bluuebunny/crossref_metadata_2025 huggingface dataset:
An electrostatic basis for the stability of thermophilic proteins
Authors: Dominy Brian N. , Minoux Hervé , Brooks Charles L.
Published: June 2004

Two factors provide key contributions to the stability of thermophilic proteins relative to their mesophilic homologues: electrostatic interactions of charged residues in the folded state and the dielectric response of the folded protein. The dielectric response for proteins in a “thermophilic series” globally modulates the thermal stability of its members, with the calculated dielectric constant for the protein increasing from mesophiles to hyperthermophiles. This variability results from differences in the distribution of charged residues on the surface of the protein, in agreement with structural and genetic observations. Furthermore, the contribution of electrostatic interactions to the stability of the folded state is more favorable for thermophilic proteins than for their mesophilic homologues. This leads to the conclusion that electrostatic interactions play an important role in determining the stability of proteins at high temperatures. The interplay between electrostatic interactions and dielectric response also provides further rationalization for the enhanced stability of thermophilic proteins with respect to cold‐denaturation. Taken together, the distribution of charged residues and their fluctuations have been shown to be factors in modulating protein stability over the entire range of biologically relevant temperatures. Proteins 2004. © 2004 Wiley‐Liss, Inc.
Wave function and quasi‐energy of conduction electrons in a field of coherent light beams
Authors: Semchuk O. Yu. , Willander M. , Karlsteen M.
Published: June 2004

In this work the influence of high‐frequency coherent light beams (CLB) on the motion of conduction electrons in a crystalline phase is studied. The wave function and the quasi‐energy of conduction electrons are calculated. It is shown that a force that is associated with a pressure from the CLB influences the conduction electrons. A new approach to construct the kinetic equation, that takes into account the effects due to a CLB field that acts as the elementary processes for quasi‐particle interaction in a crystalline phase, is presented. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Effect of germanium content on the medium range order and the vibrational analysis of Ge–Se chalcogenide glass system
Authors: Jayakumar S. , Predeep P. , Unnithan C. Harikuttan
Published: June 2004

An attempt is made to explain the Medium Range Order in the chalcogenide glass system Gex–Se1–x by computing the radial distribution function, g(r) from the available data of the structure factor, S(q). The results obtained are compared with pioneer works. The above obtained value of g(r) together with the effective interatomic potential calculated from S(q) applying Rao–Joarder equation is used for studying the vibrational eigen frequencies of the system both in the transverse and longitudinal phonon modes. From the long wavelength limit of the phonon frequency spectrum, the elastic and the thermal properties are also estimated. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Band structure, metallization and superconductivity of GaP and GaN under high pressure
Authors: Louis C. Nirmala , Iyakutti K. , Nandhini K. S. Hema , Sivakumar M. , Palaniyandi E.
Published: June 2004

The electronic band structure, metallization, structural phase transition and superconductivity of cubic zinc blende‐type GaP and GaN are investigated. The equilibrium lattice constant, bulk modulus and pressure at which the compounds undergo a structural phase transition from ZnS structure to NaCl structure are predicted from the total energy calculations. The density of states at the Fermi level (N(EF)) is enhanced after metallization, which leads to the superconductivity in GaP and GaN. The superconducting transition temperatures (Tc) of GaP and GaN are obtained as a function of pressure for both the ZnS and NaCl structures and GaP and GaN come under the category of pressure‐induced superconductors. When pressure is increased Tc increases in both the normal and high‐pressure structures. The dependence of Tc on the electron–phonon mass enhancement factor λ shows that GaP and GaN are electron–phonon‐mediated superconductors. Also, it is found that GaP and GaN retained in their normal structure under high pressure give appreciably high Tc. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Screening dependence of superconducting state parameters of Cu–Zr metallic glasses
Authors: Sharma S. , Khan H. , Sharma K. S.
Published: June 2004

The screening dependence of superconducting state parameters (λ, μ*, Tc, α and N0V) of nine metallic glasses of the Cu–Zr system has been studied in the BCS–Eliashberg–McMillan framework by employing five forms of dielectric screening function in conjunction with Ashcroft's potential. It is observed that the electron–phonon coupling strength (λ) and transition temperature (Tc) are quite sensitive to the form of the dielectric screening, whereas the Coulomb pseudopotential (μ*), isotope effect exponent (α) and effective interaction strength (N0V) show weak dependences on screening function. The RPA form of dielectric screening is observed to yield the best results for all the glasses of the Cu–Zr system studied in the present work. Present computations yield almost linear variation of Tc with concentration x of Cu in the Cu–Zr system, which is in agreement with the experimental data. A linear Tc equation is proposed by fitting the present results for RPA screening, which is in conformity with other results for the experimental data. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Localization of electronic eigenstates and spin waves in diluted magnetic semiconductors at low carrier densities
Authors: Berciu Mona , Bhatt R. N.
Published: June 2004

