Magnetic polarity stratigraphy and ages of Siwalik group rocks of the potwar plateau,Pakistan

Six magnetic polarity sections have been established over the Potwar Plateau region of Pakistan, including the major stratotypes of the Siwalik Group. In all six sections the dominant feature of the magnetic polarity stratigraphy is a long normal polarity zone, which is contained within the Nagri Formation. This conspicuous normal polarity zone has been radiometrically dated at 9.5 ± 0.6 m.y., which identifies it as magnetic Chron 9. Radiometric dates from the Upper Siwalik Formation have also been used to identify the Chron 2–3 boundary in two of the sections. The magnetic polarity stratigraphy of three of the sections has been correlated securely with the accepted magnetic polarity time scale, so that the ages of the local stratigraphy are indexed accordingly. Based exclusively on data from stratotype sections, the Chinji, Nagri and Dhok Pathan Formations have nominal age ranges of 10.1–13.1, 7.9–10.1 and 5.1–7.9 m.y. Age fluctuations on the order of 10⁵ years may be anticipated for these formational boundaries within radius of some 20 km of the designated stratotype. Mean sediment accumulation rates during the Chinji, Nagri and Dhok Pathan interval range from 13 to 52 cm/10³ yr.Essentially linear sediment accumulations are locally maintained over time intervals of several million years. The Chinji-Nagri lithofacies boundary marks a transition from slow to faster sediment accumulation over much of the Potwar Plateau, indicating a fundamental sedimentary-tectonic change at this time.     

Age and stratigraphic reassessment of the fossil-bearing Laguna Umayo red mudstone unit, SE Peru, from regional stratigraphy, fossil record, and paleomagnetism

The thick red mudstone unit that crops out at Laguna Umayo (Puno department, southern Peru), here referred as LURMU, has yielded in different levels a fossil assemblage with plants and vertebrates (including mammals). On the basis of charophytes, the unit was initially assigned to the Vilquechico Formation (Maastrichtian-Danian), of regional extension, and the dinosaurian structure of egg fragments was interpreted as consistent with that age. Revision of the regional stratigraphy leads to reassignment of this unit to the Lower Muñani Formation (Early Tertiary). Mammals from the LU-3 and Chulpas levels present affinities with forms from the Upper Paleocene of South America (Patagonia, Brazil). A bunodont marsupial, Chulpasia, is evidence for chronologic proximity to a transantarctic interchange with Australia at the end of the Paleocene. Furthermore, magnetostratigraphy of the LURMU reveals a single reverse polarity zone of 300 m thickness. Because of the new stratigraphic and paleomammalogic data, this long reverse polarity zone is likely correlative to Chron 26r (early Late Paleocene) or Chron 24r (latest Paleocene-earliest Eocene), or, less likely, to Chron 29r (latest Cretaceous-earliest Paleocene). The arguments previously invoked in favor of a Cretaceous age (charophytes, dinosaurian eggs) are critically evaluated, and correlation to Chron 24r is favored.     

The biostratigraphy and paleobiology of Oligocene planktonic foraminifera from the equatorial Pacific Ocean (ODP Site 1218)

Planktonic foraminifera from a continuous Oligocene succession with clear magnetochronology and sediment cycles at Ocean Drilling Program Site 1218 (equatorial Pacific Ocean) were studied in the interval from 27 to 30 Ma. Paragloborotalia taxa are common and we examined their size, relative abundance, and stable isotopes. Multispecies stable isotope data indicate the depth habitats of Oligocene planktonic foraminifera and suggest that “Globoquadrina” venezuelana and Dentoglobigerina globularis were probably mixed-layer dwellers, with paragloborotaliids recording heavier δ¹⁸O signatures consistent with a thermocline habitat. Cyclic variations in the abundance of Paragloborotalia match eccentricity (100 kyr) variations in percent carbonate and δ¹³C, suggesting orbitally forced upwelling in the equatorial Pacific Ocean and that Paragloborotalia were responding directly to changes in surface water productivity. The high-resolution biostratigraphy calibrated to the magnetochronology constrains the extinction of Paragloborotalia opima which marks the top of Planktonic Foraminifera Biozone O5 (P21b) at 27.456 Ma. The highest occurrence of P. opima is associated with a 50% size decrease in Paragloborotalia pseudocontinuosa taxa within Chron 9n. In addition, we find the extinction of Chiloguembelina cubensis is consistent with other deep-sea sections within Chron 10n at 28.426 Ma marking the O4/O5 (P21a/P21b) boundary.     

