Showing papers on "Literature survey published in 1993"

Crop Rotation and Intercropping Strategies for Weed Management

Abstract: Results of a literature survey indicate that weed population density and biomass production may be markedly reduced using crop rotation (temporal diversification) and intercropping (spatial diversification) strategies. Crop rotation resulted in emerged weed densities in test crops that were lower in 21 cases, higher in 1 case, and equivalent in 5 cases in comparison to monoculture systems. In 12 cases where weed seed density was reported, seed density in crop rotation was lower in 9 cases and equivalent in 3 cases when compared to monocultures of the component crops. In intercropping systems where a main crop was intersown with a "smother" crop species, weed biomass in the intercrop was lower in 47 cases and higher in 4 cases than in the main crop grown alone (as a sole crop); a variable response was observed in 3 cases. When intercrops were composed of two or more main crops, weed biomass in the intercrop was lower than in all of the component sole crops in 12 cases, intermediate between component sole crops in 10 cases, and higher than all sole crops in 2 cases. It is unclear why crop rotation studies have focused on weed density, whereas intercropping studies have focused on weed biomass. The success of rotation systems for weed suppression appears to be based on the use of crop sequences that create varying patterns of resource competition, allelopathic interference, soil disturbance, and mechanical damage to provide an unstable and frequently inhospitable environment that prevents the proliferation of a particular weed species. The relative importance and most effective combinations of these weed control tactics have not been adequately assessed. In addition, the weed-suppressive effects of other related factors, such as manipulation of soil fertility dynamics in rotation sequences, need to be examined. Intercrops may demonstrate weed control advantages over sole crops in two ways. First, greater crop yield and less weed growth may be achieved if intercrops are more effective than sole crops in usurping resources from weeds or suppressing weed growth through allelopathy. Alternatively, intercrops may provide yield advantages without suppressing weed growth below levels observed in component sole crops if intercrops use resources that are not exploitable by weeds or convert resources to harvestable material more efficiently than sole crops. Because of the difficulty of monitoring the use of multiple resources by intercrop/weed mixtures throughout the growing season, identification of specific mechanisms of weed suppression and yield enhancement in intercrop systems has so far proven elusive. Significant advances in the design and improvement of weed-suppressive crop rotation and intercropping systems are most likely to occur if three important areas of research are addressed. First, there must be continued attention to the study of weed population dynamics and crop-weed interference in crop rotation and intercropping systems. More information is needed concerning the effects of diversification of cropping systems on weed seed longevity, weed seedling emergence, weed seed production and dormancy, agents of weed mortality, differential resource consumption by crops and weeds, and allelopathic interactions. Second, there needs to be systematic manipulation of specific components of rotation and intercropping systems to isolate and improve those elements (e.g., interrow cultivation, choice of crop genotype) or combinations of elements that may be especially important for weed control. Finally, the weed-related impacts of combining crop rotation and intercropping strategies should be assessed through careful study of extant, complex farming systems and the design and testing of new integrated approaches. Many aspects of crop rotation and intercropping are compatible with current farming practices and could become more accessible to farmers if government policies are restructured to reflect the true environmental costs of agricultural production.

Review of data for the surface tension of pure metals

Abstract: A literature survey of the experimentally determined values for the surface tension γ of molten pure metals has been carried out. It is intended to provide an assessed data base for use with a mathematical model currently being developed at the National Physical Laboratory, UK, to predict the surface tension of molten metal alloys.

Determining the likelihood of malignancy in solitary pulmonary nodules with Bayesian analysis. Part I. Theory.

Abstract: Only two radiographic findings allow reliable distinction of benign from malignant solitary pulmonary nodules. Intuitively, it is clear that other radiographic and clinical findings should also be important in making this distinction. Subjectively incorporating these other findings into the decision of whether a nodule is benign or malignant is difficult. Likelihood ratios, which indicate the degree of malignancy or benignity represented by a test result or clinical finding, can be combined by means of the Bayes theorem to quantitate the probability of malignancy of a given nodule. From a literature survey, likelihood ratios were derived for six radiographic and four clinical characteristics associated with solitary pulmonary nodules. There were a total of 15 malignant and 19 benign findings, the most important of which were radiographic characteristics. For malignant nodules, the most important radiographic characteristics were thickness of the cavity wall spicular edge, and diameter of over 3 cm. For benign nodules, the most important radiographic characteristics were benign growth rate and a benign pattern of calcification.

