bluuebunny/crossref_metadata_2025 huggingface dataset:
The use of abscisic acid analogues to analyse the substrate selectivity of UGT71B6, a UDP‐glycosyltransferase of Arabidopsis thaliana
Authors: Priest David M. , Jackson Rosamond G. , Ashford David A. , Abrams Suzanne R. , Bowles Dianna J.
Published: July 2005

This study analyses the activity of an Arabidopsis thaliana UDP‐glycosyltransferase, UGT71B6 (71B6), towards abscisic acid (ABA) and its structural analogues. The enzyme preferentially glucosylated ABA and not its catabolites. The requirement for a specific chiral configuration of (+)‐ABA was demonstrated through the use of analogues with the chiral centre changed or removed. The enzyme was able to accommodate extra bulk around the double bond of the ABA ring but not alterations to the 8′‐ and 9′‐methyl groups. Interestingly, the ketone of ABA was not required for glucosylation. Bioactive analogues, resistant to 8′‐hydroxylation, were also poor substrates for conjugation by UGT71B6. This suggests the compounds may be resistant to both pathways of ABA inactivation and may, therefore, prove to be useful agrochemicals for field applications.
Conformation‐driven and semiquinone‐gated proton‐pump mechanism in the NADH‐ubiquinone oxidoreductase (complex I)
Authors: Ohnishi Tomoko , Salerno John C.
Published: July 2005

We propose that the proton pump is operated by redox‐driven conformational changes of the quinone binding protein. In the input state, semiquinone is reduced to quinol, acquiring two protons from the N (matrix) side of the mitochondrial inner membrane and an electron from the low potential (NADH) side of the respiratory chain. A conformational change brings the protons into position for release at the P (inter‐membrane space) side of the membrane via a proton‐well. Concomitantly, an electron is donated to the quinone pool at the high potential side of the coupling site. The system then returns to the original state to repeat the cycle. This hypothesis provides a useful frame work for further investigation of the mechanism of proton translocation in complex I.
Silencing of NbECR encoding a putative enoyl‐CoA reductase results in disorganized membrane structures and epidermal cell ablation in Nicotiana benthamiana
Authors: Park Jong-A , Kim Tae-Wuk , Kim Seong-Ki , Kim Woo Taek , Pai Hyun-Sook
Published: July 2005

The very long chain fatty acids (VLCFAs) are synthesized by the microsomal fatty acid elongation system in plants. We investigated cellular function of NbECR putatively encoding enoyl‐CoA reductase that catalyzes the last step of VLCFA elongation in Nicotiana benthamiana. Virus‐induced gene silencing of NbECR produced necrotic lesions with typical cell death symptoms in leaves. In the affected tissues, ablation of the epidermal cell layer preceded disintegration of the whole leaf cell layers, and disorganized cellular membrane structure was evident. The amount of VLCFAs was reduced in the NbECR VIGS lines, suggesting NbECR function in elongation of VLCFAs. The results demonstrate that NbECR encodes a putative enoyl‐CoA reductase and that the NbECR activity is essential for membrane biogenesis in N. benthamiana.
Sodium channel activators: Model of binding inside the pore and a possible mechanism of action
Authors: Tikhonov Denis B. , Zhorov Boris S.
Published: July 2005

Sodium channel activators, batrachotoxin and veratridine, cause sodium channels to activate easier and stay open longer than normal channels. Traditionally, this was explained by an allosteric mechanism. However, increasing evidence suggests that activators can bind inside the pore. Here, we model the open sodium channel with activators and propose a novel mechanism of their action. The activator‐bound channel retains a hydrophilic pathway for ions between the ligand and conserved asparagine in segment S6 of repeat II. One end of the activator approaches the selectivity filter, decreasing the channel conductance and selectivity. The opposite end reaches the gate stabilizing it in the open state.
Dietary unripe apple polyphenol inhibits the development of food allergies in murine models
Authors: Akiyama Hiroshi , Sato Yuji , Watanabe Takahiro , Nagaoka Megumi H. , Yoshioka Yasuo , Shoji Toshihiko , Kanda Tomomasa , Yamada Kiyoshi , Totsuka Mamoru , Teshima Reiko , Sawada Jun-ichi , Goda Yukihiro , Maitani Tamio
Published: July 2005

The incidence of type I allergic disorders has been increasing worldwide, particularly, the hypersensitivity to food. We first showed that apple condensed tannin (ACT) intake would inhibit the development of the oral sensitization and that the inhibition could correlate with the rise in the population of TCRγδ‐T cells in the intestinal intraepithelial lymphocytes (IEL) using W/WV mice and B10A mice which were ovalbumin (OVA)‐orally sensitized. Serum OVA‐specific immunoglobulin E and immunoglobulin G1 titers in the OVA‐orally sensitized W/WV and B10A mice ad libitium fed ACT were extremely inhibited compared to those of the control. The ACT intakes of OVA‐sensitized W/WV and B10A mice inhibited the immediate reduction of the body temperature or the rise in serum histamine induced by active systemic anaphylaxis. The proportions of the TCRγδ‐T cells in the IEL of the OVA‐orally sensitized W/WV and B10A mice ad libitium fed ACT were significantly greater than that in the controls. Furthermore, ACT feeding by itself could induce the rise in the percentage of the TCRγδ‐T cells among the IEL of the W/WV and B10A mice. This suggests that the ACT intake may prevent the development of food allergies and this effect could be correlated with the rise in the percentage of TCRγδ‐T cells among the IEL.
Medical vs. surgical evacuation of first‐trimester spontaneous abortion
Authors: Moodliar S. , Bagratee J.S. , Moodley J.
Published: July 2005

