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At least 217 records · Page 12Linked to original sources

PubMed1990

[Application of gypsum-bonded investment containing niobium carbide on casting of alloy for metal-ceramic restoration].

Experimental gypsum-bonded investments containing 0.5-5.0 wt% NbC were prepared by mechanical mixing of each powder. Setting and thermal expansion measurement, compressive strength and casting accuracy for Ni-Cr alloy for metal-ceramic restoration were investigated. Analysis of NbC during heating was carried out by X-ray diffraction, TG-DTA and SEM. NbC was oxidized to Nb2O5 with a volume change between 300-600 degrees C, as in the following equation: 2NbC + 4 1/2O2----Nb2O5 + 2CO2 The theoretical volume of 1/2Nb2O5 calculated from the lattice constants according to JCPDS file was approximately 4 times larger than that of NbC. The experimental investments of 70 wt% cristobalite and 30 wt% gypsum containing 2.0, 3.0 and 5.0 wt% NbC showed large thermal expansion of 7.0, 10.0 and 13.0% respectively. The investment containing 2.0 wt% NbC showed nearly the same casting accuracy for Ni-Cr alloys for metal-ceramic restoration as the commercial phosphate-bonded investment.

Calcium Sulfate↗

PubMed1990

[Development of dental quick casting with zircon-phosphoric acid investments].

The application of zircon (ZrSiO4) that has high refractoriness, high thermal conductivity and a low coefficient of thermal expansion, to quick casting investment was studied. Various zircon powders and phosphoric acid solutions were tested with respect to the higher thermal shock resistance. The formulation and properties of zircon-phosphoric acid investment materials such as water/powder ratio, fluidity of slurry, setting time, setting expansion, thermal expansion, thermal analysis, green and fired compressive strength were measured. Formulation of zircon slurry for coating was zircon flower #600 30%, zircon flower #350 10%, and zircon sand CP 60%, and that for sanding was zircon flower #200. The mixing liquid was 15% phosphoric acid and liquid/powder ratio was 0.1. The slurry using phosphoric acid had good fluidity and good workability. The 24-hour green strength was 1 MPa, fired strength was 10 MPa, 24-hour setting expansion was -0.04% and the thermal expansion at 1000 degrees C was 0.31%. Immediately after coating with zircon slurry, the coating layer was dried, sintered and dewaxed by thermal shock. The thermal shock consisted of the following four-step manipulations. The first is hot air drying (50 degrees C, 5 minutes), the second is heat shock (900 degrees C, 3 seconds), the third is redrying (220 degrees C, 3 minutes) and the fourth is dewaxing (550 degrees C, 3 minutes). Small casting of pure titanium and K-metal could be done successfully by the quick casting method using the zircon-phosphoric acid investments. It was found that the total expansion of the secondary investments influenced the casting adapatability.

Dental Casting Investment↗

PubMed1990

Investment of Social Security reserves in three countries.

The current buildup of the U.S. Social Security Trust Fund has caused speculation about both the potential consequences of the buildup under different policy objectives and the fund's management. As is often the case, the search for precedents under similar circumstances abroad has been quite extensive on the part of legislators and U.S. experts in the field of financial policy. This article summarizes the experiences of Canada, Japan, and Sweden--all of whom have accumulated large trust fund reserves--with a focus on their investment policies. Trust fund investments in the three countries are similar as to types of investments, but the pattern of distribution of these investments varies widely from one country to another.

Canada↗

PubMed1979

Investment generation process in hospital facilities: the response of supply to capacity utilization measures.

Hospital investment behavior is commonly explained by means of either supply or demand factors. The inherent limitations of these models have led to ambiguous conclusions. This study applies a different approach, whereby investment generation is explained by means of a stock adjustment model. The model is empirically tested on a sample of New York City hospitals. Relative investment is found to be directly related to occupancy rate, indicating rationality in the hospital investment process. Scalar factors are also shown to be significant, implying the concept of preferred hospital size.

Bed Occupancy↗

PubMed1982

Investment policies and procedures of the social security trust funds.

In this article, the Deputy Commissioner of Social Security for Programs describes the policies and procedures that have been followed in investing the assets of the Social Security trust funds, explores possible alternative investment areas, and counters criticisms of investment results and maturity durations. The author's analysis shows that a departure from the current practice of investing most of the assets in long-term special issues of Federal debt would have adverse consequences for the private industrial economy, the Treasury Department, or the economy in general. He notes that, although the interest income of the trust funds in 1980 amounted to only 2.46 percent of the Social Security program's total income, the amount involved--$3.85 billion--was 1.5 times as large as total administrative expenses.

