Parental pre-pregnancy obesity and the risk of offspring weight and body mass index change from childhood to adulthood

The purpose of this study was to examine the association of parental pre-pregnancy weight and body mass index (BMI) on offspring weight and BMI change from childhood to adulthood. We analysed BMI data from a subsample of parents (n = 1494) from the Mater-University of Queensland Study of Pregnancy cohort that started in the early 1980s in Brisbane, Australia: data were collected at pre-pregnancy and then also for offspring at 5, 14 and 21-year follow-ups. Multiple regression for continuous outcomes and multinomial regression for categorical outcomes were performed. A total of 14.7% of offspring experienced BMI change from normal at 5 years to overweight or obese (OW/OB) at 14 years, 15.3% of normal at 14 years to OW/OB at 21 years and 22.8% from normal at 5 years to OW/OB at 21 years. Overall, the strength of the association of parental BMI with offspring BMI was stronger as offspring become older. Pre-pregnancy parental BMI differentially impacts offspring OW/OB across the life course. For every unit increase in paternal and maternal BMI z-score, offspring BMI z-score increased, on average, by between 0.15% (kg m^-2 ) and 0.24% (kg m^-2 ) throughout all three stages of life when both parents were OW/OB; these associations were stronger than with one parent. Parental pre-pregnancy BMI and OW/OB is a strong predictor of offspring weight and BMI change from early life to adulthood.

Parental supply of alcohol and alcohol consumption in adolescence: prospective cohort study

BACKGROUND

Parents are a major supplier of alcohol to adolescents, yet there is limited research examining the impact of this on adolescent alcohol use. This study investigates associations between parental supply of alcohol, supply from other sources, and adolescent drinking, adjusting for child, parent, family and peer variables.

METHOD

A cohort of 1927 adolescents was surveyed annually from 2010 to 2014. Measures include: consumption of whole drinks; binge drinking (>4 standard drinks on any occasion); parental supply of alcohol; supply from other sources; child, parent, family and peer covariates.

RESULTS

After adjustment, adolescents supplied alcohol by parents had higher odds of drinking whole beverages [odds ratio (OR) 1.80, 95% confidence interval (CI) 1.33-2.45] than those not supplied by parents. However, parental supply was not associated with bingeing, and those supplied alcohol by parents typically consumed fewer drinks per occasion (incidence rate ratio 0.86, 95% CI 0.77-0.96) than adolescents supplied only from other sources. Adolescents obtaining alcohol from non-parental sources had increased odds of drinking whole beverages (OR 2.53, 95% CI 1.86-3.45) and bingeing (OR 3.51, 95% CI 2.53-4.87).

CONCLUSIONS

Parental supply of alcohol to adolescents was associated with increased risk of drinking, but not bingeing. These parentally-supplied children also consumed fewer drinks on a typical drinking occasion. Adolescents supplied alcohol from non-parental sources had greater odds of drinking and bingeing. Further follow-up is necessary to determine whether these patterns continue, and to examine alcohol-related harm trajectories. Parents should be advised that supply of alcohol may increase children's drinking.

Death Anxiety and Death Acceptance: A Preliminary Approach

Death acceptance is not necessarily the opposite of death anxiety. The two could in fact correlate positively. A third category of “death denial” should also be considered. A new scale to measure death acceptance was devised. It was found to be reliable and, in a group of students, correlated positively ( rs = .242 and .263) with two existing death anxiety scales. People can therefore accept death and be anxious about it at the same time. Religious unbelievers were found to be death-acceptant and females death-anxious. There was no relation between death attitudes and achievement motivation.

Intergenerational transmission and continuity of stress and depression: depressed women and their offspring in 20 years of follow-up

BACKGROUND

Children of depressed mothers not only have higher risk of depression, but also may experience both elevated and continuing exposure to stressful experiences. The study tested hypotheses of the intergenerational transmission of stress and depression and examined the role of early childhood adversity and maternal depression in the interplay between youth depression and stress over 20 years.

METHOD

In a longitudinal community study of 705 families selected for history or absence of maternal depression, mothers and youth were studied from pregnancy to age 5 years and at youth ages 15 and 20 years. Youth and maternal depression were assessed with diagnostic interviews, acute and chronic interview-based stress assessment in the youth and contemporaneous measures of childhood adversity obtained between pregnancy and youth age 5 years.