Objective: To determine whether management of incomplete first‐trimester abortion with vaginal misoprostol in an under‐resourced setting is a viable treatment option. Methods: A total of 94 women were randomized to 600 μg of misoprostol intravaginally or to surgical curettage. The women receiving misoprostol were administered a second dose if the abortion was incomplete; and if still not complete after a week, evacuation of retained products of conception was performed. All women had a follow‐up visit 2 weeks following complete abortion. Results: The overall success rate of medical management was 91.5%, with 15 of 47 successful cases after 1 dose of misoprostol; 8.5% of the 47 women required evacuation of retained products of conception after 1 week because of treatment failure. The success rate in the surgical arm was 100%. Patients in the medical arm had a longer duration of bleeding and a greater need for analgesia. There were no differences in hemoglobin levels, white blood cell count, adverse effects, pain score, and satisfaction with treatment at the follow‐up visit. However, more women who received the medical treatment would recommend it or choose it in the future. Conclusion: Medical management using 600 μg of misoprostol in 2 doses is effective to treat incomplete first‐trimester abortions in an under‐resourced setting when there is no evidence of uterine sepsis.
A Hand Research Fellowship Training Programme
Authors: HART R. G. , GUPTA A. , LYONS K.
Published: July 2005

There are currently 68 hand surgery fellowship programmes known to the authors in the United States and many more throughout the world. To our knowledge, there are no hand fellowships which focus on research. Such a hand surgery research fellowship is being developed to provide this training. This paper outlines the goals and objectives of the intended 2 year training programme and includes a description of the fellowship. The first year would be mostly committed to learning research methods and the second would be a clinical hand fellowship. This will combine clinical expertise in hand surgery, practical research experience and formal research training. Hand researchers would learn research methods, develop innovative research ideas and begin an active research and academic career.
Case of Trigger Finger Related to an Intertendinous Connection between the Flexor Tendons
Authors: KAZUKI K. , OKADA T. , NAKA Y.
Published: July 2005

We report a rare cause of trigger finger related to an anatomical variation of an intertendinous connection between the flexor digitorum superficialis and flexor digitorum profundus tendons in the palmar region.
Developmental arrest inCaenorhabditis elegansdauer larvae causes high expression of enzymes involved in thymidylate biosynthesis, similar to that found inTrichinellamuscle larvae
Authors: WIŃSKA P. , GOŁOS B. , CIEŚLA J. , ZIELIŃSKI Z. , FRĄCZYK T. , WAŁAJTYS-RODE E. , RODE W.
Published: July 2005

Crude extract specific activities of thymidylate synthase, dUTPase, thymidine kinase and dihydrofolate reductase were high during the development ofCaenorhabditis elegans, the dauer larva activities being similar to those previously determined inTrichinella spiralisandT. pseudospiralismuscle larvae (with the exception of thymidine kinase, not detected inTrichinella). High thymidylate synthase expression in developmentally arrested larvae, demonstrated also at the mRNA and protein levels, is in agreement with a global cell cycle arrest of dauer larvae and indicates this unusual cell cycle regulation pattern can be shared by developmentally arrested larvae ofC. elegansand the twoTrichnellaspecies. Hence, the phenomenon may be characteristic for developmentally arrested larvae of different nematodes, rather than specific for the parasiticTrichinellamuscle larvae. EndogenousC. elegansthymidylate synthase was purified and its molecular properties compared with those of the recombinant protein, expression of the latter inE. colicells confirming the NCBI database sequence identity.
Resistance mechanism development to the topoisomerase-I inhibitor Hoechst 33342 byLeishmania donovani
Authors: MARQUIS J.-F. , HARDY I. , OLIVIER M.
Published: July 2005

The bisbenzimidazole compound Hoechst 33342 (Ho342) has been identified as a specific Topoisomerase-I (Topo-I) inhibitor in mammalian cells. More recently, we have reported the ability of Ho342 to targetL. donovaniTopo-I, leading to parasite growth inhibitionin vitroby mechanisms involving DNA breakage and apoptosis-like phenomenon. As the Ho342 lead molecule (2,5′-Bi-1H-benzimidazole) can be used as a starting structure for derivative compounds more effective againstLeishmania, defining the Ho342 resistance mechanism(s) inLeishmaniarepresents an important strategic tool. In the present study, we selected resistant parasites to Ho342 (LdRHo.300). While we observed an increase of the Topo-I gene expression correlated by a higher Topo-I DNA relaxation activity, the Topo-I genes (LdTOP1AandLdTOP1B) sequencing did not reveal any mutation for the resistant parasites. Moreover, our results on Ho342 cellular accumulation suggested the presence of a potential energy-dependent Ho342 transporter in the wild-type parasite, and that an alteration of this transporter has occurred inLdRHo.300, leading to an altered drug accumulation. Collectively, Ho342 resistance characterization provided results supporting that the resistance developed byLdRHo.300involves complex mechanisms, most likely dominated by an altered drug accumulation, providing new insight in the Ho342 resistance mechanisms.
In vitroandin vivoeffects of progesterone onTrichinella spiralisnewborn larvae
Authors: NUÑEZ G. G. , GENTILE T. , COSTANTINO S. N. , SARCHI M. I. , VENTURIELLO S. M.
Published: July 2005

