bluuebunny/crossref_metadata_2025 huggingface dataset:
Ether lipids and analogs in experimental cancer therapy. A brief review of the munich experience
Authors: Berdel Wolfgang E.
Published: December 2006

This review covers the work of our laboratory on the antineoplastic activity of some ethei lipids and derivatives that are related to platelet‐activating factor (PAF). Various 1‐O‐alkyl lysophospholipid derivatives (ALP) show therapeutic activity in mouse transplant tumor models and in metastatic 3‐Lewis lung carcinoma in vivo. However, certain autochthonous mouse leukemias and radiation‐induced lymphomas are resistant to ALP treatment. The therapeutic effects of these compounds are partially due to the activation of cytotoxic macrophages and direct cytotoxicity.

Approximately 20 ether lipids and derivatives were tested for direct cytotoxicity in cells from human solid tumors and leukemias using [3H]thymidine uptake, trypan blue dye exclusion, human tumor clonogenic assays (HTCA) and cell morphology as criteria. Certain ALP, thioether lysophospholipid‐derivatives (TLP), ether0linked lipoidal amines,sn‐2 analogs of PAF, and conjugates of ether lipids and cytosine arabinoside were found cytotoxic in a dose‐ and time‐dependent fashion. Cytotoxicity of some of the ether lipids tested is based on destruction of cell membranes. Structure‐activity studies were performed to better understand the mechanisms leading to accumulation and cytotoxicity of ALP. Comparative studies with normal bone marrow cells and leukemic blasts from humans revealed preferential antileukemic cytotoxity of three ether lipids.
Pregnancy and lactation in a woman with classical galactosaemia heterozygous for p.Q188R and p.R333W
Authors: Ohlsson A. , Nasiell J. , von Döbeln U.
Published: December 2006

A 31‐year old patient who is compound heterozygous for the two galactose‐1‐phosphate uridyltransferase mutations p.Q188R and p.R333W delivered two healthy boys after uneventful spontaneous pregnancies. The patient chose to breast‐feed her first baby and her galactose metabolites in blood and urine were monitored closely. A temporary increase in her galactose‐1‐phosphate (gal‐1‐P) levels with a maximum of 0.30 mmol/L on day 2 after delivery was observed. Galactose‐1‐phosphate was normalized 10 days after delivery. At the time of weaning, 8 months after delivery, her menses returned and she had normal sex steroid levels. She became pregnant again 2 months later. The second baby was also breast‐fed. This time an increase in her gal‐1‐P values could be seen for 3 weeks with a maximum gal‐1‐P level of of 0.25 mmol/L at day 7. Only minor changes in her urine galactitol values were noted during the study period but the values stayed in the range of treated galactosaemia patients. We thus report that breast‐feeding has been possible with only small adverse effects on the levels of galactose metabolites in a patient with classical galactosaemia.
Brief report: Sexual sensation seeking and its relationship to risky sexual behaviour among African‐American adolescent females
Authors: Spitalnick Joshua S. , DiClemente Ralph J. , Wingood Gina M. , Crosby Richard A. , Milhausen Robin R. , Sales Jessica M. , McCarty Frances , Rose Eve , Younge Sinead N.
Published: December 2006

The relationship between sexual sensation seeking and sexual risk taking has been investigated among adult populations. There are limited data, however, regarding this relationship for adolescents. Since African‐American adolescent females continue to be disproportionately diagnosed with STDs, including HIV, we examined this association among a clinic‐based sample of African‐American adolescent females (N=715) enrolled in an STD/HIV prevention intervention. Participants (ages 15–21) endorsing higher levels of sexual sensation seeking reported higher levels of sexual risk‐taking behaviours (e.g. frequency of vaginal intercourse, number of sexual partners, and poorer condom use). Results remained significant after controlling for known covariates associated with sexual risk‐taking behaviours. Results are consistent with the adult literature and highlight the need for future investigations examining sexual sensation seeking among adolescents. These results, though preliminary, could be used to better inform prevention interventions and clinicians/health educators who provide direct services to adolescents.
The intracellular localisation and mobility of Type Iγ phosphatidylinositol 4P 5‐kinase splice variants
Authors: Giudici Maria-Luisa , Lee Koon , Lim Rongxuan , Irvine Robin F.
Published: December 2006

There are three known splice variants of Type Iγ phosphatidylinositol 4‐phosphate 5‐kinase (PIPkin Iγ): PIPkins Iγ87, Iγ90, and the most recently cloned (Giudici, M.L., Emson, P.C. and Irvine, R.F. (2004) A novel neuronal‐specific splice variant of Type I phosphatidylinositol 4‐phosphate 5‐kinase isoform gamma. Biochem. J. 379, 489–496) PIPkin IγC (here called PIPkin Iγ93). Here, we have explored the subcellular localisation and mobility of Type I PIPkins in transfected cells by confocal microscopy and flourescence recovery after photobleaching. The unique behaviour shown by PIPkin Iγ93 is consistent with its suggested distinct function. Moreover, the markedly different localisation and mobility of active versus inactive PIPkin Iγ93 provide insights into the factors that dictate cellular targeting of Type Iγ PIPkins.
On the interplay of gene positioning and the role of rho‐independent terminators in Escherichia coli
Authors: Yachie Nozomu , Arakawa Kazuharu , Tomita Masaru
Published: December 2006

