bluuebunny/crossref_metadata_2025 huggingface dataset:
Satellite boreal measurements over Alaska and Canada during June–July 2004: Simultaneous measurements of upper tropospheric CO, C2H6, HCN, CH3Cl, CH4, C2H2, CH3OH, HCOOH, OCS, and SF6 mixing ratios
Authors: Rinsland Curtis P. , Dufour Gaëlle , Boone Chris D. , Bernath Peter F. , Chiou Linda , Coheur Pierre‐François , Turquety Solène , Clerbaux Cathy
Published: August 2007

Simultaneous ACE (Atmospheric Chemistry Experiment) upper tropospheric CO, C2H6, HCN, CH3Cl, CH4, C2H2, CH3OH, HCOOH, and OCS measurements show plumes up to 185 ppbv (10−9 per unit volume) for CO, 1.36 ppbv for C2H6, 755 pptv (10−12 per unit volume) for HCN, 1.12 ppbv for CH3Cl, 1.82 ppmv (10−6 per unit volume) for CH4, 0.178 ppbv for C2H2, 3.89 ppbv for CH3OH, 0.843 ppbv for HCOOH, and 0.48 ppbv for OCS in western Canada and Alaska at 50°N–68°N latitude between 29 June and 23 July 2004. Enhancement ratios and emission factors for HCOOH, CH3OH, HCN, C2H6, and OCS relative to CO at 250–350 hPa are inferred from measurements of young plumes compared with lower mixing ratios assumed to represent background conditions based on a CO emission factor derived from boreal measurements. Results are generally consistent with the limited data reported for various vegetative types and emission phases measured in extratropical forests including boreal forests. The low correlation between fire product emission mixing ratios and the SF6 mixing ratio is consistent with no significant SF6 emissions from the biomass fires.
Rainfall limit of the N cycle on Earth
Authors: Ewing Stephanie A. , Michalski Greg , Thiemens Mark , Quinn Richard C. , Macalady Jennifer L. , Kohl Steven , Wankel Scott D. , Kendall Carol , McKay Christopher P. , Amundson Ronald
Published: August 2007

In most climates on Earth, biological processes control soil N. In the Atacama Desert of Chile, aridity severely limits biology, and soils accumulate atmospheric NO3−. We examined this apparent transformation of the soil N cycle using a series of ancient Atacama Desert soils (>2 My) that vary in rainfall (21 to <2 mm yr−1). With decreasing rainfall, soil organic C decreases to 0.3 kg C m−2 and biological activity becomes minimal, while soil NO3− and organic N increase to 4 kg N m−2 and 1.4 kg N m−2, respectively. Atmospheric NO3− (Δ17O = 23.0‰) increases from 39% to 80% of total soil NO3− as rainfall decreases. These soils capture the transition from a steady state, biologically mediated soil N cycle to a dominantly abiotic, transient state of slowly accumulating atmospheric N. This transition suggests that oxidized soil N may be present in an even more arid and abiotic environment: Mars.
Sea breeze signatures on line‐of‐sight microwave links in tropical coastal areas
Authors: Reddy L. Ram Gopal , Reddy B. M.
Published: August 2007

The unusual fast fading observed around middays on line‐of‐sight microwave links in a tropical coastal area is described. Fading was as deep as 20–30 dB with fade rates double the normal rates. The fading is attributed to multipath propagation produced under sea breeze circulations. Sea breeze circulations modify the boundary layer and cause the formation of a low level super‐refractive layer associated with a temperature inversion above the ground. At the same time, an elevated layer of high refractivity variance is formed at the boundary of the cool and humid marine air flowing on‐shore and the relatively dry and hot air flowing offshore. However, when there is a strong vertical heat transfer from the ground, a modified convective boundary layer with a height of about 100–150 m above the ground with a capping elevated layer at the upper boundary of the sea breeze front is formed. In both cases, specular reflections and scattering of radio signals from the layered structures, along with multiple refractive paths are expected to be the cause of the observed fast daytime fading, which is conspicuously absent on inland paths.
Signal strength variations at 2 GHz for three sea paths in the British Channel Islands: Detailed discussion and propagation modeling
Authors: Gunashekar S. D. , Warrington E. M. , Siddle D. R. , Valtr P.
Published: August 2007

Signal strength measurements at 2 GHz have recently been made on three over‐sea paths in the British Channel Islands. This paper focuses on explaining the propagation characteristics during periods of normal reception and periods of enhanced signal strength with particular emphasis on a 48.5 km transhorizon path between Jersey and Alderney. Evaporation ducting and diffraction appear to be the dominant propagation mechanisms at most times. The influence of the evaporation duct during periods of normal propagation has been confirmed by modeling the over‐sea propagation conditions using Paulus‐Jeske evaporation duct refractivity profiles as input to the parabolic equation method. During periods of enhanced propagation, which occur approximately 8% of the time on the longest path (48.5 km), the presence of additional higher‐altitude ducting/super‐refractive structures has been verified and their influence has been modeled with reasonable success.
ISOENZYME STUDIES OF GIARDIA LAMBLIA ISOLATED FROM SYMPTOMATIC CASES
Authors: Baveja Usha K , Jyoti AS , Kaur Manjit , Agarwal DS , Anand BS , Nanda R
Published: August 2007