We have previously demonstrated that during pregnancy there exists an increased parasiticide activity againstTrichinella spiralisnewborn larvae (NBL) in infected rats. In this work we analysed the contribution of peritoneal cells from non-infected pregnant rats to the mortality of the NBL in cytotoxicity assays, and evaluated the role of progesterone in this effector mechanism. Our findings suggest that progesterone can induce activation of effector peritoneal cells to destroy the NBL in a rapid and antibody-independent manner. The administration of progesterone to ovariectomized rats also led to a significant decrease in the parasite load of the animals, thus demonstrating that progesterone induces the increase of the parasiticide activity of the leukocytes involved in the mechanisms of NBL death.
A mathematical model for a new mechanism of phenotypic variation in malaria
Authors: RECKER M. , AL-BADER R. , GUPTA S.
Published: July 2005

The Py235 merozoite rhoptry protein of the rodent malaria agent Plasmodium (yoelii) yoeli is encoded by the Py235 multigene family whose members are transcribed during the parasite's asexual life-cycle in a fashion where single schizonts subsequently give rise to sets of merozoites containing distinct Py235 transcripts. Homologues of Py235 are found in other malaria species, and antibodies to both Py235 and P. falciparum homologues inhibit merozoite invasion, suggesting a unique survival strategy involving immune evasion and host adaptation. Using a mathematical approach to model this free-living stage of Plasmodium in interaction with specific antibodies and a heterogeneous red blood cell population, we investigate if, and under what conditions, this mechanism of clonal phenotypic variation can play a role in immune evasion and adaptation to a dynamic erythropoietic environment.
Complexity of the major surface protease (msp) gene organization inLeishmania (Viannia) braziliensis: evolutionary and functional implications
Authors: VICTOIR K. , AREVALO J. , DE DONCKER S. , BARKER D. C. , LAURENT T. , GODFROID E. , BOLLEN A. , LE RAY D. , DUJARDIN J. C.
Published: July 2005

The major surface protease (msp orgp63) ofLeishmaniaplays a major role in the host–parasite interaction. We analysed here the structure of the msp gene locus inLeishmania (Viannia) braziliensisand compared it to results obtained in other species. Physical mapping of cosmid contigs revealed a minimum of 37 genes per haploid genome and at least 8 different msp gene families. Within the same organism, these genes showed a nucleotide sequence varying in certain stretches from 3 to 34%, and a mosaic structure. From an evolutionary point of view, major differences were observed between subgeneraVianniaandLeishmania, both in terms of msp gene number and sequence. Within subgenusViannia, phenetic analysis revealed three clusters in which sequence variants ofL. (Viannia) braziliensisandL. (Viannia) guyanensiswere interspersed. Functional implications of our results were explored from predictedL. (Viannia) braziliensisprotein sequences: regions encoding the msp catalytic site showed a conserved sequence, while regions encoding surface domains possibly involved in the host–parasite interaction (macrophage adhesion sites and immunodominant B-cell and T-cell epitopes) were variable. We speculate that this would be an adaptive strategy of the parasite.
Parasite assemblages of crucian carp (Carassius carassius) – is depauperate composition explained by lack of parasite exchange, extreme environmental conditions or host unsuitability?
Authors: KARVONEN A. , BAGGE A. M. , VALTONEN E. T.
Published: July 2005

Recent studies on parasite communities have considered the factors which contribute to variability in parasite infections among populations of one host species. This paper examined parasite assemblages of crucian carp (Carassius carassius) in a natural set-up of two distinctive environments inhabited by the same host species and differing in respect to composition of other fish species: ponds, where extreme conditions prevent other fish species from occurring and lakes, where crucian carp coexist with other fish species. Our aim was to evaluate the significance of parasite exchange, environmental conditions and host suitability for the depauperate parasite assemblages observed in pond crucian carp. As predicted, crucian carp had more diverse parasite species composition in lakes, which supports the hypotheses of increased opportunities for parasite exchange with other fish species and better environmental conditions for the parasites. However, for instance, diplostomids were found only from few fish individuals in very low numbers. Experimental exposure trials with the eye fluke Diplostomum spathaceum in the laboratory indicated that crucian carp were totally resistant to infection, which is exceptional and suggests that the low number of these parasites in crucian carp was due to physiological unsuitability of the host. To obtain a better understanding on the mechanisms underlying the formation of parasite assemblages in these fish, further studies on the relationships between the unique physiology of crucian carp and infection success by other parasite species are needed.
Peromyscuspopulations and theirCuterebraparasites display congruent phylogeographical structure
Authors: NOËL S. , ANGERS B. , LAPOINTE F.-J.
Published: July 2005

The relationships between populations of the Deer Mouse (Peromyscus maniculatus) and the White-footed Mouse (P. leucopus) and their respectiveCuterebraparasites were examined. Population genetic structure of hosts and parasites was inferred using cytochrome oxidase mitochondrial sequences of specimens from 7 populations. Genetic analyses revealed that isolation-by-distance applies forP. maniculatusand its associated parasite (C. grisea). A significant correlation was also observed between the genetic distances of these host and parasite species. Furthermore, populations ofP. maniculatusandC. griseafrom the North and South shores of the St Lawrence River were found to be significantly different. This structure may be explained by the St Lawrence River being a dispersal barrier for both species. A robust analysis of the other species pair (P. leucopusandC. fontinella) could not be performed because of limited sample sizes.
Cost induced by viral particles manipulating superparasitism behaviour in the parasitoid Leptopilina boulardi
Authors: VARALDI J. , BOULÉTREAU M. , FLEURY F.
Published: July 2005