The majority of intrinsic rho‐independent terminator signals, reported to consist of stable hairpin structures followed by T‐rich regions, possess the potential to operate bi‐directionally and to induce transcription terminations on both strands of the DNA duplex in Escherichia coli. By using RNAMotif software, we investigated the distributions of termination motifs around the 3′‐ends of overlapping and non‐overlapping genes at the genomic level. We suggest that the positions of compactly encoded E. coli genes and rho‐independent terminators are optimized to terminate the adjoining genes on their antisense strands efficiently, and not to mis‐terminate overlapping transcripts, due to their bi‐directional properties.
Experimental verification of the acoustic characteristics of the clupeoid diel cycle in the Baltic
Authors: Orlowski Andrzej
Published: December 2006

This paper describes the results of a short-term experiment using measurements of sv from the diel, spatial, clupeoid distribution in the southern Baltic. The aim of the experiment was to verify fish-behaviour characteristics measured over the period from 1995 to 2001. It was also intended to estimate the dynamics of fish behaviour over one separate diel cycle. The studies were based on a 24 h continuous integration of fish echoes using an EY500 echosounder at 38 kHz. Measurements were carried out by RV “Baltica” travelling along the sides of a square of 4 nautical miles at a constant speed of 8 knots. The South Gotland Deep was chosen for the experiment because of the greatest amplitude there of fish vertical, diel migrations within the Polish EEZ. The duration of the experiment was limited by weather conditions, but nearly 300 EDSU samples were collected. 3-D distributions of echoes were correlated to the values of coincident environmental factors of time, depth, water temperature, salinity, and oxygen level. Fish distribution compared with environmental factors is described by different macrosounding visualizations, statistical, and mathematical models. Measurements are compared with the average characteristics of fish behaviour based on data from the autumn acoustic studies between 1995 and 2001 in a wider environment of the Gotland Deep. The results strongly confirmed the instability of the diel acoustic response of fish echoes in both situations. More precise measurements during the experiment indicated the biggest column-scattering strength (Svc) increase during the sunrise period, appearing simultaneously in the whole area. A similar increase was detected by analysis of 1995–2001 data from the South Gotland Deep environment. Major emphasis is given to the explanation of the diel irregularities. Diel instability of fish acoustic response can significantly effect the results of target-strength measurements (up to 400% during the sunrise) and, as a consequence, the calibration of acoustic fish stock-assessment models.
Fish behaviour and orientation-dependent backscatter in acoustic Doppler profiler data
Authors: Zedel Len , Patro Ranjan , Knutsen Tor
Published: December 2006

It is well known that fish target strength can be affected by fish behaviour. In particular, the specific orientation between a target (fish) and an echosounder system is critical in interpreting the apparent target strength. This situation is further complicated for Doppler current-profiler systems that have an array of diverging beams and where each beam will interact with targets with a different orientation. When targets themselves have random orientations, each beam will see the same range of target strengths and the average values would be the same. However, if targets such as schooling fish have a preferred orientation, then an asymmetry is present and different target strengths can be expected. This hypothesis is explored using observations of Norwegian spring-spawning herring (Clupea harengus) under a variety of schooling conditions. When schooling fish are migrating and have well-defined, coherent orientations, differences in backscatter strength of about 5 dB can be seen depending on beam orientation. This difference disappears when fish are not actively migrating and so do not have coherent orientation. These differences can be used to infer behaviour of schooling fish but they also indicate that caution must be exercised when averaging backscatter data from separate Acoustic Doppler Current Profiler (ADCP) beams.
RUTA LAMARMORAE (RUTACEAE), A NEW SPECIES FROM SARDINIA
Authors: BACCHETTA G. , BRULLO S. , DEL GALDO G. GIUSSO
Published: December 2006

A new species from Sardinia occurring on the Gennargentu massif, Ruta lamarmorae (Rutaceae), is described and illustrated. Its relationships with R. corsica, a species widespread in the Corsican mountains, are examined.
A REVISION OF PHELLODENDRON (RUTACEAE)
Authors: MA JINSHUANG , CAO WEI , LIU QUANRU , YU MING , HAN LIJUAN
Published: December 2006

The genus Phellodendron (Rutaceae) is revised. This work is based on herbarium collections and field observations in eastern Asia. Two species are recognized: Phellodendron amurense Rupr. and Phellodendron chinense C.K.Schneid. All other specific and infraspecific names published in the genus are reduced to synonymy or excluded from the genus. Detailed morphology, character variability, an identification key, a distribution map, line drawings, and taxonomic treatments and lists of specimens examined are provided.
FLORISTICS OF THE HERBACEOUS AND SUBSHRUB LAYER OF A MOIST GRASSLAND IN THE CERRADO BIOSPHERE RESERVE (ALTO PARAÍSO DE GOIÁS), BRAZIL
Authors: MUNHOZ C. B. R. , FELFILI J. M.
Published: December 2006

