bluuebunny/crossref_metadata_2025 huggingface dataset:
Electrocatalytic Oxidation of 2‐Thiouracil and 2‐Thiobarbituric Acid at a Carbon‐Paste Electrode Modified with Cobalt Phthalocyanine
Authors: Shahrokhian Saeed , Hamzehloei Ali , Thaghani Abdollah , Mousavi S. Reza
Published: April 2004

Voltammetric behavior of two mercaptopyrimidine derivatives (2‐thiouracil and 2‐thiobarbituric acid) has been studied by cyclic voltammetry at a cobalt phthalocyanine (CoPc)‐modified carbon‐paste electrode. The results of voltammetric determinations showed that the CoPc in the matrix of modified electrode acts as catalyst for electrooxidation of these thiols (RSH), lowering the overpotential of the reaction and significantly increasing the sensitivity for detection of thiols in neutral conditions. The results of voltammetric and polarization measurements in solutions with various pHs were used for prediction of the mechanism of electrocatalytic oxidation at the surface of modified electrode. These results showed that at the modified electrode, electrochemical oxidation of thiolate anion (RS−) is the rate‐determining step. It was found that the modified electrode exhibits good selectivity for catalytic oxidation of mercaptopyrimidines over other biologically important mercaptans such as cysteine, glutathione and thioglycolic acid. The results demonstrate that the peak current for thiol oxidation has a linear variation with the concentration in the range of 1×10−2–1×10−5 M. This system can be used for sensitive and selective voltammetric detection of mercaptopyrimidine derivatives.
Determination of Lead(II) with the Rotating Sample System
Authors: Cserey Andrea
Published: April 2004

As a result of industrialization lead is one of the most widely dispersed toxic heavy metals in the environment. There is a pressing need for a reliable, affordable and portable analytical technique for routine determination of lead at trace levels in biological and environmental samples. Despite their potential for portability and low cost, the currently available electrochemical stripping methods still have limited commercial availability. Among the reasons are the relatively large sample volumes and the large amount of reagents needed (1–3 mL), lower than required precision, and the inconvenience of a rotated electrode system. The Rotating Sample System is a unique approach to electrochemical stripping, devised for 20 μL sample droplets utilizing a large surface area electrode. This design combines the advantages of a microelectrode and a rotated electrode system. The semispherical sample drop itself is rotated by a fine gas jet directed at it tangentially, eliminating the need for a sample container. Neither fine moving mechanical parts nor sophisticated controls are required. The detection limit for lead(II) was found low enough and the reproducibility is sufficient for routine determinations in biomedical samples (5 ppb, 6%). The system can support a CDC recommended screening for blood lead levels and an on‐site analysis of environmental samples as well. Under suitable conditions calibration free direct determinations can also be performed.
Modification of Glassy Carbon Electrodes with a Poly‐L‐Lysine/Glutaraldehyde Film
Authors: Pereira F. C. , Bergamo E. P. , Stradiotto N. R. , Zanoni M. V. B. , Fogg A. G.
Published: April 2004

A film of poly‐L‐lysine (PLL) adheres better to the surface of a glassy carbon electrode when the PLL is partially cross‐linked by means of glutaraldehyde. A film composition of 97.5% PLL/2.5% glutaraldehyde gives good adhesion and retains the anionic exchange capability of the PLL. The performance of the film was tested with hexacyanoferrate(III) using electrochemical and nonelectrochemical accumulation.
Measurement and explanation of socioeconomic inequality in health with longitudinal data
Authors: Jones Andrew M. , Nicolás Angel López
Published: April 2004

This paper presents a method to compare indices of inequality in health that are based on short‐run and long‐run measures of health and income. For pure health inequality (as measured by the Gini coefficient) and income‐related health inequality (as measured by the concentration index), we show how measures derived from longitudinal data can be related to cross section Gini and concentration indices that have been typically reported in the literature to date, along with measures of health mobility inspired by the literature on income mobility. We also show how these measures of mobility can be usefully decomposed into the contributions of different factors. We apply these methods to investigate the degree of income‐related mobility in the GHQ measure of psychological well‐being in the first nine waves of the British Household Panel Survey (BHPS). This reveals that dynamics increase the absolute value of the concentration index of GHQ on income by 15%, or 1.7% per year on average, for men, and 5%, or 0.6% per year, for women. Copyright © 2004 John Wiley & Sons, Ltd.
Theta reset produces optimal conditions for long‐term potentiation
Authors: McCartney Holly , Johnson Andrew D. , Weil Zachary M. , Givens Bennet
Published: April 2004

Connections among theta rhythm, long‐term potentiation (LTP) and memory in hippocampus are suggested by previous research, but definitive links are yet to be established. We investigated the hypothesis that resetting of local hippocampal theta to relevant stimuli in a working memory task produces optimal conditions for induction of LTP. The timings of the peak and trough of the first wave of reset theta were determined in initial sessions and used to time stimulation (4 pulses, 200 Hz) during subsequent performance. Stimulation on the peak of stimulus‐reset theta produced LTP while stimulation on the trough did not. These results suggest that a memory‐relevant stimulus produces a phase shift of ongoing theta rhythm that induces optimal conditions for the stimulus to undergo potentiation. © 2004 Wiley‐Liss, Inc.
Surface activity—thermodynamic properties and light scattering studies for some novel aliphatic polyester surfactants
Authors: El‐Ghazawy R. A. , Raheem R. Abdel , Al‐Sabagh A. M.
Published: April 2004

