bluuebunny/crossref_metadata_2025 huggingface dataset:
Fetal hydrops, associated with maternal propylthiouracil exposure, reversed by intrauterine therapy
Authors: Yanai N. , Shveiky D.
Published: February 2004

Thyroid hormone is essential for fetal neurological development. Among other etiologies, fetal hypothyroidism may be caused by maternal exposure to antithyroid drugs (ATDs). The most common presentation of fetal hypothyroidism is fetal goiter, which can cause dystocia, in addition to airway obstruction in the neonate. Intra‐amniotic treatment with levothyroxine normalizes fetal thyroid status and reduces goiter size. We present a case of fetal hypothyroidism diagnosed in a patient who was treated with propylthiouracil (PTU) for Grave's disease. The fetus had marked hydrops fetalis and a large goiter. In addition, anal stenosis, vesicovaginal fistula, bilateral pyelectasia and polydactyly were diagnosed in the neonate. Intra‐amniotic treatment with levothyroxine resulted in a regression of the hydrops and a reduction in the goiter size. A euthyroid, non‐edematous, non‐goitrous neonate was delivered. At the age of 27 months the child's psychomotor development was normal. The present case indicates that hydrops fetalis may be an unusual manifestation of fetal hypothyroidism, caused by intrauterine exposure to maternal antithyroid drugs (ATDs), and that it may be resolved by treatment with intra‐amniotic levothyroxine. Copyright © 2004 ISUOG. Published by John Wiley & Sons, Ltd.
Circulating matrix metalloproteinase‐2 is elevated in patients with congestive heart failure
Authors: Yamazaki Taketoshi , Lee Jong‐Dae , Shimizu Hiromasa , Uzui Hiroyasu , Ueda Takanori
Published: January 2004

Background and aims:

It has been reported that matrix metalloproteinase (MMP) protein concentration and activity are upregulated in the failing human heart. However, there are few reports describing the role of elevated level of circulating MMPs in congestive heart failure (CHF) patients. This study examined whether circulating matrix metalloproteinases (MMPs) are also related to the pathogenesis of CHF.

Methods:

We measured circulating levels of matrix metalloproteinase‐2 (MMP‐2) in 52 patients with CHF (left ventricular ejection fraction (LVEF) <50%). The patients were also subdivided into two groups according to NYHA functional class; mild CHF (class II, n=43) and severe CHF (class III, n=9). Results: The serum level of MMP‐2 and MMP‐2/TIMP‐2 ratio were significantly higher in CHF than in controls (P<0.01). Among patient groups, serum levels of MMP‐2 were significantly higher in patients with severe CHF than in patients with mild CHF (P<0.01). Plasma levels of BNP had a significant positive correlation with circulating levels of MMP‐2 (r=0.78; P<0.01) and MMP‐2/TIMP‐2 ratio (r=0.60; P<0.01).

Conclusions:

Our data showed that the circulating MMP‐2 concentration was increased in CHF patients and that the levels were related to the plasma levels of BNP in CHF, suggesting that the elevated levels are related to developing heart failure syndrome.
Muscle strength as a predictor of long‐term survival in severe congestive heart failure
Authors: Hülsmann Martin , Quittan Michael , Berger Rudolf , Crevenna Richard , Springer Christoph , Nuhr Martin , Mörtl Deddo , Moser Petra , Pacher Richard
Published: January 2004

Aims:

The objective of the study was to test the relationship between isolated muscle strength and outcome, and its significance in the context of other exercise variables.

Methods and results:

122 consecutive patients (LVEF 21±7%) were enrolled in the study. Isokinetic strength testing of the knee extensor and flexor muscles were performed. A subset of 51 patients underwent additional upright bicycle testing with gas exchange analysis. The outcome up to 60 months was defined by event‐free survival (group A, n=59) or death (group B, n=34). Patients who had been transplanted were excluded from further analysis. The peak strength of the quadriceps muscle was comparable in both groups (N.S.). In contrast, the index (value adjusted for weight) did reveal significant differences (P<0.04), similar to the peak torque of the knee flexor muscle (P<0.04), whose index was even more significant with regard to differences (P<0.01). Multivariate analysis including muscle strength variables, pVo2 and workload into one model show that the flexor strength index is the only independent variable (x2=9 P<0.003). A cut‐off point of 68 Nm×100/kg in the strength index of the flexor muscles was used to establish a significant difference between groups with regard to outcome (P<0.01). Thus, the isokinetic strength of the knee flexor muscles is related to outcome. Moreover, this parameter is superior to variables such as peakVo2 and workload.
Association of the angiotensin‐converting enzyme gene polymorphism with chronic heart failure in Chinese Han patients
Authors: Huang Wenyan , Xie Changqing , Zhou Hongyan , Yang Tianlun , Sun Ming
Published: January 2004

Background:

An insertion/deletion (I/D) polymorphism is present in the 16th intron of the angiotensin‐converting enzyme (ACE) gene and is associated with serum and tissue ACE level. Some studies have shown that the DD genotype is associated with some cardiovascular diseases; while ACE polymorphism's effect on chronic heart failure (CHF) remains uncertain.

Aim:

To investigate the association of the ACE gene I/D polymorphism with CHF in the Chinese Han population.

Methods:

The genotype was determined by polymerase chain reaction in 102 normal controls and in 79 patients with CHF. Plasma angiotensin (Ang) levels were assessed by radio‐immunity assay. Left ventricular end‐diastolic diameters (LVDD) and left ventricular ejection fractions were assessed by echocardiography.

