bluuebunny/crossref_metadata_2025 huggingface dataset:
Meter‐scale slopes of candidate MER landing sites from point photoclinometry
Authors: Beyer Ross A. , McEwen Alfred S. , Kirk Randolph L.
Published: December 2003

Photoclinometry was used to analyze the small‐scale roughness of areas that fall within the proposed Mars Exploration Rover (MER) 2003 landing ellipses. The landing ellipses presented in this study were those in Athabasca Valles, Elysium Planitia, Eos Chasma, Gusev Crater, Isidis Planitia, Melas Chasma, and Meridiani Planum. We were able to constrain surface slopes on length scales comparable to the image resolution (1.5 to 12 m/pixel). The MER 2003 mission has various engineering constraints that each candidate landing ellipse must satisfy. These constraints indicate that the statistical slope values at 5 m baselines are an important criterion. We used our technique to constrain maximum surface slopes across large swaths of each image, and built up slope statistics for the images in each landing ellipse. We are confident that all MER 2003 landing site ellipses in this study, with the exception of the Melas Chasma ellipse, are within the small‐scale roughness constraints. Our results have provided input into the landing hazard assessment process. In addition to evaluating the safety of the landing sites, our mapping of small‐scale roughnesses can also be used to better define and map morphologic units. The morphology of a surface is characterized by the slope distribution and magnitude of slopes. In looking at how slopes are distributed, we can better define landforms and determine the boundaries of morphologic units.
Glacial‐interglacial dynamics of the eastern equatorial Pacific cold tongue‐Intertropical Convergence Zone system reconstructed from oxygen isotope records
Authors: Koutavas Athanasios , Lynch‐Stieglitz Jean
Published: December 2003

We use planktonic oxygen isotope (δ18O) records spanning the last 30,000 years (kyr) to constrain the magnitude and spatial pattern of glacial cooling in the upwelling environment of the eastern equatorial Pacific (EEP). Fourteen new downcore δ18O records were obtained from surface‐dwelling planktonic foraminifera Globigerinoides sacculifer and Globigerinoides ruber in eight cores from the upwelling tongue of the EEP. All sites have sedimentation rates exceeding 5 cm/kyr and, with one exception, lie above the modern depth of the foraminiferal lysocline. Sites directly underlying the cool band of upwelling immediately south of the equator record mean late Holocene (LH)‐Last Glacial Maximum (LGM) δ18O amplitudes ranging between 1.0 and 1.3‰. We estimate that mean sea surface temperatures (SST) in this region during the LGM were on average 1.5 ± 0.5°C lower than the LH. Larger δ18O amplitudes are observed in sites north of the equator, indicating a spatial pattern of reduced meridional SST gradient across the equator during the LGM. This result is supported by comparison of Mg/Ca SST reconstructions from two sites straddling the equator. We interpret the reduction of this gradient during the LGM as evidence for a less intense cold tongue‐Intertropical Convergence Zone (ITCZ) frontal system, a more southerly position of the ITCZ, and weaker southeast equatorial trades in the EEP.
Early Cenozoic decoupling of the global carbon and sulfur cycles
Authors: Kurtz A. C. , Kump L. R. , Arthur M. A. , Zachos J. C. , Paytan A.
Published: December 2003

Changes in carbon and sulfur cycling over geologic time may have caused considerable modification of atmospheric and oceanic composition and climate. Here we calculate pyrite sulfur (Spy) and organic carbon (Corg) burial rates from recently improved Cenozoic stable isotope records, and from these rates we infer global changes in Corg burial environments. Given predominantly normal shelf‐delta organic carbon burial, the global Spy burial flux should be coupled to Corg burial. However, we find that the major early Cenozoic peak in Corg burial coincides with a minimum in Spy burial. Although the calculated magnitude of variations in global pyrite burial flux is sensitive to our assumptions about the concentration of sulfate in paleoseawater, a non‐steady‐state isotope mass balance model indicates very low Spy burial rates during the Paleocene and a dramatic increase starting near the Paleocene‐Eocene boundary, dropping off to a fairly constant Cenozoic rate beginning in the middle Eocene. High Corg/Spy burial ratios (C/S mole ratio ≈15–30) coinciding with the Paleocene carbon isotope maximum most likely reflect enhanced accumulation of terrestrial organic carbon in Paleocene terrestrial swamps. We suggest that rapid burning of accumulated Paleocene terrestrial organic carbon could have significantly contributed to the short‐lived negative carbon isotope excursion at the Paleocene‐Eocene boundary in addition to or possibly even as an alternative to release of gas hydrates from the continental slopes. An early Eocene minimum in calculated Corg/Spy burial ratios (C/S mole ratio ≈2–4) suggests that the predominant locus of organic carbon burial shifted to euxinic environments in a warm early Eocene ocean.
Waveguide containing a backward‐wave slab
Authors: Nefedov I. S. , Tretyakov S. A.
Published: December 2003