Using mean‐field and random‐phase approximations, we perform numerical simulations on finite‐size systems to investigate the effects of disorder on the nature (localized or extended ) of both electronic states and collective magnetic (spin‐wave) excitations for a prototypical disordered system with both electronic (fermionic) and magnetic degrees of freedom. We use a simple impurity model appropriate for dilute magnetic semiconductors at low charge carrier concentrations, below and near the metal‐insulator transition. In our model, the positional disorder of the magnetic dopants is taken into account at the outset. We find that enhanced disorder implies significant inhomogeneity in magnetic properties, leading to appearance of localized electron states as well as localized collective magnetic excitations. As a result, positional disorder of the dopants can significantly influence transport and magnetic properties in such materials at low dopant and carrier densities. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Roles of interactions in electronic properties of quantum disordered wires
Authors: Mori H. , Takeuchi Y.
Published: June 2004

We studied electronic transport properties of quantum wires with electron–electron interactions and random potentials. We focus in particular on the roles of the interactions in various situations. In a single wire system the interactions would enhance the random potential effect in some cases while they would suppress it in other cases. Taking analytical and numerical approaches, we clarified the roles in Hubbard wire based on the analysis of 4kF impurity scattering. We also studied the influence of inter‐wire interactions between parallel wires in the presence of random potentials and found a rather different role of the interactions on the localization phenomena. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Electronic transport in nanoparticle arrays: The effect of structural disorder
Authors: Nikolić K.
Published: June 2004

Self‐assembled nanoparticle structures represent a very promising way of achieving nanoelectronic devices and even circuits. In this paper we analyse the electronic transport properties of nanoparticle arrays formed on the surface of ionic crystals. Results for the numerical simulations of the quantum percolation problem in the nanoparticle arrays or discontinuous metal films are given. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Conductance fluctuations in one‐ and two‐dimensional localized systems
Authors: Ortuño M. , Somoza A. M. , Prior J.
Published: June 2004

We study quantum fluctuations in the localized regime of one‐dimensional systems. We calculate the variable‐range hopping conductance including fluctuations in the size of the states. Quantum effects increase the average resistance without qualitatively changing Mott's law and cannot be neglected for a proper interpretation of experimental results. We also discuss the effects of these fluctuations in two‐dimensional systems. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Critical points and quenched disorder: From Harris criterion to rare regions and smearing
Authors: Vojta Thomas , Sknepnek Rastko
Published: June 2004

We consider the influence of quenched spatial disorder on phase transitions in classical and quantum systems. We show that rare strong disorder fluctuations can have dramatic effects on critical points. In classical systems with sufficiently correlated disorder or in quantum systems with overdamped dynamics they can completely destroy the sharp phase transition by smearing. This is caused by effects similar to but stronger than Griffiths phenomena: True static order can develop on a rare region while the bulk system is still in the disordered phase. We discuss the thermodynamic behavior in the vicinity of such a smeared transition using optimal fluctuation theory, and we present numerical results for a two‐dimensional model system. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Synthesis and identification of two potential oxidation degradants of oxymetazoline
Authors: Leader Ian P. , Halket John , Finch Paul
Published: June 2004

Two potential oxidation degradants of oxymetazoline have been isolated by liquid chromatography and monitored by electrospray single quadrupole mass spectrometry. The structures of the products are shown to be oxymetazoline N‐oxide and hydroxyamine by multiple‐stage fragmentation ion trap mass spectrometry. The product ion spectra were installed in a library database and the library was used to examine an aged commercial product; one of the degradants was detected, but at a level of less than 0.1% of the parent. Copyright © 2004 John Wiley & Sons, Ltd.
Parenting and adolescent self‐regulation
Authors: Purdie Nola , Carroll Annemaree , Roche Lawrence
Published: June 2004

This study examined the relationship between adolescents’ academic and non‐academic self‐regulation (SR), authoritative parenting (as demonstrated by high levels of Involvement, Strictness, and Autonomy Granting), and parent self‐efficacy in four areas. Participants were 214 Australian high school students and their parents. There was a moderate correlation (r=0.63) between academic and non‐academic SR. Adolescents and their parents differed significantly in their perceptions of parenting behaviours, with parents rating themselves higher than their children on Involvement, Autonomy Granting, and Strictness behaviours. A model of the relationships between the constructs was developed showing a strong path from parent self‐efficacy to both academic and non‐academic SR via high parental Involvement (as perceived by adolescents). Strict parenting and the granting by parents of psychological autonomy to their adolescent children did not appear to be important in the development of young people's self‐regulatory behaviours.
Adolescent drug trafficking trends in the United Kingdom—a 10‐year retrospective analysis
Authors: Vale Ellen Louise Eva , Kennedy Patrick John
Published: June 2004

This paper reports data from HM Customs and Excise (HMCE) of recorded cases of adolescent drug trafficking through all sea and air points of entry into the UK over a 10‐year period (May 1992–May 2002). We report the characteristics of 38 cases of mixed gender and nationality ranging in age between 13 and 18 years who have been apprehended by HMCE due to the illegal importation of drugs. Highlighted is an increasing trend in UK national male and female adolescents being apprehended for drug trafficking. Of particular note is the observation that more young adolescent females were apprehended importing large consignments of Class A substances than their male counterparts.
Increased plasma HDL cholesterol levels and biliary cholesterol excretion in hamster by LCAT overexpression
Authors: Zhang Ai-Hong , Gao Song , Fan Jiang-lin , Huang Wei , Zhao Tie-Qiang , Liu George
Published: June 2004