The preparation of 12 new polyester surfactants based on aliphatic amines and different ethylene oxide content is described. These surfactants were characterized by determining their molecular weights and polydispersity by gel permeation chromatography (GPC) and nitrogen content. Drop volume tensiometry (DVT) was used to measure the surface tension at 25, 35, 45 and 55°C. The surface tension isotherms were used to determine critical micelle concentration (CMC), maximum Gibb's adsorption (Γmax), minimum area per molecule (Amin), the effectiveness of surface tension reduction (πcmc) and the efficiency (pC20). The thermodynamic parameters of micellization (ΔGmic, ΔHmic, ΔSmic) and of adsorption (ΔGad, ΔHad, ΔSad) were calculated and the data showed that these surfactants favor micellization to adsorption. The static scattered light intensity measurements provide the calculation of the molecular weight of micelle and the aggregation number (N°), while the dynamic light scattering provide the hydrodynamic radius of micelle (RH) and the diffusion coefficient at different surfactant concentrations. The hydrodynamic radius of micelle (RH) at different surfactant concentrations could be used also to determine the CMC giving results that are comparable to those obtained by surface tension measurements. All the data are discussed regarding the chemical structure of the polymeric surfactants. Copyright © 2004 John Wiley & Sons, Ltd.
Catalytic behavior of silica‐supported chitosan‐platinum‐iron complex for asymmetric hydrogenation of ketones
Authors: Wei Wei‐Lin , Hao Shao‐Jie , Zhou Jian , Huang Mei‐Yu , Jiang Ying‐Yan
Published: April 2004

Silica‐supported chitosan‐platinum‐iron complex (SiO2‐CS‐Pt‐Fe) is prepared by a simple method from silica, chitosan, H2PtCl6 · 6H2O and FeCl3. It has been found to be an effective chiral catalyst for the asymmetric hydrogenation of 2‐hexanone to give (S)‐(+)‐2‐hexanol and methyl acetoacetate to give methyl‐(S)‐(+)‐3‐hydroxybutyrate in 85.4 and 75.0% optical yields, respectively, if a proper content of Pt and Fe in SiO2‐CS‐Pt‐Fe complex and appropriate reaction conditions are selected at room temperature and under 1 atm H2. The catalyst could be reused several times without any remarkable change in optical catalytic activity. Copyright © 2004 John Wiley & Sons, Ltd.
Preparation and catalytic properties of chitosan bound Schiff base copper complexes
Authors: Chang Yue , Wang Yunpu , Zha Fei , Wang Rongmin
Published: April 2004

Chitosan, a natural polymer, bound Schiff base copper complexes CT‐She‐Cu, CT‐o‐Bel‐Cu, CT‐m‐Bel‐Cu were prepared and characterize by inductively coupled plasma (ICP), FT‐IR and X‐ray photoelectron spectroscopy (XPS). Their catalytic activity in the oxidation of cyclohexene with molecular oxygen was studied. All the complexes have catalytic activity and the main oxidation products are 2‐cyclohexene‐ol, 2‐cyclohexene‐one and cyclohexene hydroperoxide, which were measured by gas chromatography/mass spectroscopy (GC/MS) and GC/IR. CT‐m‐Bel‐Cu was selected to study the influence of reaction temperature, amount of catalyst and additives such as acid and base on the oxidation of cyclohexene systematically. Copyright © 2004 John Wiley & Sons, Ltd.
Methacrylate modified clays and their polystyrene and poly(methyl methacrylate) nanocomposites
Authors: Su Shengpei , Jiang David D. , Wilkie Charles A.
Published: April 2004

Two methacrylate‐modified clays have been prepared and used to produce nanocomposites of polystyrene and poly(methyl methacrylate) by in situ polymerization. These nanocomposites have been characterized by X‐ray diffraction (XRD), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), cone calorimetry and the evaluation of mechanical properties. When the clay contains only a single methacrylate unit, the styrene system is exfoliated but methacrylate is intercalated. When two methacrylate units are present on the cation of the clay, both systems are exfoliated. TGA data show that the thermal stability of all the nanocomposites is improved, as expected. The relationships between the fire properties and nanostructure of the nanocomposites are complicated, as shown by cone calorimetry. The conclusions that one may reach using cone calorimetry do not completely agree with those from XRD and TEM. The evaluation of mechanical properties shows an increase in Young's modulus for all nanocomposites along with a decrease in elongation; tensile strength is decreased for methacrylate nanocomposites but increased for styrenics systems. Copyright © 2004 John Wiley & Sons, Ltd.
Assessment of hydrologic alterations caused by Chi‐Chi diversion weir in Chou‐Shui Creek, Taiwan: opportunities for restoring natural flow conditions
Authors: Shiau Jenq‐Tzong , Wu Fu‐Chun
Published: April 2004

The Range of Variability Approach (RVA) is used to investigate the hydrologic impacts of a diversion weir on Chou‐Shui Creek, Taiwan. Thirty‐two hydrologic parameters, called Indicators of Hydrologic Alteration (IHA), are used to evaluate the flow conditions before and after weir construction. One standard deviation from the mean for each of the pre‐construction hydrologic parameters is set as the management target range. Under the prevailing diversion rules, large hydrologic alterations are observed, especially for low flows. The means of 19 hydrologic parameters presently fall outside of the targets and the average non‐attainment rate for the 32 indicators is 73.2%. Increasing the instream flow release or reducing diversions could mitigate the hydrologic impacts of weir construction. Increasing the instream flow to 40 m3/s and reducing monthly water demands by variable percentages significantly improves the altered flow conditions. Under the proposed water release and diversion scheme, 29 hydrologic parameters will fall within the management targets and the average non‐attainment rate will be reduced to 35.6%, much closer to the pre‐construction value of 25.3%. Restoring the natural flow variability is expected to promote the natural stream biota. Copyright © 2004 John Wiley & Sons, Ltd.
Negative association in uniform forests and connected graphs
Authors: Grimmett G. R. , Winkler S. N.
Published: April 2004