The floristic composition of campo limpo úmido, a moist savanna grassland vegetation of the cerrado biome, is still little described, even though its herbs and subshrubs form a major component of the cerrado vegetation. The objective of this study was to characterize the floristic richness of the herbaceous and subshrub layer of a moist grassland at the Água Fria Farm, Alto Paraíso, Goiás State (14°04′8.83″S, 47°30′33.1″W). The principal use of such grasslands is to graze cattle; in addition, local people collect vast numbers of selected species of wild plants to sell for the decorative dried plant trade, or for their medicinal qualities. Little is known, however, about the sustainability of this extractivism. A survey of a 21 ha area, with intensive quarterly collections of herbarium specimens, was made from April 2000 to March 2001. Despite the small size of the study site it proved to be very rich floristically. A total of 207 species in 90 genera and 33 families was registered in the area. Thirty-one species not yet recorded in the checklist of the flora of the cerrado biome were found in this study, plus three that seem to be new to science. The richest families were Cyperaceae (30 species), Poaceae (28), Xyridaceae (23), Eriocaulaceae (20), Asteraceae (18), and Orchidaceae and Melastomataceae with 10 species each. These results suggest the need for more research on the moist grassland to provide overall estimates for the plant species richness of this widespread vegetation type and as a basis to help guide conservation and management policies.
MOLECULAR PHYLOGENY AND CHARACTER EVOLUTION OF DIDYMOCARPUS (GESNERIACEAE) IN THAILAND
Authors: PALEE P. , DENDUANGBORIPANT J. , ANUSARNSUNTHORN V. , MÖLLER M.
Published: December 2006

Until recently the genus Didymocarpus Wall. (Gesneriaceae) was used in an unwarrantably wide sense and included more than 180 species. It has now been remodelled and restricted to around 70 species. Of these, 18 species and one variety are known to occur in Thailand. To clarify the relationships among Thai species of Didymocarpus we sequenced the internal transcribed spacers (ITS) of nuclear ribosomal DNA (nrDNA) from a sample of 23 taxa, including 15 from Thailand, four from China, three from Malaysia and one from Bhutan. Seventeen morphological characters were coded for all 23 taxa and optimized onto a retention index (RI) reweighted maximum parsimony (MP) tree. The phylogenetic analyses suggested that Didymocarpus taxa formed a strongly supported monophyletic clade, with several supported subclades. The combination of molecular phylogeny and optimization of morphological characters suggests the presence of three distinct groups: the first, corresponding to Didymocarpus sect. Elati Ridl., includes plants with tall stems, yellow or white flowers and one-celled conoid or two-celled headed pigment glands; the other two groups, which represent Didymocarpus sect. Didymocarpus, both contain plants with dwarfed stems and violet or purple flowers, but are distinguished by the presence of both four-celled conoid or onecelled globose glands in one, and the absence in the other. Optimization of geographical locality onto the phylogeny led us to propose the hypothesis that, based on this sample, the geographical origin of Didymocarpus is the Malay Peninsula, and the ancestral corolla colour is white/yellow. Subsequent dispersal northward through southern and northern Thailand to China and Bhutan was accompanied by the evolution of a purple/violet corolla colour.
OBSERVATIONS ON THE VEGETATION OF NORTHEASTERN MATO GROSSO, BRAZIL. IV. AN ANALYSIS OF THE CERRADO–AMAZONIAN FOREST ECOTONE
Authors: MARIMON B. S. , DE S. LIMA E. , DUARTE T. G. , CHIEREGATTO L. C. , RATTER J. A.
Published: December 2006

A study was made of the transition between the cerrado and Amazonian forest biomes on the Serra do Roncador in the northeast of Mato Grosso State, Brazil. The transition was sampled by recording the species and circumference at breast height (cbh) of all woody species ≥ 15 cm cbh on five 20 × 10 m plots in each of the following four communities: ecotonal vegetation (Cerradão areas 1 and 2), and forest (Forest areas 1 and 2); while in the Cerrado sensu stricto a more rapid method had to be used because of time constraints. A total of 138 species was recorded and the results were analysed using Sørensen and Morisita Indices, TWINSPAN and DCA. In addition, comparisons were made with data from studies undertaken in 1968 in the same area by the Xavantina-Cachimbo Expedition. No species was common to all communities sampled but a seral succession of important species occurs along the transition. The Sørensen and Morisita Indices demonstrate this, with the Cerrado s.s. and Forest 2 at the two extremes showing no species in common (zero similarity) and Cerradão 1 and 2 giving the very high figures of Sørensen 0.64 and Morisita 0.84. The ecotonal cerradão is a very characteristic Dystrophic facies cerradão with Hirtella glandulosa, Emmotum nitens, Sclerolobium paniculatum and Vochysia haenkeana as its typical indicator species. The ecotone studied in the present work represents the comparatively abrupt transition from cerrado to the peripheral form of Amazonian forest (dry forest, mata seca) on flat terrain with a uniform very dystrophic soil. Other workers have suggested that this type of transition may be restricted to the headwaters of the Xingu basin, but one of the present authors has seen similar vegetation at localities in Maranhão, Rondônia, and on the Mato Grosso–Rondônia border. Comparison of the present vegetation with the survey made in 1968 shows that in this area the advancing face of the Amazonian forest has extended about 7 km southwards into the cerrado. However, in the majority of places this process has been obscured by forest clearing for agriculture. The study draws attention to the urgent need for the establishment of conservation areas in this extremely threatened and very little studied ecotone.
FOUR NEW SPECIES OF BEGONIA (BEGONIACEAE) FROM SULAWESI
Authors: HUGHES M.
Published: December 2006