Characteristics of a Pulse-Periodic Corona Discharge in Atmospheric Air

Pulse-periodic corona discharge in atmospheric air excited by applying a voltage pulse with a subnanosecond or microsecond rise time to a point electrode is studied experimentally. It is shown that, at a voltage rise rate of dU/dt ~10¹⁴ V/s, positive and negative ball-shaped streamers with a front velocity of ≥2 mm/ns form near the point electrode. As dU/dt is reduced to 10¹⁰?10¹¹ V/s, the streamer shape changes and becomes close to cylindrical. The propagation velocity of cylindrical streamers is found to be ~0.1 mm/ns at dU/dt ~ 2 × 10¹⁰ V/s. It is shown that the propagation direction of a cylindrical streamer can be changed by tilting the point electrode, on the axis of which the electric field strength reaches its maximum value. It is established that, for the negative polarity of the point electrode and a microsecond rise time of the voltage pulse, a higher voltage is required to form a cylindrical streamer than for the positive polarity of the point electrode.     

Integrated magnetobiochronology of the Early/Middle Eocene transition at Agost (Spain): Implications for defining the Ypresian/Lutetian boundary stratotype

In this paper, we present an integrated study of a 115‐m‐thick section that spans the Ypresian/Lutetian boundary at Agost (Betic Cordillera, SE Spain). Our study includes magnetostratigraphic results and biostratigraphic and palaeoenvironmental data derived from planktic foraminifera, small and larger benthic foraminifera, and calcareous nannofossils. Our results demonstrate that the Agost section is continuous and spans from Zones P9 to P12 (E7 to E10), Zones CP11 to CP14a (NP13 to NP16), Zones SBZ11 to SBZ15, and Chrons C22n to C19r. The first occurrence (FO) of H. nuttalli (base of P10) and the FO of G. nuttalli (base of E8) are found within Chron C20r, at a much younger age (3–5 Myr) than previously considered in standard calibration schemes. Similarly, the boundary between SBZ12 and SBZ13 is located within Chron C21n, also at a younger age than previously considered. On the contrary, the FO of B. inflatus (base of CP12b) is found within Chron C21r, which conforms to the magnetostratigraphically calibrated age of ca. 48 Ma (middle part of C21r) considered in standard calibration schemes. These results corroborate earlier studies and indicate that all the events that have been proposed to mark the Ypresian/Lutetian boundary appear at different stratigraphic intervals and have different ages. Based on our results from Agost and on data from other sections elsewhere, we suggest that the Ypresian/Lutetian boundary might be approximated by the FO of B. inflatus (base of CP12b). The Agost section might be considered as a potential candidate to locate the Global Stratotype Section and Point (GSSP) of the base of the Lutetian Stage, because it includes all the events that might be selected as marker events for the Ypresian/Lutetian boundary and it fulfils most of the geological, biostratigraphic and infrastructure requirements demanded for definition of a GSSP.     