RESULTS

Regression analyses indicated evidence of intergenerational transmission and continuity of depression over time, continuity of acute and chronic stress and reciprocal predictive associations between depression and stress. Maternal depression and exposure to adversities by child's age 5 years contributed to the youth's continuing experiences of depression and stress. An overall path model was consistent with stress continuity and intergenerational transmission and highlighted the mediating role of age 15 youth chronic interpersonal stress.

CONCLUSIONS

Youth of depressed mothers are at risk not only for depression but also for continuing experiences of acute and chronic stress from childhood to age 20. The associations among depression and stress are bidirectional and portend continuing experiences of depression and further stress.

Emotional and behavioural antecedents of young adults who screen positive for non-affective psychosis: a 21-year birth cohort study

BACKGROUND

Birth cohort studies have shown that individuals who develop non-affective psychoses display subtle deviations in behaviour during childhood and adolescence. We had the opportunity to examine the widely used Child Behavior Checklist (CBCL) and the Youth Self-Report (YSR) to explore the antecedents of non-affective psychosis.

METHOD

Based on a birth cohort of 3801 young adults, psychopathology was assessed at years 5 and 14 using the CBCL and/or the YSR. Screen-positive non-affective psychosis (SP-NAP) was assessed at year 21 by using the Composite International Diagnostic Interview (CIDI) or a self-report checklist. The association between childhood symptoms and SP-NAP was examined using logistic regression.

RESULTS

Of the cohort, 60 subjects were classified as SP-NAP. In males, SP-NAP was associated with higher scores: (a) on year 5 CBCL 'Total', 'Aggression' and 'Social, Attention and Thought' scores; (b) on year 14 CBCL 'Social', 'Attention' and 'Delinquency' scores, and (c) YSR 'Total' and many YSR subscores. These associations were less clear for females. Hallucinations at year 14 were associated with SP-NAP for both sexes. Boys with high 'Total' scores at both years 5 and 14 were at greatest risk of SP-NAP (a 5-fold risk), followed by boys and girls whose 'Social, Attention and Thought' scores either increased or remained high from years 5 to 14 (3- to 13-fold risk).

CONCLUSIONS

Individuals who screen positive for non-affective psychosis show increased psychopathology during childhood and adolescence. The psychopathological trajectory of children who go on to develop schizophrenia anticipates the heterogeneity associated with the full clinical syndrome.

Demographic correlates of psychotic-like experiences in young Australian adults

OBJECTIVE

Psychotic-like experiences (PLE) in the general community are common. The aims of this study were to examine the prevalence and demographic correlates of PLE in young adults.

METHOD

The sample consisted of 2441 subjects aged 18-23 years. Subjects completed the Composite International Diagnostic Interview (CIDI) and the 21-item Peters Delusional Inventory (PDI). Associations between age, gender, hallucinations and delusions were examined using logistic regression.

RESULTS

Both CIDI hallucinations and delusions predicted high scores on the PDI. Younger age was significantly associated with endorsement of CIDI delusions [odds ratio (OR) = 0.66, 95% confidence interval (CI) 0.48-0.92) and with PDI total scores (OR = 0.68, 95% CI 0.55-0.83). Women were significantly more likely to endorse items related to hallucinations (OR = 1.49, 95% CI 1.14-1.95) but not delusions.

CONCLUSION

PLE are common in young adults. The mechanisms underpinning the age and gender gradients in PLE may provide clues to the pathogenesis of psychotic disorders.

Early childhood adversity and adolescent depression: the mediating role of continued stress

BACKGROUND

While various conceptualizations of the link between childhood adversity and later depression have been offered, most have not accounted for the possibility that early adversity predicts continuing stress proximal to depression onset. Thus, the present study tested the possible mediating role of recent stress in the association between early adversity and depression in late adolescence.

METHOD

Study questions were examined in a longitudinal community sample of 705 youth who were contemporaneously assessed for early adversity exposure prior to age 5 years, chronic and episodic stress at age 15 years, and major depression prior to age 15 years and between 15 and 20 years.