The effects of herbivory and granivory on terrestrial plant succession

Abstract: Based on resource availability models of plant defense investment, several authors have predicted and documented that herbivores tend to accelerate the pace of plant community succession. A literature survey of experimental and observational tests of the effects of above-ground, native herbivores on terrestrial plant succession reveals a more complex pattern than anticipated from earlier reviews on this subject. Although herbivory tends to hasten succession from grasses, shrubs, and pioneer trees to persistent trees (often including conifers), it typically retards succession from earlier seres, if such seres are present (e.g., as in secondary succession of old fields) (...)

Pathological studies on sarcoidosis autopsy. I. Epidemiological features of 320 cases in Japan.

Abstract: Three hundred and twenty autopsy cases of sarcoidosis during a 32 year period were collected from the Annuals of the Pathological Autopsy Cases in Japan, published yearly since 1958, and from a literature survey. A statistical analysis of these reviewed autopsy cases was carried out on the epidemiological features of the disease and on the causes of death. The proportion of sarcoidosis autopsy cases relative to the total autopsy cases had increased during this 32 year period. The increase of sarcoidosis autopsies during this period was chiefly due to the increase in aged females; the total number of female cases was approximately two times more than that of males. As over half of the total cases had only a pathological diagnosis and not a clinical diagnosis for sarcoidosis, the actual morbidity from sarcoidosis that was estimated from the autopsy data and corrected by autopsy rate was over five times higher than that of the clinically recognized cases. Age and sex distribution of these cases peaked in the thirties for both sexes, while another very high peak was noted in females over 50 years of age. In approximately 60% of the sarcoidosis autopsies, the cause of death related to sarcoid lesions in the heart, lung or nervous system, the majority of which involved cardiac sarcoidosis. In the remaining 40% of the cases, the cause of death was from non-sarcoidosis diseases.

Total quality management—the critical success factors

Abstract: This article examines the key elements of TQM and the critical factors that influence the TQM implementation process. An extensive literature survey suggests that there are eight critical TQM factors. A survey was carried out to evaluate the experiences of a range of organizations against the identified critical factors. The survey indicated that the eight critical factors can be arranged in a hierarchy of criticality. Management behaviour is the most important critical factor.

The Moisture Content/Relative Humidity Equilibrium Relationship Of Wheat - A Review

Abstract: Thirty three sources of hygroscopic data for wheat are identified Gravimetric methods predominate in the literature, followed by hygrometric methods which largely employ a dew Point technique for relative humidity determination Hysteresis effects vary considerably in magnitude The greatest difference between adsorption and desorption isotherms occurs in the 20–40% RH region A table of equilibrium moisture contents interpolated from the data sets is presented for a Fixed set of temperatures and RH to enable comparison The isotherm equations used to fit the data are also revewed The Strohman-Yoerger, Modified-Oswin, Modified-Chung-Pfost, Chen-Clayton and Modified-Henderson equations are identified as the most suitable Further investigation is needed to compare them

Structures and Chemistry of Methanofullerenes: A Versatile Route into N-[(Methanofullerene)carbonyl]-Substituted Amino Acids

Abstract: The reaction of C60 with oxadiazole 13 afforded the dimethoxymethanofullerene 7 in 32% yield as a 6-6-ring-bridged isomer with a closed transannular bond. A literature survey showed that all 6-6-ring-bridged methanofullerenes are σ-homoaromatic with a closed transannular bond (6-6-closed) and all 6-5-ring-bridged are π-homoaromatic with an open transannular bond (6-5-open). The preference for 6-6-closed and 6-5-open structures is not due to substituent effects but is best explained with the conservation in these isomers of the favorable bonding seen in C60 with higher double-bond character at 6-6 bonds and higher single-bond character at 6-5 bonds. Reaction of C60 with diazo diester 15 gave the fullerene diester 14 which was hydrolyzed with BBr3 in benzene to the methanofullerenecarboxylic acid 10, a versatile synthon for the preparation of amphiphilic fullerene derivatives. Treatment of 10 with alcohols and amino acid esters under DCC coupling conditions afforded the esters 5 and 17 and the amino-acid derivatives 11 and 12, respectively.

Carcinoid tumors of the gut. Our experience over three decades and review of the literature.