Performance of a time-resolved IR facility for assessment of protonation states and polarity changes in carboxyl groups in a large membrane protein,mammalian cytochrome c oxidase,under turnover conditions in a sub-millisecond time resolution

Time-resolved IR analyses for the protonation and polarity changes of carboxyl groups involved in proton pump enzymes under turnover conditions are indispensable for elucidation of their proton-pump mechanisms. We have developed a new time-resolved infrared facility by introducing a flow system for transferring highly concentrated and thus viscous protein solution to a thin (50?μm) flow cell equipped in a highly sensitive IR spectrometer constructed with the femtosecond mid-IR pulse laser with spectral width of 350?cm^?1 as an IR white light source equipped with multi-channel MCT detector. This facility equipped with O₂ supply system enables the sub-millisecond time scale infrared measurements of the O₂ reduction coupled with proton pumping by bovine cytochrome c oxidase (CcO) initiated by CO-flash photolysis in the COOH (1725–1770?cm^?1) region with the accuracy of about 10?μO.D. under the background O.D. of 1. The facility identifies a band intensity change at ~1744?cm^?1 assignable to protonation of a carboxyl group coupled with a single electron transfer to the O₂ reduction center within 1?ms after initiation of the reaction. The results suggest that the facility detects protonation of a single carboxyl group included in large proteins like as CcO (210?kDa). The present facility sensitively identifies also polarity changes in COOH group by detecting shifts of the bands near 1750?cm^?1 and 1760?cm^?1, without significant intensity changes. These findings show the performance of this facility sufficiently high for providing crucial information for understanding the proton transferring mechanisms of protein carboxyl groups.     

Transport of the auxin, picloram, through petioles of bean and coleus and stem sections of pea

The transport of the synthetic auxin, picloram (4-amino-3,5,6-trichloropicolinic acid) was investigated in sections of petioles of Phaseolus vulgaris L. and Coleus blumei Benth. and stems of Pisum sativum L. Transport of ¹⁴C-picloram was basipolar in all tissues, although the degree of polarity was dependant on age. The velocity of picloram movement was calculated at between 0.75 and 1.11 mm/hr. The amount moved in a given time, the flux, was dependant on the concentration applied and the length of the sections used. Picloram did not appear to be metabolized by the tissues during the transport experiments. When compared to the movement of other growth regulators, picloram transport bears marked similarities to that of 2,4-dichlorophenoxyacetic acid.     

Major deglaciation of east Antarctica during the early Late Pliocene? Not likely from a marine perspective

We have conducted an integrated study of ice-rafted debris (IRD) and oxygen isotopes (measured on Cibicides, Globigerina bulloides, and Neogloboquadrina pachyderma, using identical samples). We used samples from the early Late Pliocene Gauss Chron from ODP Site 114–704 on the Meteor Rise in the subantarctic South Atlantic.During the early Gauss Chron, the oxygen isotopic ratios are generally up to 0.5‰–0.6‰ less than their respective Holocene values. The lowest values in this record can accommodate a warming of about 2.5 °C OR a sea-level rise of about 50 m, but not both, and probably result from some warming and a small reduction in global ice volume. Starting with isotope stage MG2 [3.23 Ma on the Berggren et al. (1985) time scale; 3.38 on the Shackleton et al. (1995b) time scale] oxygen-isotopic values generally increase (and oscillate about a Holocene mean). The first significant IRD appears at the same time. There is a subsequent increase in IRD amounts upsection. In order to reach the site, this material must have been transported by large, tabular icebergs derived from Antarctic ice shelves or ice tongues, similar to occasional, large modern icebergs.This combined record suggests strongly that the Antarctic ice sheet was essentially intact; some warming at the drill site is indicated, but not a major reduction in ice-volume on Antarctica.     

Structural Insight into Substrate Differentiation of the Sugar-metabolizing Enzyme Galactitol Dehydrogenase from Rhodobacter sphaeroides D

Galactitol 2-dehydrogenase (GatDH) belongs to the protein superfamily of short-chain dehydrogenases. As an enzyme capable of the stereo- and regioselective modification of carbohydrates, it exhibits a high potential for application in biotechnology as a biocatalyst. We have determined the crystal structure of the binary form of GatDH in complex with its cofactor NAD(H) and of the ternary form in complex with NAD(H) and three different substrates. The active form of GatDH constitutes a homo-tetramer with two magnesium-ion binding sites each formed by two opposing C termini. The catalytic tetrad is formed by Asn¹¹⁶, Ser¹⁴⁴, Tyr¹⁵⁹, and Lys¹⁶³. GatDH structurally aligns well with related members of the short-chain dehydrogenase family. The substrate binding pocket can be divided into two parts of different size and polarity. In the smaller part, the side chains of amino acids Ser¹⁴⁴, Ser¹⁴⁶, and Asn¹⁵¹ are important determinants for the binding specificity and the orientation of (pro-) chiral compounds. The larger part of the pocket is elongated and flanked by polar and non-polar residues, enabling a rather broad substrate spectrum. The presented structures provide valuable information for a rational design of this enzyme to improve its stability against pH, temperature, or solvent concentration and to optimize product yield in bioreactors.     

