bluuebunny/crossref_metadata_2025_split huggingface dataset:
Influence of carbohydrates on stability of papain in aqueous tetrahydrofuran mixture
Authors: Szabó András , Kotormán Márta , Laczkó Ilona , Simon L Mária 
Published: August 2008

AbstractBACKGROUND: The use of enzymes in organic solvents has extended the scale of their practical applications. Papain has been widely used in chemical syntheses because of its broad substrate specificity. The aim of the present study was to improve the stability of papain in aqueous tetrahydrofuran (THF) by using different saccharides. The effects of these carbohydrates on the structure of papain were followed by means of circular dichroism (CD) and fluorescence spectroscopic measurements.RESULTS: In contrast with most organic solvents, 60% (i.e. 600 mL L−1) THF practically inactivated the enzyme within 30 min. Sugars protected papain from THF‐induced inactivation in the sequence D‐ribose > D‐fructose > D‐glucose > D‐saccharose > D‐raffinose. Ribose at 1.6 mol L−1 proved the most effective stabiliser: in 60% THF in the presence of ribose, papain preserved about 55% of its initial activity after 2 h. Fluorescence and near‐UV CD spectroscopic measurements revealed local changes in the papain conformation. With decrease in the free amino group content of the enzyme, protein‐carbohydrate interactions (Schiff base formation) were detected.CONCLUSION: These results demonstrate that the catalytic activity and stability of papain may be increased in aqueous THF by using different carbohydrates, when a more compact structure of the enzyme is formed. Copyright © 2008 Society of Chemical Industry
Dehydrogenation of 11α‐hydroxy‐16α, 17‐epoxyprogesterone by encapsulated Arthrobacter simplex cells in an aqueous/organic solvent two‐liquid‐phase system
Authors: Li Jiu‐Hong , Guan Yi‐Xin , Wang Hai‐Qing , Yao Shan‐Jing 
Published: August 2008

AbstractBACKGROUND: Arthrobacter simplex cells immobilised in sodium cellulose sulfate/poly‐dimethyl‐diallyl‐ammonium chloride microcapsules were used for the microbial dehydrogenation of 11α‐hydroxy‐16α,17‐epoxyprogesterone to 11α‐hydroxy‐16α,17α‐epoxypregn‐1,4‐diene‐3,20‐dione in an aqueous/organic solvent two‐liquid‐phase system, which is a key reaction in the production of glucocorticoid pharmaceuticals. The aim of the study was to establish a suitable aqueous/organic solvent two‐liquid‐phase system for performing semi‐continuous production in an airlift loop reactor by encapsulated A. simplex cells with the addition of suitable surfactants to achieve a higher yield of the product.RESULTS: n‐Hexane was selected as the most suitable organic solvent. In optimised Tween‐80 emulsion feed mode the conversion in the airlift loop reactor was as high as 97.54% when the time of reaction was 2 h, and the reaction time was greatly shortened. In semi‐continuous production the cultivation with immobilised cells was carried out for five batches in total. The conversion in each batch was above 95% and the enzymatic activity still remained quite high after five batches of biotransformation.CONCLUSION: The results showed that performing the conversion by this method shortened the reaction time and increased the productivity, thus demonstrating the great potential of the method for the dehydrogenation of 11α‐hydroxy‐16α,17‐epoxyprogesterone. Copyright © 2008 Society of Chemical Industry
Angle‐distance image matching techniques for protein structure comparison
Authors: Chu Chia‐Han , Tang Chuan Yi , Tang Cheng‐Yin , Pai Tun‐Wen 
Published: August 2008