Abstract: We review our institution's experience with gastrointestinal (GI) carcinoid tumors over the past three decades: fifty-five cases with complete follow-up. The majority of carcinoids were from the ileum and appendix--19 cases (35%) and 17 cases (31%), respectively. Other locations included the cecum in five (9%), duodenum in three (5%), jejunum in three (5%), rectum in three (5%), and pylorus in one (2%). Four patients had metastatic carcinoid of uncertain primary (7%). Appendiceal carcinoids were frequently incidental and small (all < 1 cm). None were metastatic, and all appeared to have been cured with simple appendectomy. In contrast, ileal carcinoids were usually symptomatic and often metastatic at the time of diagnosis. Carcinoid syndrome occurred in 10 patients (18%), associated primarily with metastatic tumors from the ileum and cecum. Secondary malignancies were seen in 10 patients (18%). We provide a literature survey of GI carcinoid tumors and carcinoid syndrome.

Handbuch der Naturfarbstoffe : Vorkommen, Verwendung, Nachweis

Abstract: Describes history, applications, and methodes of natural dyes, including a literature survey, origin of natural dyes, properties and applications of inorganic pigments in coloring textiles, classification of natural dyes according to chemical structure .. etc. Identification by solubility test, thin layer chromatography (TLC), High Pressure Liquid Chromatography (HPLC), spectroscopical methods, and dyeing tests are described in detail. -- CCI=IC

Fractionation of extractable aluminum in acid soils: A review and a proposed procedure

Abstract: Different forms of soil aluminum (Al) are involved in the retention of anions and cations, phytotoxicity of Al in acid soils, CEC reduction and soil physical properties such as aggregate stability and water infiltration. Therefore it is desirable to quantify the different forms of Al in soil especially acidic soils. A rationale was developed from a literature survey to identify the following fractions of Al: (a) exchangeable quantified by 1M KC1 extraction; (b) organic bound quantified by 0.1M CuCl2 + 0.5M KCl extraction; (c) sorhed Al extractable with 1M NE4OAc at pH 4.0; (d) amorphous Al oxide and hydroxide and amorphous aluminosilicates (if present) extractable with 0.2M ammonium oxalate at pH 3.0; and (e) interlayered Al extractable with 0. 33M sodium citrate at pH 7.3. Pools (a), (b), and (c) are extracted sequentially. Amorphous Al oxide and hydroxide (pool d) is calculated from ammonium oxalate extractable Al minus (a + b + c). Interlayered Al is calculated from sodium citrate extractable ...

Agroforestry systems: integrated land use to store and conserve carbon

Abstract: Agroforestry is a promising land use practice to maintain or increase agricultural productivity while preserving or improving fertility. From the perspective of climate change and the global carbon cycle, agroforestry practices are attractive for 2 reasons: they directly store carbon in tree components, and they potentially slow deforestation by reducing the need to clear forest land for agriculture. An extensive literature survey was conducted to evaluate the carbon dynamics of agroforestry practices and to assess their potential to store carbon. Data on tree growth and wood production were converted to estimates of carbon storage. Surveyed literature showed that median carbon storage by agroforestry practices was 9 t C ha-' in semi-arid, 21 t C ha' in sub-humid, 50 t C ha-l in humid, and 63 t C ha-' in temperate ecoregions. The limited survey information available tended to substantiate the concept that implementing agroforestry practices can help reduce deforestation.

The possible role of angiogenesis in the metastatic potential of human melanoma. Clinicopathological aspects.

Abstract: In this review, we present a literature survey of angiogenesis in melanoma. Progression in melanoma is supposed to be associated with an angiogenic response. Several histological studies have shown an increase of vascular structures in malignant melanoma, which is not the case in common naevocellular naevi. Neovascularization can be caused by several angiogenic factors: the most important of those produced in melanoma are described. Proteases such as urokinase plasminogen activator and metalloproteinases are important for the migration for both endothelial cells and tumour cells. Possible effects of these factors in melanoma cells are discussed. Finally, inhibition of angiogenesis and its potential role in melanoma therapy are considered.