Strains of Giardia lamblia were isolated from symptomatic cases of giardiasis and axenized in the laboratory. Electrophoretic mobility patterns of four enzymes, viz., EC 5.3.1.9 glucose phosphate isomerase (GPI); EC 1.1.1,4.0.L‐malate; NADP+ Oxidoreductase (Oxaloacetate decarboxylating) (ME); EC 2.7.5.1 phosphoglucomutase (PGM); and EC 2.7.1.1 hexokinase (HK) of the lysates prepared from these isolates were studied using starch—gel. Based on differences in mobility patterns of PGM and HK, the four strains studied could be grouped into three different isoenzyme types (Zymodemes). ME mobility was identical in all the four strains. Some relative difference was seen in the mobility of GPI, though the pattern of mobility was similar in all the strains.
IMMUNOLOGICAL CONSEQUENCES OF INTESTINAL HELMINTH INFECTIONS. CELLULAR AND ANAMNESTIC RESPONSES TO OVALBUMIN
Authors: Price Patricia , Turner KJ
Published: August 2007

Depressed IgG responses to ovalbumin administered with the inflammatory adjuvant, Al(OH)3, have previously been demonstrated in mice immunized 5 to 13 days after infection with Nematospiroides dubius, when the parasite is encysted in the intestinal mucosa or becoming established in the lumen. This report extends these findings to show that primary IgE and delayed‐type hypersensitivity (DTH) responses, the generation of antigen‐primed cells detectable in syngeneic irradiated recipients or in vitro and the recall of immunological memory are correspondingly impaired. Co‐transfer experiments using irradiated recipients demonstrated weak suppressor activity in spleen cells from infected mice which was not attributable to T cells. The results suggest that N. dubius administered before immunization can impair the development of many classes of antigen‐primed lymphocytes. The implications of this finding with respect to parasite survival are discussed.
IMPORT OF CARBAMYLPHOSPHATE SYNTHETASE AND ORNITHINE TRANSCARBAMYLASE INTO MITOCHONDRIA OF RAT LIVER: DETECTION OF AGGREGATES OF ENZYME IN CYTOPLASM AND MITOCHONDRIA USING IMMUNOELECTRON MICROSCOPY WITH THE PROTEIN A‐GOLD METHOD
Authors: Brands Ruud , Hoogenraad Nicholas
Published: August 2007

We investigated the distribution of the nuclear encoded mitochondrial enzymes, carbamylphosphate synthetase (CPS; EC 6.3.4.16) and ornithine transcarbamylase (OTC; EC 2.1.3.3) in liver by immunocytochemistry on ultrathin sections using the protein A‐gold technique. Both enzymes were found to be present as aggregates in the cytoplasm of hepatocytes, in association with ER membranes adjacent to mitochondria. Clusters of the enzymes were also found inside the mitochondria. The aggregation of these enzymes was found only with antibodies to CPS and OTC and not with antibodies against albumin or with IgG from unimmunized serum, nor were aggregates found in cells other than hepatocytes. The results are suggestive of localized uptake of clusters of enzyme or co‐translational uptake of enzyme at discrete localizations and that endoplasmic reticulum (ER) associations may be necessary for uptake of the precursor forms of CPS and OTC. The possible involvement is discussed of micropinosomes which are seen associated with inner membrane, intermembrane space and outer membrane in mitochrondria obtained from a perinuclear pellet where ER and mitochondria are frequently found in close association.
PROTEIN COMPOSITION OF THE LUMINAL FLUID AND PROTEIN SYNTHESIS IN VITRO BY THE OVIDUCTS AND UTERI OF OVARIECTOMIZED, PRO‐OESTRUS AND 5‐DAY PREGNANT RATS
Authors: Wang RX , Brooks DE
Published: August 2007

Serum, oviducal and uterine luminal fluid proteins from rats at three different physiological stages of reproduction were analysed by polyacrylamide gel electrophoresis. Protein synthesis and secretion were also studied by short–term incubation of tissue pieces in vitro with radioactive leucine. In ovariectomized animals and 5‐day pregnant animals, uterine weight and the protein content of the luminal fluid was significantly lower than in pro‐oestrus animals. These differences were much less marked in the oviduct. The protein patterns of oviducal fluid and uterine fluid were significantly different from those o f blood serum. However, certain proteins, such as those of 51, 56, 68 and 80K are clearly derived from blood serum. The protein profile of oviducal fluid and extracts of oviducal tissue showed no obvious differences at the three physiological stages. However, some differences at the three physiological stages were evident in proteins of uterine fluid and in extracts of uterine tissue.

Oviducal and uterine tissue fragments incubated in vitro with radioactive leucine synthesized soluble proteins and released significant amounts of newly synthesized proteins into the incubation medium. However, specific proteins whose synthesis and secretion were selectively altered under the different physiological states appeared to be minor constituents of the total secretory profile. The extensive range of newly synthesized and secreted radioactive proteins revealed by gel fluorography suggests that most proteins present in luminal fluids are directly synthesized by oviducal and uterine tissue in vivo.
AN EXPERIMENTAL STUDY AND COMPUTER SIMULATION OF THE TURNOVER OF CHOLINE IN ERYTHROCYTES OF PATIENTS TREATED WITH LITHIUM CARBONATE
Authors: Beilharz GR , Middlehurst CR , Kuchel PW , Hunt GE , Johnson GFS
Published: August 2007

The mechanism by which choline accumulates in erythrocytes during treatment with lithium salts has been elucidated. A component of the study was a kinetic description of erythrocyte phospholipase‐D, which catalyses the release of intracellular choline from phospholipids. Apparent steady‐state kinetic parameters for calcium ions were determined: Km (± SD) = 0·6 ± 0·3 mmol/l aqueous cell volume and Vmax (± SD) = 12 + 4 μmol/l packed red blood cells (RBC) min−1. Competitive inhibition of the phospholipase‐D by barium ions was also observed. Other information concerning choline and lithium levels and red cell life‐time was obtained from the literature. Details of the kinetics were used to develop a comprehensive dynamic model of choline metabolism by erythrocytes. The scheme is as follows; phosphatidylcholine associated with high density lipoproteins exchanges with the erythrocyte membrane phospholipids, the neutral phospholipids undergo two dimensional translational and rotational motion and also flip between each layer of the bilayer thus becoming exposed to an intracellularly‐located phospholipase‐D, whereupon the choline is hydrolysed and released into the intracellular milieu. A choline transport protein, which is able to be inhibited by lithium, mediates the influx and efflux of choline. The differential equations that describe reactant flux in this scheme were integrated numerically and the choline accumulation profiles under various conditions of transport and enzyme inhibition are presented. Computer solution of the model, by using as input values plasma lithium levels in the upper limit of the therapeutic range, required that the red cell life‐time be reduced in order to explain the previously observed negative association between choline and increasing lithium levels.

