bluuebunny/crossref_metadata_2025 huggingface dataset:
Work, Family, and Mental Health: Testing Different Models of Work‐Family Fit
Authors: Grzywacz Joseph G. , Bass Brenda L.
Published: February 2004

Using family resilience theory, this study examined the effects of work‐family conflict and work‐family facilitation on mental health among working adults to gain a better understanding of work‐family fit. Data from the National Survey of Midlife Development in the United States (MIDUS) were used to compare different combinations of work‐family conflict and work‐family facilitation. Results suggest that family to work facilitation is a family protective factor that offsets and buffers the deleterious effects of work‐family conflict on mental health. The results across these outcomes suggest that work‐family conflict and facilitation must be considered separately, and that adult mental health is optimized when family to work facilitation is high and family to work and work to family conflict is low.
Women's Economic Standing, Marriage Timing, and Cross‐National Contexts of Gender
Authors: Ono Hiromi
Published: February 2004

Proponents of the theory of specialization and exchange hypothesize that in any national context, women's higher economic standing will decrease their chance of marriage. Some researchers suggest, however, that only in industrialized countries with a high degree of role differentiation by gender does the inverse relationship between women's economic standing and the chance of marriage exist. To evaluate contrasting cross‐national predictions, I test with longitudinal data and standardized methods whether the inverse relationship exists in 3 similarly affluent industrialized countries that vary in their degree of role differentiation by gender: the United States, Japan (a context more differentiated by gender than the United States), and Sweden (a context less differentiated by gender than the United States). Contrary to the prediction that develops out of the theory of specialization and exchange, results indicate that women's higher levels of income discourage first marriage formation in Japan, but encourage it in the United States and Sweden.
Generational Effects on Marriage Patterns: Jewish Immigrants and Their Descendants in Israel
Authors: Gshur Binyamin , Okun Barbara S.
Published: February 2004

We analyze various effects of generational status on marriage patterns of Jewish immigrants and their descendants in Israel over the last 4 decades. We report the following findings: (a) important, independent effects of generational endogamy on marriage patterns in all periods; (b) steady declines in ethnic endogamy among the native born, along with stability in levels of ethnic endogamy among first‐generation immigrants over the past 3 decades; (c) effects of generational status on the propensity to marry in all periods. Our results suggest an increase over time in the relative importance of generational factors in marriage patterns. This conclusion contrasts with previous research documenting general declines in the importance of ascriptive characteristics in marriage behavior.
Premarital Living Arrangements and the Transition to First Marriage in Japan
Authors: Raymo James M.
Published: February 2004

This article evaluates the relevance of a popular emphasis on the benefits of extended coresidence with parents as an explanation for the trend toward later marriage in Japan. Estimating hazard models for the transition to first marriage separately by gender, living arrangements, and birth cohort, I find that the trend toward later marriage is indeed more pronounced among young men and women living with parents. Conditional on coresidence, however, there is little evidence that access to parental provision of financial resources and domestic services is negatively associated with marriage. I suggest alternative scenarios in which parental resources may contribute to later marriage by facilitating children's independence rather than by keeping them at home.
Marital Relationships Following the Korean Economic Crisis: Applying the Family Stress Model
Authors: Kwon Hee‐Kyung , Rueter Martha A. , Lee Mi‐Sook , Koh Seonju , Ok Sun Wha
Published: February 2004

In response to the recent economic crisis in Korea and its negative effects on families, the current study examined the interrelationships among economic pressure, emotional distress, marital conflict, and marital satisfaction for 236 Korean couples. The family stress model (Conger & Elder, 1994; Conger, Rueter, & Conger, 2000; Conger, Rueter, & Elder, 1999) was tested using structural equation modeling. The results generally supported the theoretical model, showing that economic pressure negatively affects marital satisfaction via emotional distress and marital conflict. The results also implied cultural differences in the process of family stress. Korean husbands' emotional distress did not affect marital conflict or marital satisfaction, suggesting that Korean husbands may differ from their wives in their reaction to emotional distress from economic pressure.
The Role of Family Income in the Intergenerational Association of AFDC Receipt
Authors: Martin Molly A.
Published: February 2004

Daughters from low‐income families who did not receive Aid to Families with Dependent Children (AFDC) are compared to daughters from low‐income families who did receive assistance to better account for family income in the intergenerational association of AFDC. The research models the timing of a daughter's first birth and, for those who become mothers, the number of years a daughter receives any AFDC. Women whose families received AFDC during their childhood are more likely to receive AFDC as adults relative to those women whose families did not receive AFDC. Controlling for family income in a more careful and comprehensive way than past research explains part but not all of the effects of childhood AFDC receipt. Among daughters from chronically poor families, however, parental AFDC use is not associated with additional years of AFDC participation. Although the present research cannot confirm or deny a causal role for parental welfare use, the intergenerational transmission of financial resources does explain part of the intergenerational association of welfare use.
Income Changes and Cognitive Stimulation in Young Children's Home Learning Environments
Authors: Votruba‐Drzal Elizabeth
Published: February 2004