Results:

The ACE gene polymorphism distribution was similar in patients and control subjects. However, ACE gene DD polymorphism was associated with a more severe condition, greater LVDD [mm: DD: 71±7, ID: 62±5, II: 60±5, P<0.001 DD vs. ID, P<0.001 DD vs. II] and higher plasma Ang II level [pg/ml DD: 92±19, ID: 79±21, II: 65±17 P<0.05 DD vs. ID, P<0.001 DD vs. II].

Conclusion:

In Chinese Han patients with CHF, ACE gene DD polymorphism might be a marker of a more severe condition, and a higher level of activation of the renin–angiotensin system.
Importance of chronic obstructive pulmonary disease for prognosis and diagnosis of congestive heart failure in patients with acute myocardial infarction
Authors: Kjøller Erik , Køber Lars , Iversen Kasper , Torp‐Pedersen Christian ,   on behalf of the Trace Study Group
Published: January 2004

Aims:

To evaluate the importance of chronic obstructive pulmonary disease for prognosis and diagnosis of congestive heart failure in patients with acute myocardial infarction.

Methods and results:

Prospective registration of 6669 consecutive patients admitted with infarction and screened for a randomised controlled trial. A history of COPD was present in 765 (11.5%) patients. Thirty‐day and 5‐year survival in patients with chronic obstructive pulmonary disease was 86.3 and 42.9%. In patients without pulmonary disease the figures were 87.7 and 57.5%, respectively, giving a relative risk of 1.49 (1.35–1.65). In multivariate analysis the relative risk was 1.15 (1.04–1.28). The prevalence of congestive heart failure was 65.9% in patients with chronic obstructive pulmonary disease and 52.0% in patients without. This difference was most distinct in patients with normal or only slightly decreased left ventricular systolic function. In patients without congestive heart failure, chronic obstructive pulmonary disease was of prognostic importance [RR=1.44 (1.17–1.78)], but not in patients with congestive heart failure [RR=1.09 (0.96–1.23)].

Conclusion:

Chronic obstructive pulmonary disease is a predictor of long‐term mortality in patients with acute myocardial infarction without congestive heart failure, but is also a confounding factor for the diagnosis of congestive heart failure.
Does aerobic training lead to a more active lifestyle and improved quality of life in patients with chronic heart failure?
Authors: van den Berg‐Emons Rita , Balk Aggie , Bussmann Hans , Stam Henk
Published: January 2004

Background:

Due to dyspnea and fatigue, patients with chronic heart failure (CHF) are often restricted in the performance of everyday activities, which gradually may lead to hypoactivity.

Aims:

To assess whether aerobic training leads to a more active lifestyle and improved quality of life (QoL) in patients with CHF.

Methods:

Patients with stable CHF (NYHA II/III; 59 (11) years) were randomly assigned to a training group (n=18; 3‐month aerobic program above standard treatment) or control group (n=16; standard treatment without special advice for exercise). Measurements were performed on level of everyday physical activity (PA, novel accelerometry‐based activity monitor) and QoL, and on several related parameters.

Results:

Training did not result in a more active lifestyle or improved QoL, but improved (P<0.05) peak power (17%), 6‐min walk distance (10%), muscle strength (13–15%) and depression (−1.3 unit). Changes in level of everyday PA were related to changes in peak Vo2 (r=0.58, P=0.01) and knee extension strength (r=0.48, P=0.05).

Conclusions:

At group level training did not result in a more active lifestyle or improved QoL. However, correlations between training‐related changes in parameters suggest that aerobic training has the potential to increase levels of everyday PA in CHF.
Clinical trials update from the American Heart Association meeting: Ω‐3 fatty acids and arrhythmia risk in patients with an implantable defibrillator, ACTIV in CHF, VALIANT, the Hanover autologous bone marrow transplantation study, SPORTIF V, ORBIT and PAD and DEFINITE
Authors: Cleland John G.F. , Freemantle Nick , Kaye Gerry , Nasir Mansoor , Velavan Periaswamy , Lalukota Krishna , Mudawi Telal , Shelton Rhidian , Clark Andrew L. , Coletta Alison P.
Published: January 2004

The American Heart Association meeting reported the results of several clinical trials of particular interest to those who care for patients with heart failure. Ω‐3 fatty acids were associated with a trend to increased recurrence of ventricular arrhythmias but not mortality in patients with an implantable debrillator. The ACTIV in CHF study provides more evidence of a therapeutic role for arginine vasopressin antagonists in the treatment of heart failure. The VALIANT study provides further evidence to suggest that a combination of angiotensin receptor antagonist and ACE inhibitor does not reduce mortality but may reduce morbidity in post‐MI patients with heart failure or major LV systolic dysfunction. A study of autologous bone marrow cell transplantation into myocardial scar give gave encouraging results. SPORTIF V showed ximelagation to be as effective as warfarin but with improved safety. ORBIT and PAD showed public access defibrillators saved lives but questioned their cost effectiveness. DEFINITE supported a role for ICDs in patients with non‐ischemic cardiomyopathy, although cost‐effectiveness remains in doubt.
Estimation of the age-specific rate of natural mortality for Shetland sandeels
Authors: Cook R.M.
Published: February 2004