RESULTS

Total youth stress burden at age 15 years mediated the effect of early adversity on depression between ages 15 and 20 years, and none of the observed relationships were moderated by onset of depression prior to age 15 years.

CONCLUSIONS

These findings suggest that continued stress exposure proximal to depression onset largely accounts for the association between early adversity and depression in late adolescence. Intervention should thus focus on disrupting the continuity of stressful conditions across childhood and adolescence. Future studies of the neurobiological and psychosocial mechanisms of the link between early experiences and depression should explore whether the effects of early experiences are independent of continuing adversity proximal to depressive onset.

Relative predispositional effects of HLA class II DRB1-DQB1 haplotypes and genotypes on type 1 diabetes: a meta-analysis

The direct involvement of the human leukocyte antigen class II DR-DQ genes in type 1 diabetes (T1D) is well established, and these genes display a complex hierarchy of risk effects at the genotype and haplotype levels. We investigated, using data from 38 studies, whether the DR-DQ haplotypes and genotypes show the same relative predispositional effects across populations and ethnic groups. Significant differences in risk within a population were considered, as well as comparisons across populations using the patient/control (P/C) ratio. Within a population, the ratio of the P/C ratios for two different genotypes or haplotypes is a function only of the absolute penetrance values, allowing ranking of risk effects. Categories of consistent predisposing, intermediate ('neutral'), and protective haplotypes were identified and found to correlate with disease prevalence and the marked ethnic differences in DRB1-DQB1 frequencies. Specific effects were identified, for example for predisposing haplotypes, there was a statistically significant and consistent hierarchy for DR4 DQB1*0302s: DRB1*0405 =*0401 =*0402 > *0404 > *0403, with DRB1*0301 DQB1*0200 (DR3) being significantly less predisposing than DRB1*0402 and more than DRB1*0404. The predisposing DRB1*0401 DQB1*0302 haplotype was relatively increased compared with the protective haplotype DRB1*0401 DQB1*0301 in heterozygotes with DR3 compared with heterozygotes with DRB1*0101 DQB1*0501 (DR1). Our results show that meta-analyses and use of the P/C ratio and rankings thereof can be valuable in determining T1D risk factors at the haplotype and amino acid residue levels.

The properties of the International Classification of the External Cause of Injury when used as an instrument for injury prevention research

OBJECTIVE

To demonstrate properties of the International Classification of the External Cause of Injury (ICECI) as a tool for use in injury prevention research.

METHODS

The Childhood Injury Prevention Study (CHIPS) is a prospective longitudinal follow up study of a cohort of 871 children 5-12 years of age, with a nested case crossover component. The ICECI is the latest tool in the International Classification of Diseases (ICD) family and has been designed to improve the precision of coding injury events. The details of all injury events recorded in the study, as well as all measured injury related exposures, were coded using the ICECI. This paper reports a substudy on the utility and practicability of using the ICECI in the CHIPS to record exposures. Interrater reliability was quantified for a sample of injured participants using the Kappa statistic to measure concordance between codes independently coded by two research staff.

RESULTS

There were 767 diaries collected at baseline and event details from 563 injuries and exposure details from injury crossover periods. There were no event, location, or activity details which could not be coded using the ICECI. Kappa statistics for concordance between raters within each of the dimensions ranged from 0.31 to 0.93 for the injury events and 0.94 and 0.97 for activity and location in the control periods.

DISCUSSION

This study represents the first detailed account of the properties of the ICECI revealed by its use in a primary analytic epidemiological study of injury prevention. The results of this study provide considerable support for the ICECI and its further use.

Cohesion among nurses: a comparison of bedside vs. charge nurses' perceptions in Australian hospitals

AIM

This study examines the extent to which hospital nurses view their working environment in a positive sense, working as a cohesive group.

BACKGROUND

Despite the fact that nursing in Australia is now considered a profession, it has been claimed that nurses are an oppressed group who use horizontal violence, bullying and aggression in their interactions with one and other.