Early home learning environments are the result of interactions between the developing children and the opportunity structures provided by their families. Income is one of several resources that affect the cognitive stimulation that children experience. Using data from the National Longitudinal Survey of Youth (N= 2,174) this study examines the influence of household income on cognitive stimulation during the transition to school (aged 3–4 years to 7–8 years). Cross‐sectional and longitudinal fixed effects regressions are estimated to examine income's effect. Household income was positively related to the level of cognitive stimulation in children's home environments across both sets of analyses. Home environments of children in low‐income households were particularly sensitive to income changes over time. The implications of these results for programs and policies that reduce disparities in school readiness are discussed.
Costs and Rewards of Children: The Effects of Becoming a Parent on Adults' Lives
Authors: Nomaguchi Kei M. , Milkie Melissa A.
Published: February 2004

How do new parents differ from their childless counterparts in social and psychological resources, daily strains, and psychological well‐being? Using a nationally representative panel of 1,933 adults who were childless at the first interview, we compare 6 indicators of adults' lives for those who became parents and those remaining childless several years later, controlling for earlier states. Becoming a parent is both detrimental and rewarding. With the exception of social integration, which is greater for all groups of new parents compared with their childless counterparts, the effects of parental status on adults' lives vary markedly by gender and marital status. Unmarried parents report lower self‐efficacy and higher depression than their childless counterparts. Married mothers' lives are marked by more housework and more marital conflict but less depression than their childless counterparts. Parental status has little influence on the lives of married men.
Variations in Child Care by Grandparents During the First Three Years
Authors: Vandell Deborah Lowe , McCartney Kathleen , Owen Margaret Tresch , Booth Cathryn , Clarke‐Stewart Alison
Published: February 2004

Routine child care by grandparents was examined for 1,229 children who were participants in the National Institute of Child Health and Human Development (NICHD) Study of Early Child Care. Four groups were identified: extended full‐time care, extended part‐time care, sporadic care, and no routine care during the first three years. The odds of sporadic child care by grandparents were higher when mothers were relatively young and worked nonstandard hours. The odds of extended full‐time grandparent care versus extended part‐time grandparent care were higher for mothers of color and mothers with more extensive full‐time employment. All types of grandparent care were more likely when a grandparent lived in the household. These findings suggest that grandparent care is heterogeneous and may occur in response to different family circumstances.
The Influence of Religion on Fathers' Relationships With Their Children
Authors: King Valarie
Published: February 2004

This study explores how aspects of a father's religiousness are related to the type and quality of involvement with his children. Factors that potentially confound or explain the connection between religiousness and fathering are also examined. Multiple measures of religiousness and father–child ties are considered in a series of bivariate and multivariate regression models. The sample of 810 fathers comes from the National Survey of Midlife Development in the United States (MIDUS). Results indicate that religious fathers are more involved fathers and that they report higher quality relationships; this is true for both married and divorced fathers. The greater involvement of religious fathers is explained only in part by demographic factors and the mediating influences of traditional attitudes and marital quality.
Social Support to Parents‐in‐Law: The Interplay of Gender and Kin Hierarchies
Authors: Lee Eunju , Spitze Glenna , Logan John R.
Published: February 2004

Using data from a representative sample of middle‐aged married persons, we compare men's and women's contact and assistance to older parents‐in‐law and parents. Women have more visits and phone contact with their parents than do men, and men talk on the phone more with their in‐laws than do women. There are no gender differences in assistance patterns. Multivariate analysis shows that women contact and help parents more than in‐laws, whereas for men there are no such differences. There is little direct evidence that the presence of one set of parents affects relations with the other. Our findings suggest that although women clearly give priority to relations with their own parents, men experience pulls in both directions.
Family Contingencies Across the Generations: Grandparent‐Grandchild Relationships in Holistic Perspective
Authors: Mueller Margaret M. , Elder Glen H.
Published: February 2004

Family relationships do not occur in isolation but rather are embedded within greater systems of family ties. In recognition of the need to study families holistically, we explore how relations between grandparents and grandchildren are contingent upon a matrix of intergenerational relationships. Using data from the Iowa Youth and Families Project, our analyses focus on person‐centered types of grandparent‐grandchild relationships and the legacy of social ties across the generations, as mediated by other family relationships. We find multiple dimensions of grandparents' involvement with their grandchildren to be associated with (a) whether the grandparents knew their own grandparents when they were young, (b) the grandparent's perceptions of contact and closeness with the target grandchild, and (c) nuances in the relationships of grandparents with the parent generation.
Assistance to Aging Parents and Parents‐In‐Law: Does Lineage Affect Family Allocation Decisions?
Authors: Shuey Kim , Hardy Melissa A.
Published: February 2004