Four new species of Begonia (Begoniaceae) are described from the Indonesian island of Sulawesi. All four species (Begonia chiasmogyna M.Hughes, Begonia macintyreana M.Hughes, Begonia mendumae M.Hughes and Begonia stevei M.Hughes) belong to Begonia section Petermannia, and they increase the number of Begonia species known from the island to 30.
NEW HIGHER TAXA OF COMPLEX THALLOID LIVERWORTS (MARCHANTIOPHYTA – MARCHANTIOPSIDA)
Authors: LONG D. G.
Published: December 2006

Recent studies on molecular phylogeny of complex thalloid liverworts (Marchantiopsida) have revealed the need to recognize four new higher taxa: Family Neohodgsoniaceae, Order Neohodgsoniales, Order Lunulariales and Family Dumortieraceae. These are formally described along with notes on their differences from other complex thalloid liverworts.
A PRELIMINARY CHECKLIST OF THE VASCULAR PLANTS OF THE CHIQUIBUL FOREST, BELIZE
Authors: BRIDGEWATER S. G. M. , HARRIS D. J. , WHITEFOORD C. , MONRO A. K. , PENN M. G. , SUTTON D. A. , SAYER B. , ADAMS B. , BALICK M. J. , ATHA D. H. , SOLOMON J. , HOLST B. K.
Published: December 2006

Covering an area of 177,000 hectares, the region known within Belize as the Chiquibul Forest comprises the country's largest forest reserve and includes the Chiquibul Forest Reserve, the Chiquibul National Park and the Caracol Archaeological Reserve. Based on 7047 herbarium and live collections, a checklist of 1355 species of vascular plant is presented for this area, of which 87 species are believed to be new records for the country. Of the 41 species of plant known to be endemic to Belize, four have been recorded within the Chiquibul, and 12 species are listed in The World Conservation Union (IUCN) 2006 Red List of Threatened Species. Although the Chiquibul Forest has been relatively well collected, there are geographical biases in botanical sampling which have focused historically primarily on the limestone forests of the Chiquibul Forest Reserve. A brief review of the collecting history of the Chiquibul is provided, and recommendations are given on where future collecting efforts may best be focused. The Chiquibul Forest is shown to be a significant regional centre of plant diversity and an important component of the Mesoamerican Biological Corridor.
Increases in Arousal Are Associated with Reductions in the Human Nociceptive Flexion Reflex Threshold and Pain Ratings
Authors: Edwards Louisa , Ring Christopher , McIntyre David , Carroll Douglas , Clarke Richard , Webb Oliver , Martin Una
Published: December 2006

The nociceptive flexion reflex has been regarded as an objective correlate of pain perception. This study examined whether the nociceptive flexion reflex is modulated by physiological arousal in the same manner as pain. Cardiovascular activity, nociceptive flexion reflex thresholds, and pain ratings were measured in 40 healthy adults under three conditions that demanded varying degrees of physiological arousal: Rest, number repetition, and mental arithmetic. Heart rates were faster and R-wave to pulse intervals shorter during mental arithmetic than number repetition, whereas heart rates were slower and R-wave to pulse intervals longer during rest compared to number repetition. Both mental arithmetic and number repetition were associated with reduced nociceptive flexion reflex thresholds compared to rest. Although the nociceptive flexion reflex thresholds were the same during mental arithmetic and number repetition, pain ratings were lower during mental arithmetic than number repetition and rest. The results indicate that nociception was facilitated but pain was inhibited by increased physiological arousal. This dissociation suggests that the nociceptive flexion reflex threshold is not a suitable correlate of pain during states of increased arousal.
Impact of Low-Frequency Transcranial Magnetic Stimulation on Brain Automatic Information Processing
Authors: Laloyaux O. , Ansseau M. , Hansenne M.
Published: December 2006

Repetitive transcranial magnetic stimulation (rTMS) is considered a powerful method for the study of the relationships between cortical activity and cognitive processes. Previous ERPs studies that focused on P300 response have shown that inhibitory/excitatory effects on prefrontal cortex (PFC), induced by low- and high-frequency rTMS, were able to modulate controlled but not automatic information processing. The present study assessed the impact of inhibition over left and right PFC induced by rTMS on mismatch negativity (MMN), which is known to represent automatic cerebral processes for detecting change. Auditory MMN was recorded in 20 subjects before and after application of left and right PFC 1-Hz rTMS for 15 min. MMN was also recorded before and after a sham-occipital 1-Hz rTMS as control condition. Results showed that 1-Hz rTMS induced no modification to either MMN latency or amplitude. In addition, N100 and P200 components to the frequent tones were not affected by rTMS. These results are consistent with previous findings showing that rTMS over both PFC is unable to disrupt automatic information processing. However, since two sites were stimulated in the present study, no definite conclusions about the inability of rTMS to disrupt automatic processing can be made.
Cardiovascular Measures of Attention to Illusory and Nonillusory Visual Stimuli
Authors: Wetzel Jacob M. , Quigley Karen S. , Morell Jill , Eves Elizabeth , Backs Richard W.
Published: December 2006