Vertically transmitted symbionts can be maintained in a host population only if they do not reduce host fitness, unless they compensate by manipulation of their host's reproduction or have alternative mode of transmission. In Leptopilina boulardi, a parasitoid of Drosophila larvae, some females are infected by viral particles showing both maternal and horizontal transmission. Horizontal transmission occurs when larvae from infected and uninfected individuals of L. boulardi compete in the same host. This situation is facilitated by the increasing tendency to accept already parasitized hosts that viral infection induces in L. boulardi females. Estimation of the adaptive significance of this behavioural modification requires measuring the effect of viral presence on other parasitoid physiological features. Here, we show that viral infection in females imposes no cost on adult survival, a low cost on developmental rate and tibia length, and leads to a strong reduction of locomotor activity. Surprisingly, infected females show higher egg load which could be accounted for by a redirection of energy allocation to egg production. The high intensity of superparasitism in infected females induced a dramatic decrease in pre-imaginal survival of the parasitoid's offspring, representing a potential indirect cost of infection. Low overall pathogeny induced by viral particles appears to be well suited to both transmission modes, both of them requiring females ability to locate and (super)parasitize hosts.
Temporal host-parasite relationships of the wild rabbit,Oryctolagus cuniculus(L.) as revealed by stable isotope analyses
Authors: NEILSON R. , BOAG B. , HARTLEY G.
Published: July 2005

Natural abundances of the stable isotopes,15N/14N (δ15N) and13C/12C (δ13C), were used to study temporal host-parasite relationships of the wild rabbit,Oryctolagus cuniculus(L.). During the 12-month sampling period, temporal isotopic shifts in δ15N were noted for dietary vegetation, host rabbit faeces and fur, but not for muscle or stomach contents. δ15N varied temporally for the parasitic cestode species,Mosgovoyia pectinatabut not forCittotaenia denticulata. Similarly, intestinal parasitic nematodes had apparent species-specific δ15N patterns. Only rabbit fur and intestinal parasitic nematodes did not exhibit temporal shifts in δ13C. Overall, host faeces and stomach contents were isotopically indistinct as a likely consequence of coprophagy. Relative to their host, parasitic nematodes were15N-enriched, consistent with an increase in trophic level status. Conversely, cestodes were15N-depleted. Isotopically, each parasite reflected a species-specific relationship with their rabbit host. This technique could be utilized to integrate parasites into food-web studies.
Preparation ofEntamoeba histolyticaantigens without enzymatic inhibitors
Authors: FLORES M. S. , TAMEZ-TREVIÑO E. , CASTAÑEDA F. , TIJERINA-MENCHACA R. , GALAN-WONG L. , RANGEL R.
Published: July 2005

The goal of this work is to report a novel assay that preserves antigenicity of extracts with high protease content without using enzymatic inhibitors. A great reduction of proteolytic activity in the insoluble chloroform/methanol and heated amoebic fraction (IC[ratio ]MC) was obtained by this method, even in the presence of sodium dodecyl sulphate and 2-mercaptoethanol. The substrates azo-casein and the hide powder azure were used to determine the reduction of proteolytic activity of IC[ratio ]MC compared with the activity of crude extract and crude extract with iodoacetamide. The IC[ratio ]MC SDS-PAGE pattern shows a higher quantity of bands than extract with the inhibitor iodoacetamide or than crude extract. In addition, anti-Entamoeba histolyticaantibodies from amoebic liver abscess patients recognized a richer antigenic Western blot pattern in the IC[ratio ]MC fraction than in crude extract alone or with inhibitor. The described method has proved to be suitable to preserve amoebic antigens for its use in diagnostic tests and it can be used for immunological response studies againstE. histolyticaantigens. Furthermore we propose that this method to obtain the IC[ratio ]MC fraction can be applied for the study of other microorganisms or cells with high enzymatic content.
A direct interview family study of obsessive–compulsive disorder. II. Contribution of proband informant information
Authors: LIPSITZ JOSHUA D. , MANNUZZA SALVATORE , CHAPMAN TIMOTHY F , FOA EDNA B. , FRANKLIN MARTIN E. , GOODWIN RENEE D. , FYER ABBY J.
Published: July 2005

Background. Overall findings of our first direct interview family study of obsessive–compulsive disorder (OCD) indicated that OCD is familial. In this replication study, we carefully examined the role of informant data in ascertaining OCD in relatives.

Method. We interviewed 112 relatives of 57 OCD patients and 115 relatives of 41 not ill controls predominantly by telephone. Additional analyses included a combined sample of relatives about whom any diagnostic information was available (228 OCD and 239 controls). To examine the contribution of proband information about relatives, we considered two sets of best-estimate diagnoses. First, we ascertained best-estimate diagnoses for relatives using information from direct interviews and from all informants except the proband. Then, we re-diagnosed relatives based on all available information, including reports from the proband about their relatives.