Economics↗

PubMedDate not supplied

[Sensitivity analysis in health investment projects].

This paper discusses some of the concepts and methodologies frequently used in sensitivity analyses in the evaluation of investment programs. In addition, a concrete example is presented: a hospital investment in which four indicators were used to design different scenarios and their impact on investment costs. This paper emphasizes the importance of this type of analysis in the field of management of health services, and more specifically in the formulation of investment programs.

Cost-Benefit Analysis↗

PubMed1992

Male investment under changing conditions among chacma baboons at Suikerbosrand.

Male investment in infant baboons was measured by frequency of carrying from 1978 through 1985. A series of hypotheses was generated and tested with the carrying data, based on the assumptions that: male baboons have some capacity to estimate likelihood of paternity; where paternity probability is greater, males will invest more, where potential benefits to males or infants are higher, males will invest more. Carrying was affected by probability of paternity, availability of estrous females, season of conception and season of carrying, infant age, subtrooping, and predation risk. Infants were carried by probable fathers, siblings, mothers' siblings, and unrelated "suitors." Male investment increased female reproductive fitness: carried infants were more likely to survive, and mothers of carried infants had shorter interbirth intervals. Males appeared to estimate paternity both by observed copulations by other males and by the likelihood that copulations could have occurred without being observed. Male care of infant baboons may also be affected by female choice among males, the distribution of probable infants in time, male tenure at alpha rank, the number of males per troop, the probability of infanticide, and energy demands. Subtrooping seems to be historically crucial, by initially creating a situation in which some males have high paternity certainty.

Animals↗

PubMed2005

Examining the terminal investment hypothesis in humans and chimpanzees: associations among maternal age, parity, and birth weight.

The terminal investment hypothesis (Williams [1966] Adaptation and Natural Selection; Princeton, NJ: Princeton University Press) holds that reproductive effort should increase over time in iteroparous species in which reproductive value declines with age. Attempts to model this hypothesis and test it in various species have produced mixed results. Clutton-Brock ([ 1984] Am. Nat. 123:212-229) argued that simply testing for changes in propagule size with age fails to recognize that the costs of producing offspring of a given size may increase over the lifespan, hence absence of a positive correlation does not defeat the hypothesis. However, this interpretation is weakened by evidence of sequential increases in propagule size independent of age, as such changes reveal a capacity to increase absolute investment over time. Humans and chimpanzees meet the preconditions of the terminal investment hypothesis. Surveying the obstetrics literature, we show that the majority of published studies indicate that parity has a positive effect on birth weight, but age has no effect. Analyzing 436 captive chimpanzee births, we document a positive influence of parity and a negative influence of age. We therefore conclude that, though it is yet to be replaced by a more compelling alternative, the terminal investment hypothesis is not supported in these two species, as absence of a positive effect of age on birth weight cannot be interpreted in a manner congruent with the hypothesis.

Age Factors↗

PubMed2005

Global differences in blood pressure control and clinical outcomes in the INternational VErapamil SR-Trandolapril STudy (INVEST).

BACKGROUND: The INternational VErapamil SR-Trandolapril Study (INVEST), a prospective, randomized, antihypertensive trial, found that two different medication regimens produced similar blood pressure (BP) control with equivalent cardiovascular (CV) outcomes (death from any cause, nonfatal myocardial infarction [MI], or nonfatal stroke). HYPOTHESIS: The study was undertaken to investigate whether differences exist by global regions in demographics, treatment, and outcomes in the INVEST trial. METHODS: Data were analyzed for 22,576 patients with stable coronary artery disease (CAD) enrolled in INVEST. We investigated differences in patient characteristics, treatment approaches, BP control, and clinical outcomes by creating three global regions based on geographical location: Northern Americas (NA), Caribbean (CA), and Eurasia (EA). RESULTS: We observed significant regional differences in patient characteristics, treatment patterns, BP control, and CV outcomes. At baseline, patients from NA were older and had greater body mass index, higher rates of diabetes, peripheral vascular disease, and coronary revascularization, but lower rates of MI or left ventricular hypertrophy than patients in CA and EA. At 24 months, there were regional differences in both study and nonstudy antihypertensive drug use. Despite having higher mean baseline BP, patients from CA and EA achieved lower mean systolic BP throughout study follow-up. Furthermore, patients from both CA and EA had lower rates of all-cause mortality, fatal or nonfatal MI, fatal or nonfatal stroke, and newly diagnosed diabetes than patients from NA. CONCLUSIONS: In INVEST, regional differences in medication utilization, BP control, and CV outcomes were identified. These disparities warrant further investigation to define appropriate care for patients with hypertension and stable CAD from an international public health perspective.