This study was an extension of the Berntson, Cacioppo, and Fieldstone (1996) study that found that attending to visual illusions presented with text (usually a question directing attention to the illusory property) lengthened heart period via uncoupled vagal activation. Eighty participants were assigned to one of four groups that received either the original Berntson et al. illusions or a modification formed by the factorial combination of whether the illusion and its related text were present or absent. Participants also performed the same serial-subtraction mental-arithmetic task from Berntson et al. During the mental-arithmetic task heart period (HP) shortened, respiratory sinus arrhythmia (RSA) was reduced, and preejection period (PEP) shortened, which indicated a reciprocally coupled sympathetic activation and parasympathetic inhibition mode of cardiac control. Although idiographic analyses found this to be the most common control mode, all other modes were also obtained – especially the nonreciprocal modes of coactivation and coinhibition. During the visual task, PEP lengthened for all groups indicating uncoupled sympathetic inhibition while attending to the stimuli; however, HP differed depending upon the illusion factor. HP lengthened when illusions were absent, but unlike Berntson et al. it shortened when illusions were present. Idiographic analyses found that although most participants showed sympathetic inhibition, approximately equal numbers of participants showed parasympathetic activation and inhibition. Variation in response stereotypy may mask cardiac responses elicited by subtle cognitive phenomena such as the processing of visual illusions, especially in passive viewing tasks. We also suggest that individual differences in mental effort needed to integrate top-down and bottom-up perceptual processes, or personality variables such as the need for cognition, may contribute to response variability in the visual task.
The Impact of Workload on Heart Rate and Blood Pressure in En-Route and Tower Air Traffic Control
Authors: Vogt Joachim , Hagemann Tim , Kastner Michael
Published: December 2006

This paper reports three studies on the application of ambulatory monitoring in air traffic control (ATC). The aim of the first study was to explore a set of psychophysiological measures with respect to ATC workload sensitivity and feasibility at the workplace. Nearly all physiological measures showed the expected changes during work. Significant positive correlations were found between cardiovascular responses and the number of aircraft under control, especially heavy, fast, climbing, and descending aircraft. The following en-route (Study 2) and tower (Study 3) simulations identified the relative impact of air traffic features. Heart rate, systolic blood pressure, self-reported concentration, and upset were significantly higher in the simulations with 12 aircraft continuously under control compared to only 6. A high versus low number of potential conflicts between aircraft in the en-route setting (Study 2) also caused significant increases of heart rate, systolic blood pressure, self-reported concentration, and upset. On the basis of these results, a new workload model for air traffic controllers was suggested and implemented.
A numerical study of the upwelling circulation off central Chile: Effects of remote oceanic forcing
Authors: Leth Ole , Middleton John F.
Published: December 2006

A numerical ocean model is used to study the upwelling circulation off central Chile in response to local winds and remote forcing. In an idealized study of equatorial‐forced, intraseasonal variability (period of 50 days), a first mode coastal trapped wave (CTW) paddle is applied to the northern boundary with coastal sea level amplitude of 12 cm. Without this CTW forcing, the steady seasonal winds upwell undercurrent water from depths of 250–320 m to depths of 180–250 m. The subsequent formation of mesoscale and headland eddies drive this water into the Gulf of Arauco and to depths of 50–120 m. With the CTW paddle, the circulation is strongly modified. The mesoscale and headland eddies reform during the CTW upwelling phase. During the CTW upwelling phase, the upwelling over winds and eddies is enhanced by up to 40 m on the shelf. Model simulations are undertaken using realistic winds and a CTW paddle modulated by observed sea level. Without CTW forcing included in the model the agreement with data is poor. In the Gulf of Arauco area the variability of alongshore currents below 130 m is dominated by CTW activity. Above 130 m, wind‐driven current variability dominates. In agreement with the idealized CTW analysis, water is found to be upwelled from depths of 320 m to 100 m or less, and 10°C undercurrent water is found at the surface and within the Gulf.
Observational evidence of a hemispheric‐wide ice–ocean albedo feedback effect on Antarctic sea‐ice decay
Authors: Nihashi Sohey , Cavalieri Donald J.
Published: December 2006

The effect of ice–ocean albedo feedback (a kind of ice‐albedo feedback) on sea‐ice decay is demonstrated over the Antarctic sea‐ice zone from an analysis of satellite‐derived hemispheric sea ice concentration and European Centre for Medium‐Range Weather Forecasts (ERA‐40) atmospheric data for the period 1979–2001. Sea ice concentration in December (time of most active melt) correlates better with the meridional component of the wind‐forced ice drift (MID) in November (beginning of the melt season) than the MID in December. This 1 month lagged correlation is observed in most of the Antarctic sea‐ice covered ocean. Daily time series of ice concentration show that the ice concentration anomaly increases toward the time of maximum sea‐ice melt. These findings can be explained by the following positive feedback effect: once ice concentration decreases (increases) at the beginning of the melt season, solar heating of the upper ocean through the increased (decreased) open water fraction is enhanced (reduced), leading to (suppressing) a further decrease in ice concentration by the oceanic heat. Results obtained from a simple ice–ocean coupled model also support our interpretation of the observational results. This positive feedback mechanism explains in part the large interannual variability of the sea‐ice cover in summer.
Propagation of signals in basin‐scale ocean bottom pressure from a barotropic model
Authors: Stepanov Vladimir N. , Hughes Chris W.
Published: December 2006