We consider three probability measures on subsets of edges of a given finite graph G, namely, those which govern, respectively, a uniform forest, a uniform spanning tree, and a uniform connected subgraph. A conjecture concerning the negative association of two edges is reviewed for a uniform forest, and a related conjecture is posed for a uniform connected subgraph. The former conjecture is verified numerically for all graphs G having eight or fewer vertices, or having nine vertices and no more than 18 edges, using a certain computer algorithm which is summarized in this paper. Negative association is known already to be valid for a uniform spanning tree. The three cases of uniform forest, uniform spanning tree, and uniform connected subgraph are special cases of a more general conjecture arising from the random‐cluster model of statistical mechanics. © 2004 Wiley Periodicals, Inc. Random Struct. Alg., 2004
Fetal salvage with cervical cerclage
Authors: Wright E.A.
Published: April 2004

A prospective study to evaluate the fetal salvage rate, cervical morbidity and cesarean section rate in patients with cervical incompetence using a cerclage procedure was conducted at the Jos University Teaching Hospital, Jos, Nigeria. The study group consisted of 71 patients who gave a history suggestive of cervical incompetence, had a dilated cervix at booking and included emergency patients in whom the cervix had dilated because of a febrile illness but had never undergone a cervical cerclage procedure. The fetal salvage rate was 23.7% in pregnancies occurring before and 94.4% after cervical cerclage procedure was performed. There were 57 term pregnancies, 10 pre‐term deliveries, and 4 abortions. The study clearly demonstrates the beneficial effects of cervical cerclage operations in patients who have suffered from preventable fetal losses because their incompetent cervix was undiagnosed. Our results were compared with those of other series. The diagnosis of cervical incompetence is discussed with particular emphasis on the use of screening tests in the detection and identification of cervical incompetence.
Serial serum ferritin and other hematological parameters in normal Nigerian primigravidae
Authors: Abudu O.O. , Macaulay K. , Oluboyede O.A.
Published: April 2004

Serial hematological indices using Coulter Counter and serum ferritin using radioimmunoassay techniques were determined in 20 healthy Nigerian primigravidae with hemoglobin genotype AA. PCV fell significantly (P < 0.001) to a minimum value at 28 weeks that was 6% lower than the mean value at 8 weeks postpartum. PCV at 36 weeks was still significantly (P < 0.001) lower than the post partum value. There was an insignificant but progressive increase in MCV values throughout pregnancy. Changes in MCH and MCHC were insignificant. Ferritin levels in both the non‐pregnant and pregnant subjects were high and probably reflected the high iron content of Nigerian foods. Though the cord serum ferritin level was significantly higher (P < 0.001) than maternal ferritin at delivery there was no significant correlation between the two.
Shoulder dystocia: its incidence and associated risk factors
Authors: Sandmire H.F. , O'Halloin T.J.
Published: April 2004

A case‐control study (73 cases, 146 controls) was conducted to evaluate maternal, obstetrical and fetal factors associated with shoulder dystocia. Several factors were identified that were associated with a higher incidence of shoulder dystocia. However, none of them accurately predict those deliveries that will be complicated by shoulder dystocia. Among the 73 shoulder dystocia cases there were no perinatal deaths and all birth‐related injuries associated with shoulder dystocia were temporary except for two cases of mild muscular weakness among 12 brachial palsy cases.
Radical vulvectomy for squamous cell carcinoma of the vulva
Authors: Ayhan Ali , Yüce K. , Pekin S. , Ayhan Ayse , Özen E.
Published: April 2004

Twenty‐one patients with squamous cell carcinoma of the vulva who were subjected to radical vulvectomy and inguinal‐pelvic lymphadenectomy were studied. The overall mortality rate was 24%. Operative‐ and tumor‐related mortalities were 9.5% and 14.2%, respectively. Recurrence was seen in 5 patients. The most common complication was wound infection and breakdown.
Is routine episiotomy beneficial in the low birth weight delivery?
Authors: The T.G.
Published: April 2004

The outcome of 439 idiopathic singleton low birth weight spontaneous vertex deliveries in the university hospital of a developing country was analyzed. Any patient with a known complication of pregnancy was excluded from the study. The effects of maternal age were minimized by including only those mothers between the age of 17 and 34. The effect of maternal parity was minimized by analyzing the study in two parity groups. The birth weight distributions of the episiotomized and non‐episiotomized groups were comparable. There was no significant difference in the Apgar scores and neonatal mortality rates between these neonates delivered with an episiotomy and those without. This was the case, regardless of parity. The value of an episiotomy in the delivery of the low birth weight infant is questioned.
Early spontaneous rupture of the post myomectomy gravid uterus
Authors: Golan D. , Aharoni A. , Gonen R. , Boss Y. , Sharf M.
Published: April 2004

Rupture of a pregnant uterus is a serious threat to the mother's life and her fetus. Most of these cases have predisposing factors of which a post myomectomy scar is rare. Rupture of a post myomectomy gravid uterus usually occurs in the third trimester of pregnancy or during labor. We present a case of a very early spontaneous rupture which occurred at the 20th week of gestation in a post myomectomy uterus. To the best of our knowledge no previous report of a ruptured myomectomy scarred uterus has been described at such an early stage.
Combined subsequent development of intrauterine and extrauterine gestations
Authors: Vitoratos N. , Gregoriou O. , Chrysicopoulos A. , Zourlas P.A.
Published: April 2004