Results. When relative diagnoses were derived without the benefit of proband informant reports, no evidence of familial OCD transmission was found. When diagnoses were made including information from the proband about the relative, evidence of familial OCD was found, but only when the diagnostic threshold was lowered to include cases with probable OCD or OCD symptoms. Other diagnoses (generalized anxiety disorder, social phobia, drug use disorder) were also higher among OCD relatives.

Conclusions. This second study provides less robust support for familial transmission of OCD. Evidence for familial transmission of OCD was found only when diagnoses were made using information from the affected proband about their relatives. Taken in context of past findings, our own inconsistent results suggest that OCD may be heterogeneous with regard to familial transmission. Also, more careful attention should be paid to the contribution of informant reports, especially from relatives affected by the same disorder.
Normal levels of prepulse inhibition in the euthymic phase of bipolar disorder
Authors: BARRETT SUZANNE LUCIA , KELLY CHRISTOPHER , WATSON DAVID ROBERT , BELL ROBERT , KING DAVID JOHN
Published: July 2005

Background. Deficits in prepulse inhibition (PPI) of the acoustic startle response have been suggested as a potentially useful endophenotype for schizophrenia spectrum disorders and may explain certain symptoms and cognitive deficits observed in the psychoses. PPI deficits have also been found in mania, but it remains to be confirmed whether this dysfunction is present in the euthymic phase of bipolar disorder.

Method. Twenty-three adult patients with DSM-IV bipolar disorder were compared to 20 controls on tests of acoustic startle reactivity and PPI of the startle response. Sociodemographic and treatment variables were recorded and symptom scores assessed using the Hamilton Depression Inventory and the Young Mania Rating Scale.

Results. Overall, the patient and control groups demonstrated similar levels of startle reactivity and PPI, although there was a trend for the inter-stimulus interval to differentially affect levels of PPI in the two groups.

Conclusions. In contrast to bipolar patients experiencing a manic episode, general levels of PPI were normal in this euthymic sample. Further studies are required to confirm this finding and to determine the mechanisms by which this potential disruption/normalization occurs. It is suggested that an examination of PPI in a high-risk group is required to fully discount dysfunctional PPI as a potentially useful endophenotype for bipolar disorder.
Saccadic distractibility is elevated in schizophrenia patients, but not in their unaffected relatives
Authors: MacCABE JAMES H. , SIMON HELEN , ZANELLI JOLANTA W. , WALWYN REBECCA , McDONALD COLM D. , MURRAY ROBIN M.
Published: July 2005

Background. Saccadic distractibility, as measured by the antisaccade task, has attracted attention as a putative endophenotypic marker for schizophrenia. Some studies have suggested that this measure is elevated in the unaffected relatives of schizophrenia patients. However, recent studies have called this into question and the topic remains controversial.

Method. Saccadic distractibility was measured in 53 patients with DSM-IV schizophrenia, 80 unaffected first-degree relatives and 41 unaffected controls.

Results. Schizophrenia patients performed worse than relatives and controls combined (p<0·00001), but relatives did not differ significantly from controls. Performance in multiply affected families was no worse than that in singly affected families. Relatives with a high presumed genetic risk for schizophrenia performed no worse than other relatives. The performance of the patients did not predict that of their relatives.

Conclusions. These results demonstrate that saccadic distractibility is strongly associated with disease status but not with genetic loading for schizophrenia. We conclude that saccadic distractibility is unlikely to be useful as an endophenotypic marker in schizophrenia.
Teaching the use of context to infer meaning: a longitudinal survey of L1 and L2 vocabulary research
Authors: Walters JoDee
Published: July 2005

This article examines research in the area of instruction in the use of context to infer the meanings of unknown words. This issue is addressed initially from a first language perspective, in which approaches to teaching the use of context fall into three broad categories: general strategy instruction, context clue instruction, and the use of cloze exercises to increase awareness of context. Studies in second language vocabulary acquisition and the instruction of context are then examined, and the conclusion is drawn that, while the existing research demonstrates that students benefit from having their attention drawn to the use of context, the question of how, if at all, they should be taught to deal with context is still unanswered. The article concludes with suggestions for the direction and aims of future research in this area.
Modeling glacial‐interglacial changes in global fire regimes and trace gas emissions
Authors: Thonicke Kirsten , Prentice I. Colin , Hewitt Chris
Published: July 2005

Climate at the Last Glacial Maximum (LGM) together with low atmospheric CO2 concentration forced a shift in vegetation zones, generally favored grasses over woody plants and allowed the colonization of continental shelves. Many studies using models and/or palaeo data have focused on reconstructing climate and vegetation changes between LGM and present, but the implications for changes in fire regime and atmospheric chemistry have not previously been analyzed. We have investigated possible global changes in fire regime using climate model simulations of the LGM to drive the Lund‐Potsdam‐Jena Dynamic Global Vegetation Model (LPJ) with its embedded fire model, Glob‐FIRM. Simulation results reveal a pronounced shift of pyrogenic emission sources to lower latitudes. Global total emissions were slightly reduced. Enhanced nitrogen oxides emissions in the tropics could potentially have increased the oxidizing capacity of the atmosphere, helping to explain the low atmospheric methane concentrations during glacial periods as observed in the ice core records.
Nutrient cycling in the Indian sector of the Southern Ocean over the last 50,000 years
Authors: Crosta X. , Shemesh A. , Etourneau J. , Yam R. , Billy I. , Pichon J. J.
Published: July 2005