In this analysis we used data from the Health and Retirement Study to examine how couples organize transfers of assistance to aging parents and whether the flow of assistance is structured by family lineage. We found evidence of a tradeoff between types of assistance and a unilineal pattern of assistance. Few couples provided both time and money, and few assisted parents and parents‐in‐law. The determinants of assistance varied by type of care, recipient, and patterns of parental survival. Couples were more responsive to the needs of the wife's parent(s) and were less likely to exclude her parents from care even under circumstances of competition. Controlling for resources, African American and Hispanic couples were consistently more likely to provide assistance.
Separations, Reconciliations, and Living Apart in Cohabiting and Marital Unions
Authors: Binstock Georgina , Thornton Arland
Published: February 2004

Using data from a panel study of White young adults containing complete marital and cohabiting union histories from age 15 through 31, our goal is to track and compare the paths along which young adults arrange and time the entries and exits from marital and cohabiting unions. We focus on the incidence, duration, and outcomes of 2 dimensions that embrace residential separation: (a) separations that relate to discord in the relationship and (b) living apart from the partner or spouse for reasons other than discord. Our results show that union trajectories are dynamic and involve a heterogeneous and multidirectional array of transitions. We also find consistent differences supporting the idea that marital unions are more stable and durable than cohabiting unions.
Premarital Sex, Premarital Cohabitation, and the Risk of Subsequent Marital Dissolution Among Women
Authors: Teachman Jay
Published: February 2004

Using nationally representative data from the 1995 National Survey of Family Growth, I estimate the association between intimate premarital relationships (premarital sex and premarital cohabitation) and subsequent marital dissolution. I extend previous research by considering relationship histories pertaining to both premarital sex and premarital cohabitation. I find that premarital sex or premarital cohabitation that is limited to a woman's husband is not associated with an elevated risk of marital disruption. However, women who have more than one intimate premarital relationship have an increased risk of marital dissolution. These results suggest that neither premarital sex nor premarital cohabitation by itself indicate either preexisting characteristics or subsequent relationship environments that weaken marriages. Indeed, the findings are consistent with the notion that premarital sex and cohabitation limited to one's future spouse has become part of the normal courtship process for marriage.
Investigating Gender Differences in the Meaning of Household Chores and Child Care
Authors: Kroska Amy
Published: February 2004

This study examines factors related to the affective meanings (evaluation, potency, and activity) that spouses and cohabitors (N= 309) attach to child care, baby care, and 9 household chores. Gender is related to about a third of these task meanings. Consistent with the feminine care hypothesis, women consider baby care and laundry especially good, potent, and active and consider meal preparation particularly powerful, although contrary to this hypothesis women evaluate washing dishes less positively than men. Consistent with the masculine care hypothesis, men consider auto work and yard work especially good and powerful. When paid and unpaid work patterns are controlled, however, 9 of the 12 gender differences become nonsignificant and 4 new gender differences are identified, suggesting that work patterns both mediate and suppress some gender differences in task meanings. Gender also moderates the relationship between work and 12 task meanings. In several of these equations, women's proportion of nonmasculine work is negatively related to the goodness or the power they associate with a nonmasculine task.
Parent‐Adolescent Communication About Sex: Retrospective Reports by Latino College Students
Authors: Raffaelli Marcela , Green Stephanie
Published: February 2004

Latina female (n= 97) and Latino male (n= 69) college students (M age = 21.4 years) completed self‐report surveys regarding family of origin experiences, including sexual communication with parents while growing up. Latino parents of this comparatively highly educated sample tended to use direct rather than indirect strategies for communicating about sexuality with their children. Young women reported higher levels of sexual communication with mothers while growing up than did young men, and respondents reported less communication with fathers than mothers. Among young women, sexual communication with mother was positively associated with non‐Mexican origin and negatively associated with having older brothers living at home. In contrast, maternal education was positively associated with mother‐son communication about sex. Paternal education and the absence of older brothers positively predicted communication with both sons and daughters. The analyses provide novel information regarding sexual communication in Latino families and suggest directions for future research.
Spillover Between Marital Quality and Job Satisfaction: Long‐Term Patterns and Gender Differences
Authors: Rogers Stacy J. , May Dee C.
Published: February 2004

We used data from a 12‐year panel survey of a nationally representative sample of married individuals (not couples) and structural equation modeling to investigate the process of spillover between marital quality (satisfaction and discord) and job satisfaction among married individuals. We considered three questions: whether job satisfaction and marital quality are related over the long term, whether influence flows primarily from work to family or if there is a pattern of mutual effects between job satisfaction and marital quality, and whether job satisfaction and marital quality are related in similar ways for married women and married men over the long term. We found that marital quality and job satisfaction are related over the long term and that marital quality is the more influential of these domains. We found evidence of both positive and negative spillover from marital quality to job satisfaction over the long term. Specifically, increases in marital satisfaction were significantly related to increases in job satisfaction, and increases in marital discord were significantly related to declines in job satisfaction. Finally, our results indicated that these processes operate similarly for married women and married men.
An Experimental Study of Unsteady Partial Cavitation
Authors: Leroux Jean-Baptiste , Astolfi Jacques Andre´ , Billard Jean Yves
Published: February 2004