A case of combined subsequent development of intrauterine and extrauterine pregnancy is reported. Signs of normal pregnancy associated with abdominal pains and an adnexal mass were the most significant symptoms and the final diagnosis was verified by laparoscopy in both cases. We consider that drugs for induction of ovulation (chlomiphene citrate and menopausal gonadotropins) were the causative factors of this rare obstetric complication.
Structural elements involved in electron‐coupled proton transfer in cytochrome c oxidase
Authors: Namslauer Andreas , Brzezinski Peter
Published: April 2004

Haem‐copper oxidases are the last components of the respiratory chains in aerobic organisms. These membrane‐bound enzymes energetically couple the electron transfer (eT) reactions associated with reduction of dioxygen to water, to proton pumping across the membrane. Even though the mechanism of proton pumping at the molecular level still remains to be uncovered, recent progress has presented us with the structural features of the pumping machinery and detailed information about the eT and proton‐transfer reactions associated with the pumping process.
A tradeoff between protein stability and conformational mobility in homotrimeric dUTPases
Authors: Takács Enikő , Grolmusz Vince K. , Vértessy Beáta G.
Published: April 2004

Oligomerization directs active site formation in homotrimeric 2′‐deoxyuridine triphosphate pyrophosphatases (dUTPases). Stability of the homotrimer is a central determinant in enzyme function. The present comparative studies of bacterial and fruitfly dUTPases with homologous 3D structures by differential scanning microcalorimetry; fluorescence, circular dichorism and infrared spectroscopies, demonstrate that unfolding is a two‐state highly cooperative transition in both dUTPases excluding a significantly populated intermediate state of dissociated and folded monomers. The eukaryotic protein is much less resistant against either thermal or guanidine hydrochloride‐induced denaturation. Results suggest that hydrophobic packing of the inner threefold channel of the dUTPase homotrimer greatly contributes to stability.
The hafstramb and margygr of the King's Mirror: an analysis
Authors: Lehn Waldemar H. , Schroeder Irmgard I.
Published: April 2004

Greenland and Iceland are described with unusual scientific accuracy in the King's Mirror. However this thirteenth-century manuscript contains a few ‘wonders’ that appear more mythological than rational. They include the hafstramb and the margygr, commonly translated respectively as merman and mermaid. The mermaid has a long history in western civilisation. The commonly accepted theory that it evolved from the classical Greek siren is critically examined here. The margygr is shown to be a distinct creature based on independent observation in northern Europe. The characteristics of these observations actually modified the siren of the Physiologus, a bird-woman, into the fish-woman known today. Observations of hafstramb and margygr are explained as superior mirages. These are caused by atmospheric refraction, which distorts and magnifies distant objects. Computer simulations and photographs show that mirages of an orca, a walrus, or even a boulder match almost point for point the descriptions in the King's Mirror. Thus the apparently mythical components in the Greenland account are in fact careful scientific observations.
Can the Important Bird Area approach improve the Antarctic Protected Area System?
Authors: Harris Jane W. , Woehler Eric J.
Published: April 2004

The selection of sites that comprise the existing network of Antarctic protected areas has been largely ad hoc, driven by national interests rather than concerted efforts to ensure systematic and representative coverage of the Antarctic environment. Consequently there are gaps in coverage of all major ecosystems, in particular areas kept inviolate from human activity, inland lakes, and marine protected areas. Annex V of the 1991 Protocol on Environmental Protection to the Antarctic Treaty provides a list of values to be protected within a network of Antarctic Specially Protected Areas (ASPAs), but provides no quantitative methods for site identification and prioritisation. The Antarctic Important Bird Area (IBA) Inventory is a joint initiative of BirdLife International and the Scientific Committee on Antarctic Research Group of Experts on Birds (formerly the Bird Biology Subcommittee). The Antarctic IBA Inventory has identified 119 candidate IBAs, 97 of which are not currently protected as ASPAs. The IBA Inventory can improve the Antarctic Protected Area System (PAS) in that it provides a method by which to identify and prioritise sites for their potential inclusion in the Antarctic PAS.
Environmental pollutants from the Scott and Shackleton expeditions during the ‘Heroic Age’ of Antarctic exploration
Authors: Blanchette Robert A. , Held Benjamin W. , Jurgens Joel A. , Aislabie Jackie , Duncan Shona , Farrell Roberta L.
Published: April 2004

Early explorers to Antarctica built wooden huts and brought huge quantities of supplies and equipment to support their geographical and scientific studies for several years. When the expeditions ended and relief ships arrived, a rapid exodus frequently allowed only essential items to be taken north. The huts and thousands of items were left behind. Fuel depots with unused containers of petroleum products, asbestos materials, and diverse chemicals were also left at the huts. This investigation found high concentrations of polyaromatic hydrocarbons in soils under and around the historic fuel depots, including anthracene, benzo[b]fluoranthene, benzo[k]fluoranthene, chrysene, fluorene, and pyrene, as well as benzo[a]anthracene, benzo[a]pyrene, and fluoranthene, which are recognized carcinogens. Asbestos materials within the huts have been identified and extensive amounts of fragmented asbestos were found littering the ground around the Cape Evans hut. These materials are continually abraded and fragmented as tourists walk over them and the coarse scoria breaks and grinds down the materials. A chemical spill, within the Cape Evans hut, apparently from caustic substances from one of the scientific experiments, has caused an unusual deterioration and defibration on affected woods. Although these areas are important historic sites protected by international treaties, the hazardous waste materials left by the early explorers should be removed and remedial action taken to restore the site to as pristine a condition as possible. Recommendations are discussed for international efforts to study and clean up these areas, where the earliest environmental pollution in Antarctica was produced.
Older labour migrants' well being in Europe: the case of Switzerland
Authors: BOLZMAN CLAUDIO , PONCIONI-DERIGO RAFFAELLA , VIAL MARIE , FIBBI ROSITA
Published: April 2004