We have considered theoretically the waveguide properties of a plane two‐layered waveguide, whose one layer is a usual magnetodielectric (forward‐wave medium), but another one is a slab of so‐called backward‐wave material (BW‐material), whose both permittivity and permeability are negative. We have analyzed the properties of eigenwaves in this waveguide. In particular, it was found that there exist waves of both TE and TM polarizations, whose fields decay exponentially from the interface of the two slabs inside both layers, and their slow‐wave factor tends to infinity at small frequencies. Thus, this waveguiding system supports superslow waves with extremely short wavelengthes, as compared to the free‐space wavelength and the cross section size. Other peculiarities of the spectrum are also discussed.
Shortening of an overriding plate and its implications for slip on a subduction thrust, central Hikurangi Margin, New Zealand
Authors: Nicol Andrew , Beavan John
Published: December 2003

At subduction plate boundaries, strains accumulate within the overriding plate in response to motion of the down‐going plate. To a first approximation, margin‐normal interplate slip and shortening in the overriding plate sum to the total plate convergence. Therefore margin‐normal interplate slip can be estimated by measuring shortening in the overriding plate and total plate convergence. Here we quantify margin‐normal interplate slip by measuring shortening of the upper plate along a profile which extends up to 480 km across, and approximately normal to, the central Hikurangi Margin, New Zealand. Long‐term deformation is estimated for periods of millions of years using data from seismic reflection lines and cross sections, while contemporary strain rates are derived from Global Positioning System (GPS) geodetic velocities. These data permit comparison of plate convergence rates determined by seafloor spreading data with the rates of contraction over short (∼7 years) and long (∼2.5 and 5 Myr) periods of time. On this part of the plate boundary, total margin‐normal shortening in the overriding plate over the last ∼5 Myr was ∼9–28 km and accounts for ∼6–19% of the total convergence (145–160 km) at rates of ∼2–6 mm/yr. The remaining ∼80% or more of plate convergence has been accommodated by slip on the subduction thrust. GPS contraction along approximately the same profile indicates ∼14–16 mm/yr of contemporary shortening across the terrestrial part of the upper plate, which is approximately modeled by ∼80% interplate coupling on the subduction interface down to depths of ∼30 km. The contrasting proportions of inferred interplate coupling for contemporary and geological data sets are consistent with stick‐slip behavior on the plate interface and with slip being principally achieved during intermittent large earthquakes. The general shapes of short‐ and long‐term shortening profiles are similar and suggest that the highest strains occur at, or immediately east of, the Mohaka Fault. These strain profiles are consistent with a model where high strains in the upper plate are concentrated near the down‐dip end of the contemporary locked zone on the plate interface. This model requires that the down‐dip end of the interseismic locked zone has, on average, been approximately stable over a period of at least 2.5–5 Myr.
Bed load transport in managed steep‐gradient headwater streams of southeastern Alaska
Authors: Gomi Takashi , Sidle Roy C.
Published: December 2003

Bed load transport was investigated in four headwater streams in southeastern Alaska subjected to different management and disturbance regimes. Bed load yield was positively correlated to peak discharge during the fall 1999 monitoring period. Fine bed load materials (1–11 mm) that were supplied from hillslope sources were equally mobilized during most storm events. Medium‐sized bed materials (11–200 m) were only partially mobilized even during large storms, whereas large particles (>200 mm) were immobile and often formed interlocking channel structures. The transport distances of medium‐size materials depended on amount of channel obstructions (e.g., woody debris) and sediment supply conditions; both of these factors were influenced by the occurrence of mass movement, timber harvesting, and the related recovery processes. The highest total bed load yield was observed in a channel affected by a debris flow in 1993. Total sediment yields are similar among channels with old‐growth, clear cut (logged 4 years before monitoring), and young alder (affected by landslides and debris flows in 1961) riparian stands. By comparing the old‐growth and young alder channels, it appears that bed load yield recovers from debris flow disturbances in about 40 years; however, recovery of channel conditions (e.g., reach types and woody debris) may take much longer. Effects of timber harvesting on bed load transport are controlled by sediment linkages between hillslopes and channels related to the occurrence of mass movement.
Downstream hydraulic geometry relations: 1. Theoretical development
Authors: Singh Vijay P. , Yang Chih Ted , Deng Z. Q.
Published: December 2003

In this study, it is hypothesized that (1) the spatial variation of the stream power of a channel for a given discharge is accomplished by the spatial variation in channel form (flow depth and channel width) and hydraulic variables, including energy slope, flow velocity, and friction, and (2) that the change in stream power is distributed among the changes in flow depth, channel width, flow velocity, slope, and friction, depending on the constraints (boundary conditions) the channel has to satisfy. The second hypothesis is a result of the principles of maximum entropy and minimum energy dissipation or its simplified minimum stream power. These two hypotheses lead to four families of downstream hydraulic geometry relations. The conditions under which these families of relations can occur in field are discussed.
Downstream hydraulic geometry relations: 2. Calibration and testing
Authors: Singh Vijay P. , Yang Chih Ted , Deng Zhi‐Qiang
Published: December 2003