METHODS

After ethical approval, a random sample of 666 nurses working directly with patients and all 333 critical care nurses employed in three large tertiary Australian hospitals were invited to participate in the study in the late 1990s. A mailed survey examined the perceptions of interaction nurses had with each other. The hypothesis, that level of employment (either Level I bedside nurses or Level II/III clinical leaders) and area of work (either critical care or noncritical care) would influence perceptions of cohesion, as measured by the cohesion amongst nurses scale (CANS) was tested.

RESULTS

In total 555 (56%) surveys were returned. Of these, 413 were returned by Level I and 142 by Level II/III nurses. Of this sample, 189 were critical care and 355 noncritical care nurses. There was no difference between Level I and II/III nurses in mean CANS scores. It is interesting to note that the item rated most positively was "nurses on the units worked well together", however, the item rated least positive was "staff can be really bitchy towards each other" for both Level I and II/III nurses. There was no difference in CANS scores between critical care and noncritical care nurses.

CONCLUSIONS

Nurses working in Australian hospitals perceived themselves to be moderately cohesive but, as would be expected in other work settings, some negative perceptions existed.

Factors influencing job valuation: a comparative study of critical care and non-critical care nurses

This study sought to identify the relationship between three predictor variables, perceived collaboration with medical staff, autonomy and independent actions and an outcome, the value hospital nurses placed on their work. In total 189 critical care and 366 non-critical care nurses completed a mailed survey. Critical care nurses perceived themselves to have a more collaborative relationship with the medical staff, described performing actions independent of medical orders more frequently and perceived their jobs to have more value than non-critical care nurses. However the latter group perceived themselves to have more autonomy in their work. Within both groups collaboration and autonomy were significantly, but weak to moderately correlated with job valuation. Simply expanding the work hospital nurses do is unlikely to result in nurses valuing their jobs more, however promoting an environment of respect and sharing between the medical and nursing staff and supporting nurses when they act in an autonomous fashion may positively influence nurses' perceptions of their work.

Developing specialty knowledge: the case of Australian critical care nursing

The generation of new knowledge is important to the evolution of the nursing profession and its specialties and is a fundamental requirement for the development of the discipline. This study documents the growth of empirical knowledge in Australian critical care nursing by examining the research published in one critical care specialty journal and a second generalized nursing research journal between 1994 and 1998. The proportion of research published in the specialty journal increased from 25 to 69%, with almost one-half focusing on patient therapies and treatments. The proportion of research in the general journal was consistently high, approximately 80 to 90%, with one to two critical care research articles per year. Nurses were first authors on the vast majority of these research articles. Approximately half of the critical care research focused on patient care. The results support the claim that Australian critical care nurses are conducting research to promote best practice in patient care and are thus contributing to the development of the discipline of nursing.

A descriptive study of nurses employed by general practitioners in south-east Queensland

The aim of this study was to describe the demographic and occupational characteristics of a sample of nurses employed by general medical practitioners and the factors perceived to be influential in their role development. Telephone and mail surveys were undertaken within one general practice division in South-East Queensland. Thirty-seven of the 67 (55%) practice nurses responded to the mailed questionnaire. Of these respondents, ten were collectively interviewed to elaborate on the survey results. Findings indicated that the primary work of these nurses is one of assistant to the doctor. Autonomous nursing initiatives are largely opportunistic. Perceived barriers to role expansion included Medicare restrictions, inadequate basic and ongoing education programs, financial and space limitations of the practice, reluctance of general practitioners, and a lack of professional support.

Nursing's contribution to general practice: general practitioners' and practice nurses' views

This study was instigated by the paucity of knowledge relating to the work of nurses employed by general practitioners in Australia and the phenomenal development of the practice nurse role in the United Kingdom. A mailed survey of general practitioners and practice nurses within one Division of General Practice in South-East Queensland, sought, among other things, their views about the current and potential contribution of nursing to general practice. Eighty-four out of 164 (51%) general practitioners and 37 out of 67 (55%) practice nurses responded to the survey. Results indicated that both general practitioners and practice nurses appreciated the value of nursing services in general practice and would sanction the employment of more nurses especially for the purpose of preventive care. The majority of nurses were agreeable to the notion that the nurse's role could, and should, be expanded to include autonomous functioning while most of the doctors were amenable to some extension of nursing practice but reticent or opposed to any independent interventions.