This paper examines several aspects of the social situation of the older immigrant population in Switzerland. It reviews their demographic history and characteristics and provides profiles of their health and well being, their material standard of life and access to social security and related benefits. It reports selected findings from an original survey of older Italian and Spanish citizens who are resident in the country, which show relatively high rates of disadvantage and poverty. The determination of a large proportion of the immigrant population to remain in Switzerland after they have ceased work demonstrates that the minorities who entered the country as labour migrants will become a permanent element of the Swiss population and its society. Neither the politicians nor the general public in Switzerland have yet accepted the reality of this new diversity. Given the continuation and indeed growth of international labour migration, the paper concludes by discussing the social policy and attitudinal options that face the governments and the population of Switzerland and many other European countries.
Psychosociological anchoring and structural dynamics in social representations of the heterosexual/homosexual couple
Authors: Rateau Patrick
Published: April 2004

This article reports an experimental study on structural variations in a representational field as a function of social regulations activated in symbolic intergroup relations. Two centrality questionnaires were used (refutation technique), one on the representation of the heterosexual couple and one on the representation of the homosexual couple. These questionnaires were administered in the opposite order to two groups of 80 heterosexual men. When there was no intergroup comparison, the participants exhibited the same representation of the two types of couple. In the implicit comparison situation they differentiated the two categories, both by reorganizing the central-system hierarchy of their heterosexual-couple representation, and by over-activating its peripheral elements. Datas are analyzed in terms of the links between the structural dynamics of social representations and the identity dynamics upon which social relations are based.
Interpersonal conflicts in borderline personality disorder: An exploratory study using the CCRT-LU
Authors: Drapeau Martin , Perry J. Christopher
Published: April 2004

This exploratory study compared the relationship patterns of 12 patients with borderline personality disorder (BPD) with those of 11 patients without Axis II pathology using the newly developed CCRT-LU. Results showed that the most prevalent wishes of patients with BPD reflect both a desire and a fear of establishing relationships with significant others. Results also showed that BPDs felt dissatisfied and scared, and determined by others, dependent and weak in interpersonal situations. When comparing BPD and non-BPD subjects, results indicated that BPD subjects display fewer wishes to attend to others, perceive others as more loving and subjugating, more often feel dissatisfied and scared, and are less attacking than subjects without BPD.
Telegrapher equations for arbitrary frequencies and modes: Radiation of an infinite, lossless transmission line
Authors: Nitsch Jürgen , Tkachenko Sergey
Published: April 2004

Maxwell's equations for an infinite, lossless transmission line above a perfectly conducting ground are transformed into telegrapher equations with new generalized per‐unit‐length parameters of the conductor. These new line parameters are complex‐valued, frequency‐dependent, and contain the radiation resistance. Their explicit expressions depend on the chosen gauge, but there is also a gauge‐independent representation for them. In the quasi‐static approach of the Maxwell‐Telegrapher equations the line parameters become real‐valued, and radiation is absent. A Poynting vector analysis leads to a deeper physical understanding and interpretation of the new parameters.
Long‐term decrease in the global atmospheric burden of tetrachloroethene (C2Cl4)
Authors: Simpson Isobel J. , Meinardi Simone , Blake Nicola J. , Rowland F. Sherwood , Blake Donald R.
Published: April 2004

We present a 14‐year record of tropospheric tetrachloroethene (C2Cl4) mixing ratios measured each season at remote surface locations throughout the Pacific Basin (71°N–47°S). Our calculated annual mean C2Cl4 mixing ratio for the extra‐tropical northern hemisphere (NH) was 13.9 ± 0.5 pptv in 1989, but declined to less than half this value (to 6.5 ± 0.2 pptv) by 2002. Mid‐latitude southern hemisphere (SH) mixing ratios, which were much smaller than NH values, showed interannual variations comparable to measured long‐term changes, and the SH annual mean was slightly less in 2002 than in 1989. Driven by the relatively large decrease in NH values, the global C2Cl4 mixing ratio declined from 6.3 ± 0.6 pptv in 1989 to 3.5 ± 0.2 pptv in 2002. These values suggest that the global C2Cl4 burden decreased by roughly 205 Gg between 1989–2002, which is consistent with industrial estimates of declining NH emissions over a similar period.
Modeling methane emission from rice paddies with various agricultural practices
Authors: Huang Yao , Zhang Wen , Zheng Xunhua , Li Jin , Yu Yongqiang
Published: April 2004