It is generally difficult to obtain reliable direct estimates of natural mortality, M, from conventional fisheries data and stock assessments. However, as a result of the closure of the Shetland sandeel (Ammodytes marinus) fishery from 1991 to 1994 and in the absence of any significant fishery in other years, research vessel survey data offer a rare opportunity to obtain estimates of M directly. A model is described that assumes that M can be decomposed into an age effect and year effects. Application of the model to the survey data produces values of M that decline from 2.1 for 0-group fish to 0.6 at age 2. There is some indication of an increase for ages 4 and older. Although there does not appear to be an overall trend in the mean value of M for the period 1985–1999, the annual values change by up to 50%. The values calculated from the model are in line with estimates obtained for the North Sea from multispecies virtual population analysis (MSVPA).
Induction of 1,N2‐etheno‐2′‐deoxyguanosine in DNA exposed to β‐carotene oxidation products
Authors: Marques Sabrina A , Loureiro Ana Paula M , Gomes Osmar F , Garcia Camila C.M , Di Mascio Paolo , Medeiros Marisa H.G
Published: February 2004

Epidemiological studies testing the effect of β‐carotene in humans have found a relative risk for lung cancer in smokers supplemented with β‐carotene. We investigated the reactions of retinal and β‐apo‐8′‐carotenal, two β‐carotene oxidation products, with 2′‐deoxyguanosine to evaluate their DNA damaging potential. A known mutagenic adduct, 1,N
2‐etheno‐2′‐deoxyguanosine, was isolated and characterized on the basis of its spectroscopic features. After treatment of calf thymus DNA with β‐carotene or β‐carotene oxidation products, significantly increased levels of 1,N
2‐etheno‐2′‐deoxyguanosine and 8‐oxo‐7,8‐dihydro‐2′‐deoxyguanosine were quantified in DNA. These lesions are believed to be important in the development of human cancers. The results reported here may contribute toward an understanding of the biological effects of β‐carotene oxidation products.
‘O sibling, where art thou?’‐ a review of avian sibling recognition with respect to the mammalian literature
Authors: Nakagawa Shinichi , Waas Joseph R.
Published: February 2004

Avian literature on sibling recognition is rare compared to that developed by mammalian researchers. We compare avian and mammalian research on sibling recognition to identify why avian work is rare, how approaches differ and what avian and mammalian researchers can learn from each other. Three factors: (1) biological differences between birds and mammals, (2) conceptual biases and (3) practical constraints, appear to influence our current understanding. Avian research focuses on colonial species because sibling recognition is considered adaptive where‘mixing potential’of dependent young is high; research on a wide range of species, breeding systems and ecological conditions is now needed. Studies of acoustic recognition cues dominate avian literature; other types of cues (e.g. visual, olfactory) deserve further attention. The effect of gender on avian sibling recognition has yet to be investigated; mammalian work shows that gender can have important influences. Most importantly, many researchers assume that birds recognise siblings through‘direct familiarisation’(commonly known as associative learning or familiarity); future experiments should also incorporate tests for‘indirect familiarisation’(commonly known as phenotype matching). If direct familiarisation proves crucial, avian research should investigate how periods of separation influence sibling discrimination. Mammalian researchers typically interpret sibling recognition in broad functional terms (nepotism, optimal outbreeding); some avian researchers more successfully identify specific and testable adaptive explanations, with greater relevance to natural contexts. We end by reporting exciting discoveries from recent studies of avian sibling recognition that inspire further interest in this topic.
Posttraumatic stress disorder and health status among female and male medical patients
Authors: Ouimette Paige , Cronkite Ruth , Henson Brandy R. , Prins Annabel , Gima Kristian , Moos Rudolf H.
Published: February 2004

Posttraumatic stress disorder (PTSD) is associated with objective health problems in specific populations, such as Vietnam veterans. Less is known about PTSD and health among medical samples, especially PTSD patients with different etiologic traumas. This study examined PTSD and health in medical patients within the Department of Veterans Affairs healthcare system. A total of 134 patients completed an interview and questionnaires. Data on physician‐diagnosed illnesses were gathered from medical records. PTSD diagnosis and symptoms were associated with a higher likelihood of circulatory and musculoskeletal disorders. In addition, PTSD symptoms were associated with more medical conditions. PTSD symptoms and diagnoses were also associated with poorer health related quality of life. Most of these findings remained significant after controlling for comorbid depressive, generalized anxiety disorder, and panic attack symptoms. Overall, gender did not moderate the relationship between PTSD and poorer health.
Meteor trail advection observed during the 1998 Leonid Shower
Authors: Grime Brent W. , Kane Timothy J. , Liu Alan , Papen George , Gardner Chester S. , Kelley Michael C. , Kruschwitz Craig , Drummond Jack
Published: February 2004

Sodium resonance lidar observations of meteor trails are reported from the 1998 Leonid shower experiment at the Starfire Optical Range, Kirtland Air Force Base, NM (35.0° N, 106.5° W). The lidar was operating in a spatially scanning mode that allowed tracking for up to one half‐hour. Three trails are presented here whose motion allowed inference of radial as well as vector wind components and apparent diffusivities. The winds are derived independently using the narrow linewidth sodium (Na) resonance Doppler lidar technique and are compared with the tracking results.
Sensitive determination of nonlinear properties of berea sandstone at low strains
Authors: Smith Eric , TenCate James A.
Published: February 2004

