 9.5 and below 4.5. (11) Repetitive firing is enhanced by increasing pH values, depressed by reducing pH values. (12) Effect of excess potassium produces depolarization, reduced membrane resistance, inactivation and abolition of repetitive firing, may be relieved by applied hyperpolarization. (13) Potassium lack results in membrane potential and resistance irreversible decline, permanent inactivation, total loss of excitability. Partial restoration by strong hyperpolarization if applied before effect is complete. Potassium replacement in solution only slows or temporarily arrests the overall membrane deterioration. (14) Conclusions ‐ sodium controls spike, potassium controls after potential, calcium (magnesium) controls membrane permeability, pH controls amount of available ionized calcium. Repetitive firing requires proper ratio 3.3/1 of (Nao)/(Ca0), pH above 7.6 and potassium at 15 mM in solution.
The activity of selected soluble enzymes in the avian nasal salt gland
Authors: McFarland L. Z. , Martin K. D. , Freedland R. A. 
Published: February 2005

AbstractTen adult western gulls (Larus occidentalis) ranging in weight from 761–1,004 gm were studied. The gulls were fed 3% NaCl in their drinking water. They were killed by decapitation, and the salt glands, weighing 0.51–0.78 gm were cooled, homogenized in 0.14 M KCl, centrifuged at 0–4°C at 20,000 × G for 30 minutes and the supernatant used for all enzymes assays. All assays were conducted at 25°C by observing the changes in absorbancy with time using a Gilford Multiple Absorbance Recorder. The enzymes were assayed by measuring either the appearance or disappearance of NADH or NADPH at 340 mμ. The average units of enzyme activity (the amount of enzyme required to form 1 μM of substrate per minute ) per gram of salt gland were as follows: phosphoglucomutase, 0.62; glucose‐6‐phosphate dehydrogenase, 1.40; aldolase, 2.86; lactic dehydrogenase, 90.1; isocitric dehydrogenase, 5.08; malic enzyme, 0.92; glutamic‐oxaloacetic transaminase, 100.5; and glutamic‐pyruvic transaminase, 0.50. The protein content of the salt glands varied from 62.5–87.6 mg protein/gm. On the basis of an adjusted calculation of energy yields from the glycolytic scheme and the Krebs cycle, it would appear that only one‐third of the energy derived from these pathways would be necessary to maintain the maximum rate of salt secretion, leaving the other two‐thirds for other cellular processes. Glutamate metabolism may also be important as an energy source in the salt gland.
Metabolic adaptation and the regulation of metabolism of a flagellate protozoan
Authors: Cantor Marvin H. , James Thomas W. 
Published: February 2005

AbstractEvidence is presented indicating metabolic adaptation for the utilization of propionate and butyrate by the flagellate, Polytomella agilis. The existence of a lag phase prior to exponential growth, and the inability of acetate‐grown cells to readily oxidze these substrates support ths concluson.Two aspects of metabolic regulation are discussed. The inhibitory effect of azide on the growth and on oxidation of propionate and butyrate implicates the importance of ATP availability in the control mechanism.Oxidative metabolism is regulated to maintain a constant extent of substrate oxidation regardless of growth conditions. The Qo2 is related to the carbon source for growth, and not on the substrate to be oxidized. The rate of substrate utilization by adapted cells is less than that of unadapted cells.
Systemic effects of epinephrine in the frog
Authors: Watlington Charles O. , Burke Patrick K. , Campbell Addison D. , Huf Ernst G. 
Published: February 2005

AbstractThe intact frog (R. pipiens) is both very sensitive to i.v. injection of l‐epinephrine (E) in small amounts (a few micrograms), and very tolerant to large doses (several milligrams) of the hormone. A small dose increased the P.D. and the short circuit current (Is) in skin, and strongly increased the strength of auricular contraction of the heart in vivo; ventricular contractions decreased, and heart rate remained normal. Large doses of E depressed P.D. and Is after, occasionally, elevating both for a brief period following treatment. The mucous glands of the skin emptied their content shortly after E, then began to fill again with secretory materials in spite of uninterrupted E infusions. Ventricular and auricular contractions were remarkably little altered and there were no significant changes in heart rate. Changes were seen, however, in the ECG, e.g.: inversion of the P and T waves. No alteration in the QRS complex or in the rhythm was ever noted. Serum glucose remained within normal limits. A transient calorigenic effect, lasting for 10–20 minutes occurred, in which the O2 consumption rose from a normal of 6 to 7 ml/100 g/hr to several times this value. Unanesthetized frogs tolerated without great harm 10 mg of E given s.c. within one hour. Signs of prostration and a moderate increase in respiration were noted for some time following treatment. Great tolerance of frogs to hormones which do play a physiological role is also known for thyroxine and insulin, but is especially notable for epinephrine which is least tolerated by warmblooded animals treated with large doses of E. The reasons for these species differences are unknown.
Modification of cardiac and respiratory rhythms in crayfish following carbohydrate chemoreception
Authors: Ashby Ebert A. , Larimer James L. 
Published: February 2005