Using 456 data sets under bank‐full conditions obtained from various sources, the geometric relations, derived in part 1 [Singh et al., 2003], are calibrated and verified using the split sampling approach. The calibration of parameters shows that the change in stream power is not shared equally among hydraulic variables and that the unevenness depends on the boundary conditions to be satisfied by the channel under consideration. The agreement between the observed values of the hydraulic variables and those predicted by the derived relations is close for the verification data set and lends credence to the hypotheses employed in this study.
Improving Skilled Attendance at Delivery: A Preliminary Report of the SAFE Strategy Development Tool
Authors: Bell Jacqueline , Hussein Julia , Jentsch Birgit , Scotland Graham , Bullough Colin , Graham Wendy
Published: December 2003

Abstract:  Background:  Increasing the proportion of births with skilled attendance is advocated by international agencies as a key factor in reducing maternal and perinatal mortality and morbidity. The SAFE Strategy Development Tool is designed to enable policy makers and planners to gather and interpret information systematically to develop strategies for improving skilled attendance at birth.

Method:  Five modules were developed with partners in Bangladesh, Ghana, Jamaica, Malawi, and Mexico to guide the identification of problems related to skilled attendance, the collection of primary and secondary evidence, and the synthesis of this evidence to formulate strategies. The involvement of key players, including policy makers, is emphasized throughout the application of the tool and is vital to its success.

Results:  The SAFE Strategy Development Tool was field tested in five collaborating countries. The methods employed by this tool were found to be feasible and produced evidence that will be useful in the formulation of strategies. Application of the tool can be completed in 3 to 5 months, and was estimated to cost between US$12,938 and US$15,627 for applications at district or subdistrict level. The final strategy options developed from the findings were presented at an international workshop in Aberdeen, Scotland, in February 2003.

Conclusion:  The SAFE Strategy Development Tool is now available to governments, organizations, and institutions involved in the implementation of maternal health programs. (BIRTH 30:4 December 2003)
Feeling in Control During Labor: Concepts, Correlates, and Consequences
Authors: Green Josephine M. , Baston Helen A.
Published: December 2003

Abstract:  Background:  Many studies have revealed that a sense of control is a major contributing factor to a woman's birth experience and her subsequent well‐being. Since not all studies conceptualize “control” in the same way or distinguish between “external” and “internal” control, the purpose of this study is to advance understanding of how these senses of control relate to each other.

Methods:  Questionnaires were sent to women 1 month before birth to assess their preferences and expectations and at 6 weeks after birth to discover their experiences and assess psychological outcomes. Data are presented from 1146 women. Three control outcomes were considered: feeling in control of what staff do to you, feeling in control of your own behavior, and feeling in control during contractions.

Results:  Women were less likely to report being in control of staff (39.5%) than in control of their own behavior (61.0%). Approximately one‐fifth of the sample felt in control in all three ways, and another one‐fifth did not feel in control in any of them. Parity was strongly associated with feeling in control, with multiparas feeling more in control than primiparas in all cases. In logistic regression analyses, feeling in control of staff was found to relate primarily to being able to get comfortable, feeling treated with respect and as an individual, and perceiving staff as considerate. Feeling in control of one's behavior and during contractions were primarily related to aspects of pain and pain relief, but also to antenatal expectations of control. Worry about labor pain was also an important antenatal predictor for primiparas. All three control outcomes contributed independently to satisfaction, with control of staff being the most significant; relationships with emotional well‐being were also demonstrated.

Conclusions:  All three types of control were important to women and contributed to psychological outcomes. Internal and external control were predicted by different groups of variables. Caregivers have the potential to make a significant difference to a woman's experience of childbirth. The ways in which women are helped to deal with pain will affect internal control; the extent to which they feel that they are actually cared about, rather than care being something that is done to them, will affect external control. Both contribute to satisfaction and emotional well‐being. (BIRTH 30:4 December 2003)
Women's Memory of Childbirth at Two Months and One Year after the Birth
Authors: Waldenström Ulla
Published: December 2003

Abstract:  Background:  Studies of women's memory of labor and birth have generally concluded that women's recall is fairly accurate, but the findings are not unanimous. The aim of this study was to compare women's experiences of labor pain and overall experience of the birth at 2 months and 1 year after the delivery.

Methods:  A longitudinal cohort study of 2,428 women recruited in early pregnancy from all antenatal clinics in Sweden during 3 weeks evenly spread during 1999–2000 was conducted. In addition to a questionnaire in early pregnancy including background data, the women completed a questionnaire at 2 months and 1 year after the birth including the same 7‐point rating scale of pain intensity and the same question about overall experience of labor and birth.

Results:  Forty‐seven percent of the women made the same assessment of pain intensity, and 60 percent of childbirth overall, at 1 year as they did at 2 months after the birth. One year after the birth, 35 percent recalled pain as less severe, and 18 percent as more severe, and 24 percent said labor and birth overall was more negative, whereas 16 percent said it was more positive.