AbstractProteins that contain similar structural elements often have analogous functions regardless of the degree of sequence similarity or structure connectivity in space. In general, protein structure comparison (PSC) provides a straightforward methodology for biologists to determine critical aspects of structure and function. Here, we developed a novel PSC technique based on angle‐distance image (A‐D image) transformation and matching, which is independent of sequence similarity and connectivity of secondary structure elements (SSEs). An A‐D image is constructed by utilizing protein secondary structure information. According to various types of SSEs, the mutual SSE pairs of the query protein are classified into three different types of sub‐images. Subsequently, corresponding sub‐images between query and target protein structures are compared using modified cross‐correlation approaches to identify the similarity of various patterns. Structural relationships among proteins are displayed by hierarchical clustering trees, which facilitate the establishment of the evolutionary relationships between structure and function of various proteins.Four standard testing datasets and one newly created dataset were used to evaluate the proposed method. The results demonstrate that proteins from these five datasets can be categorized in conformity with their spatial distribution of SSEs. Moreover, for proteins with low sequence identity that share high structure similarity, the proposed algorithms are an efficient and effective method for structural comparison. Copyright © 2008 John Wiley & Sons, Ltd.
Extracting statistical moments of output quantities from a small number of time‐domain simulations
Authors: de Menezes Leonardo , Ajayi Ajibola , Christopoulos Christos , Sewell Phillip , Borges Geovany A. 
Published: August 2008

AbstractThis work investigates the behavior of the time‐ and frequency‐domain approximations used in the combination of transmission line modeling (TLM) and the unscented transform (UT). The analysis of the accuracy of the approximation indicates that higher‐order schemes may be used as an indicator of the accuracy of the time‐domain results of the second‐order approximation. However, the frequency‐domain counterpart shows that the second‐order approximation is sufficiently accurate in the low‐frequency range. The UT+TLM technique is expanded for the estimation of the probability density function and two independent random variables. The UT+TLM combination is validated in both time and frequency domains using a 2D TLM program. The results are verified by comparison with Monte Carlo solutions. Copyright © 2008 John Wiley & Sons, Ltd.
Mixed‐mode analysis of the sensitivity of a radiofrequency oscillator disturbed by parasitic signals
Authors: Gontrand Christian , Bouhouche Manel , Nuñez Perez José‐Cruz , Valorge Olivier , Calmon Francis , Verdier Jacques , Latreche Saïda 
Published: August 2008

AbstractThe first step of this work is to study the susceptibility of a radiofrequency oscillator to deterministic disturbance sources.A Colpitts oscillator, working around a 4 GHz frequency, contains a heterojunction bipolar transistor with a silicon–germanium base as an active device. A mixed‐mode analysis is involved, applying a microscopic drift diffusion model to the device, whereas the rest of the circuit used is governed by Kirchhoff's laws.We assume that this tool is very relevant to grasp the influence of intrinsic or extrinsic noisy sources of the oscillator. Our first simulation raw results motivate us to discuss, and perhaps extend, via some analytical models, the so‐called impulse sensitivity function model.In this paper, we try to develop quantitative predictions about the phase noise of such oscillators, and to give some new tracks on this field. Copyright © 2008 John Wiley & Sons, Ltd.
Revisiting the maximum intensity of recurving tropical cyclones
Authors: Knaff John A. 
Published: August 2008

AbstractPrevious studies have indicated that recurving western North Pacific tropical cyclones, initially westward moving tropical cyclones that turn toward the east, often reach their maximum intensity close to the time of recurvature. Those results have often been cited in the literature and sometimes inferred to be valid in other tropical cyclone basins. This study revisits this topic in the western North Pacific, North Atlantic and Southern Hemisphere tropical cyclone basins. The timing of lifetime maximum intensity associated with recurving tropical cyclones is examined using best track datasets from the United States' Joint Typhoon Warning Center and the National Hurricane Center, Miami during the period 1980–2006. Results reveal that tropical cyclones are less likely to experience peak intensity within ± 12 h and ± 24 h of recurvature than has been previously reported in the western North Pacific. Furthermore, it is shown that tropical cyclones that become most intense (i.e. intensities greater than 52 m s−1) have a greater tendency to reach peak intensity before recurvature than weaker storms save for in the South Pacific where the most intense storms have a slightly greater probability of reaching their maximum intensity following recurvature. It also appears that weak tropical cyclones (i.e. lifetime peak intensities less than 33 m s−1) often reach peak intensity prior to or close to recurvature in all tropical cyclone basins as others have reported. However, findings suggest that the cumulative distributions of maximum intensity with respect to the time of recurvature can be quite different for other intensity ranges suggesting that a universal relationship between peak intensity and time of recurvature does not exist. Copyright © 2008 Royal Meteorological Society
Ages and inferred causes of Late Pleistocene glaciations on Mauna Kea, Hawai'i
Authors: Pigati Jeffrey S. , Zreda Marek , Zweck Chris , Almasi Peter F. , Elmore David , Sharp Warren D. 
Published: August 2008