Lecithin cholesterol acyltransferase (LCAT) is a key enzyme in the metabolism of high density lipoprotein (HDL), which has been found inversely correlated with atherosclerosis. Adenovirus mediated overexpression of human LCAT (hLCAT) in hamsters resulted in increased levels of plasma total cholesterol, HDL cholesterol, phospholipids and enlarged particle size of HDL. It also increased cholesterol and total bile acid concentrations in bile. Hepatic mRNA level of cholesterol 7α‐hydroxylase increased 2.7‐fold in hamsters. However, such effects were not observed in mice in a parallel experiment. This study suggests that overexpression of hLCAT in hamsters facilitated reverse cholesterol transport. Similar metabolic changes in humans might modify atherogenic risk.
Angiogenic activity of human CC chemokine CCL15 in vitro and in vivo
Authors: Hwang Jungsu , Kim Chan Woo , Son Kyung-No , Han Kyu Yeon , Lee Kyung Hee , Kleinman Hynda K , Ko Jesang , Na Doe Sun , Kwon Byoung S , Gho Yong Song , Kim Jiyoung
Published: June 2004

CCL15 is a novel human CC chemokine and exerts its biological activities on immune cells through CCR1 and CCR3. Because a number of chemokines induce angiogenesis and endothelial cells express CCR1 and CCR3, we investigated the angiogenic activity of CCL15. Both CCL15(1‐92) and N‐terminal truncated CCL15(25‐92) stimulate the chemotactic endothelial cell migration and differentiation, but CCL15(25‐92) is at least 100‐fold more potent than CCL15(1‐92). Treatment with pertussis toxin (PTX), with anti‐CCR1, or with anti‐CCR3 antibody inhibits the CCL15(25‐92)‐induced endothelial cell migration. CCL15(25‐92) also stimulates sprouting of vessels from aortic rings and mediates angiogenesis in the chick chorioallantoic membrane assay. Our findings demonstrate that CCL15(25‐92) has in vitro and in vivo angiogenic activity, and suggest roles of the chemokine in angiogenesis.
Senescence marker protein‐30 is a unique enzyme that hydrolyzes diisopropyl phosphorofluoridate in the liver
Authors: Kondo Yoshitaka , Ishigami Akihito , Kubo Sachiho , Handa Setsuko , Gomi Keiko , Hirokawa Kozo , Kajiyama Naoki , Chiba Tsuyoshi , Shimokado Kentaro , Maruyama Naoki
Published: June 2004

Senescence marker protein‐30 (SMP30) was originally identified as a novel protein in the rat liver, the expression of which decreases androgen‐independently with aging. We have now characterized a unique property of SMP30, the hydrolysis of diisopropyl phosphorofluoridate (DFP), which is similar to the chemical warfare nerve agents sarine, soman and tabun. Hydrolysis of DFP was stimulated equally well by 1 mM MgCl2, MnCl2 or CoCl2, to a lesser extent by 1 mM CdCl2 but not at all by 1 mM CaCl2. No 45Ca2+‐binding activity was detected for purified SMP30, suggesting that SMP30 is not a calcium‐binding protein, as others previously stated. Despite the sequence similarity between SMP30 and a serum paraoxonase (PON), the inability of SMP30 to hydrolyze PON‐specific substrates such as paraoxon, dihydrocoumarin, γ‐nonalactone, and δ‐dodecanolactone indicate that SMP30 is distinct from the PON family. We previously established SMP30 knockout mice and have now tested DFPase activity in their livers. The livers from wild‐type mice contained readily detectable DFPase activity, whereas no such enzyme activity was found in livers from SMP30 knockout mice. Moreover, the hepatocytes of SMP30 knockout mice were far more susceptible to DFP‐induced cytotoxicity than those from the wild‐type. These results indicate that SMP30 is a unique DFP hydrolyzing enzyme in the liver and has an important detoxification effect on DFP. Consequently, a reduction of SMP30 expression might account for the age‐associated deterioration of cellular functions and enhanced susceptibility to harmful stimuli in aged tissue.
Human chorionic gonadotrophin and progesterone levels in pregnancies of unknown location
Authors: Condous G. , Lu C. , Van Huffel S.V. , Timmerman D. , Bourne T.
Published: June 2004