The exchange of atmospheric plus oceanic mass between ocean basins is investigated using a global barotropic ocean model. We find two particular cases of exchange between two basins. At periods of 4–6 days, the exchange is between the Atlantic and Pacific basins, and represents a known oscillation forced by atmospheric pressure. This mode represents a failure of the inverse‐barometer relationship due to the large scale and high frequency of atmospheric forcing, and the presence of continents. Significant exchange between Atlantic and Pacific also occurs at longer periods. The second case is most prominent at periods longer than 30 days (strongest at periods longer than 100 days), and represents a mass exchange between the Southern Ocean and the Pacific. The Southern Ocean part of this exchange is clearly related to the Southern Mode of fluctuations in Antarctic circumpolar transport, forced by Southern Ocean wind stress. The reason for the exchange being with the Pacific rather than other basins is explored, and is found to be related to the balance of wind stress by form stress in Drake Passage: exchange with the Atlantic and Indian oceans becomes dominant if Drake Passage topography is removed. While recognizing the limitations of a barotropic model, we contend that it is necessary to understand the barotropic adjustment process in order to make sense of longer timescale processes. Accordingly, we end with speculation on the possible importance of the barotropic results for global sea level and tropical dynamics.
A system analysis approach for atmospheric observations and models: Mesospheric HOx dilemma
Authors: Smith Gregory P. , Frenklach Michael , Feeley Ryan , Packard Andrew , Seiler Peter
Published: December 2006

A systematic consistency analysis and optimization procedure is applied to models of representative ozone, OH, and HO2 observations in the mesosphere and upper stratosphere. The approach considers both measurement and rate parameter uncertainties. The results show some data point inconsistencies and the inability of the accepted photochemical mechanism to predict observations without unfavored large alterations of many rate constants from their consensus values. Optimization results do favor larger rate constants for OH + O and photolytic ozone and OH production.
On the importance of the decay of 234Th in determining size‐fractionated C/234Th ratio on marine particles
Authors: Cai Pinghe , Dai Minhan , Chen Weifang , Tang Tiantian , Zhou Kuanbo
Published: December 2006

Accurate determination of the POC/234Th ratio on sinking particles is essential for the application of 234Th as a proxy for the export of particulate organic carbon (POC) from the upper ocean. Previous studies have shown that POC/234Th ratios may vary by as much as two orders of magnitude, but the mechanism for this variability remains poorly understood. In this study, POC/234Th and POC/228Th ratios in three particle size classes were examined for samples collected from the upper 500 m at a station in the South China Sea. Our results indicate that changes in the POC/234Th ratio with particle size at a given depth are mostly driven by simple decay of 234Th. In fact, various trends in the POC/234Th ratio versus particle size are explained by a combination of 234Th decay and the preferential remineralization of POC relative to Th during particle aggregation. We also observed a trend of decreasing 234Th/228Th ratios with particle size. This trend is consistent with results expected from a Brownian‐pumping model.
Possible linkages of late‐Holocene drought in the North American midcontinent to Pacific Decadal Oscillation and solar activity
Authors: Tian Jian , Nelson David M. , Hu Feng Sheng
Published: December 2006

Paleorecords are key for evaluating the long‐term patterns and controls of drought. We analyzed calcite in annually laminated sediments from a Minnesota lake for oxygen‐isotopic composition (δ18O). The δ18O record of the past ∼3100 years reveals that droughts of greater severity and duration than during the 20th century occurred repeatedly, especially prior to 300 AD. Drought variability was anomalously low during the 20th century; ∼90% of the variability values during the last 3100 years were greater than the 20th‐century average. δ18O is strongly correlated with the index of the Pacific Decadal Oscillation (PDO) during the past 100 years, and periodicities of the late‐Holocene δ18O record are similar to those of the PDO. Furthermore, time series of δ18O and atmospheric Δ14C are generally coherent after 700 AD. Both the Pacific climate and solar irradiance probably played a role in drought occurrence, but their effects were non‐stationary through the late Holocene.
Interaction between forearc and oceanic plate at the south‐central Chilean margin as seen in local seismic data
Authors: Haberland C. , Rietbrock A. , Lange D. , Bataille K. , Hofmann S.
Published: December 2006

We installed a dense, amphibious, temporary seismological network to study the seismicity and structure of the seismogenic zone in southern Chile between 37° and 39°S, the nucleation area of the great 1960 Chile earthquake. 213 local earthquakes with 14.754 onset times were used for a simultaneous inversion for the 1‐D velocity model and precise earthquake locations. Relocated artificial shots suggest an accuracy of the earthquake hypocenter of about 1 km (horizontally) and 500 m (vertically). Crustal events along trench‐parallel and transverse, deep‐reaching faults reflect the interseismic transpressional deformation of the forearc crust due to the subduction of the Nazca plate. The transverse faults seems to accomplish differential lateral stresses between subduction zone segments. Many events situated in an internally structured, planar seismicity patch at 20 to 40 km depth near the coast indicate a stress concentration at the plate's interface at 38°S which might in part be induced by the fragmented forearc structure.
Density functional study of vibrational and thermodynamic properties of ringwoodite
Authors: Yu Yonggang G. , Wentzcovitch Renata M.
Published: December 2006

Phonon dispersions and vibrational density of states (VDoS) of Mg2SiO4 ringwoodite have been calculated by first principles as a function of pressure up to 30 GPa using density functional perturbation theory. The predicted zone center frequencies are in close correspondence with existing Raman and infrared experimental data. The pressure dependence of phonon frequencies is linear and agrees well with experiments. The calculated VDoS has then been used in conjunction with the quasi‐harmonic approximation to compute the Helmholtz free energy and thermodynamic properties, most of which agree very well with experiments.
Contribution of ion‐induced nucleation to new particle formation: Methodology and its application to atmospheric observations in Boulder, Colorado
Authors: Iida Kenjiro , Stolzenburg Mark , McMurry Peter , Dunn Matthew J. , Smith James N. , Eisele Fred , Keady Pat
Published: December 2006