AbstractReflex inhibitions of cardiac and ventilation rates of the crayfish, Procambarus simulans, have been used as indices of chemical sensitivity in an assay of configurational specificity among 30 carbohydrates and related compounds. Cardiac activity was determined from electrocardiograms and the bilateral ventilation frequencies were recorded with low‐level pressure transducers. The responses were followed simultaneously on a commercial polygraph. Test solutions were introduced into the region of the branchial chamber with the ventilation stream. Positive responses consisted of inhibition or cessation of activity in both systems.Analysis of results from sugars with various configurations involving carbons 2, 4, and 5 of the pyranose ring indicated these positions were not critical in evoking the responses. Sugars lacking carbon 6, e.g., D‐xylose and D‐arabinose, were also effective stimuli. Blocking of the ‐OH at the C1, as found in glycosides, converts a stimulating configuration into a non‐stimulating one, except where the substituent contains a free ‐OH group at the terminal carbon, e.g., maltose or cellobiose. Stimulating disaccharides were all 1–4 glycosides and possessed a free ‐OH at C1. The disaccharides with linkages other than 1–4 were non‐stimulatory, e.g., gentiobiose, trehalose, and melibiose, as were the trisaccharides, raffinose and melizitose. Linear and cyclic polyhydroxy alcohols, e.g., erythritol and inositol, and short chain aldoses, e.g., erythrose, were also ineffective.Stimulation of the receptors seems to require the pyranose ring and access to a free hydroxyl group on C1. Isolation of the receptor and measurement of single unit activity are required before incontrovertible statements of specificity can be made. A basis for such investigations has been made.
Photodynamic and fluorochromic properties of the antibiotic actinomycin D
Authors: Zhdanov Victor M. , Yershov Felix I. 
Published: February 2005

AbstractActinomycin D was studied as a photodynamic agent and fluorochrome. With Venezuelan equine encephalitis virus propagated in chick fibroblasts, it was shown that actinomycin D induces both direct and indirect photoactivation of the virus. Some capacity of antibiotic‐treated and irradiated virus to produce plaques larger than usual was not retained with passage of virus isolated from large plaques. Cells stained with actinomycin D exhibited a weak brownish fluorescence of nuclear structure.
DNA lesions induced in nuclei and nucleoli of monkey kidney cells in tissue culture by simian vacuolating virus (SV40)
Authors: Kasten Frederick H. , Vendrely Colette , Tournier Paul , Wicker René 
Published: February 2005

AbstractSusceptible monkey kidney cultures were infected with SV40. DNA alterations were studied in stained preparations and by quantitative cytophotometry. Early changes included a decrease in mitotic rate. Later, enlarged DNA granules formed at the nuclear membrane, followed by massive production of refractile inclusion particles of DNA in the nuclear interior. This heavily stained mass often included separate, larger DNA viral bodies surrounded by halos. Also present within this mass was a hypertrophied nucleolus enveloped by an intense ring of DNA and a halo. Prominent DNA granules were observed within nucleoli. Strands of DNA passed between the mass of inclusion particles and the nucleolar‐associated DNA and nucleolus. Nuclei with inclusions contained increased DNA in well‐developed cases which was at least five times that found in normal cells. Two types of abnormal nuclei were observed, one of which was large, appeared early, and contained inclusions (Stage 1), while the other appeared later and was pyknotic (Stage 2). It is suggested that SV40 induces arrest of the cell cycle in the G2 phase which causes a decreased mitotic rate and a scarcity of infected nuclei in the euploid DNA class.
The effect of triton X‐100 on the permeability of erythrocytes to non‐electrolytes
Authors: Ospina Bertha , George Jaime , Hunter F. R. 
Published: February 2005