Most high‐southern latitude records of carbon and nitrogen isotopic ratios and elemental ratios are from the Antarctic and Polar Front zones, thus hindering a comprehensive view of nutrient cycling in the Southern Ocean. We present, for the first time, two records from the Subantarctic Zone and the southern Subtropical Zone of the Indian Ocean. These records provide a latitudinal transect covering the main oceanographic systems of the Southern Ocean. Carbon and nitrogen content of the diatom‐bound organic matter increases during the last glacial in the Antarctic and Subantarctic zones but does not show a clear climate‐related signal in the Subtropical Zone. Comparison of these records with sea‐surface temperatures reconstructed at the core locations and record of dust deposition over Antarctica suggests that eolian iron input possibly switched diatom physiology toward higher carbon to silica and nitrogen to silica uptake and storage south of the Subantarctic Front due to the dependency of photosynthesis on iron concentration levels. Conversely, the northernmost core was too remote from any iron source over the last 50,000 years. Antarctic diatoms therefore have the sole potential to change the nutrient content of the waters escaping from the Southern Ocean, hence providing partial support to the silicic leakage hypothesis as a potential cause of lower glacial atmospheric CO2.
In vitro and in situ gross primary and net community production in the North Pacific Subtropical Gyre using labeled and natural abundance isotopes of dissolved O2
Authors: Juranek L. W. , Quay P. D.
Published: July 2005

We measured gross primary productivity (GPP) in vitro and GPP and net community production (NCP) in situ on four cruises to the Hawaii Ocean Time series (HOT) station ALOHA during 2002–2003. In vitro GPP, determined by 18O labeling, yielded integrated production (0–100 m) that was on average 1.5 times the 14C integrated production. Mean integrated productivity from two winter and two summer cruises was 575 mg C m−2d−1 and 930 mg C m−2d−1, respectively. In situ GPP, determined from the triple‐isotope composition of dissolved O2, averaged 910 mg C m−2d−1 in the winter and 1225 mg C m−2d−1 in the summer/fall, with an uncertainty of ±40%. The NCP/GPP ratio, determined using O2/Ar gas ratio and oxygen isotope measurements, was around 0.1 in the summer, close to the canonical f‐ratio for the open ocean, indicating station ALOHA is a net autotrophic system during summer months. The consistently higher gross carbon production measured by the in situ method, which integrates production over the ∼2‐week residence time of O2 in the mixed layer, suggests that aperiodic bursts of production contribute significantly to time‐averaged mean productivity at station ALOHA.
Saturation of the ionospheric polar cap potential during the October–November 2003 superstorms
Authors: Hairston Marc R. , Drake Kelly Ann , Skoug Ruth
Published: July 2005

The question of whether the cross polar cap potential drop in the Earth's ionosphere saturates under conditions of extreme electric field in the solar wind has been tested observationally during the past several years. The challenge to proving the existence of this phenomenon is that periods of such extreme electric fields in the solar wind are relatively rare. The three superstorms of October and November 2003 provided ideal cases for testing this idea. We first review the earlier evidence of the saturation seen by the DMSP‐F13 spacecraft during the 31 March 2001 superstorm and other storm events during the 1998–2002 time period. Then we present observations from the DMSP‐F13 spacecraft during the October and November 2003 superstorms that show definite evidence of this saturation. In addition, some of the electric fields during these superstorms were almost twice as large as the largest fields previously studied, thus increasing the range of our sample set and further increasing our confidence in the existence of the saturation phenomenon. The data are compared with the saturated potentials predicted by the Hill‐Siscoe model to test its validity. The DMSP measurements indicate that the saturation limit of the cross polar cap is about 260 kV.
Ionospheric disturbances over Alma‐Ata during the October–November 2003 magnetic storms
Authors: Gordienko G. I. , Vodyannikov V. V. , Yakovets A. F.
Published: July 2005

The ionospheric effects of the great geomagnetic storms of 30–31 October and 20–21 November 2003 observed over Alma‐Ata (43.25°N, 76.92°E) were studied experimentally using ground‐based ionosondes. The observations showed a number of unusual (for the Alma‐Ata location) ionospheric phenomena during the active phase of the geomagnetic storms. It is a very high F2 layer (h′F ≥ 490 km), an anomalous formation of the E, E2, and F1 layers at nighttime, and the appearance of auroral‐type sporadic E layers. Processes of interaction of energetic neutrals with the upper atmosphere modeled by Bauske et al. (1997) for magnetically disturbed conditions seem to explain the phenomena of ionization of F1 and E regions at night.
Finite frequency tomography of D″ shear velocity heterogeneity beneath the Caribbean
Authors: Hung Shu‐Huei , Garnero Edward J. , Chiao Ling‐Yun , Kuo Ban‐Yuan , Lay Thorne
Published: July 2005