AbstractGlacial landforms on Mauna Kea, Hawai'i, show that the summit area of the volcano was covered intermittently by ice caps during the Late Pleistocene. Cosmogenic 36Cl dating of terminal moraines and other glacial landforms indicates that the last two ice caps, called Older Makanaka and Younger Makanaka, retreated from their maximum positions approximately 23 ka and 13 ka, respectively. The margins and equilibrium line altitudes of these ice caps on the remote, tropical Pacific island were nearly identical, which would seem to imply the same mechanism for ice growth. But modelling of glacier mass balance, combined with palaeotemperature proxy data from the subtropical North Pacific, suggests that the causes of the two glacial expansions may have been different. Older Makanaka air atop Mauna Kea was likely wetter than today and cold, whereas Younger Makanaka times were slightly warmer but significantly wetter than the previous glaciation. The modelled increase in precipitation rates atop Mauna Kea during the Late Pleistocene is consistent with that near sea level inferred from pollen data, which suggests that the additional precipitation was due to more frequent and/or intense tropical storms associated with eastward‐moving cold fronts. These conditions were similar to modern La Niña (weak ENSO) conditions, but persisted for millennia rather than years. Increased precipitation rates and the resulting steeper temperature lapse rates created glacial conditions atop Mauna Kea in the absence of sufficient cooling at sea level, suggesting that if similar correlations existed elsewhere in the tropics, the precipitation‐dependent lapse rates could reconcile the apparent difference between glacial‐time cooling of the tropics at low and high altitudes. Copyright © 2008 John Wiley & Sons, Ltd.
Late Pleistocene mountain glaciation in Alaska: key chronologies
Authors: Briner Jason P. , Kaufman Darrell S. 
Published: August 2008

AbstractMoraine sequences of mountain glaciers can be used to infer spatial and temporal patterns of climate change across the globe. Alaska is an accessible high‐latitude location in the Northern Hemisphere and contains a rich record of alpine glaciation. Here, we highlight the key chronologies from three mountain ranges in Alaska that reveal the timing and spatial extent of Late Pleistocene glaciation, and pay particular attention to age of the penultimate glaciation. The most extensive glacier advance of the last glaciation occurred prior to the last global glacial maximum. Cosmogenic exposure ages from moraine boulders in three sites spanning 800 km indicate that this penultimate advance most likely culminated during marine isotope stage (MIS) 4 or early MIS 3. During MIS 2, more limited glacier expansion generated multiple moraines that span from prior to the global Last Glacial Maximum (LGM) through the Lateglacial period. Glaciers retreated from their terminal positions ca. 27–25 ka in arctic Alaska and ca. 22–19 ka in southern Alaska. Moraines in at least two ranges date to 12–11 ka, indicating a glacial advance during the Younger Dryas period. Reconstructed equilibrium‐line altitudes of both penultimate and MIS 2 glaciers were lowered only 300–600 m – much less than elsewhere in the Americas. Alaska is documented to have been more arid during MIS 2, perhaps due in large part to the exposure of the Bering–Chukchi platform during eustatic sea‐level lowering. The restricted ice extent is also consistent with the output of climate models that simulate a lack of significant summer cooling. Copyright © 2008 John Wiley & Sons, Ltd.
Chronology of the last glacial cycle in the European Alps
Authors: Ivy‐Ochs Susan , Kerschner Hanns , Reuther Anne , Preusser Frank , Heine Klaus , Maisch Max , Kubik Peter W. , Schlüchter Christian 
Published: August 2008