AbstractStudies of the effect of triton X‐100 on the fragility of rabbit erythrocytes and on shape and volume changes of rabbit and sheep erythrocytes suspended in an isotonic salt solution suggest that this subtance alters the erythrocytes of other species in a manner similar to that reported previously for human red cells. Using a densimeter technique it was found that the permeability of relatively slowly moving non‐electrolyte‐carrier‐complexes is decreased by triton X‐100 but more rapidly penetrating systems are not affected by this substance. The permeability of some molecules which cross the membrane by diffusion is increased by triton X‐100. It is suggested that triton X‐100 affects both the aqueous channels and the portion of the membrane across which carriers move. Its action is less than that of tannic acid or butanol.
Seasonal changes in energy reserves in the common frog, Rana pipiens
Authors: Mizell Sherwin 
Published: February 2005

AbstractSeasonal changes in blood glucose content, liver glycogen conten, and fat body weight have been studied in Rana pipiens. Over a 12‐month period frogs were maintained at room temperature in tap water for a minimum of 14 days before observations were made. The frogs were not fed while in the laboratory. Blood glucose content was high in the summer (June through August) and fall (September through August) and fall (September through November) and low in the winter (December through February) and spring (March through May). The value for summer (60 mgm per 100 cm3 blood) was not signficantly different from the blood glucose level in the fall (60 mgm %). However, the blood glucose content in the winter (52 mgm % ) and the spring (49 mgm % ) were significantly different from each other and from the summer and fall. Liver glycogen content was high in the fall (1.16 gm/100 gm body weight). This decreased through the winter (0.85 gm/100 gm body weight) and spring (0.50 gm/100gm body weigh) until the annual low was reached in the summer (0.27 gm/100 gm body weight). All seasons were significantly diferent from each other when tested statistically. Fat body weights also exhibited a seasonal variation. All seasons were significantly different from each other. The high was in the summer (203.3 mgm/100 gm body weight). Fat body weights then decreased to 87.1 mgm/100 body weight in the fall, 32.7 mgm/100 gm body weight in the winter, and 25.1 mgm/100 gm body weight in the spring. These data are important when studying metabolic changes in this common laboratory animal.
The spatial distribution of dividing and DNA‐synthesizing cells in mouse epithelium
Authors: Cameron Ivan L. , Gosslee David G. , Pilgrim Christoph 
Published: February 2005

AbstractCells of the germinal layer of mouse esophageal epithelium were used for quantitative assessment of the spatial distribution of proliferating cells. In tritiated thymidine autoradiographs the nonsynthesizing cells between synthesizing (or dividing) cells were counted, rather than counting the dividing cells in pre‐established grid units. Dividing and DNA‐synthesizing cells are almost random in spatial distribution, but there is an excess of labeled or dividing cells immediately adjacent to one another over what would be expected if the spatial distribution were random. Two possible explanations for the excess of adjacent proliferating cells are suggested: (a) direct cellular interaction or local humoral influences, and (b) phasing of adjacent cells which have a common line of descent.
Graph minors and linkages
Authors: Chen G. , Gould R. J. , Kawarabayashi K. , Pfender F. , Wei B. 
Published: February 2005

AbstractBollobás and Thomason showed that every 22k‐connected graph is k‐linked. Their result used a dense graph minor. In this paper, we investigate the ties between small graph minors and linkages. In particular, we show that a 6‐connected graph with a K minor is 3‐linked. Further, we show that a 7‐connected graph with a K minor is (2,5)‐linked. Finally, we show that a graph of order n and size at least 7n−29 contains a K minor. © 2005 Wiley Periodicals, Inc. J Graph Theory 49: 75–91, 2005
Studies on lymphocytes IV. Further observations upon the hemopoietic effects of splenectomy in frogs
Authors: Jordan H. E. , Speidel C. C. 
Published: February 2005

AbstractTotal splenectomy in the frog means practically complete extirpation of the erythropoietic apparatus. Out of sixty‐four operations it was followed by:

Stimulation of erythropoiesis in the kidney (mesonephros), 35 to 46 per cent.
Stimulation of erythropoiesis in the fat‐bodies, 5 per cent; lymphocytopoiesis, 8 per cent.
Stimulation of erythropoiesis in the bone‐marrow, 11 per cent.
Formation of a new spleen, 8 per cent.
No perceptible erythropoletic stimulation, 24 per cent. The latter leads to a condition of anemia followed by death within about sixty days.
Partial splenectomy leads to spleen regeneration.The life tenure of the frog erythrocyte is approximately 100 days.Total splenectomy experiments indicate that the chief function of the spleen in the frog inheres largely in its lymphocyte content and in the transformation of lymphocytes into erythrocytes.