Objective: To evaluate accuracy, user variability and impact of experience on the use of serum hCG and progesterone in women who have a pregnancy of unknown location (PUL's). Materials and methods: This was a retrospective study. Presenting 1932 consecutive women to an Early Pregnancy Unit had a transvaginal scan. The location of the pregnancy could not be found in 189 women (Pregnancy of unknown location, PUL), and so blood was taken to measure serum hCG and progesterone at presentation and subsequently after 48 h, according to the protocol. All women were monitored at regular intervals until the final outcome was known, which was a failing PUL, a viable or failing intra‐uterine pregnancy, an ectopic pregnancy or a persisting PUL. The final study group comprised 185 PUL, as four cases of persisting PUL were treated and excluded from the analysis. Five investigators assessed the hormonal data independently. The investigator's experience as defined by the number of years working in obstetrics and gynecology ranged from 2 to 15 years. Each investigator knew the women were clinically stable and that the scan result was consistent with a PUL, i.e. there were no signs of intra‐ or extra‐uterine pregnancy, and there was no hemoperitoneum on TVS. When assessing the PUL's, each investigator was given the hormonal results at time 0 and 48 h for serum hCG and progesterone and asked to classify the PUL's as failing PUL's, immediately viable intra‐uterine PUL's and ectopic PUL's. No other clinical information about the women was made available. Results: Complete data 185 women (89%): 102 failing PUL's, 63 immediately viable intra‐uterine PUL's and 20 ectopic PUL's (total 185). The most experienced investigator obtained the best accuracy 163/185 (88.1%); not significantly different from those obtained by less experienced investigators (range 85.9–87.6%). Mean correct classification of failing PUL and immediately viable intra‐uterine PUL's was 93% (range 89–95%); corresponding value for ectopic PUL's was 42% (range 25–60%). Agreement between observers for classification of failing PUL's and immediately viable intra‐uterine PUL's was almost perfect (Cohen's kappa 0.86–0.90), whereas the value for ectopic PUL's group was fair to moderate (Cohen's kappa 0.39–0.67). All 5 investigators misdiagnosed same 35% of ectopic PUL's. Conclusions: Serum hCG and progesterone levels at defined times can be used to predict the immediate viability of a PUL, but cannot be used reliably to predict its location. Clinical experience does not significantly improve the ability to assess PUL outcome.
Seasonal variation of the oxygen isotopic ratio of atmospheric carbon dioxide in a temperate forest, Japan
Authors: Kato Taro , Nakazawa Takakiyo , Aoki Shuji , Sugawara Satoshi , Ishizawa Misa
Published: June 2004

In order to examine the role of terrestrial biospheric activity in the seasonal variation of δ18O of atmospheric CO2, we measured δ18O values of CO2 and H2O in the soil and the canopy air in a temperate forest in the northern part of the main island of Japan for the period August 2000–December 2001. It was found that the δ18O value of the soil water near the surface varied seasonally almost in phase with that of precipitation, except for spring. On the other hand, its seasonal variation at 70 cm depth showed a 3‐month delay compared to those at 10 and 40 cm depths, owing to slow penetration of precipitation into the soil. The measured δ18O values of CO2 in the soil air at 10, 40, and 70 cm depths agreed well with the results calculated under the assumption that CO2 in the soil air was isotopically equilibrated with its surrounding soil water. On the basis of the measurement results, we derived the seasonally varying oxygen isotopic discrimination factors for respiration and photosynthesis processes. Using these discrimination factors as well as biospheric CO2 fluxes estimated by employing an ecosystem model, we calculated the seasonal variation of δ18O of atmospheric CO2 in the forest canopy. The result showed a good agreement with the observation, indicating that the isotopic contribution of photosynthesis to the atmospheric δ18O was strong in spring and fall, while that of respiration was dominant in summer and winter.
Long‐term (1936–2003) ultraviolet and photosynthetically active radiation doses at a north Norwegian location in spring on the basis of total ozone and cloud cover
Authors: Engelsen O. , Hansen G. H. , Svenøe T.
Published: June 2004

We have reconstructed a homogeneous and consistent 68‐year time series of ultraviolet (UVR) and photosynthetically active radiation (PAR) doses for the spring period at a marine location in northern Norway. The time series is simulated mainly on the basis of the Tromsø total ozone series and routine meteorological observations of cloud cover. All other relevant input parameters were fixed at realistic values determined by local measurements and climatology. Our approach is applicable to a wide range of locations worldwide where routine ozone measurements and cloud observations are done. For the whole period 1936–2003, we find trends of +4.5%, +2.8% and +1.3% per decade for the monthly UVB doses in March, April and May, respectively. UVA and PAR doses, which are not affected by total ozone, reveal smaller trends (+1–2% per decade) in March and April, while the May trend is comparable to UVB. At shorter term, however, the radiation trends were very variable.
Seasonal variation of HF radar F region echo occurrence in the midnight sector
Authors: Koustov A. V. , Sofko G. J. , André D. , Danskin D. W. , Benkevitch L. V.
Published: June 2004

Long‐term data (1996–2001) for a number of Super Dual Auroral Radar Network (SuperDARN) HF radars in both the Northern and Southern Hemispheres are used to study the midnight F region echo occurrence. We confirm the previously reported increase of echo occurrence toward the solar cycle maximum for all radars considered and a clear winter maximum for some of them. The echo occurrence rate experiences clear equinoctial maxima for many radar locations, especially at higher latitudes and in Antarctica. We attribute the solar cycle echo increase in the midnight sector to the more frequent occurrence of enhanced electric fields and strong plasma density gradients. The equinoctial maxima are believed to be controlled entirely by the electric field increase due both to the Russell‐McPherron effect and to differences in conjugate ionospheric conductances controlled by the tilt of the Earth's axis. For the low geographic latitude portion of the Saskatoon radar observations, the echo statistics differ from the other radars; there is a clear summer maximum in echo occurrence and no definite signature of equinoctial maxima. A summer maximum in low‐latitude echo occurrence also is observed by the Hankasalmi radar during the solar cycle minima. The effect is attributed to improved propagation conditions for HF radio waves during summer periods for the latitudes where, for other seasons, there is a deficiency in the electron density.
Spin axis behavior of the LAGEOS satellites
Authors: Andrés J. I. , Noomen R. , Bianco G. , Currie D. G. , Otsubo T.
Published: June 2004