Several models have been developed over the past decade to estimate CH4 emission from rice paddies. However, few models have been validated against field measurements with various parameters of soil, climate and agricultural practice. Thus reliability of the model's performance remains questionable particularly when extrapolating the model from site microscale to regional scale. In this paper, modification to the original model focuses on the effect of water regime on CH4 production/emission and the CH4 transport via bubbles. The modified model, named as CH4MOD, was then validated against a total of 94 field observations. These observations covered main rice cultivation regions from northern (Beijing, 40°30′N, 116°25′E) to southern China (Guangzhou, 23°08′N, 113°20′E), and from eastern (Hangzhou, 30°19′N, 120°12′E) to southwestern (Tuzu, 29°40′N, 103°50′E) China. Both single rice and double rice cultivations are distributed in these regions with different irrigation patterns and various types of organic matter incorporation. The observed seasonal amount of CH4 emission ranged from 3.1 to 761.7 kg C ha−1 with an average of 199.4 ± 187.3 kg C ha−1. In consonance with the observations, model simulations resulted in an average value of 224.6 ± 187.0 kg C ha−1, ranging from 13.9 to 824.3 kg C ha−1. Comparison between the computed and the observed seasonal CH4 emission yielded a correlation coefficient r2 of 0.84 with a slope of 0.92 and an intercept of 41.1 (n = 94, p < 0.001). It was concluded that the CH4MOD can reasonably simulate CH4 emissions from irrigated rice fields with a minimal number of inputs and parameters.
Estimating the state of the thermospheric composition using Kalman filtering
Authors: Minter C. F. , Fuller‐Rowell T. J. , Codrescu M. V.
Published: April 2004

To determine the propagation parameters of high‐frequency radio waves, an accurate estimate of the ionosphere is desirable. Estimating the ionosphere, especially during geomagnetic storm times, is strongly dependent on perturbations in the neutral composition. Because of this coupling between the ionosphere and neutral atmospheric chemistry, accurate knowledge of the neutral atmospheric composition is critical in estimating the ionosphere. In the research presented here, a data assimilation system is constructed to optimally estimate the neutral composition, and the necessity for implementing an optimized filtering method, like the Kalman filter, is shown. To demonstrate the data assimilation system, an artificial “truth” thermosphere is created using a physical model. This thermosphere is sampled according to an instrument and satellite simulation algorithm, creating the measurement data set. Noise is then added to the measurement data, to represent observation errors. Data are assimilated, and noise from this data is reduced using a Kalman filter in combination with a state propagation model. Results show that the error in the estimate can be greatly reduced (usually to <6%), even if the observation errors are large (15%), by using a Kalman filter. Best results are obtained by using a Kalman filter together with an accurate physical model.
Rise velocity of an air bubble in porous media: Theoretical studies
Authors: Corapcioglu M. Yavuz , Cihan Abdullah , Drazenovic Mirna
Published: April 2004

The rise velocity of injected air phase from the injection point toward the vadose zone is a critical factor in in‐situ air sparging operations. It has been reported in the literature that air injected into saturated gravel rises as discrete air bubbles in bubbly flow of air phase. The objective of this study is to develop a quantitative technique to estimate the rise velocity of an air bubble in coarse porous media. The model is based on the macroscopic balance equation for forces acting on a bubble rising in a porous medium. The governing equation incorporates inertial force, added mass force, buoyant force, surface tension and drag force that results from the momentum transfer between the phases. The momentum transfer terms take into account the viscous as well as the kinetic energy losses at high velocities. Analytical solutions are obtained for steady, quasi‐steady, and accelerated bubble rise velocities. Results show that air bubbles moving up through a porous medium equilibrate after a short travel time and very short distances of rise. It is determined that the terminal rise velocity of a single air bubble in an otherwise water saturated porous medium cannot exceed 18.5 cm/s. The theoretical model results compared favorably with the experimental data reported in the literature. A dimensional analysis conducted to study the effect of individual forces indicates that the buoyant force is largely balanced by the drag force for bubbles with an equivalent radius of 0.2–0.5 cm. With increasing bubble radius, the dimensionless number representing the effect of the surface tension force decreases rapidly. Since the total inertial force is quite small, the accelerated bubble rise velocity can be approximated by the terminal velocity.
Diurnal variability of dust aerosol optical thickness and Angström exponent over dust source regions in China
Authors: Wang Jun , Xia Xiangao , Wang Pucai , Christopher Sundar A.
Published: April 2004

Using 22 months of Sunphotometer Aerosol Optical Thickness (AOT) data collected near the Taklamakan and Gobi dust source regions (Dunhuang, 40.09°N, 94.41°E) in China; we examine the diurnal and seasonal change of dust aerosol properties. Most dust events are during the spring through early summer months with a season‐invariant diurnal change of more than ±10% for AOT and ±30% for Angström exponent, with larger AOT and smaller Angström exponent values late in the afternoon. These values are much larger when compared to recent studies that have reported a much smaller (±5%) diurnal variability of dust AOT over various AERONET sites where dust is a major contributor to AOT. The differences are largely due to the geographical locations and meteorological conditions and such large diurnal changes of aerosol properties at or near dust source regions may be significant enough for consideration in regional radiative forcing, air quality and numerical modeling studies.
Overexpression of vasopressin (V3) and corticotrophin‐releasing hormone receptor genes in corticotroph tumours
Authors: De Keyzer Y. , René P. , Beldjord C. , Lenne F. , Bertagna X.
Published: April 2004

OBJECTIVE

The molecular mechanisms underlying ACTH‐secreting tumour formation remain unknown. Transmembrane signalling pathways play an important role in several endocrine disorders including pituitary tumours. To investigate the role of the pituitary vasopressin (V3) receptor (R) in ACTH‐secreting tumours we have qualitatively and quantitatively analysed its mRNA.