This paper investigates the role of ion‐induced nucleation (IIN) in new particle formation events observed near ground level at a sampling site located near Boulder, Colorado (14 March 2004 to 27 October 2005). Measurements of mobility distributions of small and intermediate ions (0.4–6.3 nm), size distributions of total particles (3 nm to 5 μm), and charged fractions (2.5–25 nm) were carried out. The relative contributions of neutral nucleation and IIN were inferred using both qualitative and quantitative analyses. First, a simple theoretical analysis is performed to show what can be learned about the initial charge state of the nucleated particles from charged fractions measured after they had grown to 3.0–5.5 nm. We found that for much of our data the charge fractions of freshly nucleated particles below 5 nm were significantly below stationary‐state values, and that this tendency increased with decreasing size, indicating that neutral nucleation was dominant. However, the data also show that there were occasionally asymmetries between negative and positive charge fractions that we could not explain unless positive or negative IIN occurred to some extent. A quantitative analysis is then performed to estimate the fractional contribution of positive and negative IIN to new particle formation rates for each nucleation event observed during this period. The results show the average contribution of IIN is about 0.5% for both polarities indicating that IIN was a relatively insignificant contributor to new particle formation in this study. This result is consistent with the direct mass spectrometric measurements of sulfuric acid ion cluster compositions and concentrations performed at the same measurement site.
Trajectory model validation using newly developed altitude‐controlled balloons during the International Consortium for Atmospheric Research on Transport and Transformations 2004 campaign
Authors: Riddle Emily E. , Voss Paul B. , Stohl Andreas , Holcomb Daniel , Maczka Darren , Washburn K. , Talbot Robert W.
Published: December 2006

During the summer of 2004, five altitude‐controlled tracking balloons were flown as part of the International Consortium for Atmospheric Research on Transport and Transformations (ICARTT) campaign. These Controlled Meteorological (CMET) balloons, newly developed at the University of Massachusetts, are notable for their light weight (∼1 kg mass), efficient altitude control, ease of launch, long‐duration flight capability, and ability to perform repeated quasi‐Lagrangian soundings. The balloons were embedded in urban plumes from New York and Boston which they tracked over New England, eastern Canada, and the Atlantic Ocean while maintaining a nearly constant altitude. The flights ranged from 10 to 111 hours and covered a maximum distance of 3000 km. Balloon flight tracks are used here to assess the accuracy of trajectory models during intensive aircraft sampling periods. A new method is presented for increasing the number of available reference trajectories by dividing the balloon flights into shorter segments for statistical analysis. For trajectory durations between 2 and 12 hours, mean trajectory errors are found to be approximately 26% and 34% of the flight distance for ECMWF‐based and GFS‐based trajectories, respectively. Anomalously large model errors observed during three of the flights are found to be the result of a narrow low‐level jet (15 July) and synoptic‐scale flow patterns (9 and 10 August). The results from this study should be useful to researchers evaluating the performance of trajectory models and chemical transport models during the ICARTT campaign. Complete CMET balloon and model trajectory data sets are available as a supplement to this paper.
Establishing Lagrangian connections between observations within air masses crossing the Atlantic during the International Consortium for Atmospheric Research on Transport and Transformation experiment
Authors: Methven J. , Arnold S. R. , Stohl A. , Evans M. J. , Avery M. , Law K. , Lewis A. C. , Monks P. S. , Parrish D. D. , Reeves C. E. , Schlager H. , Atlas E. , Blake D. R. , Coe H. , Crosier J. , Flocke F. M. , Holloway J. S. , Hopkins J. R. , McQuaid J. , Purvis R. , Rappenglück B. , Singh H. B. , Watson N. M. , Whalley L. K. , Williams P. I.
Published: December 2006

The ITCT‐Lagrangian‐2K4 (Intercontinental Transport and Chemical Transformation) experiment was conceived with an aim to quantify the effects of photochemistry and mixing on the transformation of air masses in the free troposphere away from emissions. To this end, attempts were made to intercept and sample air masses several times during their journey across the North Atlantic using four aircraft based in New Hampshire (USA), Faial (Azores) and Creil (France). This article begins by describing forecasts from two Lagrangian models that were used to direct the aircraft into target air masses. A novel technique then identifies Lagrangian matches between flight segments. Two independent searches are conducted: for Lagrangian model matches and for pairs of whole air samples with matching hydrocarbon fingerprints. The information is filtered further by searching for matching hydrocarbon samples that are linked by matching trajectories. The quality of these “coincident matches” is assessed using temperature, humidity and tracer observations. The technique pulls out five clear Lagrangian cases covering a variety of situations and these are examined in detail. The matching trajectories and hydrocarbon fingerprints are shown, and the downwind minus upwind differences in tracers are discussed.
Epigenetic mechanisms governing seed development in plants
Authors: Köhler Claudia , Makarevich Grigory
Published: December 2006