The shear velocity structure in the lowermost 500 km of the mantle beneath the Caribbean and surrounding areas is determined by seismic tomography applied to a suite of Sd‐SKS, ScS‐S, (Scd + Sbc)‐S, and ScS‐(Scd + Sbc) differential times, where (Scd + Sbc) is a pair of overlapping triplication arrivals produced by shear wave interaction with an abrupt velocity increase at the top of the D″ region. The inclusion of the triplication arrivals in the inversion, a first for a deep mantle tomographic model, is possible because of the widespread presence of a D″ velocity discontinuity in the region. The improved ray path sampling provided by the triplication arrivals yields improved vertical resolution of velocity heterogeneity within and above the D″ region. The reference velocity model, taken from a prior study of waveforms in the region, has a 2.9% shear velocity discontinuity 250 km above the core‐mantle boundary (CMB). Effects of aspherical structure in the mantle at shallower depths than the inversion volume are suppressed by applying corrections for several different long‐wavelength shear velocity tomography models. Born‐Fréchet kernels are used to characterize how the finite frequency data sample the structure for all of the differential arrival time combinations; inversions are performed with and without the kernels. The use of three‐dimensional kernels stabilizes the tomographic inversion relative to a ray theory parameterization, and a final model with 60‐ and 50‐km correlation lengths in the lateral and radial dimensions, respectively, is retrieved. The resolution of the model is higher than that of prior inversions, with 3–4% velocity fluctuations being resolved within what is commonly described as a circum‐Pacific ring of high velocities. A broad zone of relatively high shear velocity material extends throughout the lower mantle volume beneath the Gulf of Mexico, with several percent lower shear velocities being found beneath northern South America. Concentrated low‐velocity regions extend through the D″ layer under the Caribbean, Colombia, and Ecuador, suggestive of small‐scale plumes in the boundary layer and possible lateral variations of the D″ discontinuity. One scenario consistent with the imaged features involves subducted Farallon plate ponding at the base of the mantle and laterally displacing hot boundary layer material that piles up and destabilizes on its margins.
Insights from the Paleogene tropical Pacific: Foraminiferal stable isotope and elemental results from Site 1209, Shatsky Rise
Authors: Dutton Andrea , Lohmann Kyger C , Leckie R. Mark
Published: July 2005

Stable isotope and elemental measurements were conducted on foraminifera from a sequence of calcareous pelagic ooze at Ocean Drilling Program Site 1209 to document the thermal evolution of the North Pacific water column over Shatsky Rise and to address long‐standing questions about the nature of oceanic circulation in the early Paleogene. A major change in seasonality and water column structure in the early Eocene marks a change in tropical Pacific climate and circulation just prior to the early Eocene climatic optimum. Subsequent long‐term cooling is interrupted by a transient positive δ18O excursion identified in planktonic and benthic foraminifera during the late early Eocene that is interpreted as evidence for ephemeral formation of deep water from a low‐latitude, saline source. Paired analysis of benthic Mg/Ca and δ18O was undertaken to assess the relative contribution of temperature and seawater oxygen isotope composition to the benthic δ18O record. Stratigraphic trends of benthic δ18O and Mg/Ca decouple during two intervals in the early Eocene and early middle Eocene. Although variable seawater δ18O is the most likely candidate to explain decoupling of benthic δ18O and Mg/Ca, it is difficult to argue for substantial change in continental ice volume during a presumably ice‐free interval of time.
Shear‐induced roll structure of fog observed by a millimeter‐wave scanning Doppler radar
Authors: Uematsu Akihisa , Yamamoto Masayuki K. , Hashiguchi Hiroyuki , Hirashima Koichi , Fukao Shoichiro
Published: July 2005

Three‐dimensional fog roll structure induced by Kelvin‐Helmholtz instability (KHI) is studied, based on observations made with a millimeter‐wave scanning Doppler radar and a rawinsonde. Roll structure in a fog layer was observed below 150 m altitude when extremely large vertical shear (exceeding 100 m s−1 km−1) existed at 50–60 m altitude. The direction of the shear was perpendicular to the roll direction. The Richardson number was less than 0.25 at the shear altitude, which indicates that the fog roll structure was induced by KHI.
Convective outflow of South Asian pollution: A global CTM simulation compared with EOS MLS observations
Authors: Li Qinbin , Jiang Jonathan H. , Wu Dong L. , Read William G. , Livesey Nathaniel J. , Waters Joe W. , Zhang Yongsheng , Wang Bin , Filipiak Mark J. , Davis Cory P. , Turquety Solene , Wu Shiliang , Park Rokjin J. , Yantosca Robert M. , Jacob Daniel J.
Published: July 2005

A global 3‐D chemical transport model is used to analyze observations of carbon monoxide (CO) and upper tropospheric clouds from the EOS Microwave Limb Sounder (MLS). MLS observations during 25 August–6 September 2004 reveal elevated CO and dense high clouds in the upper troposphere over the Tibetan plateau and southwest China, collocating with the upper level Tibetan anticyclone. Model simulations indicate the transport of boundary layer pollution by Asian summer monsoon (ASM) convection and orographic lifting to the upper troposphere over South Asia, where simulated distributions of CO resemble MLS observations. Model results also show elevated aerosols in the anticyclone region. Analysis of model simulated CO and aerosols indicate that the Tibetan anticyclone could ‘trap’ anthropogenic emissions lifted from northeast India and southwest China. These aerosols may be responsible for the formation of some of the dense high clouds.
Carbon monoxide measured by the EOS Microwave Limb Sounder on Aura: First results
Authors: Filipiak Mark J. , Harwood Robert S. , Jiang Jonathan H. , Li Qinbin , Livesey Nathaniel J. , Manney Gloria L. , Read William G. , Schwartz Michael J. , Waters Joe W. , Wu Dong L.
Published: July 2005