The results of the computer simulations under varying initial conditions of plasma and erythrocyte lithium and choline concentrations permit, for the first time, a comprehensive description of those factors affecting erythrocyte choline levels.
THE ROLE OF A FUNCTIONALLY DISTINCT IgM ANTI‐TYPE III PNEUMOCOCCAL POLYSACCHARIDE (SIII) IN LOW‐DOSE PARALYSIS TO SIII IN MICE
Authors: Kearney R , Andrews J , Johnstone S
Published: August 2007

Prior treatment (priming) with a weakly immunogenic dose of Type III pneumococcal polysaccharide (SIII) results in the development of an antigen‐specific state of unresponsiveness termed low‐dose paralysis which is believed to be mediated by suppressor T cells. The present findings show that the passive administration of functionally distinct non‐complement‐fixing (NCF) IgM anti‐SIII antibodies either in monoclonal form or from protein‐A absorbed immune serum could significantly suppress the direct plaque‐forming cell (PFC) response to an immunogenic dose of SIII administered concurrently. The degree of suppression was comparable with that induced by low–dose paralysis. Low‐dose paralysis was consistently induced in athymic (nude) mice 4 days, but not 3 days, after priming with a low dose of SIII, and was associated with the delayed appearance of NCF‐IgM anti‐SIII in the serum of athymic mice. In contrast, low‐dose paralysis was readily induced in normal BALB/c mice 3 days after priming when NCF‐IgM anti‐SIII antibodies were present. Comparable inhibiton of the direct anti‐SIII PFC response was observed when Concanavalin A (Con A) or NCF‐IgM anti‐SIII serum was administered with SIII antigen. That Con A and NCF‐IgM anti‐SIII together did not produce additive suppression was attributed to the adsorption of NCF‐IgM anti‐SIII antibodies to Con A. Complement‐dependent single radial haemolysis mediated by CF hybrid IgM/A or CF‐IgM anti‐SIII serum was blocked by monoclonal NCF‐IgM or IgA anti‐SIII antibodies and indicated that each of the antibodies was specific for the same SIII‐determinant. Evidence is presented to show that low‐dose paralysis in the CF‐IgM response to SIII is not mediated by suppressor T cells but can be attributed to highly avid NCF‐IgM anti‐SIII antibodies, formed preferentially to low doses of SIII, being able to reduce the immunogenicity of SIII administered subsequently.

We propose that low‐dose paralysis to SIII is the result of an immunobiological function of highly avid NCF‐IgM anti‐SIII antibodies which not only confer resistance against capsulated pneumococci but preferentially bind soluble SIII‐antigen to reduce its immunogenicity and thereby protect specific CF‐IgM positive B cells from being rendered tolerant by direct contact with higher doses of SIII antigen.
EFFECT OF HAEMORRHAGE ON HEPATIC GLUTATHIONE CONCENTRATION: AN EXPERIMENTAL STUDY IN THE PIG
Authors: Shi ECP , Rose MA , Ham JM
Published: August 2007

Depletion in the hepatic concentration of reduced glutathione (GSH) may potentiate liver injury resulting from toxic metabolites. Patients who have had severe haemorrhage frequently develop hepatic dysfunction and we have shown that the hepatic GSH level is decreased in these patients. The present study has examined the time‐course effect of a 30% haemorrhage on the hepatic GSH level by sequential biopsies of the liver. Acute and chronic experiments were performed and, in both, the hepatic concentration of GSH fell during the first 6 h after haemorrhage; this fall was followed by a significant rebound elevation at 24 h. In the chronic haemorrhage experiment the hepatic GSH level was normal at 1 week after haemorrhage. Thus, the susceptibility of the liver to toxic metabolite injury after haemorrhage persists for less than 24 h in this experimental model and haemorrhage appears to have no long term effect on the hepatic GSH concentration.
FREQUENCY OF MURINE CYTOTOXIC T CELL PRECURSORS REACTIVE TO PLASMA CELL TUMOUR‐ASSOCIATED ANTIGENS AS COMPARED TO MAJOR HISTOCOMPATIBILITY ANTIGENS
Authors: Burton Robert C
Published: August 2007

The frequency of cytotoxic T lymphocyte precursors (CTL‐P) reactive to plasmacytoma (PCT) tumour‐associated antigens (TAA) was studied in BALB/c mouse spleen. Progressively decreasing numbers of responder BALB/c spleen cells were cultured with mitomycin C‐treated stimulator MPC‐11 BALB/c PCT cells, and a Poisson analysis was performed of the wells scored positive in a 51Cr release assay with PCT target cells. It was found that approximately 2 per million BALB/c spleen cells were CTL‐P reactive to TAA of MPC‐11, and about one in three of these precursors responded to a TAA expressed by MPC‐11 which was shared with the C3H PCT C1.18. The frequency of CTL‐P reactive to TAA was shown to be 30 to 500 fold lower than that for CTL reactive to various major histocompatibility complex alloantigens, and the addition of exogenous Interleukin‐2 only resulted in a 2‐3 fold increase in this CTL‐P frequency. These results suggest that the weak levels of tumour immunity induced in vivo by immunisation of BALB/c mice with MPC‐11 are, at least in part, due to a very low frequency of CTL‐P reactive to TAA of that PCT.
PURIFICATION AND CHARACTERIZATION OF TOXOPLASMA GONDII TACHYZOITE DNA
Authors: Johnsont Alan M , Dubey JP , Dame John B
Published: August 2007