Lateral mobility of plasma membrane lipids in Xenopus eggs: Regional differences related to animal/vegetal polarity become extreme upon fertilization

Regional differences in the lateral mobility properties of plasma membrane lipids have been studied in unfertilized and fertilized Xenopus eggs by fluorescence photobleaching recovery (FPR) measurements. Out of a variety of commonly used lipid probes only the aminofluorescein-labeled fatty acids HEDAF (5-(N-hexadecanoyl)-aminofluorescein) and TEDAF (5-(N-tetradecanoyl)-aminofluorescein) appear to partition into the plasma membrane. Under all experimental conditions used these molecules show partial recovery upon photobleaching indicating the existence of lipidic microdomains. In the unfertilized egg the mobile fraction of plasma membrane lipids (～50%) has a fivefold smaller lateral diffusion coefficient (D = 1.5 × 10^?8 cm²/sec) in the animal than in the vegetal plasma membrane (D = 7.6 × 10^?8 cm²/sec). This demonstrates the presence of an animal/vegetal polarity within the Xenopus egg plasma membrane. Upon fertilization this polarity is strongly (>100×) enhanced leading to the formation of two distinct macrodomains within the plasma membrane. At the animal side of the egg lipids are completely immobilized on the time scale of FPR measurements (D ? 10^?10 cm²/sec), whereas at the vegetal side D is only slightly reduced (D = 4.4 × 10^?8 cm²/sec). The immobilization of animal plasma membrane lipids, which could play a role in the polyspermy block, probably arises by the fusion of cortical granules which are more numerous here. The transition between the animal and the vegetal domain is sharp and coincides with the boundary between the presumptive ecto- and endoderm. The role of regional differences in the plasma membrane is discussed in relation to cell diversification in early development.     

The late Maastrichtian nannofossil record of climate change in the South Atlantic DSDP Hole 525A

The phytoplankton response (calcareous nannofossils) to the Late Maastrichtian climate evolution is investigated in the South Atlantic DSDP Hole 525A and compared to published geochemical and micropaleontological data. The results point to a succession of dramatic climatic fluctuations. “Cool-water indicators” (Ahmuellerella octoradiata, Kamptnerius magnificus and Nephrolithus frequens) suggest cool surface water conditions prevailed during Chron C30n. At the top of C30n, their sudden drop in abundance, the last occurrence of B. constans and the concomitant increase in the tropical species Micula murus suggest warming and lower surface water productivity. An M. murus acme within Chron C29r reflects maximum warming. During the last 100 kyr of the Maastrichtian, the decrease in M. murus and increase in cool-water indicators reflect rapid cooling with the cool climate persisting over. The calcareous nannoplankton response to climate change correlate with similar findings in the Equatorial Atlantic Hole 1258A and parallels the stable isotope record of planktic and benthic foraminifera of DSDP Hole 525A as well as the decline in ¹⁸⁷Os/¹⁸⁸Os. Comparison of this marine record and the continental climate record in North America suggests a link between Deccan volcanism and the late Maastrichtian warm event.     