Conclusion:  This study showed great variation in women's memories of labor and birth, and conclusions by some other studies, often based on analyses of group data rather than on the responses of the individual participants were, to some extent, challenged. (BIRTH 30:4 December 2003)
Effect of Operative Delivery in the Second Stage of Labor on Breastfeeding Success
Authors: Patel Roshni R. , Liebling Rachel E. , Murphy Deirdre J.
Published: December 2003

Abstract:  Background:Operative delivery rates are currently rising in many countries, but the effects of this factor on the initiation and duration of breastfeeding are unclear. The purpose of this study was to evaluate breastfeeding success after instrumental vaginal delivery or cesarean section at full dilatation, and to investigate whether timing of discharge after operative delivery affects breastfeeding rates.

Methods:  A prospective cohort study was conducted of 393 women with term, singleton, live, cephalic pregnancies who required delivery in theater during the second stage of labor between February 1999 and February 2000. Postal questionnaires were mailed to participants at 6 weeks and 1 year. Logistic regression models were used to explore the relationships between infant feeding and mode of delivery, controlling for factors previously correlated with breastfeeding success.

Results:  Rates of exclusive breastfeeding at discharge and 6 weeks postpartum were 70 and 44 percent, respectively. No significant differences occurred when instrumental vaginal delivery was compared with cesarean section, adjusted OR 0.84 (95% CI 0.50, 1.41) and 1.15 (95% CI 0.69, 1.93) respectively. Breastfeeding rates after failed instrumental delivery were similar to those after immediate cesarean section, adjusted OR 0.99 (95% CI 0.72, 1.38) and 1.28 (95% CI 0.91, 1.78). Women who had a longer in‐patient stay after cesarean section were more likely to achieve exclusive breastfeeding at hospital discharge (78% vs 66%, p = 0.03).

Conclusions:  Method of operative delivery in the second stage of labor does not appear to influence initiation or duration of exclusive breastfeeding. A longer inpatient stay may help cesarean‐delivered women to initiate breastfeeding. (BIRTH 30:4 December 2003)
Breastfeeding Support from Partners and Grandmothers: Perceptions of Swedish Women
Authors: Ekström Anette , Widström Ann‐Marie , Nissen Eva
Published: December 2003

Abstract:  Background: Support from the mother's network of relatives, friends, and professional caregivers during childbirth is likely to be important for breastfeeding success. Few studies have been conducted to examine mothers’ perceptions of breastfeeding support. The objective of this study was to describe breastfeeding support and feelings of confidence of primiparas and multiparas in relation to duration of breastfeeding.

Methods:  Mothers who delivered vaginally were eligible for inclusion. After receiving a questionnaire when their children were 9 to 12 months of age, 194 primiparas and 294 multiparas responded to questions on breastfeeding history and on perceived and overall breastfeeding support and feelings of confidence.

Results:  Feelings of overall breastfeeding support were correlated with duration of exclusive breastfeeding in both primiparas (p < 0.001) and multiparas (p < 0.001). Multiparas who knew how long they were breastfed as a child showed a longer duration of exclusive (p = 0.006) and total (p = 0.007) breastfeeding than multiparas who did not know. The time during which the partner was present after labor was correlated with the duration of exclusive (p < 0.001) and total breastfeeding (p = 0.002) in primiparas. Feelings of confidence when the baby was 6 to12 months old, as retrospectively rated on a visual analog scale, was correlated with feelings of confidence in the partner during childbirth in both primiparas (p < 0.001) and multiparas (p < 0.001) and the experience of overall breastfeeding support (primiparas, p = 0.002; multiparas, p < 0.001). Both groups were more content with breastfeeding information they received from midwives in the maternity wards, compared with that from antenatal midwives and postnatal nurses (p < 0.001).

Conclusions:  A helpful support strategy for mothers with respect to breastfeeding outcome is for health professionals to discuss the grandmother's perception of breastfeeding with the mother. It is important for perinatal caregivers to provide an environment that enables the family to stay together after delivery. A helpful support strategy for health professionals might be to mobilize grandmothers with positive breastfeeding perception to provide support for their daughters’ breastfeeding. (BIRTH 30:4 December 2003)
Women's Recognition of the Spontaneous Onset of Labor
Authors: Gross Mechthild M. , Haunschild Tanja , Stoexen Tina , Methner Viola , Guenter Hans H.
Published: December 2003

Abstract:  Background: Despite extensive research on the onset of labor, almost no data are available on women's perception of labor onset. We undertook a study to assess how women experience spontaneous onset of term labor.

Methods:  A semistructured questionnaire was given to 235 women admitted in spontaneous labor at term. Women noted when labor had started, whether and when membranes had ruptured, and answered an open question about how labor had announced itself. Two investigators independently subdivided women's experiences on how labor had started into 369 sampling units corresponding to 8 predefined categories.

Results:  Nearly two‐thirds of the sampling units (63.4%) related to recurrent and nonrecurrent pain, and the ratio between the two types was higher for multiparas than for nulliparas. The number of women and sampling units were identical for each of the following categories: watery fluid (n = 47), blood‐stained loss (n = 33), gastrointestinal symptoms (n = 10) and altered sleep patterns (n = 11); 22 sampling units relating to emotional upheaval were mentioned by 16 women. Although 33.6 percent of women experienced rupture of membranes before admission, only 21.6 percent associated it with their onset of labor, either alone (11.5%) or in association with other categories (10.1%).