Resonant response functions of a sandstone bar, measured at strain magnitudes between 10−8 and 10−6 at several temperatures, are used to extract Young's modulus and loss tangent as functions of frequency and driving force. Expressing the distorted shape of nonlinear resonances in terms of shifts in the resonant frequency and Q enables correlation analysis of these functions against components of the strain response function. Resonance shifts are found to be strongly correlated with somewhat complicated functions of strain, but only weakly with frequency or phase of the response. Decomposing the data along contours of constant strain magnitude yields the quantitative scaling of resonance shifts with strain, which shows a superposition of both conventional and necessarily hysteretic nonlinear sources. No statistically significant temperature dependence is found in the coefficients of the fits.
Are fast‐growing martian dust storms compressible?
Authors: Parsons Jeffrey D.
Published: February 2004

A simple scale analysis demonstrates that rapidly‐expanding Martian dust storms are driven by extremely large density differences. Thermal gradients appear to be inadequate to produce these density contrasts. When dust produces the densities required, the storms become compressible because of the slowing of the speed of sound due to the addition of particles. Though compressible, particle‐laden flows have never been analyzed due to their highly complex nature, pressure waves produced by these flows could be hypothesized to provide a positive feedback capable of producing rapid growth.
Actively growing anticlines beneath catania from the distal motion of Mount Etna's Decollement measured by SAR interferometry and GPS
Authors: Borgia A. , Lanari R. , Sansosti E. , Tesauro M. , Berardino P. , Fornaro G. , Neri M. , Murray J. B.
Published: February 2004

We used SAR interferometry and GPS to measure the rise of an anticline beneath the urban area of Catania (Italy), which originates from outward thrusting above the basal decollement of Etna volcano. The anticline grows at a rate of over 0.015 m a−1 of SE thrusting and about 0.007 m a−1 of relative uplift. By relating this growth to the simultaneous extension measured at the summit of the volcano, we demonstrate the occurrence of active volcanic spreading. This process may exert a control on eruptions, earthquakes, sector collapses, and landslides.
Characteristics of Fe ablation trails observed during the 1998 Leonid Meteor Shower
Authors: Chu Xinzhao , Pan Weilin , Papen George , Gardner Chester S. , Swenson Gary , Jenniskens Peter
Published: February 2004

Eighteen Fe ablation trails were observed during the 17/18 Nov 1998 Leonid meteor shower with an airborne Fe lidar aboard the NSF/NCAR Electra aircraft over Okinawa. The average altitude of the 18 trails from the high velocity (72 km/s) Leonid meteors, 95.67±0.93 km, is approximately 6.7 km higher than previously observed for slower (∼30 km/s) sporadic meteors. This height difference is consistent with the assumption that meteors ablate when atmospheric drag reaches a critical threshold. The average age of the Fe trails, determined by a diffusion model, is 10.1 min. The youngest ages were observed below 92 km and above 98 km where chemistry and diffusion dominate, respectively. The average abundance of the trails is 10% of the abundance of the background Fe layer. Observations suggest that the 1998 Leonid shower did not have a significant impact on the abundance of the background Fe layer.
Conjunction of tail satellites for substorm study: ISTP event of 1997 January 2
Authors: Lui A. T. Y. , Liou K. , Newell P. T. , Meng C. I. , Ohtani S. , McEntire R. W. , Fox N. J. , Lepping R. P. , Paterson W. R. , Sigwarth J. B. , Frank L. A. , Kokubun S. , Parks G. K. , Moretto T. , Yumoto K.
Published: February 2004

The interval of 1997 January 1–2 was identified as a favorable conjunction of Geotail and IMP‐8 to examine substorm activity in the mid‐tail region prior to data acquisition. On January 2, 1997, global auroral observations from Polar indicated a substorm onset at ∼0120 UT followed by a substorm intensification at ∼0154 UT at a local time spatially separated from the initial substorm activity region. During this event, both Geotail and IMP‐8 were in the mid‐tail near the midnight meridian (Geotail (X, Y) ≈ (−30, −3)RE and IMP‐8 (X, Y) ≈ (−37, 2)RE). Observations indicated that the substorm onset activity was localized in the postmidnight region. After the onset, Geotail detected a transient dipolarization which was not accompanied by large plasma flows (i.e., | Vx |≤ 200 km/s). The subsequent substorm intensification produced enduring dipolarization at Geotail and highly fluctuating magnetic field (mostly northward Bz) at IMP‐8. Observations for this substorm showed no indication of mid‐tail activities occurring prior to auroral brightening for both onset and intensification even though the satellites observed activities subsequently. Close examination of data indicates that the delays were not due to a dawn‐dusk expansion of mid‐tail activity. These results are consistent with substorm activity beginning in the near‐Earth region first, followed by activity in the mid‐tail region later.
Mid‐latitude temperatures at 87 km: Results from multi‐instrument Fourier analysis
Authors: Drob Douglas P. , Picone J. Michael , Eckermann Stephen D. , She C. Y. , Kafkalidis J. F. , Ortland D. A. , Niciejewski R. J. , Killeen T. L.
Published: February 2004

Using a novel Fourier fitting method we combine two years of mid‐latitude temperature measurements at 87 km from the High Resolution Doppler Imager, the Colorado State University lidar, and the Peach Mountain Interferometer. After accounting for calibration bias, significant local‐time variations on the order of 10 K were observed. Stationary planetary waves with amplitudes up to 10 K were observed during winter, with weaker wave amplitudes occurring during other seasons. Because of calibration biases among these instruments, we could estimate the annual mean temperature to no better than 193.5±8.5 K.
Tropical cirrus clouds: A possible sink for ozone
Authors: Roumeau S. , Brémaud P. , Rivière E. , Baldy S. , Baray J. L.
Published: February 2004