Toxoplasma gondii DNA from RH strain tachyzoites was purified from contaminating murine DNA by isopycnic density gradient ultracentrifugation in CsCI containing the fluorescent dye Hoechst 33258. Quantitative hybridization studies with DNA from uninfected mice and DNA extracted from oocysts of the ME49 strain of T. gondii confirmed that RH strain DNA could be obtained at least 90% pure with a high recovery. Preliminary characterization studies on such purified DNA showed that it had a G + C content of 50% and was not significantly methylated.
HAEMOPOIETIC DEVELOPMENT IN THE FOETAL LAMB FROM 85‐135 DAYS MEASURED BY (3H)‐THYMIDINE INCORPORATION IN VITRO
Authors: Smeaton TC
Published: August 2007

Cell suspensions from the bone marrow (BM), spleen, thymus, liver and lymph nodes of 14 foetal lambs from 85‐135 days gestation were incubated in vitro with 3H ‐thymidine (TdR). Cells from the long bones, the humerus, tibia and femur, yielded similar results, viz., (a) the total leucocyte population of the bone increased from a mean of 8 8×106 at 85‐90 days (N = 4) to a mean of 487×106 at 130‐135 days (N = 3); (b) the rate of incorporation of TdR varied from 22460‐45960 c.p.m./h/106 cells with no clear trend related to foetal age; this rate is consistent with active mitosis occurring in the expanding BM cell population; (c) bone weight and cell number/bone increased in parallel, and the total mitotic capacity of the bone showed a similar pattern. In the liver, spleen and thymus the incorporation of TdR per 106 cells decreased during the latter part of gestation. Despite growth of the liver (from 18 g to 71 g), the number of white blood cells (WBC) extracted from this tissue was lower at 135 days than at 85 days, suggesting that the haemopoietic capacit of the liver declined during this period. The marked increase in total WBC numbers in the thymus suggests tihs tissue may be supplying circulating lymphocytes to the growing foetus.
CATECHOLAMINE CONTENTS OF RABBIT GINGIVA AND DENTAL PULP
Authors: Parker I , Parker DAS , de la Lande IS
Published: August 2007

The contents of endogenous noradrenaline (NA) in rabbit gingiva and dental pulp were approximately 15‐fold greater than either adrenaline (A) or dopamine (DA). Whereas catecholamine contents of maxillary incisor pulps were similar to those in mandibular incisor pulps, variations existed between gingiva excised from different regions. Both reserpine pretreatment and chronic sympathetic denervation greatly decreased the NA contents. These findings support the view that NA is the sympathetic neurotransmitter in dental pulp and gingiva.
THE ORIGIN OF THE N20 COMPONENT OF THE SOMATOSENSORY EVOKED POTENTIAL IN MAN
Authors: Shaw NA
Published: August 2007

Somatosensory evoked potentials (SEPs) were recorded from a 63 year old male who had sustained severe right sided cortical damage including infarction of the primary sensory hand area. When SEPs were recorded following right median nerve stimulation, both cervical and cortical waveforms were of normal configuration. When SEPs were recorded following left median nerve stimulation, the cervical potential was intact but the cortical waveform was absent and replaced with a positive‐negative complex which was probably a far field reflection of thalamic activity. These findings suggest that the first negative component of the cortical SEP (N20) is not generated in the diencephalon but represents the initial response of the somatosensory cortex.
MAMMALIAN CELL FUNCTIONS MEDIATING RECOMBINATION OF GENETIC ELEMENTS: TOPOLOGICAL RESTRAINTS
Authors: Upcroft Peter
Published: August 2007

In extending the scope of our previous analyses of tiie functions that mammalian cells engender to recombine elements of genetic information (Upcroft, Carter and Kidson, 1980a and b), I describe the capacity of cells to recognise differentially combinations of open‐ended and closed molecules. The frequency of successful recombination, as assayed by the generation of viable SV40 genomes from appropriate substrates, was shown to decrease with the loss of free termini capable of invasion of an homologous DNA duplex and to be influenced by the presence of non‐homologous flanking sequences, the length of homology and whether the sequence was internal or terminal. The effect of stabilisation with long homologous regions on recombination over short homologous regions and inter‐ versus intramolecular DNA sequence homologies was also investigated.
A METHOD FOR PREDICTING MURRAY VALLEY ENCEPHALITIS IN SOUTHEAST AUSTRALIA USING THE SOUTHERN OSCILLATION
Authors: Nicholls Neville
Published: August 2007

Clinical cases of Murray Valley Encephalitis in southeast Australia have tended to occur in summer and autumn following extended periods of above average rainfall over most of eastern and northern Australia. The Southern Oscillation, an important mode of climatic fluctuations over the Indian and Pacific Oceans, is closely related to eastern and northern Australian rainfall. The Southern Oscillation has been used previously to develop methods for predicting rainfall fluctuations over Australia and their biological and economic impacts. The relationship, therefore, between the Southern Oscillation and Murray Valley Encephalitis in southeast Australia was examined. Darwin atmospheric pressure, an index of the Southern Oscillation, was found to be well below average during the autumn, winter and spring preceding the occurrence of Murray Valley Encephalitis. It is suggested that this relationship can be used to provide a simple, objective early warning system.
The contribution of toll‐like receptors to the pathogenesis of asthma
Authors: Phipps Simon , Lam Chuan En , Foster Paul S , Matthaei Klaus I
Published: August 2007