Unsteady partial cavitation can cause damage to hydraulic machinery and understanding it requires knowledge of the basic physics involved. This paper presents the main results of a research program based on wall-pressure measurements aimed at studying unsteadiness in partial cavitation. Several features have been pointed out. For cavity lengths that did not exceed half the foil chord the cavity was stated to be stable. At the cavity closure a peak of pressure fluctuations was recorded originating from local cavity unsteadiness in the closure region at a frequency depending on the cavity length. Conversely, cavities larger than half the foil chord were stated to be unstable. They were characterized by a cavity growth/destabilization cycle settled at a frequency lower than the previous ones. During cavity growth, the closure region fluctuated more and pressure fluctuations traveling in the cavity wake were detected. When the cavity was half the foil chord, cavity growth was slowed down and counterbalanced by large vapor cloud shedding. When the cavity length was maximum (l/c∼0.7–0.8), it was strongly destabilized. The reason for such destabilization is discussed at the end of the paper. It is widely believed that the cavity instability originates from a process involving the shedding of vapor clouds during cavity growth, a re-entrant jet, and a shock wave phenomenon due to the collapse of a large cloud cavitation.
Compressibility Effects on the Extended Crocco Relation and the Thermal Recovery Factor in Laminar Boundary Layer Flow
Authors: van Oudheusden B. W.
Published: February 2004

The relation between velocity and enthalpy in steady boundary layer flow is known as the Crocco relation. It describes that for an adiabatic wall the total enthalpy remains constant throughout the boundary layer, when the Prandtl number (Pr) is one, irrespective of pressure gradient and compressibility. A generalization of the Crocco relation for Pr near one is obtained from a perturbation approach. In the case of constant-property flow an analytic expression is found, representing a first-order extension of the standard Crocco relation and confirming the asymptotic validity of the square-root dependence of the recovery factor on Prandtl number. The particular subject of the present study is the effect of compressibility on the extended Crocco relation and, hence, on the thermal recovery in laminar flows. A perturbation analysis for constant Pr reveals two additional mechanisms of compressibility effects in the extended Crocco relation, which are related to the viscosity law and to the pressure gradient. Numerical solutions for (quasi-)self-similar as well as non-similar boundary layers are presented to evaluate these effects quantitatively.
On the Leak Through a Spiral-Groove Metallic Static Ring Gasket
Authors: Geoffroy S. , Prat M.
Published: February 2004

The diffusive and viscous leaks through a model spiral groove static ring gasket are studied analytically. This system is characterized by a transition from a leak through radial passages to a leak following the spiral groove as the load increases. The study concentrates on the transition. The results indicate a sharp (“critical”) transition with variations of several order of magnitudes in the leak flow rates for small changes in the contact area, i.e. the applied load. It is also shown how results for a diffusive leak and a viscous leak can be combined for identifying the transition. The influence of surface errors of form (waviness) is also considered. Although generally detrimental to tightness, it is however shown that errors of form could be beneficial to tightness for the high loads if their amplitudes are slightly smaller than the groove average depth.
Analysis of Two-Phase Homogeneous Bubbly Flows Including Friction and Mass Addition
Authors: Mor Marat , Gany Alon
Published: February 2004

The present work is a theoretical investigation of two-phase bubbly flows. The main objective is to get a better insight of the basic phenomena associated with such flows through nozzles via physical modeling and mathematical formulation. Introducing Mach number into the flow equations, we find novel, closed-form analytical solutions and expressions for homogeneous bubbly flows including the influence of wall friction and mass addition. The expressions obtained demonstrate an analogy to those of classical, single-phase gas flows. The study deals with homogeneous flows, however, its approach and results can also be applied to investigate flows with unequal phase velocities, to study instability phenomena, as well as to design and analyze water jet propulsion systems.
Unsteadiness of the Port Feed and Jet Flows Within a Gas Turbine Combustion System
Authors: Hughes N. J. , Carrotte J. F.
Published: February 2004

This paper describes an experimental investigation on a gas turbine combustor geometry that is typical of current aerospace applications. The isothermal investigation has concentrated on the flow approaching and passing through a primary port, and the subsequent jet formed by this flow within the flame tube. It is widely accepted that the jet formed by a port in such a geometry is influenced by the mean approach flow conditions. This paper, though, addresses whether the high levels of turbulence and unsteadiness, as is typically found within the approach flow of these systems, can also affect the time dependent jet and flow field generated by the port. Measurements using both hot wire anemometry (HWA) and a three component Laser Doppler Anemometry (LDA) system were therefore used to characterize the flow field. Cross correlation of simultaneous measurements indicated that velocity fluctuations in the feed annulus correlate with fluctuations inside the port and flame tube. The sign and magnitude of the correlations are presented between various feed annulus, port and flame tube spatial locations. The results suggest the time dependent external flow field can influence the flow field within the flame tube and hence, potentially, flame stability, mixing and emissions.
Flow at the Centrifugal Pump Impeller Exit With Circumferential Distortion of the Outlet Static Pressure
Authors: Hong Soon-Sam , Kang Shin-Hyoung
Published: February 2004