Using 7 years of ozone, humidity and temperature radiosoundings performed every two‐weeks at Reunion Island (21°S, 55°E), a systematic diminution of ozone mixing ratio at level of tropical cirrus clouds is evidenced. The average depletion of ozone concentration, as compared to adjacent levels, is above 25%. This effect is further documented using concomitant Lidar and radiosounding data. Ice cloud particles evidenced from polarization and backscattering Lidar data are observed at the same level than the ozone depletion in a detailed case study. The ozone concentration is 30% weaker at this level than outside the cirrus cloud. Backtrajectory analyses further indicate that the advection of O3‐poor layer injected from lower levels is not likely.
Raman LIDAR detection of cloud base
Authors: Demoz Belay , Starr David , Whiteman David , Evans Keith , Hlavka Dennis , Peravali Ravindra
Published: February 2004

Advantages introduced by Raman lidar systems for cloud base determination during precipitating periods are explored using two case studies of light rain and virga conditions. A combination of the Raman lidar derived profiles of water vapor mixing ratio and aerosol scattering ratio, together with the Raman scattered signals from liquid drops, can minimize or even eliminate some of the problems associated with cloud boundary detection using elastic backscatter lidars.
Wavelet analysis of the variable Chandler wobble
Authors: Liu L. T. , Hsu H. T. , Gao B. X. , Wu B.
Published: February 2004

We develop a new wavelet analysis technique, namely wavelet amplitude‐period spectrum (WAPS) to study the variations of the Chandler wobble (CW). The variable period and amplitude of the CW during 1900–1990 are quantified by using the WAPS technique. We show that the double‐frequency spectrum of the CW is related to the large variation in its period with respect to time. We find that amplitude and period of the CW clearly fit exponential laws during 1912–1928 and 1936–1948, corresponding to the strong damping and the strong excitation respectively. Our study suggests that the excitation and damping of the CW might well be in an equilibrium status during 1962–1990.
Terrestrial ecosystem responses to global environmental change across the Cretaceous‐Tertiary boundary
Authors: Lomax B. H. , Beerling D. J. , Upchurch G. R. , Otto‐Bliesner B. L.
Published: February 2004

Investigations of long‐term (10³–105 yr) environmental change across the Cretaceous‐Tertiary (K/T) boundary resulting from the impact of a large bolide indicate increases in temperature and precipitation due to the impact‐related release of CO2. We evaluate the effects of these long‐term changes in the global environment on terrestrial ecosystems using a vegetation‐biogeochemistry model forced with a ‘best guess’ modified latest Cretaceous climate simulation by the GENESIS atmospheric general circulation model. The imposition of long‐term global environmental changes after the K/T impact resulted in spatially heterogeneous increases in canopy leaf area index, net primary productivity, and soil carbon concentrations, relative to the latest Cretaceous preimpact situation. Terrestrial carbon storage increased by circa 2000 Gt.
Modeling of nitrogen species measured by CRISTA
Authors: Riese M. , Küll V. , Tie X. , Brasseur G. , Offermann D. , Lehmacher G. , Franzen A.
Published: February 2004

We present an analysis of odd nitrogen species measured by the CRISTA experiment during the Space Shuttle mission STS 66 in November 1994. Observations of several nitrogen species are compared with modeled fields obtained from three‐dimensional simulations performed with a chemical transport model (CTM). A sequential trace gas assimilation system is used in order to constrain the simulations by CRISTA observations of long‐lived species, and total amounts of stratospheric nitrogen (NOy) derived from measurements of individual nitrogen components (NO2, N2O5, HNO3, and ClONO2). Comparisons of measured and modeled NOy species focus on significant diurnal variations and intense longitudinal variations observed by CRISTA.
Seismic heterogeneity in the upper crust near the 1991 eruption site on the East Pacific Rise, 9°50′N
Authors: Tian T. , Wilcock William S. D. , Toomey Douglas R. , Detrick Robert S.
Published: February 2004

We report the results of a small‐aperture uppercrustal tomography experiment conducted on the East Pacific Rise near 9°50′N, the site of a volcanic eruption in 1991. The experiment geometry comprised 3 ocean bottom seismometers and 491 airgun shots fired in a 16 × 16 km² area. Two‐ and three‐dimensional inversions indicate that the average upper crustal velocities, both on and off axis, increase by ∼0.2 km/s north of 9°52′N. This location coincides with the northern limit of the 1991 eruption and of vigorous hydrothermalism. Our data can be explained by a 100 m southward increase in layer 2A thickness. On axis, previous work indicates that layer 2A thickness does not vary in this region. We infer that the sheeted dikes above the axial magma chamber are thermally segmented with the dike layer south of 9°52′N being on average at least 300°C warmer than to the north. Off axis, layer 2A may be thicker south of 9°52′N if a higher proportion of eruptions flow off axis.
The role of nonlinear source terms in geophysics
Authors: Kardashov Victor R. , Eppelbaum Lev V. , Vasilyev Oleg V.
Published: February 2004