Asthma is a major disease in the westernized world and its incidence has significantly increased over the past 40 years. Our understanding of the pathogenesis of asthma remains rudimentary, and for this reason, little has been accomplished by way of targeted intervention, either at a population level (to reduce the overall prevalence) or at an individual level (to treat the cause). Instead, the management strategy currently in use relies on broad‐spectrum anti‐inflammatory agents, generally glucocorticoids and long‐acting β2 agonists. The recent discovery of toll‐like receptors (TLRs), with their role as the initiators of the innate immune response and inflammation, suggests that modulating these receptors may be beneficial in the treatment of allergic disorders. We review here the cellular distribution of TLR in the lung and their potential contribution to the processes that promote T helper 2 (Th2) immunity and infection‐induced exacerbations of allergic lung disease.
Mammalian NLR proteins; discriminating foe from friend
Authors: Kaparakis Maria , Philpott Dana J , Ferrero Richard L
Published: August 2007

Eukaryotic organisms of the plant and animal kingdoms have developed evolutionarily conserved systems of defence against microbial pathogens. These systems depend on the specific recognition of microbial products or structures by molecules of the host innate immune system. The first mammalian molecules shown to be involved in innate immune recognition of, and defence against, microbial pathogens were the Toll‐like receptors (TLRs). These proteins are predominantly but not exclusively located in the transmembrane region of host cells. Interestingly, mammalian hosts were subsequently found to also harbour cytosolic proteins with analogous structures and functions to plant defence molecules. The members of this protein family exhibit a tripartite domain structure and are characterized by a central nucleotide‐binding oligomerization domain (NOD). Moreover, in common with TLRs, most NOD proteins possess a C‐terminal leucine‐rich repeat (LRR) domain, which is required for the sensing of microbial products and structures. Recently, the name ‘nucleotide‐binding domain and LRR’ (NLR) was coined to describe this family of proteins. It is now clear that NLR proteins play key roles in the cytoplasmic recognition of whole bacteria or their products. Moreover, it has been demonstrated in animal studies that NLRs are important for host defence against bacterial infection. This review will particularly focus on two subfamilies of NLR proteins, the NODs and ‘NALPs’, which specifically recognize bacterial products, including cell wall peptidoglycan and flagellin. We will discuss the downstream signalling events and host cell responses to NLR recognition of such products, as well as the strategies that bacterial pathogens employ to trigger NLR signalling in host cells. Cytosolic recognition of microbial factors by NLR proteins appears to be one mechanism whereby the innate immune system is able to discriminate between pathogenic bacteria (‘foe’) and commensal (‘friendly’) members of the host microflora.
Density functional analysis of the structural evolution of Gan (n=30–55) clusters and its influence on the melting characteristics
Authors: Krishnamurty Sailaja , Joshi Kavita , Zorriasatein Shahab , Kanhere D. G.
Published: August 2007

Recent experimental results have reported surprising variations in the shapes of the heat capacity curves and melting temperatures of gallium clusters in the size range of 30–55 atoms [G. A. Breaux et al., J. Am. Chem. Soc. 126, 8628 (2004)]. In the present work, we have carried out an extensive density functional investigation on ten selected clusters in the above mentioned size range. In particular, we have analyzed the ground state geometry and the nature of bonding in these clusters using electron localization function. We demonstrate that the existence or otherwise of a large island of atoms bonded with similar strength (i.e., the local order) in the ground state geometry is responsible for the variation in the shape of the heat capacity curve. We attribute the observed higher melting temperatures of some of the clusters (viz., Ga45–Ga48) to the presence of a distinct core and strong covalent bonds between the core and surface atoms. The present work clearly demonstrates that it is possible to understand the general trends observed in the heat capacity curves across the entire series on the basis of the analysis of their ground state.
Steady growth of nanowires via the vapor-liquid-solid method
Authors: Roper Steven M. , Davis Stephen H. , Norris Scott A. , Golovin Alexander A. , Voorhees Peter W. , Weiss Mark
Published: August 2007

Understanding the dynamics of the growth of nanowires by the vapor-liquid-solid (VLS) process is essential in order to relate the properties of the wire to their processing conditions. A theory for VLS growth is developed that incorporates the surface energy of the solid-liquid, liquid-vapor, and solid-vapor interfaces, allows for supersaturation of growth material in the droplet, and employs contact-line conditions. We predict the profile of catalyst concentration in the droplet, the degree of supersaturation, and the modification to the shape of the solid-liquid interface due to growth, as functions of the material properties and process parameters. Under typical experimental conditions the interface deflection due to growth is predicted to be practically zero. We also find that the growth rate of the wire inherits the same dependence on diameter as the flux of growth material at the liquid-vapor interface; thus, if we assume that the flux is independent of radius, we obtain a growth rate that is also independent of radius. To make a prediction about the actual variation with diameter requires a detailed knowledge of the decomposition kinetics at the liquid-vapor interface.
Observation of a uniform temperature dependence in the electrical resistance across the structural phase transition in thin film vanadium oxide (VO2)
Authors: Mani R. G. , Ramanathan S.
Published: August 2007