The effects of circumferential outlet distortion of a centrifugal pump diffuser on the impeller exit flow were investigated. A fence with sinusoidal width variation was installed at the vaneless diffuser exit. The flow field was measured at the impeller exit with and without the fence, using a hot film probe and an unsteady pressure sensor. Flow parameters varied with the circumferential position and the mean flow parameters plotted against the local flow rate at each circumferential position showed loops along the quasi-steady curves, which were obtained from the result without the fence. Simple theoretical calculations were used to predict the velocity components at the impeller exit with the relative flow angle or total pressure assumed. Good result was obtained when the relative flow angle was assumed to vary quasi-steadily, not constant with the local flow rate. The radial velocity was also reasonably predicted when the total pressure was assumed to vary quasi-steadily. A simple method is proposed to predict the impeller exit flow with downstream blockage in two-step sequence: the first step deals with the diffuser alone to obtain static pressure distribution at the diffuser inlet, while the second step deals with the impeller alone to obtain velocity components distribution at the impeller exit.
Circular Dynamic Stereoscopy and Its Application for Fluid Measurement
Authors: Kawasue Kikuhito , Oya Yuichiro , Ishimatsu Takakazu
Published: February 2004

By attaching a refractor to the lens of a Video Capture Device (e.g., CCD Video Camera) it is possible to record optical displacements from the original position of any object (tracer particle) within the image plane. If the refractor is physically rotated around the optical axis at high speed, the tracer particles create annular streaks due to the effect caused by the refractor’s circular shift. The perceived displacements are added to the image being recorded by the Video Capture Device (VCD). Additionally, these displacements are directly related to the distance between the VCD and the particle being measured: the magnitude of displacement on the image plane being inversely proportional to the distance between the VCD and point of measurement. Since the radius of each annular streak, of a point being measured, is inversely proportional to its distance from the VCD, it is therefore possible by analyzing these annular streaks, to determine the three dimensional positional information of the point. Thus the radius of the annular streaks on the image plane determines the z coordinate, while the geometric center provides the x and y coordinates. The theory and setup of such a measuring system is subsequently presented, and the measurement of a moving surface, such as moving water, is used to demonstrate a typical application of such a system.
Computational Analysis of Wall Roughness Effects for Liquid Flow in Micro-Conduits
Authors: Kleinstreuer C. , Koo J.
Published: February 2004

Fluid flow in microchannels or microtubes may differ in terms of wall frictional effects, and hence flow rates, when compared to macrochannels. Focusing on steady laminar fully developed flow of a liquid in different micro-conduits, relative surface roughness is captured in terms of a porous medium layer (PML) model. The new approach allows the evaluation of microfluidics variables as a function of PML characteristics, i.e., layer thickness and porosity, uncertainties in measuring hydraulic diameters as well as the inlet Reynolds number. Specifically, realistic values for the PML Darcy number, relative surface roughness, and actual flow area are taken into account to match observed friction factors in micro-conduits. The model predictions compared well with measured data sets for systems with significant relative roughness values. Although other surface effects may have influenced the experimental results as well, surface roughness is found to affect the friction factor and hence the flow parameters in relatively rough channels, e.g., those which are made of aluminum or stainless steel by way of micro-cutting processes.
Multi-Modal Forcing of the Turbulent Separated Shear Flow Past a Rib
Authors: Panigrahi P. K. , Acharya S.
Published: February 2004

Experiments have been conducted to study the development of flow behind a surface mounted rib under different phase controlled excitation. Single mode excitation and multi-mode excitation with different relative phases are studied. The results presented include the coherent and random components of the turbulent energy and shear stresses, the energy exchange with the mean flow and between the modes, and the phase decorrelation of the coherent components. The fundamental-subharmonic excitation does not provide any significant improvements in the shear layer growth over the fundamental excitation. The shear layer growth correlates with the subharmonic mode development. The large scale structures are significant even after the reattachment region as evident from the magnitude of the coherent components of the turbulent energy and the shear stress. The binary exchange terms are significant in the near-field region whose sign is phase dependent, i.e., it reverses its sign based on the phase difference between the fundamental and 1st subharmonic mode. The location of the fundamental and subharmonic peaks are different from the peak location of their respective energy exchange with the mean flow; this is attributed to the significance of the binary energy exchange between the fundamental and the subharmonic mode in this region. The excitation regularizes the flow leading to low phase jitter in the near field region. The origin and development of phase decorrelation is attributed primarily to the subharmonic instability.
Three-Dimensional Turbulent Flow in the Exit Head Section of a Heat Exchanger
Authors: Nie J. H. , Armaly B. F. , Tao W. Q. , Wang Q. W.
Published: February 2004