DESIGN

RT–PCR, denaturing gradient gel electrophoresis and S1 nuclease protection experiments were used to analyse V3 mRNA structure in ACTH‐secreting tumours. We also developed a competitive RT–PCR system to compare the levels of expression of POMC, V3 and CRH‐R genes. This system used as competitor a single mutant template (termed multi‐mutant) containing primers for the three genes flanking an unrelated core sequence allowing multiple quantifications from the same cDNA preparations. We analysed 12 normal pituitaries, 15 corticotroph pituitary adenomas and 6 ACTH‐secreting bronchial carcinoids.

RESULTS

The V3 mRNA structure and sequence were found to be identical in normal and tumoural pituitary indicating that the tumoural Vs mRNA codes for a normal receptor. POMC RT–PCR signals in the pituitary tumour group were approximately 7‐fold higher than in the normal pituitary group. Similarly, V3 and CRH‐R signal were increased in pituitary tumors (mean ± SEM: 5.87 × 10−6 ± 1.73 × 10−6, and 2.33 × 10−4 ± 1.4 × 10−4, respectively), when compared to normal pituitaries (1.19 × 10−7 ± 2.39 × 10−8, and 1.7 × 10−6 ± 4.65 × 10−7, respectively) suggesting that these two genes are expressed at very high levels in corticotroph tumours. When expressed relative to the corresponding POMC signals, increases in V3 and CRH‐R signals reached 49‐fold and 137‐fold, respectively, in pituitary tumours. In ACTH‐secreting bronchial carcinoids V3 gene expression level was also higher than in normal pituitary, whereas CRH‐R signals were detected in only 4 of the 6 tumours with wide variations.

CONCLUSION

Our results show that both vasopressin and CRH receptor genes are overexpressed in ACTH‐secreting pituitary tumours. They suggest that overexpression of G protein‐coupled receptors may be an additional mechanism through which membrane receptors may play a role in human tumours.
Therapieoptionen der Psoriasis im Kindes‐ und Jugendalter
Authors: Zappel Kristina , Sterry Wolfram , Blume‐Peytavi Ulrike
Published: April 2004

Der Zeitpunkt der Erstmanifestation einer Psoriasis liegt bei etwa 30 % aller Psoriatiker im Kindes‐ und Jugendalter. Bei ¼ dieser Kinder zeigen sich psoriasiforme Hautveränderungen sogar schon um das 2. Lebensjahr. Die Behandlung der kindlichen Psoriasis unterscheidet sich in einigen Punkten wesentlich von der Psoriasistherapie im Erwachsenenalter, da nicht nur Lebensalter und Ausprägungsgrad, sondern auch Entwicklungszustand, prognostische Kriterien und soziales Umfeld berücksichtigt werden sollten. Richtlinien, qualitativ hochwertige Studien und konkrete Empfehlungen zur Therapieauswahl fehlen für die kindliche Psoriasis jedoch meistenteils.

Dieser Artikel soll einen Überblick über das therapeutische Management der Psoriasis im Kindes‐ und Jugendalter geben. Wir diskutieren nach aktueller Literatur umfassend externe und interne Therapieoptionen unter kritischer Wertung und Berücksichtigung des Aspektes der Prävention und Verbesserung der Lebensqualität.
Elementanalytische Untersuchungen von Tätowierungsfarbstoffen – Besteht eine potentielle Gefährdung durch Tätowierungsfarbstoffe?
Authors: Schmitz I. , Müller K.‐M.
Published: April 2004

Hintergrund: Auch heute verwendete, im Rahmen der Tätowierung kutan inkorporierte Farbstoffe können Fremdkörperreaktionen auslösen.

Methodik: Da es für die Zusammensetzung der Inhaltsstoffe von Tattoofarben noch keine Richtlinien gibt, untersuchten wir in Tätowierungs‐Studios verwendete „neuere” Tattoofarbstoffe auf ihre Elementzusammensetzung, um Hinweise auf eine potentielle Gefährdung durch diese zu finden. Die elementanalytische Charakterisierung erfolgte im Rasterelektronenmikroskop mittels der energiedispersiven Röntgenmikroanalyse. Diese EDS‐Analyse weist Elemente ab der Natriumlinie nach und dient vor allem zum Beleg von Metallkomponenten; über chemische Bindungsverhältnisse können keine Aussagen getroffen werden.

Ergebnisse: Unsere Untersuchungen zeigten, daß auch in heute verwendeten Tattoofarbstoffen vielfach Metallkomponenten nachweisbar sind, die als Ursachen persistierender Fremdkörperreaktion bekannt sind. Silizium, Aluminium, Titan und Kupfer fanden sich insbesondere in gelben, grünen und roten Farbstoffen einzelner Chargen. Die Zusammensetzung von Tattoofarben mit gleichen Farbtönen war in verschiedenen Chargen oft divergierend.

Schlußfolgerungen: Auch die heute verwendeten „neueren” Tattoofarbstoffe sind nicht als „gewebe‐inert” zu werten und potentielle Ursachen von Fremdkörperreaktionen, die sich noch Jahre nach ihrer Inkorporation einstellen können.
Confinement of plasmas of arbitrary neutrality in a stellarator
Authors: Pedersen Thomas Sunn , Boozer Allen H. , Kremer Jason P. , Lefrancois Remi
Published: April 2004

The equilibrium, stability, and transport of pure electron plasmas confined on magnetic surfaces is reviewed. The prospects for creation of partly neutralized plasmas and electron–positron plasmas confined in a stellarator are discussed. The Columbia Non-neutral Torus, a small ultrahigh vacuum stellarator being constructed at Columbia University, is being built to systematically study non-neutral plasmas confined on magnetic surfaces. The experimental design is discussed in the context of relevant physics parameters, and the initial experimental plans for creation and diagnosis of pure electron plasmas are discussed.
The structure of turbulence in clouds measured by a high power 94 GHz radar
Authors: Manheimer W. M. , Fliflet A. W. , Linde G. J. , Cheung W. J. , Gregers-Hansen V. , Ngo M. T. , Danly B. G.
Published: April 2004