An electrical study of thin VO2 films in the vicinity of the structural phase transition at 68°C shows (a) that the electrical resistance R follows log(R)∝−T over the T range, 20<T<80°C covering both sides of the structural transition, and (b) a history dependent hysteresis loop in R upon thermal cycling. These features are attributed here to transport through a granular network.
Vertically standing carbon nanotubes as charge storage nodes for an ultimately scaled nonvolatile memory application
Authors: Ryu Seong-Wan , Huang Xing-Jiu , Choi Yang-Kyu
Published: August 2007

Vertically standing single-walled carbon nanotube (SSWCNT)-embedded transistors have been demonstrated for a flash memory application. The performance of the SSWCNT device was compared with a lying SWCNT (LSWCNT) device to verify the directional effect of immobilized SWCNTs. The SSWCNT device shows a better program/erase transient and a threefold enhanced retention characteristics over the LSWCNT device due to the high coupling ratio and the defect immunity based on the isolated distribution and vertical directionality nature of the SSWCNT.
Growth of pinhole-free ytterbium silicide film by solid-state reaction on Si(001) with a thin amorphous Si interlayer
Authors: Jiang Yu-Long , Xie Qi , Detavernier Christophe , Van Meirhaeghe R. L. , Ru Guo-Ping , Qu Xin-Ping , Li Bing-Zong , Chu Paul K.
Published: August 2007

A thin amorphous Si (α-Si) interlayer is produced between the sputtering deposited ytterbium layer and Si(001) substrate, and the growth of the ytterbium silicide (YbSi2−x) film is investigated in this paper. Formation of YbSi2−x was verified by x-ray diffraction (XRD). The silicide film morphology was examined by scanning electron microscopy (SEM) and atomic force microscopy (AFM). SEM results reveal that without the α-Si interlayer, pinholes form during YbSi2−x formation on Si(001). Furthermore, the XRD results demonstrate that there is a strong epitaxial relationship between the formed YbSi2−x and Si(001) substrate, and it is believed to be the reason for the formation of pinholes. To suppress the formation of pinholes, a thin α-Si interlayer with different thicknesses is introduced on the Si(001) substrate prior to Yb film deposition. The α-Si interlayer is produced by either sputter deposition employing a Si target or by Si ion implantation induced amorphization. In the presence of this thin α-Si interlayer, epitaxial growth of YbSi2−x is greatly suppressed even when the α-Si interlayer is so thin that full silicidation of the deposited Yb film still requires consumption of Si atoms from the Si(001) substrate. Fabrication of a pinhole-free YbSi2−x film is also demonstrated by SEM and AFM. The growth mechanism of the pinhole-free YbSi2−x film in the presence of a thin α-Si interlayer is discussed.
InAs quantum well Hall devices for room-temperature detection of single magnetic biomolecular labels
Authors: Mihajlović Goran , Xiong Peng , von Molnár Stephan , Field Mark , Sullivan Gerard J.
Published: August 2007

Hall sensors with cross width of ∼1μm were fabricated from InAs∕AlSb quantum well semiconductor heterostructures containing two-dimensional electron gas. The room-temperature device characteristics were examined by Hall effect and electronic noise measurements along with analytical calculations. In the low-frequency range, from 20Hzto1.6kHz, the noise-equivalent magnetic field resolution was found to be limited by 1∕f and generation-recombination noise from 22to3.5μT∕Hz. The corresponding noise-equivalent magnetic moment resolution reached 106μB∕Hz at ∼700Hz and was even lower at higher frequencies. Using a phase-sensitive measurement technique, detection of a single 1.2μm diameter bead, suitable for biological applications, was achieved with a signal to noise ratio of ∼33.3dB, as well as detection of six 250nm beads with a signal to noise of ∼2.3dB per bead. The work demonstrates the efficacy of InAs quantum well Hall devices for application in high sensitivity detection of single magnetic biomolecular labels.
Interface effects at a half-metal/ferroelectric junction
Authors: Yamauchi Kunihiko , Sanyal Biplab , Picozzi Silvia
Published: August 2007

Magnetoelectric effects are investigated ab initio at the interface between half-metallic and ferroelectric prototypes: Heusler Co2MnSi and perovskite BaTiO3. For the Co-termination ferroelectricity develops in BaTiO3 down to nanometer thicknesses, whereas for the MnSi termination a paraelectric and a ferroelectric state energetically compete, calling for a full experimental control over the junction atomic configuration whenever a ferroelectric barrier is needed. Switch of the electric polarization largely affects magnetism in Co2MnSi, with magnetoelectric coupling due to electronic hybridization at the MnSi termination and to the structural effects at the Co-termination. Half metallicity is lost at the interface, but recovered already in the subsurface layer.
Superhydrophobic modification of gate dielectrics for densely packed pentacene thin film transistors
Authors: Kim Chang Su , Jo Sung Jin , Kim Jong Bok , Ryu Seung Yoon , Noh Joo Hyon , Baik Hong Koo , Lee Se Jong , Kim Youn Sang
Published: August 2007

Pentacene organic thin film transistors (OTFTs) with low-k and high-k hybrid gate dielectrics by CF4 plasma treatment exhibited excellent device performance with field effect mobilities (maximum 1.41cm2∕Vs), a low threshold voltage of +1V, and on/off current ratios of 105 at −5V gate bias. After CF4 plasma treatment, fluorine atoms diffuse into the interior low-k polymer and eliminate ionic impurities which reduce the leakage current density and overall pentacene initial growth on the superhydrophobic surface is significantly improved. It seems apparent that proper surface treatment is desirable for higher quality pentacene film and improving the performance of OTFTs.
Suppression of secondary phase formation in Fe implanted ZnO single crystals
Authors: Potzger K. , Zhou Shengqiang , Reuther H. , Kuepper K. , Talut G. , Helm M. , Fassbender J. , Denlinger J. D.
Published: August 2007