The satellites LAGEOS‐I and LAGEOS‐II are essential for the scientific study of various (geo)physical phenomena, such as geocenter motion and absolute scale. The high quality of such science products strongly depends on the absolute quality of the SLR observations and that of the orbit description. Therefore all accelerations experienced by the spacecraft need to be modeled as accurately as possible, the thermal radiation forces being one of them. Traditionally, this is done by estimating so‐called empirical accelerations. However, the rotational dynamics of LAGEOS‐I in particular no longer allows such a simple approach: a full modeling of the spin behavior, the temperature distribution over the spacecraft surface and the resulting net force prove necessary to achieve the best results. As a first step, a new model, Lageos Spin Axis Model (LOSSAM) has been developed. It is unique in its combination of analytical theory and empirical observations. Its mathematics is taken after previous investigators, although flaws have been corrected. LOSSAM describes the full spin behavior of LOSSAM based on the following phenomena: (1) the geomagnetic field, (2) the Earth's gravity field, (3) the satellite center of pressure offset, and (4) the effective difference in reflectivity between the satellite hemispheres. Its accuracy has been demonstrated by an improvement of about a 50% in the RMS residual of the Yarkovsky‐Schach effect signal (as shown by Lucchesi et al. [2004]). Such a high‐quality model for rotational behavior is indispensable for a proper force modeling, and hence also for the quality of typical LAGEOS science products.
Analysis of extreme sea level along the east coast of India
Authors: Unnikrishnan A. S. , Sundar D. , Blackman D.
Published: June 2004

Hourly tide gauge data were analyzed for extreme sea level for three stations, Paradip, Vishakhapatnam, and Chennai, along the east coast of India. These stations are tidally dominant, with the magnitudes of tides exceeding those of surges, in general. During the period of analysis (1974–1988), two to four storm surge events were identified in a year, on average, with the maximum number occurring in Vishakhapatnam followed by Paradip and the least in Chennai. A statistical analysis involving the r‐largest annual maximum method, the joint probability method (JPM) as well as the revised joint probability method (RJPM) was performed to estimate the return periods of extreme sea level. JPM gave an underestimate of levels for long return periods, which is improved in RJPM. The results of RJPM and r‐largest methods are consistent and are within 95% confidence limits. The flexibility of the r‐largest method is used to include two historical extreme sea level events in the analysis for Paradip, including the surges due to the super cyclone that occurred in October 1999. It is shown that the inclusion of these events showed an increase of about 79 cm for the estimated 100‐year return period.
Chemical characterization of ozone formation in the Houston‐Galveston area: A chemical transport model study
Authors: Lei Wenfang , Zhang Renyi , Tie Xuexi , Hess Peter
Published: June 2004

An episodic simulation is conducted to characterize ozone (O3) formation and to investigate the dependence of O3 formation on precursors in the Houston‐Galveston (HG) area using a regional chemical transport model (CTM). The simulated net photochemical O3 production rates, P(O3), in the Houston area are higher than those in most other U.S. urban cities, reaching 20–40 ppb hr−1 for the daytime ground NOx levels of 5–30 ppb. The NOx turnaround value (i.e., the NOx concentration at which P(O3) reaches a maximum) is also larger than those observed in most other U.S. cities. The large abundance and high reactivity of anthropogenic volatile organic compounds (AVOCs) and the coexistence of abundant AVOCs and NOx in this area are responsible for the high O3 production rates and the NOx turnaround value. The simulated O3 production efficiency is typically 3–8 O3 molecules per NOx molecule oxidized during the midday hours. The simulation reveals a RO2 peak up to 70 ppt at night, and the reactions of alkene‐NO3 and alkene‐O3 are responsible for more than 80% of the nighttime RO2 in the residual layer, contributing to over 70% and about 10%, respectively. Isoprene accounts for about 40% of the nighttime RO2 peak concentration. The nighttime RO2 level is limited by the availability of alkenes. Hydrolysis of N2O5 on sulfate aerosols leads to an increase of HNO3 by as much as 30–60% but to a decrease of NOx by 20–50% during the night in the lower troposphere. Heterogeneous conversion of NO2 to HONO on the surfaces of soot aerosol accelerates the O3 production by about 1 hour in the morning and leads to a noticeable increase of 7 ppb on average in the daytime O3 level. The sensitivity study suggests that the near‐surface chemistry over most of the Houston metropolitan area is in or close to the NOx‐VOC transition regime on the basis of the current emission inventory. Doubling AVOC emissions leads to the NOx sensitive chemistry. Biogenic VOCs contribute about 5% on the average to the total near‐surface O3 in the Houston area.
Spatial and temporal variation of MOPITT CO in Africa and South America: A comparison with SHADOZ ozone and MODIS aerosol
Authors: Bremer Holger , Kar Jayanta , Drummond James R. , Nichitu Florian , Zou Jiansheng , Liu Jane , Gille John C. , Deeter Merritt N. , Francis Gene , Ziskin Daniel , Warner Juying
Published: June 2004