AbstractChronological data for glacier advances in the European Alps between the Last Interglacial (Eemian) and the Holocene are summarised (115 to 11 ka). During this time glaciers were most extensive, extending tens of kilometres out onto the forelands, between 30 and 18 ka, that is, synchronous with the global ice volume maximum of Marine Isotope Stage (MIS) 2. Evidence for ice expanding to just past the mountain front for an earlier major glacier advance comes from Swiss sites, where advances have been luminescence dated to MIS 5d (100 ka) and MIS 4 (70 ka). Up to now no such evidence has been found in the Eastern Alps. By 18 ka, more than 80% of the Late Würmian ice volume had gone. Subsequently glaciers readvanced, reaching into the upper reaches of the main valleys during the Lateglacial Gschnitz stadial, which likely occurred around 17 ka, with final moraine stabilisation no later than 15.4 ka. The link of the Egesen stadial with the Younger Dryas climate deterioration is supported by exposure ages from four sites as well as minimum‐limiting radiocarbon dates from bogs within former glacier tongue areas. Key questions on the spatial and temporal variability of ice extents throughout the last glacial cycle have yet to be answered. Copyright © 2008 John Wiley & Sons, Ltd.
Quaternary glaciation of the Himalayan–Tibetan orogen
Authors: Owen Lewis A. , Caffee Marc W. , Finkel Robert C. , Seong Yeong Bae 
Published: August 2008

AbstractGlacial geological evidence from throughout the Himalayan–Tibetan orogen is examined to determine the timing and extent of late Quaternary glaciation in this region and its relation to similar changes on a global scale. The evidence summarised here supports the existence of expanded ice caps and extensive valley glacier systems throughout the region during the late Quaternary. However, it cannot yet be determined whether the timing of the extent of maximum glaciation was synchronous throughout the entire region or whether the response was more varied. The lack of organic material needed for radiocarbon dating has hindered past progress in glacial reconstruction; however, application of optically stimulated luminescence and terrestrial cosmogenic radionuclide methods has recently expanded the number of chronologies throughout the region. Limits to the precision and accuracy available with these methods and, more importantly, geological uncertainty imposed by processes of moraine formation and alteration both conspire to limit the time resolution on which correlations can be made to Milankovitch timescales (several ka). In order to put all studies on a common scale, well‐dated sites have been re‐evaluated and all the published terrestrial cosmogenic nuclide ages for moraine boulders and glacially eroded surfaces in the Himalayan–Tibetan orogen have been recalculated. Locally detailed studies indicate that there are considerable variations in the extent of glaciation from one region to the next during a glaciation. Glaciers throughout monsoon‐influenced Tibet, the Himalaya and the Transhimalaya are likely synchronous both with climate change resulting from oscillations in the South Asian monsoon and with Northern Hemisphere cooling cycles. In contrast, glaciers in Pamir in the far western regions of the Himalayan–Tibet orogen advanced asynchronously relative to the other regions that are monsoon‐influenced regions and appear to be mainly in phase with the Northern Hemisphere cooling cycles. Broad patterns of local and regional variability based on equilibrium‐line altitudes have yet to be fully assessed, but have the potential to help define changes in climatic gradients over time. Copyright © 2008 John Wiley & Sons, Ltd.
The timing and magnitude of mountain glaciation in the tropical Andes
Authors: Smith Jacqueline A. , Mark Bryan G. , Rodbell Donald T. 
Published: August 2008

AbstractThe Andes of Ecuador, Peru and Bolivia host the majority of the world's tropical glaciers. In the tropical Andes, glaciers accumulate during the wet season (austral summer) and ablate year‐round. Precipitation is delivered mainly by easterlies, and decreases both N–S and E–W. Chronological control for the timing of glacial advances in the tropical Andes varies. In Ecuador, six to seven advances have been identified; dating is based on radiocarbon ages. Timing of the local Last Glacial Maximum (LGM) and the existence of Younger Dryas advances remain controversial. In Peru, local variability in glaciation patterns is apparent. Surface exposure dating in the Cordillera Blanca and Junin Plain suggests that the local LGM may have been early (∼30 ka), although uncertainties in age calculations remain; the local LGM was followed by a Lateglacial readvance/stillstand and preceded by larger glaciations. In contrast, preliminary data from an intervening massif indicate that the largest moraines are Lateglacial. Chronologies from Bolivia also suggest local variability. In leeward Milluni and San Francisco Valleys, local LGM moraines descend to ∼4300 m above sea level (a.s.l.), whereas in windward Zongo Valley Lateglacial moraines reach ∼3400 m a.s.l. Atlantic and Pacific sea surface temperatures, El Niño–Southern Oscillation and insolation changes all likely play roles in mediating tropical Andean glacial cycles. Copyright © 2008 John Wiley & Sons, Ltd.
Timing and nature of late Quaternary mountain glaciation
Authors: Thackray Glenn D. , Owen Lewis A. , Yi Chaolu 
Published: August 2008