The prevalence and perception of pain amongst hospital in-patients

The aim of this paper is to describe the prevalence and perceptions of pain and pain management amongst hospital in-patients. A cross-sectional descriptive survey of 205 patients was conducted. Presence and severity of pain was assessed using verbal descriptor and visual analogue scales, and perceptions of pain were assessed using multi-item scales. Although the severity of pain reported was consistent across age groups and clinical areas, women in the study sample were significantly more likely to report high levels of pain than men. Differences in how men and women communicate their pain were observed, with women indicating that they were less willing to ask for help with their pain. Results suggest that pain continues to be an important problem for a large number of men and women in hospital, and that the experience of pain impacts negatively upon their well-being. Gender differences in the experience of and response to pain remain important considerations for clinical nurses who have major responsibilities for the management of pain in hospitalized patients.

Issues of death and dying: the perspective of critical care nurses

A major shift in the care of terminally ill people, due to advances in technology, and the development of legislation regarding patient self-determination and autonomy, has occurred over recent years. Critical care nurses (CCNs) are involved daily in issues of death and dying and are very aware of the needs, fears and psychosocial issues of patients and their families. Professional associations see a legitimate role for nurses in assisting the dying to achieve a dignified death. For legislation, policies and guidelines surrounding end-of-life issues to be effective, and to assist nursing staff with these sensitive, often difficult concerns, it is important that data on the opinions and perspectives of CCNs be objectively obtained. In a study by the Department of Social and Preventive Medicine at the University of Queensland, questionnaires were sent to 1100 randomly sampled community members and almost 1200 health professionals (nurses, general practitioners and specialists), including 299 CCNs. The response rate of CCNs to a 30-page postal questionnaire was 79 per cent (n = 231), indicating those nurses' high levels of interest in and/or concern regarding this area. CCNs supported the use of advance directives, the appointment of proxies and the need for doctors and nurses to give sufficient medication to relieve pain, even if this hastened the death of the patient. In addition, CCNs, more than any other professional group, supported the right of the terminally ill patient to physician-assisted suicide or euthanasia, their responses being very similar to those of community members. CCNs clearly face issues which, from legal, medical and ethical viewpoints, cause them concern. In sharing their personal experiences, CCNs stressed the need for more communication between doctors and patients, as well as between doctors and nurses. In addition, CCNs saw a clear role for themselves as advocates for patients/families in the decision-making process.

A three year outcome evaluation of a theory based drink driving education program

This study reports on the impact of a "drink driving education program" taught to grade ten high school students. The program which involves twelve lessons uses strategies based on the Ajzen and Madden theory of planned behavior. Students were trained to use alternatives to drink driving and passenger behaviors. One thousand seven hundred and seventy-four students who had been taught the program in randomly assigned control and intervention schools were followed up three years later. There had been a major reduction in drink driving behaviors in both intervention and control students. In addition to this cohort change there was a trend toward reduced drink driving in the intervention group and a significant reduction in passenger behavior in this group. Readiness to use alternatives suggested that the major impact of the program was on students who were experimenting with the behavior at the time the program was taught. The program seems to have optimized concurrent social attitude and behavior change.

Measurement And Correlation Of Asphaltene Precipitation From Heavy Oils By Gas Injection

Abstract

The nature of asphaltenes and their role in the production and processing of crude oils has been the topic of numerous studies. This is due to the fact that the economics of oil production can be seriously affected by the asphaltene deposition problem. This paper presents a novel method to visualize in situ asphaltene precipitation from heavy oils with light hydrocarbon gases, e.g. methane. propane, ethane/propane mixtures, and carbon dioxide at reservoir pressures and temperatures. Experimental results are reported for the effects of temperature (up to 100 °C), pressure (up to 20 MPa) and composition on the formation of asphaltene precipitates from heavy crude oils. A series of titration experiments were conducted with several n-alkanes to determine the amount of asphaltenes precipitated. Both the amount and nature of the precipitate varied with the solvent used. Propane was the most prolific of all the solvents used in precipitating asphaltenes from the heavy oils. A thermodynamic model proposed by Hirshberg et al. was used to correlate the experimental data.