Correct interpretation of results becomes an important issue when dealing with nonlinear phenomena of Solid Earth geophysics. Direct linearization of nonlinear processes can cause sufficient mistakes and even cardinally change the interpretation. In this paper a simple and effective procedure for structural recognition and visualization of nonlinear potential sources is presented. This procedure is based on parametric analysis of corresponding transients: switch and localized waves. Conditions for the formation of transitional waves and properties of these waves have been studied. The proposed approach is illustrated on a simple example of potential linear thermal source with nonlinear cubic disturbance. The procedure presented in this paper can be applied for detection of viscous heating and nonlinear heat diffusion in complicated media.
Upper tropospheric humidity and thin cirrus
Authors: Sandor Brad J. , Jensen Eric J. , Stone Elizabeth M. , Read William G. , Waters Joe W. , Mergenthaler John L.
Published: February 2004

Upper tropospheric water vapor data from the UARS Microwave Limb Sounder (MLS) are compared with coincident optically thin (often subvisible) cirrus cloud measurements from the UARS Cryogenic Limb Array Etalon Spectrometer (CLAES) at 147 hPa in the tropics. A strong correlation is found between mean relative humidity with respect to ice (RHI) and percent occurrence of cirrus clouds. The cloudiness‐RHI relationship is established from the coincident CLAES and MLS observations (Oct. 1991–May 1993), and used with 1991–97 MLS data to find by proxy the percent occurrence of cirrus for 1993–97. Interannual variability of cloudiness is investigated with the extended (1991–97) cirrus data, and a clear El Nino signature is seen. The observed relationship of RHI and optically thin cirrus provides a potential diagnostic of climatological behavior of atmospheric models, in which cirrus is important for radiative balance, heterogeneous chemistry, and the near‐tropopause water budget.
Recent biennial variability of meteorological features in the eastern Highland Himalayas
Authors: Bertolani Laura , Bollasina Massimo , Tartari Gianni
Published: February 2004

With meteorological data from high altitude surface stations and gridded dataset from NCEP/NCAR Reanalysis, a biennial oscillation over the Eastern Highland Himalayas from 1980 to 1998 is described. This variability concerns air temperature, precipitation, geopotential and wind speed. Evidence is given on the connections between local data and large‐scale circulation patterns. The most remarkable oscillating features are found during winter and, in general, the signals are particularly marked on the southern slope of the Himalayan Range. A possible mechanism is explained in terms of a periodicity in surface heat and moisture fluxes. Finally, the peculiarity of the region as a climatic change observatory is underlined.
Crustal compensation during mountain‐building
Authors: Zhong Shijie , Zuber Maria T.
Published: February 2004

Airy isostasy has been observed in many active orogenic regions including Himalayas/Tibetan plateau and Tian Shan. To better understand the temporal evolution of mountain building, we investigate how topography at the surface and crust‐mantle boundary (i.e., Moho) that evolves in response to crustal shortening depends on mechanical properties of continental lithosphere. Our dynamic models reveal that if the effective viscosity of continental lithosphere is less than 100 times of the viscosity of the underlying mantle, orogenic belts and their corresponding roots at Moho can grow simultaneously with the Airy isostasy being approximately maintained. This result is consistent with the relatively small viscosity inferred for continental lithosphere of actively deforming central Asia regions including Tibetan plateau.
Eddies and vortices in ocean basin dynamics
Authors: Siegel A. , Weiss Jeffrey B. , Toomre Juri , McWilliams James C. , Berloff Pavel S. , Yavneh Irad
Published: February 2004

A wind‐driven, closed‐basin quasi‐geostrophic ocean model is computed at very high horizontal resolution to study the effect of increasing Reynolds number (Re) on eddy variability. Five numerical simulations are performed with identical configurations, varying only in horizontal resolution and viscosity coefficient (and therefore Re). Qualitative changes in the structure of eddy variability are evident in the dramatic increase of isolated vortex structures at the highest Re. While the time‐mean kinetic energy is relatively independent of Re, the vortex emergence contributes to a continual increase with Re of eddy kinetic energy and meridional vorticity flux. The rate of increase slows somewhat at the highest Re, indicating the possibility of a regime where eddy variability becomes insensitive to further increases in Re.
On shifts in the long‐term Umkehr radiance records and their influence on retrieved ozone profiles
Authors: Petropavlovskikh Irina , Theisen David , DeLuisi John J. , Bojkov Rumen D. , Kosmidis Evagelis
Published: February 2004

The Umkehr technique has been used routinely for more than 40 years to assess features in the vertical distribution of ozone. The measurements represent the longest ozone profile data record in existence. A careful examination of the long‐term Umkehr N‐value (radiance) measurement record, archived at the WMO World Ozone and UV Data Center in Toronto, Canada, revealed shifts in the data. These shifts appear to be mainly related to Dobson instrument calibrations and/or to instrument changes at the observing stations. In most cases, the detected shifts exhibit solar zenith angle dependence. The standard procedure of subtracting the Umkehr measurement at 60‐degree solar zenith angle (or the next smallest SZA available) from the measurement at the other angles to eliminate the instrumental and extraterrestrial constants from measurements does not necessarily remove the shifts. The shift errors would appear as shifts in the retrieved ozone profiles and could affect any ozone profile analysis (including ozone trends) as well as comparisons with other profiles derived from satellite and lidar measurements. A preliminary approach for detecting the shifts and allowing for corrections is developed and evaluated for its potential to improve the quality of the of the Umkehr records.
Reducing satellite orbit error effects in near real‐time GPS zenith tropospheric delay estimation for meteorology
Authors: Ge Maorong , Calais Eric , Haase Jennifer
Published: February 2004