Conclusions:  Although women experience onset of labor in a variety of ways, for most it is a concrete event. Studies on duration of labor should take women's perception of onset of labor as a starting point rather than rely on surrogate measures. (BIRTH 30:4 December 2003)
Preference‐Based Approaches to Measuring the Benefits of Perinatal Care
Authors: Petrou Stavros , Henderson Jane
Published: December 2003

Abstract: Studies that measure benefits of health care interventions in natural or physical units cannot incorporate the several health changes that might occur within a single measure, and they overlook individuals’ preferences for those health changes. This paper discusses and critically appraises the application of preference‐based approaches to the measurement of the benefits of perinatal care that have developed out of economic theory. These include quality adjusted life year (QALY)‐based approaches, monetary‐based approaches, and discrete choice experiments. QALY‐based approaches use scaling techniques, such as the rating scale, standard gamble approach, and time trade‐off approach, or multi‐attribute utility measures, to measure the health‐related quality of life weights of health states. Monetary‐based approaches include the revealed preference approach, which involves observing decisions that individuals actually make concerning health risks, and the willingness‐to‐pay approach, which provides a framework for investigating individuals’ willingness to pay for benefits of health care interventions. Discrete choice experiments describe health care interventions in terms of their attributes, and elicit preferences for scenarios that combine different levels of those attributes. Empirical examples are used to illustrate each preference‐based approach to benefit measurement, and several methodological issues raised by the application of these approaches to the perinatal context are discussed. Particular attention is given to identifying the relevant attributes to incorporate into the measurement instrument, appropriate respondents for the measurement exercise, potential sources of bias in description and valuation processes, and the practicality, reliability, and validity of alternative measurement approaches. The paper's conclusion is that researchers should be explicit and rigorous in their application of preference‐based approaches to benefit measurement in the context of perinatal care. (BIRTH 30:4 December 2003)
Support During Pregnancy for Women at Increased Risk of Low Birthweight Babies
Authors: Hodnett E. D. , Fredericks S.
Published: December 2003

Background:  Studies consistently show a relationship between social disadvantage and low birthweight. Many countries have programs offering special assistance to women thought to be at risk for giving birth to a low birthweight infant. These programs may include advice and counselling (about nutrition, rest, stress management, alcohol and recreational drug use), tangible assistance (e.g., transportation to clinic appointments, help with household responsibilities), and emotional support. The programs may be delivered by multidisciplinary teams of health professionals, by specially trained lay workers, or by a combination of lay and professional workers.

Objectives:  The objective of this review was to assess the effects of programs offering additional social support for pregnant women who are believed to be at risk for giving birth to preterm or low birthweight babies.

Search strategy:  We searched the Cochrane Pregnancy and Childbirth Group trials register (30 January 2003).

Selection criteria:  Randomized trials of additional support during at‐risk pregnancy by either a professional (social worker, midwife, or nurse) or specially trained lay person, compared to routine care. Additional support was defined as some form of emotional support (e.g., counselling, reassurance, sympathetic listening) and information/advice, either in home visits or during clinic appointments, and could include tangible assistance (e.g., transportation to clinic appointments, assistance with the care of other children at home).

Data collection and analysis:  Reviewers independently assessed trial quality and extracted data. Double data entry was performed. Study authors were contacted to request additional information.

Main results:  Sixteen trials involving 13,651 women were included. The trials were generally of good to excellent quality, although 3 used an allocation method likely to introduce bias. Programs offering additional social support for at‐risk pregnant women were not associated with improvements in any perinatal outcomes, but there was a reduction in the likelihood of caesarean birth and an increased likelihood of elective termination of pregnancy. Some improvements in immediate maternal psychosocial outcomes were found in individual trials.

Reviewers’ conclusions:  Pregnant women need the support of caring family members, friends, and health professionals. While programs which offer additional support during pregnancy are unlikely to prevent the pregnancy from resulting in a low birthweight or preterm baby, they may be helpful in reducing the likelihood of caesarean birth.

Citation:  Hodnett ED, Fredericks S. Support during pregnancy for women at increased risk of low birthweight babies (Cochrane Review). In: The Cochrane Library, Issue 3, 2003. Oxford: Update Software.
Aerobic Exercise for Women During Pregnancy
Authors: Kramer M. S.
Published: December 2003

Background:  Physiological responses of the fetus (especially increase in heart rate) to single, brief bouts of maternal exercise have been documented frequently, suggesting that maternal exercise might have beneficial or adverse effects on pregnancy outcome.

Objectives:  The objective of this review was to assess the effects of advising healthy pregnant women to engage in regular (at least two to three times per week) aerobic exercise on physical fitness, labour and delivery, and the outcome of pregnancy.

Search strategy:  The Cochrane Pregnancy and Childbirth Group trials register was searched and researchers in the field were contacted. Date of last search: January 2002.

Selection criteria:  Acceptably controlled comparisons of prescribed aerobic exercise programs.

Data collection and analysis:  One reviewer assessed trial quality and extracted data. Study authors were contacted for additional information.