Introduction

Miscible and immiscible flooding of crude oil reservoirs by light hydrocarbon gases, carbon dioxide and other injection gases has become a popular method for enhanced oil recovery(1). The flooding process, however, causes a number of changes in the flow and phase behaviour of the reservoir fluids and can significantly alter rock properties. Such changes include the precipitation of asphaltenes(2) and wettability reversal which can alter recovery efficiencies. The existence of asphaltenes in crude oils and their deposition inside reservoirs and wellbores can cause severe problems and affect the efficiency and cost of petroleum production.

The important parameters that affect asphaltene precipitation during gas injection are the compositions of the crude oil and the solvent gas, and the pressure and temperature of the reservoir(3–5). Precipitation of asphaltenes is a complex process and it is generally followed by flocculation which produces an insoluble material in the heavy oi1(6). Asphaltenes are believed to be stabilized in solution by resins and aromatics and the asphaltene/resin ratio plays a key role in their precipitation. This ratio is more important than the absolute asphaltene content in determining which crudes will be subject to precipitation.

Problems arising from asphaltene deposition have been reported in the literarure(7,8) for many field projects. Some examples of these are the Ventura field in California(9), Hassi Messaoud field in Algeria(l0) and heavy oil fields in Venezuela(l1). Deposition of asphaltenes in the wellbore can be a serious production problem and may require frequent solvent washings and scrapings to maintain oil production(10). Significant damage can be caused during well acidizing because the acid can cause the asphaltenes to precipitate and form rigid films. Other problems associated with asphaltene precipitation are the seizure of downhole safety valves submersible pumps, hinderance in wireline operations and production restrictions. These problems are discussed in derail by Leontaritist(7).

Presently asphaltenes are removed either by mechanical cleaning, chemical cleaning, or by manipulating reservoir conditions (for example, pressure, production rates, etc,)(10,12). The approach taken by the oil industry has been a remedial one.

Phase Behaviour And Physical Properties Of Lindbergh Heavy Oil/CO2 Mixtures

Abstract

The objective of this work is to acquire phase behaviour and physical property data of carbon dioxide/heavy oil systems pertaining ta enhanced oil recovery by CO2 huff-n-puff and steam stimulation.

Phase behaviour and physical property measurements were carried out on Lindbergh heavy oil CO2 mixtures at 21 °C and 140 °C, and at pressures ranging up to about 15 MPa. Furthermore, the oil samples were analyzed using gas chromatographic simulated distillation. The experimental measurements were also carried out on three of the oil's fractions that can serve as "pseudo components" during equation of state correlations Of the experimental data.

The solubility of CO2 was less in the heavier hydrocarbons than in the lighter fractions and the solubility also decreased with increasing temperature. The densities of the saturated mixtures did not change significantly as the saturation pressure was increased. The extent of viscosity reduction with increasing CO2 content was larger for the heavier hydrocarbon fractions than for the lighter ones. In addition, the viscosity was sometimes seen to increase with pressure in the liquid-liquid equilibrium region of the phase diagrams. Analysis of the residual oils indicated that in some cases a small amount of their light ends had been extracted by CO2 and/or some of the heavy ends had been depleted (presumably precipitated).

Introduction

Gas (more commonly CO2) injection into heavy oil reservoirs is becoming a viable enhanced oil recovery method(l-5). Mathematical studies of this process have been presented in the literature(6–10), as have been laboratory displacement data(11–13) and phase behaviour measurements(l4–19). The main mechanism in this process is the dissolution of the injected gas into the crude oil, thereby swelling it, reducing its viscosity, and making it more mobile. Usually the process is an immiscible one, in contrast to the more common miscible gas flooding of conventional oil reservoirs.

The correlation of the phase behaviour data of conventional crude oils is usually carried out with one of the Van-der-Waals type of equations of state. Examples of these equations are those by Soave-Redlich-Kwong(20) and Peng-Robinson(21). Ideally, these equations require certain parameters to characterize each component in the mixtures under consideration. The common practice has been to represent the crude oil with a limited number (four to six, typically) of pseudo components. Several Authors(22–27) have proposed various schemes for selecting these pseudo components and evaluating their properties based on those of the crude oil.