Unwanted secondary phases are one of the major problems in diluted magnetic semiconductor creation. Here, the authors show possibilities to avoid such phases in Fe implanted and postannealed ZnO(0001) single crystals. While α-Fe nanoparticles are formed after such doping in as-polished crystals, high temperature (1273K) annealing in O2 or high vacuum before implantation suppresses these phases. Thus, the residual saturation magnetization in the preannealed ZnO single crystals is about 20 times lower than for the as-polished ones and assigned to indirect coupling between isolated Fe ions rather than to clusters.
Optimal crystal surface for efficient channeling in the new generation of hadron machines
Authors: Baricordi S. , Guidi V. , Mazzolari A. , Martinelli G. , Carnera A. , De Salvador D. , Sambo A. , Della Mea G. , Milan R. , Vomiero A. , Scandale W.
Published: August 2007

The new generation of hadron machines may profitably take advantage of channeling for steering and collimation of high-energy particle beams. In that case, the requirements on the quality of the crystal surface are rather stringent in terms of both lattice perfection and roughness. Here, the authors show the structural and morphological characterizations of crystals fabricated through a method to achieve a surface that fulfills all needed specifications for application in hadron machines.
Ferromagnetism in nanoscale BiFeO3
Authors: Mazumder R. , Sujatha Devi P. , Bhattacharya Dipten , Choudhury P. , Sen A. , Raja M.
Published: August 2007

A remarkably high saturation magnetization of ∼0.4μB∕Fe along with room temperature ferromagnetic hysteresis loop has been observed in nanoscale (4–40nm) multiferroic BiFeO3 which in bulk form exhibits weak magnetization (∼0.02μB∕Fe) and an antiferromagnetic order. The magnetic hysteresis loops exhibit exchange bias and vertical asymmetry which could be because of spin pinning at the boundaries between ferromagnetic and antiferromagnetic domains. Interestingly, both the calorimetric and dielectric permittivity data in nanoscale BiFeO3 exhibit characteristic features at the magnetic transition point. These features establish the formation of a true ferromagnetic-ferroelectric system with a coupling between the respective order parameters in nanoscale BiFeO3.
Vanadia-based equilibrium-thickness amorphous films on anatase (101) surfaces
Authors: Qian Haijun , Luo Jian
Published: August 2007

Nanometer-thick, surficial amorphous films are found to form in a model “monolayer” catalyst system: vanadia on TiO2 anatase (101) surfaces. These films exhibit a self-selecting or “equilibrium” thickness; once a thermodynamic equilibrium is reached, the film thickness, which corresponds to the Gibbsian surface excess of vanadia adsorbates, is independent of synthesis methods, the fraction of secondary vanadia phase, and the heat treatment history. These (multilayer) adsorbate films are largely amorphous (quasiliquid) at subeutectic temperatures, where analogies to premelting and prewetting phenomena are made. Reversible film thickness versus temperature (with a hysteresis loop) is observed and explained from a force-balance model.
A simple statistical model to estimate precision of 300-day milk and fat production for dairy cows
Authors: Clarke T. , Hannah M. C.
Published: August 2007

In this paper we use a statistical model to examine the relative precision of lactation milk yield and milk fat yield, under various production recording regimes with different metering and sampling precision, recording frequencies combined with empirical daily variations in milk yield and fat composition. The analysis shows that if traditional monthly production recording was performed with devices of International Committee for Animal Recording (ICAR) precision, the resultant coefficient of variation (CV) for lactation yields of milk and fat would be 2.22 and 4.81%, respectively. These values are determined primarily by measurement frequency coupled with the natural daily biological variations in animal milk yield and fat composition. Meter and sampler precision play a relatively minor role. For example, our model shows that if the devices had double the CV prescribed by ICAR, the milk and fat yield CV would increase by only 0.20 and 0.19%, respectively. These are minute losses of precision. If the ICAR precision standards for meters and samples were relaxed, it could encourage development of innovative metering and sampling technologies that could provide much more cost-effective and convenient ways for farmers to conduct production recording.
Cholera toxin induces malignant glioma cell differentiation via the PKA/CREB pathway
Authors: Li Yan , Yin Wei , Wang Xia , Zhu Wenbo , Huang Yijun , Yan Guangmei
Published: August 2007

Malignant gliomas are one of the leading causes of cancer deaths worldwide, but chemoprevention strategies for them are few and poorly investigated. Here, we show that cholera toxin, the traditional biotoxin and well known inducer of accumulation of cellular cAMP, is capable of inducing differentiation on malignant gliomas
in vitro
with rat C6 and primary cultured human glioma cells. Cholera toxin-induced differentiation was characterized by typical morphological changes, increased expression of glial fibrillary acid protein, decreased expression of Ki-67, inhibition of cellular proliferation, and accumulation of cells in the G
1
phase of the cell cycle. Cholera toxin also triggered a significant reduction in the G
1
cell-cycle regulatory proteins cyclin D1 and Cdk2 along with an overexpression of cell-cycle inhibitory proteins p21
Cip1
and p27
Kip1
. Abrogation of cAMP-dependent protein kinase A activity by protein kinase A inhibitor or silencing of cAMP-responsive element binding proteins by RNA interference resulted in suppressed differentiation. These findings imply the attractiveness of cholera toxin as a drug candidate for further development of differentiation therapy. Furthermore, activation of the protein kinase A/cAMP-responsive element binding protein pathway may be a key and requisite factor in glioma differentiation.
Development of distinct control networks through segregation and integration
Authors: Fair Damien A. , Dosenbach Nico U. F. , Church Jessica A. , Cohen Alexander L. , Brahmbhatt Shefali , Miezin Francis M. , Barch Deanna M. , Raichle Marcus E. , Petersen Steven E. , Schlaggar Bradley L.
Published: August 2007