Main results:  Ten trials involving 688 women were included. The trials were not of high methodologic quality. Five trials reported significant improvement in physical fitness in the exercise group, although differences in measures used to assess fitness prevent a quantitative pooling of results. Six trials reported on pregnancy outcomes. A statistically significant increased risk of preterm birth (relative risk (RR) = 2.29 [95% confidence interval 1.02 to 5.13]) in the exercise group is inconsistent with the absence of effect on mean gestational age [+0.0 (−0.4 to +0.4) weeks] and may have been biased by post‐randomization exclusion of women with preterm labor. Results bearing on fetal growth (birthweight, length, and head circumference) were highly variable. One trial found improvements among exercising women in several aspects of self‐reported body image, including muscle strength, energy level, and body build.

Reviewers’ conclusions:  Regular aerobic exercise during pregnancy appears to improve (or maintain) physical fitness and body image. Available data are insufficient to infer important risks or benefits for the mother or infant.

Citation:  Kramer MS. Aerobic exercise for women during pregnancy (Cochrane Review). In: The Cochrane Library, Issue 3, 2003. Oxford: Update Software.
Vibrational Spectroscopic Database on Acetylene, X̃ 1Σg+ (12C2H2, C212D2, and C213H2)
Authors: Herman M. , Campargue A. , El Idrissi M. I. , Vander Auwera J.
Published: December 2003

Information on the vibrational energy states in acetylene (12C2H2, C212D2, and C213H2) is gathered: spectroscopic constants (vibrational frequencies and anharmonicities, vibration-rotation interaction parameters), observed vibrational energy states and complete sets of predicted vibrational energies and predicted principal rotational constants Bv for states of C212H2, C212D2, and C213H2 up to 15000, 10000, and 12000 cm−1, respectively. Statistical parameters (partition functions and integrated number of states) deduced from these predicted spectroscopic data are provided for the three isotopomers. The equilibrium geometrical structure is determined to be re(CH)=106.138(35) pm and re(CC)=120.292(13) pm from constants available for C212H2, C212D2, C213H2, and C212HD.
Three-dimensional linear stability analysis of the flow in a liquid spherical droplet driven by an alternating magnetic field
Authors: Shatrov V. , Priede J. , Gerbeth G.
Published: December 2003

The paper presents a numerical stability analysis of the flow driven by an alternating (ac) magnetic field in an electromagnetically levitated liquid metal droplet. The basic axisymmetric flow is found to become unstable at Reynolds numbers in the order of 100. The critical Reynolds number Rec and the corresponding most unstable azimuthal wave number m are found for several configurations of the magnetic field depending on the skin-depth δ. For a uniform external ac magnetic field the azimuthal wave number of the most unstable mode is m=3. An additional steady (dc) magnetic field imposed along the axis of symmetry increases the stability of the flow.
The velocity distribution function in direct simulation Monte Carlo method with an application to extended thermodynamics
Authors: Marino Luca
Published: December 2003

A numerical experiment is carried out to prove the difference between the value of the kinetic temperature and that of the thermodynamic temperature in a gas in the presence of molecular transport. As a reference situation the velocity distribution function is evaluated between two concentric cylinders at different wall temperatures. A direct simulation Monte Carlo method (DSMC) is adopted for various Knudsen numbers Kn and comparisons are made with existing data. The results prove quantitatively that the difference between the two differently defined temperatures increases with Kn and with the temperature gradient, as predicted by the theory for systems which are almost in thermodynamical equilibrium. The present article does not aim to validate DSMC, but rather to illustrate how the method can be used to address fundamental issues in gas dynamics.
Chemical fronts in Hele-Shaw cells: Linear stability analysis based on the three-dimensional Stokes equations
Authors: Demuth Rainer , Meiburg Eckart
Published: December 2003

We present linear stability results based on the three-dimensional Stokes equations for chemically reacting, propagating fronts giving rise to an unstable density stratification in a Hele-Shaw cell. The results are compared with the experiments in M. Böckmann and S. C. Müller [Phys. Rev. Lett. 85, 2506 (2000)], as well as with a corresponding linear stability analysis based on the Darcy equations that was performed in A. De Wit [Phys. Rev. Lett. 87, 054502 (2001)]. The reason for the good agreement between these earlier Darcy data and the experimentally observed growth rates is found in the relatively low experimental value of the Rayleigh number, Ra=79, for which the flow is approximately of Poiseuille type. Already for Ra values as low as 300, we observe a discrepancy between the stability results based on the Darcy and Stokes equations, respectively, with the Darcy results overpredicting both the most amplified wavenumber, as well as the corresponding growth rate, by about a factor of two. This indicates that three-dimensional effects quickly gain importance as Ra increases, so that the stability analysis needs to be based on the full, three-dimensional Stokes equations. The stability results based on the Stokes equations furthermore demonstrate the stabilizing influences of both an increasing interfacial thickness, as well as increasing frontal propagation velocities, confirming the earlier Darcy-based findings by De Wit. An argument in terms of vorticity is forwarded to explain the latter effect. A more rapidly advancing front deposits vorticity over a wider layer of fluid particles, so that the concentrated regions of vorticity needed for rapid instability growth cannot form. Somewhat surprisingly, however, slowly propagating fronts are seen to be more unstable than nonreacting fronts of equivalent thickness, as the chemical reaction leads to the formation of more compact perturbations in the interfacial region.
Equilibrium similarity, effects of initial conditions and local Reynolds number on the axisymmetric wake
Authors: Johansson Peter B. V. , George William K. , Gourlay Michael J.
Published: December 2003