Atmospheric carbon monoxide (CO) is measured by the EOS Microwave Limb Sounder (MLS) on NASA's recently‐launched Aura satellite. Descent has been observed in the 2004–2005 Northern Hemisphere winter polar mesosphere and upper stratosphere. During August and September 2004 enhanced CO was observed in the upper troposphere over India and Tibet. The MLS CO measurements are described and the radiance signal due to the enhanced CO in the upper troposphere is demonstrated.
Numerical studies of fluid leakage from a geologic disposal reservoir for CO2 show self‐limiting feedback between fluid flow and heat transfer
Authors: Pruess Karsten
Published: July 2005

Leakage of CO2 from a hypothetical geologic storage reservoir along an idealized fault zone has been simulated, including transitions between supercritical, liquid, and gaseous CO2. We find strong non‐isothermal effects due to boiling and Joule‐Thomson cooling of expanding CO2. Leakage fluxes are limited by limitations in conductive heat transfer to the fault zone. The interplay between multiphase flow and heat transfer effects produces non‐monotonic leakage behavior.
Pc 1 waves and associated unstable distributions of magnetospheric protons observed during a solar wind pressure pulse
Authors: Arnoldy R. L. , Engebretson M. J. , Denton R. E. , Posch J. L. , Lessard M. R. , Maynard N. C. , Ober D. M. , Farrugia C. J. , Russell C. T. , Scudder J. D. , Torbert R. B. , Chen S.‐H. , Moore T. E.
Published: July 2005

We present observations of Pc 1 waves (∼0.6 Hz) that occurred shortly after a strong (>20 nPa) compression of Earth's magnetosphere at 1321 UT, 18 March 2002. Intense Pc 1 waves were observed at several high‐latitude ground stations in Antarctica and Greenland from 1321 UT to beyond 1445 UT. Two wave bursts were recorded at the Polar satellite at 1338 and 1343–1344 UT as it passed outbound in the Southern Hemisphere at 1154 local time (SM magnetic latitude of −22° and near L = 7.5) in good magnetic conjunction with the Antarctic. The pressure increase created a significant population of protons between a few hundred eV and several keV, whose fluxes were mostly perpendicular to B. These protons seem to have replaced the quiescent stream of protons (presumably convected from the plasma sheet) that existed before this increase. There was also a nearly two‐order‐of‐magnitude increase in the population of thermal/suprathermal (0.32–410 eV) protons. The generation of ion cyclotron waves is expected to limit the proton temperature anisotropy A, defined as T⊥/T∥ − 1. The ion cyclotron instability driven by the observed hot ion temperature anisotropy is studied using two models, with and without the presence of cold background plasma. Peaks in the calculated instability as a function of time show excellent agreement with the times of the Polar wave bursts, which were measured a few tens of seconds after maxima in the instability calculation. The time delay is consistent with the propagation time to the spacecraft from a source nearer to the equatorial plane. The hot proton population at Polar appears to be driven back to stability by a sudden increase in very field‐aligned protons having energies less than the hot perpendicular population, suggesting a different source for the two populations. These observations confirm the importance of both the energization and/or increase in population of protons transverse to B in the several keV range (possibly betatron acceleration as a result of the pressure pulse), and the presence of greatly increased fluxes of lower energy protons (100s of eV to a few keV), predominantly aligned along B, in determining whether the particle population is unstable at a given time.
Passive mechanism of decadal variation of thermohaline circulation
Authors: Sun Liang , Mu Mu , Sun De‐Jun , Yin Xie‐Yuan
Published: July 2005

The decadal variation of thermohaline circulation (THC) is investigated in a simple coupled ocean‐atmospheric two‐box model with the new approach of conditional nonlinear optimal perturbation (CNOP). First, the nonlinear optimal initial perturbations with different constrains are found by this approach. There are two different types of perturbations in the nonlinear regime. One is the freshwater flux perturbation, which is the CNOP of THC and has stronger amplification. The other is salinity flux perturbation, whose amplification is weaker. Freshwater (salt) perturbations weaken (enhance) the mean circulation and hence weaken (enhance) the stability of THC. Second, the passive variabilities of THC are investigated by superposing the initial perturbations to the thermohaline circulation. The passive variabilities found in this model are due to nonnormal and nonlinear growth of initial perturbations. These variabilities, measured as recovering time of perturbations, can cause decadal variability of THC. The results of this paper suggest that CNOP approach is applicable to the investigation of the dependence of the THC sensitivity on the background climate state and is of potential application to the interpretation of past climate change linked to THC variations in nonlinear regime.
Temporal and spatial variation of the drag coefficient of a developing sea under steady wind‐forcing
Authors: Hwang Paul A.
Published: July 2005

Field data indicate convincingly that the drag coefficient of the ocean surface is sea‐state dependent. As a result, under steady forcing by a constant wind velocity the wind stress on the ocean surface varies with time. It also varies with space if the wave development is limited by fetch. A quantitative estimation of the temporal and spatial variation of the wind stress produced by a constant wind velocity is presented. The method of computation combines the duration‐ or fetch‐limited growth functions of wind‐generated waves and the similarity relation of the ocean‐surface drag coefficient derived from wavelength scaling. The only required input is the wind speed. The results indicate that the average momentum flux from atmosphere to ocean is much larger (about 50 to 100 percent higher, and especially for shorter wind events) in comparison with calculations using the drag coefficient or dynamic roughness formulated either without the wave parameters or based on steady state wave conditions.