Aged↗

PubMed1998

Shared and unshared parental investment in the precocial goldeneye (Aves: Anatidae)

Lazarus & Inglis (Anim. Behav., 1986, 34, 1791-1804) introduced a model of the influence of brood size on the optimal level of parental investment and parent-offspring conflict and drew a distinction between shared and unshared types of parental investment. With respect to this division, we measured the parental costs in the goldeneye, Bucephala clangula, a precocial species with uniparental female care, in terms of time spent in vigilance and intraspecific aggression. We also compared levels of anti-predator vigilance and intraspecific aggression between females with and without broods. Females with broods spent considerably more time on both vigilance and intraspecific aggression, but anti-predator vigilance was independent of brood size. Furthermore, female behaviour was unaffected by brood reduction. Both these observations support the 'fixed-loss' model of unshared care, where the level of parental investment is predicted to be independent of brood size, since the predator is likely to take only a single offspring. In contrast, intraspecific aggression, mainly associated with defence of the brood's feeding area, increased with brood size. This supports the 'shared care' model where the level of parental investment increases with brood size, a type of care usually associated with altricial species. Copyright 1998 The Association for the Study of Animal Behaviour.

Journal Article↗

PubMed1999

Cumulative long-term investment in vocalization and mating success of fallow bucks, Dama dama.

We carried out behavioural observations to investigate the function of long-term investment in vocal display by fallow bucks during the breeding season. The measures of long-term investment used were the date of initiation of vocal activity, the number of days vocal during the breeding season, and the proportion of time spent vocalizing. We analysed data from 3 years (1993-1995) to assess the relationship between the date of initiation of vocal activity, and the number of days vocal, and age, dominance rank and mating success. Observations from a sample of focal males in 1996 were used to determine the effect of the proportion of time vocal during the breeding season on dominance rank and mating success. The majority of socially immature males (</=3 years old) did not vocalize; among socially mature males (>/= 4 years old), dominance rank was more important than age in explaining variation in vocal activity. The onset of vocal activity by fallow bucks was not a direct consequence of the presence of mating opportunities since the first males became vocal more than 3 weeks before any matings occurred. Long-term investment in vocal activity did not alter the dominance relationships that had been established between males before they became vocal. When we considered all mature males from 3 years of observations, the majority of matings were achieved by those that had high rank, initiated vocal activity early during the breeding season and remained vocal on most days. For the 1-year sample of mature males, the factor most highly correlated with mating success was the proportion of time that males spent vocalizing during the rut. Thus we have shown a strong relationship between the time invested in vocal display by fallow bucks and their mating success. Copyright 1999 The Association for the Study of Animal Behaviour.

Journal Article↗

PubMed1998

Buying and Selling Prices of Investments: Configural Weight Model of Interactions Predicts Violations of Joint Independence.

Judges evaluated buying and selling prices of hypothetical investments, based on the previous price of each investment and estimates of the investment's future value given by advisors of varied expertise. Effect of a source's estimate varied in proportion to the source's expertise, and it varied inversely with the number and expertise of other sources. There was also a configural effect in which the effect of a source's estimate was affected by the rank order of that source's estimate, in relation to other estimates of the same investment. These interactions were fit with a configural weight averaging model in which buyers and sellers place different weights on estimates of different ranks. This model implies that one can design a new experiment in which there will be different violations of joint independence in different viewpoints. Experiment 2 confirmed patterns of violations of joint independence predicted from the model fit in Experiment 1. Experiment 2 also showed that preference reversals between viewpoints can be predicted by the model of Experiment 1. Configural weighting provides a better account of buying and selling prices than either of two models of loss aversion or the theory of anchoring and insufficient adjustment. Copyright 1998 Academic Press.

Journal Article↗

PubMed2003

Ural owl sex allocation and parental investment under poor food conditions.

Parents are expected to overproduce the less costly sex under poor food conditions. The previously regular 3-year cycle in the abundance of voles, the main prey of the Ural owl, Strix uralensis, temporarily disappeared in 1999-2001. We studied Ural owls' parental feeding investment and sex allocation during these poor-quality years. We sexed hatchlings and embryos in unhatched eggs of all 131 broods produced during these years. Population wide, the owls produced significantly more males (56%). The parental food investment in the brood was estimated by sorting out the prey remains in the bottom of nest boxes. Food delivered to 83 broods without chick mortality showed no clear sex-specific investment. Nestling mortality was equal in both sexes. Thus, evidence for an investment-driven sex allocation is weak. Neither laying date, brood size nor the female's condition correlated with offspring sex ratios. In these poor years, parents provided less food per chick and the fledgling weight of daughters was reduced more than the weight of sons compared with years of high food abundance (1983 and 1986). We discuss, in relation to published studies, the possibility of a sex-allocation scenario where, under poor food conditions, a daughter's long-term fitness is reduced more than a son's.