The Naval Research Laboratory (NRL) has recently developed a 3–10 kW average, 80 kW peak power 94 GHz radar with scanning capability, WARLOC (W Band Advanced Radar for Low Observable Control). This radar is powered by a gyroklystron developed by a team led by NRL. One application has been to image clouds. New capabilities of WARLOC include imaging with greatly improved sensitivity and detail as well as the ability to detect much lower cloud returns. At short scale lengths (∼10 m), the cloud reflectivity has a speckle pattern indicating that it is governed at least in part by stochastic processes. Here WARLOC is used to measure correlation functions and turbulence spectra in clouds. In the inertial range, the Kolmogorov prediction for the correlation function index (2/3) agrees well with the data, but the assumption of isotropy does not. Furthermore, for longer scale lengths, the fluctuations appear to be wave like in the vertical direction, but not in the horizontal direction.
Observation and simulation of plasma mix after reshock in a convergent geometry
Authors: Parker K. , Horsfield C. J. , Rothman S. D. , Batha S. H. , Balkey M. M. , Delamater N. D. , Fincke J. R. , Hueckstaedt R. M. , Lanier N. E. , Magelssen G. R.
Published: April 2004

Experiments to study the effect of a second, counterpropagating shock on the growth of hydrodynamic instabilities in a convergent, compressible system have been performed on the Omega Laser [T. R. Boehly et al., Opt. Commun. 133, 495 (1997)] at the University of Rochester. Direct laser illumination of a cylindrical target launches a strong shock across hydrodynamically unstable interfaces formed between an epoxy ablator material on the outside, a buried aluminum marker layer and low-density CH foam on the inside. The Richtmyer–Meshkov instability mixes the marker into the two adjacent materials. Of particular interest is what happens when the mixing region is reshocked by using a second, coaxial central cylinder to reflect the incident shock back into the mixing region. These experiments have been extensively modeled, in two dimensions, using the hydrocodes NYM [P. D. Roberts et al., J. Phys. D 13, 1957 (1980)], PETRA [D. L. Youngs, Physica D 12, 32 (1984)], and RAGE [R. M. Baltrusaitis et al., Phys. Fluids 8, 2471 (1996)]. Good agreement is shown between the simulations and experimental data.
Propagation of ultra-short, intense laser pulses in air
Authors: Peñano J. R. , Sprangle P. , Hafizi B. , Ting A. , Gordon D. F. , Kapetanakos C. A.
Published: April 2004

Recent theoretical, computational, and experimental work carried out at the Naval Research Laboratory on the propagation of ultra-short laser pulses in air is presented. Fully time-dependent, three-dimensional, nonlinear equations describing the propagation of laser pulses in air under the influence of diffraction, group velocity dispersion, Kerr nonlinearity, stimulated Raman scattering, ionization, and plasma wakefield excitation are presented and analyzed. The propagation code, HELCAP [P. Sprangle, J. R. Peñano, and B. Hafizi, Phys. Rev. E 66, 046418 (2002)], is used to simulate the propagation of laser pulses in air under the influence of the physical processes mentioned above. Simulations of laser filamentation together with experimental measurements are used to confirm that the filamentation process is dependent on pulse duration. An equilibrium configuration for optical and plasma filaments in air is derived and the dynamic guiding and spectral broadening of a laser pulse is modeled. The effect of atmospheric turbulence on nonlinear self-focusing is demonstrated. Simulations of a recent electromagnetic pulse (EMP) generation experiment are also presented and the efficiency of EMP generation is determined and found to be extremely small.
Second ballooning stability in high-β, compact stellarators
Authors: Ware A. S. , Westerly D. , Barcikowski E. , Berry L. A. , Fu G. Y. , Hirshman S. P. , Lyon J. F. , Sanchez R. , Spong D. A. , Strickler D. J.
Published: April 2004

Second ballooning stability is examined in quasipoloidally symmetric, compact stellarator configurations. These high-β (volume-average β>4%) free-boundary equilibria are calculated using a reference Quasi-Poloidal Stellarator (QPS) configuration. QPS plasmas have low-shear, stellarator-like rotational transform profile with |B| that is approximately poloidally symmetric. The high-β QPS equilibria are similar in their magnetic configuration to previously studied tokamak-stellarator hybrids which have a high-shear, tokamak-like rotational transform profile. Both types of configurations have strong magnetic wells and consequently high interchange stability β limits. Free-boundary QPS equilibria have regions of second stability at high β. For infinite-n ballooning modes in QPS plasmas, the boundary for first instability is 〈β〉∼2% and the boundary for second stability is 〈β〉∼6%. Finite-n ballooning mode calculations show higher β limits, 〈β〉>5%. Increasing plasma current (for fixed plasma pressure) can lower the finite-n ballooning mode β limit to 〈β〉=3% by reducing magnetic shear. QPS plasmas with Ohmic current profiles (peaked on-axis) have both a lower infinite-n ballooning β-limit for the onset of first instability and a higher β-limit for the onset of second stability relative to QPS plasma with bootstrap current profiles (peaked off-axis). QPS plasmas are stable to low-n ideal magnetohydrodynamic kink modes and vertical modes for values of β in this range (〈β〉∼6%) due to the low level of plasma current in QPS relative to an equivalent tokamak.