We investigate the influence of using IGS predicted orbits for near real‐time zenith tropospheric delay determination from GPS and implement a new processing strategy that allows the use of predicted orbits with minimal degradation of the ZTD estimates. Our strategy is based on the estimation of the three Keplerian parameters that represent the main error sources in predicted orbits (semi‐major axis, inclination, and argument of perigee), and their associated variance directly from the real‐time GPS data set. A comparison with the use of IGS final orbits shows a negligible bias and an rms less than 6 mm in the ZTD estimates at all the stations. The improvement compared to a strategy based only on the quality index provided with the predicted orbits is 20%. The level of accuracy and turn‐around time shown here meet the current requirements for operational meteorology.
Satellite‐based monitoring of intraseasonal variations in tropical Pacific and Atlantic convection
Authors: Evans Jenni L. , Jaskiewicz Francine A.
Published: February 2004

An automated Convection Classification, Analysis and Tracking Scheme (CCATS) is used to diagnose spatial and temporal variability of convection in the tropical western Pacific and Atlantic Oceans. Three organized convection classes are differentiated; degree of organization is related to lifetime, symmetry and peak system size. A fourth category of short‐lived thunderstorms is also detected. Two cycles of the Madden Julian Oscillation (MJO) are tracked across the Pacific basin. The degree of organization of the convective systems increases as the MJO progresses through the region, preconditioning the environment for tropical cyclogenesis. Satellite‐inferred rainfall budgets reveal that tropical western Pacific and Atlantic rainfall is dominated by organized convection. This has potentially important implications for representation of the hydrologic cycle in numerical simulations of the tropics, particularly for models that do not explicitly resolve the mesoscales.
Halogen ions and NO+ in the mass spectra of aerosols in the upper troposphere and lower stratosphere
Authors: Murphy D. M. , Thomson D. S.
Published: February 2004

Mass spectra of individual aerosol particles were acquired at altitudes up to 19 km during the WB‐57 Aerosol Mission. Fluorine and chlorine were more abundant in tropospheric aerosols than in stratospheric aerosols. Chlorine in tropospheric aerosols was often associated with organics, soot, and mineral dust. Small amounts of perchlorate were observed in stratospheric sulfate aerosols, but aerosols do not represent a significant sink for total fluorine or chlorine in the lower stratosphere. Bromine was most common in aerosols just above the tropopause, where it may represent a significant fraction of inorganic Br. Both bromine and iodine were highly correlated with organics and probably were present in particles with Hg. The OH− and NO+ peak areas increased at temperatures below 195 K, providing evidence for the uptake of H2O and HNO3 by aerosols near a cold tropopause. There was evidence for uptake of chlorine but not the other halogens below 190 K.
Constant ventilation age of thermocline water in the eastern subtropical North Pacific Ocean from chlorofluorocarbon measurements over a 12‐year period
Authors: Min Dong‐Ha , Bullister John L. , Weiss Ray F.
Published: February 2004

Northeastern Pacific chlorofluorocarbon (CFC) data collected between 1982 and 1994 near Geochemical Ocean Sections Study (GEOSECS) station 1 (28.5°N, 122.5°W) record decadal timescale ventilation processes of the subtropical thermocline in this region. The CFC‐12 concentration age field versus potential density has been remarkably constant over the 12‐year period, although CFC concentrations in the upper kilometer of the water column have increased with time. Results from a simple one‐dimensional advection‐diffusion model are consistent with an advection velocity of ca. 0.8–0.9 cm s−1 from the source area. The influence of the 1982–83 El Niño is noticeable in the 1983 observations. While the main stream of subarctic source water appears to spread southward at a constant rate, during El Niño years the influence of comparatively CFC‐free tropical thermocline waters is enhanced in this region, leading to reduced vertical inventories of CFCs, but without changing the apparent CFC ages as functions of potential density. Apparent oxygen utilization rates decrease with increasing CFC age, and also appear not to have changed significantly over the 12‐year measurement period.
On the electrical structure of airglow depletion/Height layer bands over Arecibo
Authors: Kelley Michael C. , Makela Jonathan J. , Saito Akinori , Aponte Nestor , Sulzer Michael , González Sixto A.
Published: February 2004

Using a combination of airglow images and incoherent scatter radar data, we have explored the electrical structure of the airglow depleted, height layer bands over a mid‐latitude site. We find a reproducible electrical signature in both components of the electric field in all events studied. The most pronounced feature is a large northward/upward electric field in the heart of the structure. The latter is identical to the radially outward field reported for mid‐latitude conjugate electric fields [Saito et al., 1995], found to trace the poleward edge of the equatorial anomaly. We favorably compare the Arecibo drift to a typical satellite event. These electric fields may reflect a nonlinear evolved state of the Perkins instability or some, as yet, unexplained coupling between atmospheric motion and the plasma embedded in it. We show here that the F‐region Pedersen conductivity is much lower in these structures than outside and suggest that this is related to a polarization electric field inside the structure.
Observations of the radial magnetosheath profile and a comparison with gasdynamic model predictions
Authors: Němeček Z. , Šafránková J. , Zastenker G. N. , Pišoft P. , Paularena K. I. , Richardson J. D.
Published: February 2004