Animals↗

PubMed2004

Maternal investment in egg size: environment- and population-specific effects on offspring performance.

Geographic variation in maternal investment in offspring size can be adaptive if differences in investment translate into improved offspring performance in the given environments. We compared two moor frog, Rana arvalis, populations in the laboratory to test the hypothesis that investment in large eggs in populations originating from stressful (acid) environments improves offspring performance when reared in stressful (acid) conditions. We found that large initial size (hatchling mass) had moderate to strong, environment-dependent positive effects on larval and metamorphic traits in the acidic origin population, but only weak effects in the neutral origin population. Our results suggest that interactions between environmental conditions and initial size can be important determinants of individual performance, and that investment in large eggs is adaptive in acid environments. These findings emphasize the role of maternal effects as adaptations to environmental stress.

Adaptation, Physiological↗

PubMed2005

A theory of health investment under competing mortality risks.

In this paper, we present a theory of health investment when there are multiple causes of death. We analyze the optimal investment rules and the comparative statics. In particular, we examine the conditions under which a cause-specific intervention has a spillover effect. By spillover effect, we mean a price reduction in one cause-specific health investment would increase all other investments. We also study the strength of the spillover effect, which is measured in terms of cross price elasticities. We find that, while a cause-specific intervention might not be wasteful, the spillover effect would not be large either.

Humans↗

PubMed2001

Parental investment and child health in a Yanomamö village suffering short-term food stress.

The 1998 El Niño significantly reduced garden productivity in the Upper Orinoco region in Venezuela. Consequently, parents were forced to allocate food carefully to their children. Nutrition data collected from village children combined with genealogical data allowed the determination of which children suffered most, and whether the patterns of food distribution accorded with predictions from parental investment theory. For boys, three social variables accounted for over 70% of the variance in subcutaneous fat after controlling for age: number of siblings, age of the mother's youngest child, and whether the mother was the senior or junior co-wife, or was married monogamously. These results accord well with parental investment theory. Parents experiencing food stress faced a trade-off between quantity and quality, and between investing in younger versus older offspring. In addition, boys with access to more paternal investment (i.e. no stepmother) were better nourished. These variables did not account for any of the variance in female nutrition. Girls' nutrition was associated with the size of their patrilineage and the number of non-relatives in the village, suggesting that lineage politics may have played a role. An apparent lack of relationship between orphan status and nutrition is also interesting, given that orphans suffered high rates of skin flea infections. The large number of orphans being cared for by only two grandparents suggests that grooming time may have been the resource in short supply.

Adolescent↗

PubMed2000

Evolution and proximate expression of human paternal investment.

In more than 95% of mammalian species, males provide little direct investment in the well-being of their offspring. Humans are one notable exception to this pattern and, to date, the factors that contributed to the evolution and the proximate expression of human paternal care are unexplained (T. H. Clutton-Brock, 1989). The nature, extent, and influence of human paternal investment on the physical and social well-being of children are reviewed in light of the social and ecological factors that are associated with paternal investment in other species. On the basis of this review, discussion of the evolution and proximate expression of human paternal investment is provided.

Adult↗

PubMed1998

Development of cooperative relationships through increasing investment.

Reciprocal altruism can become established among selfish, unrelated individuals if they use responsive strategies such as 'tit-for-tat. This result raises the fundamental question: how altruistic should one be? The problem is difficult to solve using current 'prisoner's dilemma' based models because they allow only the discrete choice of cooperating or defecting. In reality, however, cooperation is rarely all-or-nothing. Furthermore, if cooperative investment is variable, a new and more subtle kind of cheating becomes possible: individuals may invest slightly less than their partner. A concern is that this 'short-changing' will erode cooperative ventures. Here we show that cooperation can thrive despite variable investment through the new strategy of 'raise-the-stakes'. This strategy offers a small amount on first meeting and then, if matched, raises its investment, something that no strategy in the discrete model can do. We show that such behaviour can readily invade a population of non-altruists and cannot be effectively exploited. The practice of 'testing the water' rather than making sudden cooperative 'leaps of faith' powerfully reinforces the stability and effectiveness of reciprocity.

Altruism↗