Carbon monoxide (CO) measurements from the Measurements of Pollution in the Troposphere (MOPITT) experiment are used to explore the correlation between biomass burning and ozone profiles at six tropical stations namely Reunion, Irene, Natal, Ascension, San Cristobal, and Paramaribo. Distinct seasonal patterns of CO at each station indicate the strong influence of African and South American biomass burning. All stations show enhanced CO columns during September–November (SON) corresponding to austral burning. Furthermore, the effects of Sahelian burning can be seen at Natal and Ascension. Similarly, the signature of northern Amazonian fires can be observed at San Cristobal. The CO variations are generally similar to the variations of aerosol optical depth (AOD) retrieved contemporaneously from Moderate Resolution Imaging Spectroradiometer (MODIS) at most stations, with notable differences at Irene, San Cristobal, and Paramaribo. Tropospheric ozone from Southern Hemisphere Additional Ozonesonde (SHADOZ) ozonesonde measurements at all stations show elevated levels, corresponding to the CO enhancements in SON months. However, there are several instances of ozone enhancements unaccompanied by any CO increase. This might indicate that sources other than biomass burning such as stratospheric tropospheric exchange (STE) or lightning related NOx may be operative. At San Cristobal, strong CO enhancements during March–April are not accompanied by any significant change in ozone.
Testing fast photochemical theory during TRACE‐P based on measurements of OH, HO2, and CH2O
Authors: Olson Jennifer R. , Crawford J. H. , Chen G. , Fried A. , Evans M. J. , Jordan C. E. , Sandholm S. T. , Davis D. D. , Anderson B. E. , Avery M. A. , Barrick J. D. , Blake D. R. , Brune W. H. , Eisele F. L. , Flocke F. , Harder H. , Jacob D. J. , Kondo Y. , Lefer B. L. , Martinez M. , Mauldin R. L. , Sachse G. W. , Shetter R. E. , Singh H. B. , Talbot R. W. , Tan D.
Published: June 2004

Measurements of several short‐lived photochemical species (e.g., OH, HO2, and CH2O) were obtained from the DC‐8 and P3‐B aircraft during the NASA Transport and Chemical Evolution over the Pacific (TRACE‐P) campaign. To assess fast photochemical theory over the east Asian coast and western Pacific, these measurements are compared to predictions using a photochemical time‐dependent box model constrained by coincident measurements of long‐lived tracers and physical parameters. Both OH and HO2 are generally overpredicted by the model throughout the troposphere, which is a different result from previous field campaigns. The calculated‐to‐observed ratio of OH shows an altitude trend, with OH overpredicted by 80% in the upper troposphere and by 40–60% in the middle troposphere. Boundary layer and lower tropospheric OH ratios decrease from middle tropospheric values to 1.07 for the DC‐8 and to 0.70 for the P3‐B. HO2 measured on the DC‐8 is overpredicted by a median of 23% and shows no trend in the agreement with altitude. Three subsets of data which compose 12% of the HO2 measurements represent outliers with respect to calculated‐to‐observed ratios: stratospherically influenced air, upper tropospheric data with NO > 135 pptv, and data from within clouds. Pronounced underpredictions of both HO2 and OH were found for stratospherically influenced air, which is in contrast to previous studies showing good agreement of predicted and observed HOx in the stratosphere. Observational evidence of heterogeneous uptake of HO2 within low and middle tropospheric clouds is presented, though there is no indication of significant HO2 uptake within higher‐altitude clouds. Model predictions of CH2O are in good agreement with observations in the median for background concentrations, but a large scatter exists. Factors contributing to this scatter are examined, including the limited availability of some important constraining measurements, particularly CH3OOH. Some high concentrations of CH2O near the coast are underpredicted by the box model as a result of the inherent neglect of transport effects of CH2O and its precursors via the steady state assumption; however, these occurrences are limited to ∼1% of the data. For the vast majority of the atmosphere, transport is unimportant in the budget of CH2O, which may be considered to be in steady state.
Reduction of neutron data from Lunar Prospector
Authors: Maurice S. , Lawrence D. J. , Feldman W. C. , Elphic R. C. , Gasnault O.
Published: June 2004