AbstractCompilations of regional‐ to subcontinental‐scale mountain glacier chronologies from five continents, plus Hawaii, examine the temporal and spatial patterns of mountain glaciation. The compilations yield key insights into the nature of past fluctuations in temperature and precipitation in mountains and adjacent regions, and provide baseline data for examining the dynamics of glacier responses to climate change. Key insights from these compilations include the wide variability of glacier responses to fluctuations in insolation, temperature and precipitation and the regionally specific variations in climatic variables through late Quaternary time. The compilations highlight the need to improve the density and quality of geochronological data and to enhance the understanding of the links between climate and glaciation. Copyright © 2008 John Wiley & Sons, Ltd.
Experimental and theoretical study of the structure and vibrational spectra of valpromide, C7H15CONH2
Authors: Comelli Nieves C. , Massa Nestor E. , Castro Eduardo A. , Blanch Luis Bruno , Jubert Alicia H. 
Published: August 2008

AbstractIn this work, we present results of the conformational and vibrational properties of valpromide (Vpd), an amide with antiepileptic activity, studied by IR and Raman spectroscopy at 300 and 77 K, and 300 K, respectively. Experimental data are compared against ab initio calculations performed at B3LYP level with the inclusion of solvatation effects.Experimental results, reinforced by theoretical calculations, point out that Vpd has three conformers on the potential energy surface, with different structures that can be identified in the CO and NH spectral regions. These conformers are defined by different angular arrays of the dihedral angles formed with the CO, CN and C〈H, CC of the aliphatic chain bonds.The existence of different conformations and structures are discussed on the basis of results derived from electronic localization function (ELF) and natural orbital bond (NBO) analysis. Copyright © 2008 John Wiley & Sons, Ltd.
Large‐scale submerged fermentation of Antrodia cinnamomea for anti‐hepatoma activity
Authors: Pan Jih‐Hung , Chen Yi‐Song , Sheen Lee‐Yen , Chiang Been‐Huang 
Published: August 2008

AbstractBACKGROUND: Submerged cultivation of Antrodia cinnamomea was carried out for manufacturing the fermentation product with anti‐hepatoma activity. The fermentation process was optimized for different parameters at shake flask level to obtain products with high inhibition potency against Hep G2 hepatoma cells. Scale‐up of the fermentation process was then achieved from 250 mL shake flask to 5 L, 500 L and 5‐ton fermenters.RESULTS: Glucose and malt extract were found to be the best carbon and nitrogen sources, respectively. The initial pH of 5.0 and an operating temperature of 22 °C were the best for a product with lowest IC50 value. A shorter cultivation time was required when the scale of fermentation increased from 5 L to 5 tons. The reducing sugar and solids contents of the broth filtrate were correlated exponentially with the IC50 of the ethanolic extract of mycelium for hepatoma cells, and the level of ergosterol in the mycelium extract follows the same profile as the increase in Hep G2 cells inhibition.CONCLUSION: When Antrodia cinnamomea is cultured in a 5‐ton fermenter, 4 weeks are required for the fermentation product to reach the highest anti‐hepatoma activity. The solid and reducing sugar contents of the broth filtrate as well as the ergosterol content in the ethanol extract of mycelium can serve as the marker during fermentation for manufacturing product with anti‐hepatoma activity. Copyright © 2008 Society of Chemical Industry