Measurements of three-dimensional turbulent flow in the exit head section of a shell-and-tube heat exchanger were performed using three-component laser Doppler velocimeter. The test geometry is half of a hemispherical cap with two outlet-tubes and with a cylindrical inlet section. Distributions of the velocity vector field, the three mean velocity components, and the Reynolds stress components are reported, and the complex nature of flow in the head section and in the neighborhood of the outlet-tube is quantified. The radial and the streamwise velocity components are of the same order of magnitude in the neighboring region of the outlet-tubes, and they are not symmetric relative to the center plane intersection of the outlet-tubes. The friction factor that was measured across the exit head section of the heat exchanger decreases as the Reynolds number increases from 25,000 to 50,000. These results are useful for validating turbulent flow simulation codes and are needed for improving the design of the exit head section of shell-and-tube heat exchangers.
Analysis of the Influence of Diesel Nozzle Geometry in the Injection Rate Characteristic
Authors: Benajes J. , Pastor J. V. , Payri R. , Plazas A. H.
Published: February 2004

An experimental research study was carried out to analyze the influence of different orifice geometries (conical and cylindrical) on the injection rate behavior of a Common-Rail fuel injection system. For that purpose, injection tests in two different injection test rigs were conducted. This behavior of the injection rate in the different nozzles was characterized by using the non-dimensional parameters of cavitation number (K), discharge coefficient (Cd) and Reynolds number (Re). First, some relevant physical properties of the injected fuel were accurately characterized (density, kinematic viscosity and sound speed in the fluid) in a specific test rig as a function of the operating conditions (pressure and temperature). The behavior of both nozzles was analyzed at maximum injector needle lift under steady flow conditions in a cavitation test rig. Injection pressure and pressure at the nozzle discharge were controlled in order to modify the flow conditions. In addition, the nozzles were characterized in real unsteady flow conditions in an injection-rate test rig. From the raw results, the values of the relevant parameters were computed, and the occurrence of cavitation was clearly identified. The results evidenced interesting differences in the permeability of both nozzle geometries and a clear resistance of the conical nozzle to cavitation.
A Phase-Averaged Analysis of Droplet Dispersion in the Wake of a Square Cylinder in a Uniform Stream
Authors: Fohanno S. , Martinuzzi R. J.
Published: February 2004

Time-averaged and phase-averaged size and velocity distributions of water droplets in the turbulent wake of a square cross-section cylinder, measured with a phase-Doppler anemometer, are presented for a Reynolds number ReD=18,500, based on the free stream velocity, U∞, and cylinder side dimension, D. It is shown that the coherent motion strongly influences the particle distribution and that the mean flow representation can be misleading in interpreting mixing. The results show that small particle concentration is largest in the very near wake. The mean particle distributions are homogeneous as early as 4D downstream of the cylinder, but the influence of vortex shedding on instantaneous distributions persists much longer. It is also observed that at the point of maximum mean streamline curvature, which also coincides with the region of maximum streamwise velocity fluctuations, particle separation is most effective.
Understanding Magnetic Field Gradient Effect From a Liquid Metal Droplet Movement
Authors: Gao Donghong , Morley Neil B. , Dhir Vijay
Published: February 2004

A two-dimensional liquid metal droplet moving into magnetic field gradient regions in a vacuum space in the absence of gravity has been simulated in VOF-CSF method. The general one-fluid VOF model for tracking free surfaces, and associated CSF model for applying surface tension to free surfaces are formulated. The calculations show us that the droplet encounters strong magnetohydrodynamics (MHD) drag from the field gradient along moving path. Interaction of liquid motion with a magnetic field induces electrical currents and Lorentz force on the droplet. The force is always to oppose the liquid motion in both increased and decreased field conditions. More attention is given to understanding the MHD equations and numerical results.
Double-Species Slurry Flow in a Horizontal Pipeline
Authors: Skudarnov P. V. , Lin C. X. , Ebadian M. A.
Published: February 2004

Slurry transport experiments were performed with five double-species slurries composed of glass beads and water. The double-species glass beads were various combinations of beads having two widely different densities and three narrow particle size distributions. Pressure gradients for double-species slurries were compared to those for individual components at the same solids volume concentrations. Effect of mean particle diameter on pressure gradient of double-species slurry in the pipe was studied. Experiments were performed in a horizontal pipe flow loop of 23 mm internal diameter. Obtained data are useful for pipeline systems design and also valuable for verification of numerical simulations of the slurry flows.
Rotating Choke in Cavitating Turbopump Inducer
Authors: Semenov Yury A. , Fujii Akira , Tsujimoto Yoshinobu
Published: February 2004

During the development stage of the liquid hydrogen turbopump for the main engine LE-7A of the H-IIA rocket, a new type of cavitation instability was observed. This instability occurs at lower cavitation numbers where the head of the inducer starts to decrease due to choke. The disturbance rotates around the rotor at about 50% of the inducer rotational speed. So, it is called “rotating choke.” In order to predict the instability, a cavity model with a cavity wake is developed. The region of instability and the frequency predicted by the model are in agreement with experiment. Discussions are made as to the relationship between rotating choke and rotating cavitation.
Interfacial Electrokinetic Effect on the Microchannel Flow Linear Stability
Authors: Tardu Sedat
Published: February 2004