From January 1998 to July 1999, Lunar Prospector continuously measured the leakage flux of neutrons from the Moon in four distinct energy ranges from 0 eV to 8 MeV. These measurements were made using two 3He tubes within the Neutron Spectrometer (NS) and the anticoincidence shield of the Gamma‐Ray Spectrometer (GRS). This publication details the reduction of raw neutron data (level 0) to develop four maps of neutron counting rates, which can be interpreted in terms of elemental composition of the lunar regolith. Details are given to convert level 0 data into level 1 data, where corrupted and unusable records have been removed because of transmission errors, solar energetic‐particle events, or cross‐talk with other instruments. At level 2, time series data have been corrected for observational biases and variations of the response function of the instruments. At level 3 the highest‐quality neutron data (low‐altitude, high time resolution) are mapped onto the Moon. The main characteristics of each map are, for thermal neutrons, energy range 0–0.4 eV, dynamic range 95%, precision 2.7%, and half width at half maximum (HWHM) resolution 23 km, in units of counts/8‐s; for epithermal neutrons, energy range 0.4 eV < E < 0.7 MeV, dynamic range 15%, precision 1%, and HWHM resolution 22 km, in units of counts/8‐s; for moderated neutrons, energy range 0–0.8 MeV, dynamic range 15%, precision 1.8%, and HWHM resolution <45 km, in units of counts/32‐s; and for fast neutrons, energy range 0.8–8 MeV, dynamic range 30%, precision 1.6%, and HWHM resolution 23 km, in units of counts/32‐s. All maps are normalized to 30 km altitude, at the equator; and to the flux of cosmic rays in January 1998. They are presented as 720 × 360 arrays equally spaced in latitude and longitude. Results are reproducible from raw data that are available at the Planetary Data System (PDS), together with guidance and numerical values in this publication.
Impact crater related surficial deposits on Venus: Multipolarization radar observations with Arecibo
Authors: Carter Lynn M. , Campbell Donald B. , Campbell Bruce A.
Published: June 2004

The distribution of surficial deposits in the vicinity of impact craters on Venus was studied using measurements of the polarization properties of the reflected radar wave. Subsurface scattering of an incident circularly polarized radar signal results in a linearly polarized component in the radar echo due to the differing transmission coefficients at a smooth (at wavelength scales) atmosphere‐surface boundary for the horizontal (H) and vertical (V) linearly polarized components of the incident wave. Arecibo 12.6 cm wavelength radar observations in 1999 and 2001 provided images of the surface of Venus in the full Stokes polarization parameters of the reflected echo, from which images in the degree of linear polarization were derived. These images show that substantial areas of Sedna, Guinevere, and Lavinia Planitias return a radar echo with a significant degree of linear polarization, indicating that mantling deposits may be relatively widespread on the plains of Venus. The areas showing linear polarization enhancements are strongly correlated with topographic features, primarily impact craters, dome fields, and windblown deposits, including dune fields. A strong linearly polarized echo component (∼10–40% linear polarization) is found from regions near 45 impact craters, including 5 parabolas. These linear polarization features typically correspond to diffuse, higher backscatter cross‐section (bright) regions in Magellan images. The linearly polarized component in these regions is attributed to subsurface echoes from a mantled substrate or from buried rocks.
TEM radiation from a parallel‐plate waveguide with an arbitrarily flanged surface of finite size
Authors: Chien Dao Ngoc , Tanaka Kazuo , Tanaka Masahiro
Published: June 2004

The properties of radiation from a parallel‐plate waveguide with an arbitrarily flanged surface of finite size are investigated by means of the boundary element method (BEM) based on guided‐mode extracted integral equations (GMEIEs). The reflection coefficient, the reflected and radiated powers, as well as the radiation pattern are numerically calculated for the incidence of a transverse magnetic guided‐mode wave. For a number of cases of flanged parallel‐plate waveguide, a variety of interesting phenomena have been presented numerically. These effects may be important in the design of antenna systems.
The fictitious diurnal cycle of aerosol optical depth: A new approach for “in situ” calibration and correction of AOD data series
Authors: Cachorro V. E. , Romero P. M. , Toledano C. , Cuevas E. , de Frutos A. M.
Published: June 2004

Aerosol optical depth (AOD) very often shows a distinct diurnal cycle pattern, which seems to be an artifact. This phenomenon is the result of a deficient calibration (or an equivalent effect, as filter degradation). The fictitious sinusoidal shape of the AOD diurnal cycle is a function of the cosine of the solar zenith angle (SZA) and its effect is more accentuated during mid‐day. The observation of this effect is not easy at current field stations and only those stations with excellent weather conditions permit an easier detection and correction. By taking advantage of this diurnal cycle behavior because of its dependence on the cosine of the SZA, we propose an improved “in situ” calibration correction procedure. The method is named KCICLO because the determination of a constant K and the behavior of AOD as a cycle (ciclo, in Spanish). It can be seen as a modification of the classical Langley technique (CLT) with the same level of accuracy when CLT is applied at high‐altitude stations, and results in an accuracy of 0.2–0.5% for the calibration ratio constant K (or 0.002–0.005 in AOD). The application of this correction method to current and old data series at sunny stations is a significant improvement over “in situ” methods, because no other information beyond the AOD data is necessary.
Aerosol radiative forcing over a tropical urban site in India
Authors: Pandithurai G. , Pinker R. T. , Takamura T. , Devara P. C. S.
Published: June 2004

Using collocated measurements of aerosol radiative properties and radiative fluxes, aerosol radiative forcing is estimated at a tropical urban site in India, located between the sub‐continent and the Indian Ocean Experiment [INDOEX] sites. Observed sun/sky radiance data are used to derive aerosol spectral optical depth, single scattering albedo [SSA], asymmetry parameter, precipitable water and total column ozone. These serve as inputs to a radiative transfer model, to estimate aerosol forcing at the surface, the top‐of‐the atmosphere [TOA] and the atmosphere. During the dry season of 2001 and 2002 [November–April], these were found to be −33, 0 and 33 Wm−2, respectively. Using measured radiative fluxes during different aerosol loading conditions yield a surface forcing of −31 Wm−2. The surface forcing efficiency as computed from the two independent methods is found to be −88 and −84 Wm−2, respectively, while mean SSA at 500 nm is found to be 0.81.
Subtropical cirrus cloud extinction to backscatter ratios measured by Raman Lidar during CAMEX‐3
Authors: Whiteman D. N. , Demoz B. , Wang Z.
Published: June 2004