Human attentional control is unrivaled. We recently proposed that adults depend on distinct frontoparietal and cinguloopercular networks for adaptive online task control versus more stable set control, respectively. During development, both experience-dependent evoked activity and spontaneous waves of synchronized cortical activity are thought to support the formation and maintenance of neural networks. Such mechanisms may encourage tighter “integration” of some regions into networks over time while “segregating” other sets of regions into separate networks. Here we use resting state functional connectivity MRI, which measures correlations in spontaneous blood oxygenation level-dependent signal fluctuations between brain regions to compare previously identified control networks between children and adults. We find that development of the proposed adult control networks involves both segregation (i.e., decreased short-range connections) and integration (i.e., increased long-range connections) of the brain regions that comprise them. Delay/disruption in the developmental processes of segregation and integration may play a role in disorders of control, such as autism, attention deficit hyperactivity disorder, and Tourette's syndrome.
NudE and NudEL are required for mitotic progression and are involved in dynein recruitment to kinetochores
Authors: Stehman Stephanie A. , Chen Yu , McKenney Richard J. , Vallee Richard B.
Published: August 2007

NudE and NudEL are related proteins that interact with cytoplasmic dynein and LIS1. Their functional relationship and involvement in LIS1 and dynein regulation are not completely understood. We find that NudE and NudEL each localize to mitotic kinetochores before dynein, dynactin, ZW10, and LIS1 and exhibit additional temporal and spatial differences in distribution from the motor protein. Inhibition of NudE and NudEL caused metaphase arrest with misoriented chromosomes and defective microtubule attachment. Dynein and dynactin were both displaced from kinetochores by the injection of an anti-NudE/NudEL antibody. Dynein but not dynactin interacted with NudE surprisingly through the dynein intermediate and light chains but not the motor domain. Together, these results identify a common function for NudE and NudEL in mitotic progression and identify an alternative mechanism for dynein recruitment to and regulation at kinetochores.
Distinct functions of the Drosophila Nup153 and Nup214 FG domains in nuclear protein transport
Authors: Sabri Nafiseh , Roth Peggy , Xylourgidis Nikos , Sadeghifar Fatemeh , Adler Jeremy , Samakovlis Christos
Published: August 2007

The phenylanine-glycine (FG)–rich regions of several nucleoporins both bind to nuclear transport receptors and collectively provide a diffusion barrier to the nuclear pores. However, the in vivo roles of FG nucleoporins in transport remain unclear. We have inactivated 30 putative nucleoporins in cultured Drosophila melanogaster S2 cells by RNA interference and analyzed the phenotypes on importin α/β−mediated import and CRM1-dependent protein export. The fly homologues of FG nucleoporins Nup358, Nup153, and Nup54 are selectively required for import. The FG repeats of Nup153 are necessary for its function in transport, whereas the remainder of the protein maintains pore integrity. Inactivation of the CRM1 cofactor RanBP3 decreased the nuclear accumulation of CRM1 and protein export. We report a surprisingly antagonistic relationship between RanBP3 and the Nup214 FG region in determining CRM1 localization and its function in protein export. Our data suggest that peripheral metazoan FG nucleoporins have distinct functions in nuclear protein transport events.
A collective form of cell death requires homeodomain interacting protein kinase
Authors: Link Nichole , Chen Po , Lu Wan-Jin , Pogue Kristi , Chuong Amy , Mata Miguel , Checketts Joshua , Abrams John M.
Published: August 2007

We examined post-eclosion elimination of the Drosophila wing epithelium in vivo where collective “suicide waves” promote sudden, coordinated death of epithelial sheets without a final engulfment step. Like apoptosis in earlier developmental stages, this unique communal form of cell death is controlled through the apoptosome proteins, Dronc and Dark, together with the IAP antagonists, Reaper, Grim, and Hid. Genetic lesions in these pathways caused intervein epithelial cells to persist, prompting a characteristic late-onset blemishing phenotype throughout the wing blade. We leveraged this phenotype in mosaic animals to discover relevant genes and establish here that homeodomain interacting protein kinase (HIPK) is required for collective death of the wing epithelium. Extra cells also persisted in other tissues, establishing a more generalized requirement for HIPK in the regulation of cell death and cell numbers.
Impaired T lymphocyte trafficking in mice deficient in an actin-nucleating protein, mDia1
Authors: Sakata Daiji , Taniguchi Hiroyuki , Yasuda Shingo , Adachi-Morishima Aki , Hamazaki Yoko , Nakayama Rika , Miki Takashi , Minato Nagahiro , Narumiya Shuh
Published: August 2007

Trafficking of immune cells is controlled by directed migration of relevant cells toward chemotactic signals. Actin cytoskeleton undergoes continuous remodeling and serves as machinery for cell migration. The mDia family of formins and the Wiskott-Aldrich syndrome protein (WASP)–Arp2/3 system are two major actin nucleating–polymerizing systems in mammalian cells, with the former producing long straight actin filaments and the latter producing branched actin meshwork. Although much is known about the latter, the physiological functions of mDia proteins are unclear. We generated mice deficient in one mDia isoform, mDia1. Although mDia1−/− mice were born and developed without apparent abnormality, mDia1−/− T lymphocytes exhibited impaired trafficking to secondary lymphoid organs in vivo and showed reduced chemotaxis, little actin filament formation, and impaired polarity in response to chemotactic stimuli in vitro. Similarly, mDia1−/− thymocytes showed reduced chemotaxis and impaired egression from the thymus. These results suggest that mDia1 plays a distinct role in chemotaxis in T lymphocyte trafficking.