Equilibrium similarity considerations are applied to the axisymmetric turbulent wake, without the arbitrary assumptions of earlier theoretical studies. Two solutions for the turbulent flow are found: one for infinite local Reynolds number which grows spatially as x1/3; and another for small local Reynolds number which grows as x1/2. Both solutions can be dependent on the upstream conditions. Also, the local Reynolds number diminishes with increasing downstream distance, so that even when the initial Reynolds number is large, the flow evolves downstream from one state to the other. Most of the available experimental data are at too low an initial Reynolds number and/or are measured too near the wake generator to provide evidence for the x1/3 solution. New results, however, from a laboratory experiment on a disk wake and direct numerical simulations (DNS) are in excellent agreement with this solution, once the flow has had large enough downstream distance to evolve. Beyond this the ratio of turbulence intensity to centerline velocity deficit is constant, until the flow unlocks itself from this behavior when the local Reynolds number goes below about 500 and the viscous terms become important. When this happens the turbulence intensity ratio falls slowly until the x1/2 region is reached. No experimental data are available far enough downstream to provide unambiguous evidence for the x1/2 solution. The prediction that the flow should evolve into such a state, however, is confirmed by recent DNS results which reach the x1/2 solution at about 200 000 momentum thicknesses downstream. After this the turbulence intensity ratio is again constant, until box-size affects the calculation and the energy decays exponentially.
Statistical theory of compressible turbulence based on mass-weighted averaging, with an emphasis on a cause of countergradient diffusion
Authors: Yoshizawa Akira
Published: December 2003

Statistical theory of inhomogeneous compressible turbulence is formulated on the basis of mass-weighted averaging. The velocity and the concentration of matters are resolved into the mass-weighted means and the fluctuations around them, whereas the density and the pressure are resolved into the ensemble means and the fluctuations around them. The former fluctuations multiplied by the density are normalized by the mean density, leading to new variables characterizing velocity and concentration fluctuations. In the use of those variables, turbulent fluxes may be examined in the presence of spatially varying mean velocity and scalar, as in incompressible flow. With the aid of the theoretical results about the fluxes, a cause of countergradient diffusion is discussed in the context of a premixed turbulent flame.
The undular hydraulic jump in turbulent open channel flow at large Reynolds numbers
Authors: Grillhofer Wolfgang , Schneider Wilhelm
Published: December 2003

Plane flow over a bottom of constant slope is considered in the double limit of very large Reynolds numbers, i.e., Reτ→∞, and Froude numbers approaching the critical value, i.e., Fr=1+32ε with ε→0. Fully developed turbulent flow far upstream is assumed. Owing to the large Reynolds number the inclination angle of the bottom, α, is small. The undular jump is analyzed for a parameter regime that is characterized by values of α that are of the same order of magnitude as ε2, i.e., α/ε2=O(1). The first-order perturbation equations contain unknown functions that are determined from a solvability condition of the second-order equations. Without making use of a turbulence model or empirical parameters, the following equation is obtained for the shape of the free surface: (d3H1/dX3)+(H1−1)(dH1/dX)−βH1=0, with H1→0 as X→−∞. H1(X) denotes the first-order perturbation of the surface elevation as a function of the nondimensional longitudinal coordinate X, and the parameter β=13αε−3/2 characterizes the slow changes of amplitudes and wavelengths, respectively. Numerical solutions of this ordinary differential equation are compared with experimental data.
The effect of electric fields on the rupture of thin viscous films by van der Waals forces
Authors: Savettaseranee K. , Papageorgiou D. T. , Petropoulos P. G. , Tilley B. S.
Published: December 2003

We examine the stability of a thin two-dimensional incompressible liquid film when an electric field is applied in a direction parallel to the initially flat bounding fluid interfaces, and study the competition between surface tension, van der Waals, viscous, and electrically induced forces. The film is assumed to be sufficiently thin, and the surface tension and electrically induced forces are large enough that gravity can be ignored to the leading order. We analyze the nonlinear stability of the flow by deriving and numerically solving a set of nonlinear evolution equations for the local film thickness and the horizontal velocity. We find that the electric field forces enhance the stability of the flow and can remove rupture. If rupture occurs then the form of the singularity, to leading order, is that found in the absence of an electric field.
Experimental friction factor of a liquid flow in microtubes
Authors: Brutin D. , Tadrist L.
Published: December 2003