The importance of the B10 amino acid residue to the biological activity of insulin. [Lys10-B] human insulin

An analog of human insulin, which differs from the parent molecule in that the histidine residue at position 10 of the B chain (B¹⁰) is replaced by lysine, has been synthesized and isolated in purified form. This analog, [10-lysine-B] insulin ([Lys¹⁰-B] insulin), in stimulating lipogenesis and in radioimmunoassays, exhibited potencies of 14.2% and 14.7%, respectively, as compared to the natural hormone. In insulin receptor binding in rat liver membranes, [Lys¹⁰-B] insulin was found to possess a potency of ～17% compared to insulin. We have shown previously that substitution of the B¹⁰ polar residue histidine with the nonpolar leucine results in an analog exhibiting inin vivo assays ～50% of the activity of the parent molecule. It is speculated that in insulin the relative size of the amino acid residue at B¹⁰, rather than its polarity, is the most important factor in maintaining a structure commensurate with high biological activity.     

Temporal fractal in the feeding behavior ofDrosophila melanogaster

A temporal fractal is clearly shown in the feeding behavior ofDrosophila as a self-similar pattern of locomotive velocity and inverse power law distributions of food dwelling time over the time scale range of 10³. The fractality was observed in the dwelling time distribution immediately after the fly was placed to feeding site or on inferior food in a two-choice situation. Fractality may be understood as adaptive, and an intrinsic property of animal behavior that reflects complex information processing in the CNS ofDrosophila.     

The solvent polarity dependent conformational equilibrium of the carboxylic ionophore narasin: A proton NMR study

Two dimensional homonuclear (¹H-¹H) chemical shift correlation, double resonance and nuclear Overhauser effect difference spectroscopy were used to determine spectral parameters of narasin acid in different solvents approximating the range of polarities encountered within a biological membrane. The observed chemical shift and coupling constant changes were consistent with a polarity mediated shift between two conformational states, with the major conformational adjustments occurring in two specific backbone regions of the molecule previously described as “hinges” (1,2). Evidence suggests that the conformational equilibrium is not only mediated by solvent polarity but may in part be determined by the intrinsic propensity of narasin to form inclusion complexes with H⁺.     

Investigation of the electrostatic charge of basidiospores of the Phellinus igniarius group

The polarity and magnitude of primary electric charges carried by basidiospores in the airborne state were investigated in living fungal fruiting bodies under natural forest conditions using a portable experimental device designed by the author. The operating principle was the falling of spores in the homogeneous horizontal electric field. The vertical and horizontal components of the trajectories of the spores were determined according to their deposition sites on electrodes (vertical metal plates). Altogether 33 samples of spores were examined for polarity, 10 of these samples (with 10⁴–10⁶ spores per sample) also were used to calculate the mean spore charge-to-mass quotient and the mean spore charge. The detection limits of spore charge-to-mass quotient varied in the range from (4.9±2.3)×10^?5 to (1.36±0.33)×10^?4 C kg^?1. Basidiospores (subglobose, smooth, diameter of 4–6 μm) of the closely related (sibling) species Phellinus alni, P. nigricans, P. populicola and P. tremulae (Hymenochaetales, Basidiomycota) carried positive electrical charges that have mean values from 48 to 305 elementary charges. The intraspecies variation of the spore charge could depend on the natural variation in spore size.     

Phytochrome and potassium uptake by mung bean hypocotyl sections

Uptake of potassium (K) and ⁸⁶rubidiumlabelled potassium (⁸⁶Rb) by sub-hypocotyl hook sections of Phaseolus aureus L. was inhibited by red light. The effect was reversible with far red light. Using short exposures of high irradiance the effect on ⁸⁶Rb-labelled K uptake was observed after 5 min. The response showed no specificity for a particular anion. Uptake of ⁸⁶Rb-labelled K by sections cut immediately below the cotyledons was enhanced by red light after 10 min incubation and was also far red reversible. These results are interpreted as a rapid phytochrome-induced change in membrane properties resulting in modified K uptake.Abbreviations P Phytochrome - Pr red absorbing form of P - Pfr far red absorbing form of P - R red light - F far red light     

Influence of 2,3,5-Triiodobenzoic Acid and 1-N-Naphthylphthalamic Acid on Indoleacetic Acid Transport in Carnation Cuttings: Relationship with Rooting