The gasdynamic model of the magnetosheath flow predicts changes of plasma parameters across the magnetosheath. According to this model, the ion flux peaks at the bow shock and decreases toward the magnetopause. MHD models predict a further plasma depletion near the magnetopause for specific orientations of the interplanetary magnetic field. We present a statistical study of ion flux measurements on the dusk flank of the magnetosheath and its comparison with present magnetosheath models. The study is based on three years of INTERBALL‐1 measurements supported by simultaneous WIND solar wind observations. Our results reveal a much flatter magnetosheath radial profile than was expected from the gasdynamic prediction. The profile becomes steeper for higher upstream Mach number or plasma beta. The depletions of the ion flux behind the bow shock and at the magnetopause are attributed to the reflection and acceleration of particles in the bow shock region and magnetopause reconnection, respectively. A comparison of the measured and predicted ion fluxes suggests that the magnetosheath thickness is a rising function of the IMF magnitude.
2D hybrid simulations of the solar wind interaction with a small scale comet in high Mach number flows
Authors: Hopcroft M. W. , Chapman S. C.
Published: February 2004

We investigate the structure and dynamics of the interaction between high Mach number solar wind flows and a cometary source that is “small scale” with respect to the cometary ion gyroscales, examples being Grigg‐Skjellerup or P/Wirtanen. A series of 2D hybrid simulations are used and we focus on IMF orientations parallel and perpendicular to the simulation plane, these permit or prohibit propagation of modes with a component of k parallel to B0. The perpendicular cases show the onset of magnetosonic turbulence as MA is increased; introducing a parallel B0 field component significantly changes this turbulence and the apparent shock structure seen on a ‘fly‐by'. This implies that the Alfvén‐ion cyclotron mode plays a critical role in the observed structure, and we suggest the relevant mechanism must be resonant growth of such waves in the presence of magnetosonic turbulence from either the unstable ring beam distribution of the pickup ions, or shock reflected solar wind protons.
FUV emissions on Io: Role of Galileo‐observed field‐aligned energetic electrons
Authors: Michael Marykutty , Bhardwaj Anil
Published: February 2004

The excitation of Io's atmosphere by Galileo‐observed magnetically field‐aligned energetic (0.1–100 keV) electrons have been studied using a Monte Carlo model. The calculated OI and SI FUV emissions are compared with HST‐STIS observations. It is found that Galileo EPD‐observed 15–100 keV electron beams are an insignificant source of OI and SI emissions on Io since they are too energetic to be degraded in Io's atmosphere. We show that Galileo PLS‐observed field‐aligned 0.1–5 keV electron fluxes can explain the HST‐observed S and O FUV brightness provided a fraction of these electrons precipitate into Io's atmosphere. The absorption of FUV emissions by SO2 is found to be less than 10%. From the qualitative scenario of a correlation between Jovian FUV emissions from IFT footprint and Io's FUV emissions we suggest a dual role of field‐aligned IFT electrons in producing emissions at Io and Jupiter.
Plasma densities in the vicinity of Callisto from Galileo plasma wave observations
Authors: Gurnett D. A. , Persoon A. M. , Kurth W. S. , Roux A. , Bolton S. J.
Published: February 2004

The Galileo spacecraft has made seven close flybys of Jupiter's moon Callisto. During the closest of these (C22), which approached to within 535 km of the surface, the plasma wave instrument detected a very clear upper hybrid emission as the spacecraft passed near the moon. The peak electron density indicated by the upper hybrid resonance emission was 400 cm−3, almost one‐thousand times the electron density in the magnetosphere of Jupiter at the orbit of Callisto. These observations indicate that Callisto is probably surrounded by a dense ionospheric‐like plasma.
Use of Fe charge state changes as a tracer for solar wind entry to the magnetosphere
Authors: Perry C. H. , Grande M. , Zurbuchen T. H. , Hefti S. , Gloeckler G. , Fennell J. F. , Wilken B. , Fritz T.
Published: February 2004

We present a comparison of high charge state ion composition measurements from ACE located near the L1 point and POLAR in the mid‐altitude cusp/cleft, during the 13 May 1998 CME event. Using the frozen in charge state of the solar wind origin Fe ions as a tracer, we demonstrate the connectivity between the ACE observations and the high latitude measurements from POLAR. The ion charge state distributions were observed to show abrupt changes with variations in the average charge state of Fe between +6 and +15 corresponding to changes in the coronal source temperature of 4×105 to 2×106 K. A good correlation between the measurements at L1 and in the cusp/cleft was found, indicating direct entry of solar wind material during periods of southward IMF. In addition there is possible evidence for delayed entry during a period of predominantly northward IMF that may indicate a less direct entry mechanism for this configuration.
On the two‐phase decay of the Dst‐variation
Authors: Feldstein Y. I. , Dremukhina L. A. , Mall U. , Woch J.
Published: February 2004

We discuss the well known observation that during the storm recovery phase the Dst‐variation shows a two‐stage decay pattern, decaying first quickly and then decaying with a larger decay parameter. This finding is discussed in the context of the magnetic storm which was observed on November 25–27, 1986. Contrary to frequently used interpretations as two spatially separated ion populations or two different atomic ion components, we propose an alternative explanation for this feature. We argue that during the recovery phase of the magnetic storm the Dst decay is controlled by the decay of a two current system: the ring current (DR) and the magnetospheric tail current (DT).