Most of the methods that have been developed for the characterization of crude oils were derived from data of light oil systems and these are usually directly applied to heavy oil data. This may not be an optimum approach since heavy oils have a much larger proportion of heavy ends, asphaltenes, and resins, and a much lower content of C5-C30 hydrocarbons than light oils. In addition, heavy oil reservoirs are usually shallower than light oil reservoirs and, consequently, have lower pressures and temperatures. Alternatively, enhanced oil recovery of heavy oil reservoirs is often carried out using thermal methods, such as steam or fire flooding, in which very high temperatures (> 200 °C) are encountered.

Multiple Contact Phase Behaviour In The Displacement Of Crude Oil With Nitrogen And Enriched Nitrogen

Abstract

Phase behavior tests were carried out on a Nisku crude oil (a candidate reservoir for nitrogen flooding) with nitrogen and nitrogen mixed with carbon dioxide or propane. These measurements were carried out in a batch wise multiple contact mode to simulate what occurs when gas displaces oil in a porous medium. None of the mixtures achieved miscibility with the oil in four contacts at pressures up to 35 MPa. Nitrogen and methane were exchanged between the gas and oil phases in an almost 1:1 ratio, while gas enrichment with C2–5 hydrocarbons proceeded at a much slower pace.

The experimental data were matched using the Peng-Robinson equation of stale. Good agreement between experimental and calculated results was obtained in most cases. This applies to the equilibrium phase compositions, as well as to the liquid phase densities and gas/oil ratios. The largest deviations were in the amount of heavy ends found in the vapour phase.

Introduction

Nitrogen may be applied for enhanced oil recovery (EOR) in several modes, e.g. pressure maintenance, cycling condensate reservoirs, attic oil production, producing gas-cap gas, chase gas for hydrocarbon or carbon dioxide slugs and miscible displacement of oil.

These applications were discussed by Clancy et al.(1) and reviewed in detail by Sayegh et al.(2). Recently Leonard(3) summarized EOR activity worldwide. From this article it was noted that there are seven nitrogen injection projects in the U.S.A., four of which have already showed profit, while it is too early to tell the remaining three. In addition, there are three flue gas injection projects. In Canada, two ongoing floods utilize nitrogen. The first is in a Pembina Nisku reef, wherein the injection gas consists of a mixture rich in nitrogen along with carbon dioxide and light hydrocarbons. The second is the Willisden Green flood, where nitrogen is being used as a chase gas for a hydrocarbon slug.

The advantages of using nitrogen for EOR include: widespread availability from air liquefaction, non-toxicity, non-flammability and non-corrosivity.

In addition, the price of nitrogen appears to be competitive with that of dry hydrocarbons, although it is difficult to give more precise estimates because of the many variables involved in costing. Wilson(4) noted that nitrogen has some disadvantages in its use for enhanced oil recovery, which include:The cost of separating nitrogen from the produced hydrocarbon gases. This is offset if the produced gases are recycled into the reservoir.Nitrogen asphyxia.If air separation units are used to produce nitrogen, then a by-product stream rich in oxygen is produced. This stream has to be well separated from any hydrocarbon streams in the vicinity.

In summary, the use of nitrogen in enhanced oil recovery has many advantages that can outweigh its disadvantages. This is a new topic, and there are many gaps in the information available for its proper application. It is the purpose of this work to try and fill in some of these gaps.

Patient characteristics that elicit negative responses from family physicians

Responding anonymously to a questionnaire asking them to list medical conditions and social characteristics of patients that evoked negative responses, 439 family physicians specified 1,846 medical conditions and 1,519 social characteristics. Of the medical conditions, the largest category (60 percent) represented conditions for which medical treatment offered little or no likelihood of cure or alleviation. Of the social characteristics, the largest category (33 percent) involved behavior that violated the physician's personal norms, even through it had little or no bearing on the patient's health. It appears that the responses accurately reflect the Protestant Ethic value system characteristics of Western Europe and the United States, but this constellation of values is accentuated in physicians by their selection and their professional training. Although negative responses to patient characteristics do not inevitably lead to inferior treatment of the negatively perceived patient, negative feelings might be reduced through changes in both the undergraduate and graduate levels of medical education.