³H-IAA transport in excised sections of carnation cuttings was studied by using two receiver systems for recovery of transported radioactivity: agar blocks (A) and wells containing a buffer solution (B). When receivers were periodically renewed, transport continued for up to 8 h and ceased before 24 h. If receivers were not renewed, IAA transport decreased drastically due to immobilization in the base of the sections. TIBA was as effective as NPA in inhibiting the basipetal transport irrespective of the application site (the basal or the apical side of sections). The polarity of IAA transport was determined by measuring the polar ratio (basipetal/acropetal) and the inhibition caused by TIBA or NPA. The polar ratio varied with receiver, whereas the inhibition by TIBA or NPA was similar. Distribution of immobilized radioactivity along the sections after a transport period of 24 h showed that the application of TIBA to the apical side or NPA to the basal side of sections, increased the radioactivity in zones further from the application site, which agrees with a basipetal and acropetal movement of TIBA and NPA, respectively. The existence of a slow acropetal movement of the inhibitor was confirmed by using ³H-NPA. From the results obtained, a methodological approach is proposed to measure the variations in polar auxin transport. This method was used to investigate whether the variations in rooting observed during the cold storage of cuttings might be related to changes in polar auxin transport. As the storage period increased, a decrease in intensity and polarity of auxin transport occurred, which was accompanied by a delay in the formation and growth of adventitious roots, confirming the involvement of polar auxin transport in supplying the auxin for rooting. Received April 19, 1999; accepted December 2, 1999     

Raman spectroscopic studies of different forms of cholesterol and its derivatives in the crystalline state

A Raman spectroscopic study has been carried out on a number of cholesterols and cholesterol derivatives in the crystalline state, in order to obtain some empirical correlations between the Raman spectra and structure of each cholesterol form.Although the Raman spectra of the various cholesterols are highly complex it was found that three regions of the spectrum yield considerable information about the crystalline chain packing in each form. They are: (1) the low frequency region below 300 cm^?1, giving information on the inter- and intramolecular vibrations in the cholesteryl moiety; (2) the methylene rocking/deformation region between 1400 and 1500 cm^?1 giving information on chain packing in the crystalline state, and (3) the C–H stretching region between 2700 and 3100 cm^?1 which appears to indicate that there is a correlation between branching in the side chains of the cholesterols, polarity of the substituent groups in the various derivatives studied and relative chain order in the packing arrangements in the crystalline state.A study of two branched chain aerosol derivatives, bis(di-2-octyl)sodium sulphosuccinate and its isomer bis(di-2-ethylhexyl)sodium sulphosuccinate, indicate that branched chain amphiphiles are good Raman spectroscopic models for the cholesterols, similar to previous Raman spectroscopic studies which have found straight chain amphiphiles to be good models for more complex phospholipids.     

Maintenance of polarity of auxin movement by basipetal transport

The polar, basipetal transport of indoleacetic acid helps to maintain polarity of auxin movement in coleoptiles of Avena sativa L. by opposing acropetal diffusion. This conclusion is supported by 3 different kinds of experiments. In all 3 experiments, sections took up ¹⁴C carboxyl-labeled indole-3-acetic acid anaerobically, and the distribution of auxin within all sections was similar at the end of uptake.

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Effects of Flavonoids on the Polar Transport of Auxins

The effect of some flavonoids on the polar transport of auxins was investigated in hypocotyl sections of dark grown seedlings of cucumber, Cucumis sativus L., by means of ¹⁴C labelled auxins. In experiments of 4–6 h duration quercitrin, morin, dihydroquercetin, naringin, sulfuretin and ferulic acid increased the polarity of the transport of indol-3yl-acetic acid (stimulation of basipetal, inhibition of acropetal transport). Naringenin, genistein and pinobanksin, on the other hand, decreased the polarity of this transport. For NAA no increase in the polarity of the transport could be observed, but all the substances tested inhibited the basipetal transport. There was no simple correlation between the effects on the polar transport and the effects on IAA oxidase.