The friction factor of a water laminar flow through fused silica microtubes with diameters ranging from 50 to 530 μm is investigated experimentally. The existing works in the literature are analyzed. They show a range of experimental results which agree or not with the conventional theory. Pressure drops and flowing masses are measured to determine the flow characteristics using a transient method. Several experiments are developed for two fluids (distilled and tap water) and tube compositions. The experimental results are discussed. The disparity from the classical theory is found to be due to the fluid’s ionic composition. The experimental results for tap water and classical fused silica surfaces indicate a disparity from the conventional theory. A friction factor increase with small uncertainties (<5%) is observed for decreasing diameters.
Vortex streets generated by a moving momentum source in a stratified fluid
Authors: Voropayev S. I. , Smirnov S. A.
Published: December 2003

The aim of this paper is to present the results of experiments conducted in a stratified fluid with a momentum source modeled by a moving jet in the asymptotic case when the size of the source is negligibly small but the resulting force (momentum flux), which acts on the fluid, remains finite. In this case the forcing may be considered as a “point” force moving in the fluid and the problem has no obvious characteristic length scale, compared to the case of a bluff body. The latter, towed horizontally in the stratified fluid, frequently leaves behind a highly organized vortex street, the characteristics of which strongly depend on the body diameter. It is shown that a similar type of the vortex streets may be generated by a “point” momentum source and conditions when this occurs are found. Experimental data on the characteristics of the vortex streets are presented and compared with the towed body case.
Vapor flows condensing at incidence onto a plane condensed phase in the presence of a noncondensable gas. I. Subsonic condensation
Authors: Taguchi Satoshi , Aoki Kazuo , Takata Shigeru
Published: December 2003

A steady flow of a vapor in a half space condensing onto a plane condensed phase of the vapor at incidence is considered in the case where another gas that neither evaporates nor condenses (the noncondensable gas) is present near the condensed phase. The behavior of the vapor and noncondensable gas is investigated on the basis of kinetic theory under the assumption that the molecules of the noncondensable gas are mechanically identical with those of the vapor. In particular, the relation, among the parameters of the vapor at infinity (the pressure, temperature, and flow velocity of the vapor), those related to the condensed phase (the temperature of the condensed phase and the corresponding saturation pressure of the vapor), and the amount of the noncondensable gas, that admits a steady solution is obtained numerically by the use of a model Boltzmann equation proposed by Garzó et al. [Phys. Fluids A 1, 380 (1989)]. The present analysis is the continuation of an earlier work by Sone et al. [Transp. Theory Stat. Phys. 21, 297 (1992)], where the case in which the vapor flow is condensing perpendicularly onto the condensed phase is investigated exclusively. The case with subsonic condensation is discussed in the present paper (the case with supersonic condensation is left to the subsequent paper).
Vorticity production and turbulent cooling of “hot channels” in gases: Three dimensions versus two dimensions
Authors: Kurzweil Yair , Livne Eli , Meerson Baruch
Published: December 2003

Hot channels (HCs), created in a gas by a rapid energy release in the quasi-cylindric geometry, cool anomalously fast by turbulent flow. Picone and Boris [Phys. Fluids 26, 365 (1983)] suggested that turbulent mixing results from the vorticity generation by the baroclinic mechanism during the early, shock-wave dominated stage of the dynamics. This scenario was confirmed, with important modifications, in a recent series of two-dimensional (2D) hydrodynamic simulations. This work reports three-dimensional (3D) hydrodynamic simulations of the HC evolution, and compares the results with those of 2D simulations. Assuming a small perturbation of the cylindric shape of the energy release region, we followed a typical HC up to 200 acoustic times. The simulations capture well the phenomenology of the HC cooling. The details of vorticity production, that results in a fast mixing of the cold ambient gas into the HC, are clearly identified. The cooling process can be interpreted as turbulent diffusion. The empiric diffusion coefficient and cooling time agree with experiment. The late-time morphology of the HC and the empiric turbulent diffusion coefficient are dimension-dependent, the 3D cooling being faster than 2D cooling.
The statistics of power injected in a closed turbulent flow: Constant torque forcing versus constant velocity forcing
Authors: Titon Jean Hugues , Cadot Olivier
Published: December 2003

A confined turbulent flow forced by two counter-rotating stirrers is investigated. Two processes of energy injection are studied. In the first one, called the Ω mode, the forcing devices are driven at constant angular velocity. In the second, called the Γ mode, the forcing devices are driven with a constant torque. For each forcing mode, the power injected and the wall pressure fluctuations are simultaneously measured in the range of Reynolds numbers from 20 000 to 500 000. For each mode, the probability density functions of the injected power are approximately Gaussian with slight reversed skewness between both modes. These asymmetries are due to an excess of low dissipation events compared to high dissipation events. For each mode, the skewness varies as the logarithm of the Reynolds number. On the other hand, the fluctuation rate of the injected power does not depend on the Reynolds number whatever the forcing modes, however, their magnitudes are drastically different. A value of only 5.9% is obtained for the Γ mode against 10.9% for the Ω mode. The local properties of the turbulence at smaller scales, deduced from either hot film anemometry or wall pressure measurements, are identical for both forcing modes. The mean dissipated power remains unchanged as well. It is then deduced that the injected power fluctuations are caused by the turbulence feedback rather than the turbulence production. The difference in the fluctuation rates is a consequence of the natural control of the turbulence feedback that occurs for the Γ mode.