The NASA/GSFC Scanning Raman Lidar was stationed on Andros Island, Bahamas for the third Convection and Moisture Experiment (CAMEX 3) held in August–September, 1998 and acquired an extensive set of cirrus cloud measurements [Whiteman et al., 2001]. Distinct differences in the optical properties of the clouds are found when the cirrus are hurricane‐induced versus non‐hurricane‐induced. Hurricane‐induced cirrus clouds are found to generally possess lower values of extinction‐to‐backscatter ratio (S) than non‐hurricane‐induced clouds. Comparison of the S measurements made here with those of other studies reveal at times large differences. Given that S is often a required parameter for space‐based retrievals of cloud optical depth using backscatter lidar, these large differences in S measurements imply difficulties in developing a parameterization of S for use in space‐based lidar retrievals.
Pre‐Columbian mural paintings from Mesoamerica as geomagnetic field recorders
Authors: Goguitchaichvili A. , Soler A. M. , Zanella E. , Chiari G. , Lanza R. , Urrutia‐Fucugauchi J. , Gonzalez T.
Published: June 2004

This paper reports a reconnaissance archeomagnetic study of mural paintings in various pre‐Columbian sites in Mexico. The magnetic measurements of the pigments show that at least four murals (sites: Cacaxtla, Cholula and Templo Mayor) retain a remanent magnetization carried by a mixture of magnetite and minor hematite grains. In most specimens, a characteristic remanent magnetization is successfully isolated by alternating field demagnetization. The mean directions are reasonably well determined for each mural and within the range of secular variation during the last centuries. Studied Mesoamerican murals apparently retain the direction of the magnetic field at the time they were painted and therefore are an invaluable source of information concerning its secular variation. The archeomagnetic study of pre‐Columbian mural paintings opens new alternatives to drawing a reliable reference master curve for the region and may largely contribute to the Mesoamerican absolute chronology.
Changes in seasonal cloud cover over the Arctic seas from satellite and surface observations
Authors: Schweiger Axel J.
Published: June 2004

Winter and spring changes in cloudiness are compared over the arctic seas (ocean areas north of 60°N) from the TOVS (TIROS Operational Vertical Sounder) Polar Pathfinder retrievals and two separate datasets derived from the Advanced Very High Resolution Radiometer (AVHRR). All satellite products exhibit significant decreases in cloud fraction over the arctic seas during winter (December, January, February) on the order of 5 %/decade. An equally striking increase in spring (March, April, May) cloudiness is evident from the TOVS Pathfinder (TPP) and the extended AVHRR Polar Pathfinder (APP‐x) projects. In the Central Arctic these positive trends can be as large as 15 %/decade. Surface observations from the Russian drifting meteorological stations are consistent with satellite‐ observed changes during the 1980s. Negative trends in spring cloudiness reported by Comiso [2003] are in conflict with these findings. Spring changes in cloudiness are associated with changes in the atmospheric circulation. These dramatic, large‐scale changes may have substantial impacts on the surface energy balance.
On the relationship between shock‐induced polar magnetic bays and solar wind parameters
Authors: Liou K. , Newell P. T. , Meng C.‐I. , Wu C.‐C. , Lepping R. P.
Published: June 2004

There has been an impression for more than half a century that reductions in the north‐south component of the Earth's magnetic field in the polar region (often called “negative magnetic bays” or “polar magnetic bays”) may occur immediately after compression of the magnetosphere by interplanetary (IP) shock impacts, in particular when the magnetosphere is “preconditioned” by southward interplanetary magnetic field (IMF). A literature search suggests that this view has not been rigorously verified nor disproved. This paper reports a study of 43 IP shock events to illustrate the effect of IP shock‐magnetosphere coupling on the high‐latitude auroral electrojets. Specifically, we correlate the strength of magnetic bays (inferred from minimum values of the AL index within a 30‐min window after shock impact) with solar wind parameters and their combinations within the same time window. It is surprisingly found that the strength of magnetic bays correlates much better with solar wind parameters downstream of a shock (correlation coefficient, r, up to 0.86) than solar wind parameters upstream of a shock (r up to 0.6). Therefore whether or not an interplanetary shock can “induce” a magnetic bay depends on the concurrent solar wind and IMF conditions. This strongly suggests that enhancements of the westward auroral electrojet during magnetosphere compression are primarily associated with a directly driven process. It is also found that the solar wind dynamic pressure, which is traditionally considered a secondary effect, contributes equally with IMF Bz to the westward auroral electrojet.
Human Exploration, Space Weather, and Fundamental Space Plasma Research
Authors: Lanzerotti Louis J.
Published: June 2004

NASA must continue to fund basic space weather research to reach its goals of human space exploration.