The electrostatic double layer (EDL) effect on the linear hydrodynamic stability of microchannel flows is investigated. It is shown that the EDL destabilizes the Poiseuille flow considerably. The critical Reynolds number decreases by a factor five when the non-dimensional Debye-Huckel parameter κ is around ten. Thus, the transition may be quite rapid for microchannels of a couple of microns heights in particular when the liquid contains a very small number of ions. The EDL effect disappears quickly for κ⩾150 corresponding typically to channels of heights 400 μm or larger. These results may explain why significantly low critical Reynolds numbers have been encountered in some experiments dealing with microchannel flows.
Flow Through a Finite Packed Bed of Spheres: A Note on the Limit of Applicability of the Forchheimer-Type Equation
Authors: Montillet Agne`s
Published: February 2004

The variation of the pressure drop measured as a function of the fluid velocity through a packed bed of spheres is presented and discussed in the range of particle Reynolds number 30–1500. Based on previous studies, the observed limit of validity of the so-called Forchheimer law may be attributed to the concomitant effects of the finite character of the tested bed and of the transition of flow regime which is marking the beginning of the fully developed turbulent flow regime. The limit of validity of the Forchheimer-type law was formerly noticed by several authors.
Oil Sands Slurry Flow in Flexible Pipe
Authors: Frimpong Samuel , Ayodele Oluropo Rufus , Szymanski Jozef
Published: February 2004

Production cost and efficiency optimization for the Athabasca oil sands is a key to securing North America’s energy supply. Current oil sands production cost is about $13/bbl compared with $1.25/bbl for conventional crude oil. The effort to reduce production cost must focus on truck haulage because it contributes the dominant component of the production cost of about 26%. Toward this objective, hydraulic transportation has become a competitive means for materials handling. There is a desire to extend the hydraulic transport system to production faces using mobile train of flexible pipelines to optimize the system efficiency and cost. This flexible arrangement introduces a unique set of hydraulic transport problems, which must be addressed through rigorous modeling and analysis. This paper provides multiphase oil sand slurry models in flexible pipelines. New mathematical models are developed to characterize the multi-phase flow of oil sands slurry. The models combine the effects of dispersed particles and the carrier continuous phases. The coupled equations of each field are solved numerically for flexible pipe configuration. The models yield the productivity and deliverability of bitumen slurry between two mine facilities. The flexible arrangement allows modeling in elbow-type joint at different angles and in conventional linear pipelines, enabling adaptation of pipelines to various mine outlays. Numerical examples are presented to show the applicability of the new model and to ascertain optimum operational conditions of the flexible pipes in mine layouts.
Low-Reynolds Number Turbulence Models: An Approach for Reducing Mesh Sensitivity
Authors: Bredberg Jonas , Davidson Lars
Published: February 2004

This study presents a new near-wall treatment for low-Reynolds number (LRN) turbulence models that maintains accuracy in ‘coarse’ mesh predictions. The method is based on a thorough examination of approximations made when integrating the discretized equations in the near-wall region. A number of modifications are proposed that counteract errors introduced when an LRN-model is used on meshes for which the first interior node is located at y+≈5. Here the methodology is applied to the k−ω turbulence model by Bredberg et al., although similar corrections are relevant for all LRN models. The modified model gives asymptotically, in the sense of mesh refinement, identical results to the baseline model. For coarser meshes y+⩽10, the present method improves numerical stability with less mesh-dependency than the non-modified model. Results are included for fully developed channel flow, a backward-facing step flow and heat transfer in a periodic rib-roughened channel.
Gene Targeting in Stem Cells from Individuals with Osteogenesis Imperfecta
Authors: Chamberlain Joel R. , Schwarze Ulrike , Wang Pei-Rong , Hirata Roli K. , Hankenson Kurt D. , Pace James M. , Underwood Robert A. , Song Kit M. , Sussman Michael , Byers Peter H. , Russell David W.
Published: February 2004

Adult stem cells offer the potential to treat many diseases through a combination of ex vivo genetic manipulation and autologous transplantation. Mesenchymal stem cells (MSCs, also referred to as marrow stromal cells) are adult stem cells that can be isolated as proliferating, adherent cells from bones. MSCs can differentiate into multiple cell types present in several tissues, including bone, fat, cartilage, and muscle, making them ideal candidates for a variety of cell-based therapies. Here, we have used adeno-associated virus vectors to disrupt dominant-negative mutant
COL1A1
collagen genes in MSCs from individuals with the brittle bone disorder osteogenesis imperfecta, demonstrating successful gene targeting in adult human stem cells.
Attention to Intention
Authors: Lau Hakwan C. , Rogers Robert D. , Haggard Patrick , Passingham Richard E.
Published: February 2004