Seed development in flowering plants is initiated by the fusion of two male gametes with two female gametes—the egg cell and the central cell—which leads to the formation of an embryo and an endosperm, respectively. Fertilization‐independent seed formation is actively repressed by the FERTILIZATION‐INDEPENDENT SEED (FIS) Polycomb group (PcG) proteins, an evolutionarily conserved class of proteins that ensures the stable transmission of developmental decisions. The FIS proteins act together in a complex and modify their target genes by applying repressive methylation on histone H3 lysine 27. In addition to its function before fertilization, the FIS complex restricts endosperm proliferation. This function is likely to be achieved by imprinting the maternal alleles of FIS target genes. However, imprinting in the endosperm is controlled not only by the FIS complex but also by DNA methylation, and the interconnections between these two processes are now being investigated.
Genome‐wide natural antisense transcription: coupling its regulation to its different regulatory mechanisms
Authors: Lapidot Michal , Pilpel Yitzhak
Published: December 2006

Many genomic loci contain transcription units on both strands, therefore two oppositely oriented transcripts can overlap. Often, one strand codes for a protein, whereas the transcript from the other strand is non‐encoding. Such natural antisense transcripts (NATs) can negatively regulate the conjugated sense transcript. NATs are highly prevalent in a wide range of species—for example, around 15% of human protein‐encoding genes have an associated NAT. The regulatory mechanisms by which NATs act are diverse, as are the means to control their expression. Here, we review the current understanding of NAT function and its mechanistic basis, which has been gathered from both individual gene cases and genome‐wide studies. In parallel, we survey findings about the regulation of NAT transcription. Finally, we hypothesize that the regulation of antisense transcription might be tailored to its mode of action. According to this model, the observed relationship between the expression patterns of NATs and their targets might indicate the regulatory mechanism that is in action.
High magnetic field generation for laser-plasma experiments
Authors: Pollock B. B. , Froula D. H. , Davis P. F. , Ross J. S. , Fulkerson S. , Bower J. , Satariano J. , Price D. , Krushelnick K. , Glenzer S. H.
Published: December 2006

An electromagnetic solenoid was developed to study the effect of magnetic fields on electron thermal transport in laser plasmas. The solenoid, which is driven by a pulsed power system supplying 30 kJ, achieves magnetic fields of 13 T. The field strength was measured on the solenoid axis with a magnetic probe and optical Zeeman splitting. The measurements agree well with analytical estimates. A method for optimizing the solenoid design to achieve magnetic fields exceeding 20 T is presented.
Magnetization processes in hard Co-rich Co–Pt films with perpendicular anisotropy
Authors: Ghidini M. , Zangari G. , Prejbeanu I. L. , Pattanaik G. , Buda-Prejbeanu L. D. , Asti G. , Pernechele C. , Solzi M.
Published: December 2006

We present a study of the magnetic properties and magnetization processes in hard Co-Pt (Pt∼20at.%) films. Co-rich Co-Pt films, with thickness t ranging from 5nm up to 2μm, were prepared by electrodeposition on (0001)-oriented Ru underlayers. All samples displayed strong perpendicular magnetic anisotropy and high coercivity. Virgin magnetic domain structures for varying thickness were investigated by magnetic force microscopy (MFM). The observed increase of domain width with film thickness is well understood by full two-dimensional micromagnetic computations with no adjustable parameters. The easy-axis magnetization process, as observed by measuring virgin curves by magnetometry and imaging the corresponding magnetization configurations by MFM in variable field, consists of two stages separated by a well-defined critical field, marking the onset of domain wall propagation. A thorough analysis of the out-of-plane angular dependence of the switching field points out that unpinning of domain walls is the dominant magnetization process.
A nonperturbative calculation of nonlinear spectroscopic signals in liquid solution
Authors: Ka Being J. , Geva Eitan
Published: December 2006

Nonlinear spectroscopic signals in liquid solution were calculated without treating the field-matter interaction in a perturbative manner. The calculation is based on the assumption that the intermolecular degrees of freedom can be treated classically, while the time evolution of the electronic state is treated quantum mechanically. The calculated overall electronic polarization is then resolved into its directional components via the method of Seidner et al. [J. Chem. Phys. 103, 3998 (1995)]. It is shown that the time dependence of the directional components is independent of laser intensity in the impulsive pulse regime, which allows for flexibility in choosing the procedure for calculating optical response functions. The utility and robustness of the nonperturbative procedure is demonstrated in the case of a two-state chromophore solvated in a monoatomic liquid, by calculating nonlinear time-domain signals in the strong-field, weak-field, impulsive, and nonimpulsive regimes.
The influence of phonons on the optical properties of GaN
Authors: Song D. Y. , Basavaraj M. , Nikishin S. A. , Holtz M. , Soukhoveev V. , Usikov A. , Dmitriev V.
Published: December 2006

We comprehensively examine the importance of phonons on the optical properties of GaN. Using Raman and photoluminescence (PL) spectroscopies, the energies and linewidths of optic phonons, excitons, and discrete phonon sidebands (PSBs) are studied between 20 and 325 K. The temperature dependence of the A1 (LO) phonon energy and linewidth are described by a combined two- and three-phonon decay process. The narrow E22 phonon decays by the three-phonon emission process. Three band-edge excitons are observed in PL with linewidths between 2.8 and 5.3 meV at temperature 22 K. The energy gap shrinkage and exciton linewidths are completely interpreted based on electron-phonon interactions. The shift, broadening, and asymmetry of the PSBs are explained by incorporating the decay mechanism of A1 (LO) phonon and the exciton broadening from electron-phonon interactions.