Intention is central to the concept of voluntary action. Using functional magnetic resonance imaging, we compared conditions in which participants made self-paced actions and attended either to their intention to move or to the actual movement. When they attended to their intention rather than their movement, there was an enhancement of activity in the pre-supplementary motor area (pre-SMA). We also found activations in the right dorsal prefrontal cortexand left intraparietal cortex. Prefrontal activity, but not parietal activity, was more strongly coupled with activity in the pre-SMA. We conclude that activity in the pre-SMA reflects the representation of intention.
Regulation of Cell Migration by the C2 Domain of the Tumor Suppressor PTEN
Authors: Raftopoulou Myrto , Etienne-Manneville Sandrine , Self Annette , Nicholls Sarah , Hall Alan
Published: February 2004

PTEN is a tumor suppressor protein that dephosphorylates phosphatidylinositol 3,4,5 trisphosphate and antagonizes the phosphatidylinositol-3 kinase signaling pathway. We show here that PTEN can also inhibit cell migration through its C2 domain, independent of its lipid phosphatase activity. This activity depends on the protein phosphatase activity of PTEN and on dephosphorylation at a single residue, threonine
383
. The ability of PTEN to control cell migration through its C2 domain is likely to be an important feature of its tumor suppressor activity.
Nervy Links Protein Kinase A to Plexin-Mediated Semaphorin Repulsion
Authors: Terman Jonathan R. , Kolodkin Alex L.
Published: February 2004

Cyclic nucleotides regulate axonal responses to a number of guidance cues through unknown molecular events. We report here that
Drosophila
nervy, a member of the myeloid translocation gene family of A kinase anchoring proteins (AKAPs), regulates repulsive axon guidance by linking the cyclic adenosine monophosphate (cAMP)–dependent protein kinase (PKA) to the Semaphorin 1a (Sema-1a) receptor Plexin A (PlexA). Nervy and PKA antagonize Sema-1a-PlexA–mediated repulsion, and the AKAP binding region of Nervy is critical for this effect. Thus, Nervy couples cAMP-PKA signaling to PlexA to regulate Sema-1a–mediated axonal repulsion, revealing a simple molecular mechanism that allows growing axons to integrate inputs from multiple guidance cues.
Use of CD134 As a Primary Receptor by the Feline Immunodeficiency Virus
Authors: Shimojima Masayuki , Miyazawa Takayuki , Ikeda Yasuhiro , McMonagle Elizabeth L. , Haining Hayley , Akashi Hiroomi , Takeuchi Yasuhiro , Hosie Margaret J. , Willett Brian J.
Published: February 2004

Feline immunodeficiency virus (FIV) induces a disease similar to acquired immunodeficiency syndrome (AIDS) in cats, yet in contrast to human immunodeficiency virus (HIV), CD4 is not the viral receptor. We identified a primary receptor for FIV as CD134 (OX40), a T cell activation antigen and costimulatory molecule. CD134 expression promotes viral binding and renders cells permissive for viral entry, productive infection, and syncytium formation. Infection is CXCR4-dependent, analogous to infection with X4 strains of HIV. Thus, despite the evolutionary divergence of the feline and human lentiviruses, both viruses use receptors that target the virus to a subset of cells that are pivotal to the acquired immune response.
Regulation of Fasted Blood Glucose by Resistin
Authors: Banerjee Ronadip R. , Rangwala Shamina M. , Shapiro Jennifer S. , Rich A. Sophie , Rhoades Ben , Qi Yong , Wang Juan , Rajala Michael W. , Pocai Alessandro , Scherer Phillipp E. , Steppan Claire M. , Ahima Rexford S. , Obici Silvana , Rossetti Luciano , Lazar Mitchell A.
Published: February 2004

The association between obesity and diabetes supports an endocrine role for the adipocyte in maintaining glucose homeostasis. Here we report that mice lacking the adipocyte hormone resistin exhibit low blood glucose levels after fasting, due to reduced hepatic glucose production. This is partly mediated by activation of adenosine monophosphate–activated protein kinase and decreased expression of gluconeogenic enzymes in the liver. The data thus support a physiological function for resistin in the maintenance of blood glucose during fasting. Remarkably, lack of resistin diminishes the increase in post-fast blood glucose normally associated with increased weight, suggesting a role for resistin in mediating hyperglycemia associated with obesity.
An Engineered Pathway for the Formation of Protein Disulfide Bonds
Authors: Masip Lluis , Pan Jonathan L. , Haldar Suranjana , Penner-Hahn James E. , DeLisa Matthew P. , Georgiou George , Bardwell James C. A. , Collet Jean-François
Published: February 2004

We have engineered a pathway for the formation of disulfide bonds. By imposing evolutionary pressure, we isolated mutations that changed thioredoxin, which is a monomeric disulfide reductase, into a [2Fe-2S] bridged dimer capable of catalyzing O
2
-dependent sulfhydryl oxidation in vitro. Expression of the mutant protein in
Escherichia coli
with oxidizing cytoplasm and secretion via the Tat pathway restored disulfide bond formation in strains that lacked the complete periplasmic oxidative machinery (DsbA and DsbB). The evolution of [2Fe-2S] thioredoxin illustrates how mutations within an existing scaffold can add a cofactor and markedly change protein function.