Variations in micropropagated bananas and plantains : literature survey

Abstract: Les donnees de la litterature concernant les variations chez les bananiers et les plantains multiplies in vitro ont ete analysees en incluant des resultats non publies du CIRAD-FLHOR. Les points discutes dans cette synthese sont les suivants : caracteristiques des variants, interet pour l'amelioration genetique et probleme pose pour la micropropagation de masse, origines, pourcentage et frequence d'apparition, facteurs influencant les variations, methodes de caracterisation, strategie possible pour limiter les risques de variation en propagation de masse. (Resume d'auteur)

Simulation of the early startup period of high-temperature heat pipes from the frozen state by a rarefied vapor self-diffusion model

Abstract: The heat pipe startup process is described physically and is divided into five periods for convenience of analysis. The literature survey revealed that none of the previous attempts to simulate the heat pipe startup process numerically were successful, since the rarefied vapor flow in the heat pipe was not considered. Therefore, a rarefied vapor self-diffusion model is proposed, and the early startup periods, in which the rarefied vapor flow is dominant within the heat pipe, are first simulated numerically. The numerical results show that large vapor density gradients existed along the heat pipe length, and the vapor flow reaches supersonic velocities when the density is extremely low. The numerical results are compared with the experimental data of the early startup period with good agreement.

Determination of Verdet constant from combined ac and dc measurements

Abstract: Two methods of determination of the Verdet constant (V) for an optically transparent medium are described. These methods use the same apparatus in which the intensity of a monochromatic beam of light is modulated by passing it, successively, through a polarizer, the medium under test (contained within a solenoid which carries ac of frequency f in its windings), and an analyzer. The emergent beam is incident on a detector which produces a steady output voltage Uo for the special conditions of the optical system set for maximum transmittance and, simultaneously, zero modulation. Methods I and II, which were tested by determining V for water for the wavelength 643.3 nm, are based, respectively, on the ratios u1/Uo and u2/Uo, where u1 is the rms value of detector output voltage varying at frequency f and u2 is the corresponding output varying at frequency 2 f. The three mean values of V from method I, method II, and a literature survey agree to within 1%. The standard deviation in the values of V by method I ...

Adams-Oliver syndrome: a case with juvenile chronic myelogenous leukemia and chylothorax.

Abstract: We report on a patient with Adams-Oliver syndrome and report new findings: a chylous pleural effusion and juvenile chronic myelogenous leukemia. Also, our patient had congenital heart disease, confirming that heart lesions are a manifestation in this syndrome. The major manifestations of this disorder are summarized. Included are cases not previously recognized as having Adams-Oliver syndrome identified in a literature survey. Distal limb deficiency is commonest with more frequent and more severe involvement of the lower limbs. Scalp defects are the second commonest manifestation, while an underlying skull defect is not infrequent. Cutis marmorata telangiectatica and dilated scalp veins are significant signs of this condition. This review highlights unresolved questions about Adams-Oliver syndrome.

Evaluating sympathetic activity in human hypertension.

Abstract: AIM: To review the use of plasma norepinephrine to evaluate sympathetic activity in humans, and to discuss the improvement in assessment of human sympathetic activity brought about by the norepinephrine spillover method and by microneurography. METHOD: Literature survey. RESULTS: These methods have limitations, and an accurate assessment of sympathetic cardiovascular control should not be limited to an investigation of sympathetic nerve firing or norepinephrine secretion but include cardiac and vascular responses. These responses can be assessed by traditional pharmacological means (for example, a reduction in vascular resistance induced by alpha-adrenergic blockade) or by a variety of approaches aimed at examining sympathetic cardiovascular modulation in a more integrated fashion, such as the recently developed power spectrum analysis of blood pressure and heart rate. CONCLUSION: The sensitivity and specificity of all these methods is still under investigation, but in almost every case an increase in sympathetic cardiovascular influence has been reported to occur in hypertension, indicating that sympathetic activation has a pathogenic effect on this condition.

Study of liquid retention in fixed-bed reactors with upward flow of gas and liquid

Abstract: A literature survey of the measurement techniques for the determination of liquid retention in cocurrent upward gas and liquid flow in fixed-bed reactors is presented. A number of these techniques were used in this work in columns of different diameters (Dc = 0.05 m, 0.10 m, and 0.15 m). Porous alumina particles of two different diameters (dp = 0.002 m and 0.0028 m) with both nonfoaming (water, cyclohexane, heptane, and propanol) and foaming liquids (kerosene, LCO, and diesel fuel) have been investigated. The gas used was either air or N[sub 2]. The methods investigated include volumetry, gravimetry, gammametry, and determination of residence-time distribution by tracer technique. A simple correlation for the prediction of total gas and liquid retention for bubble and pulsed flow is proposed and verified.

Features in integrated modelling of products and their production

Abstract: This paper summarizes the reasons for considering new ways of modelling products and processes. Three different concepts for describing parts and products are described including different types of features, skeletons and hierarchical models. Two approaches for linking CAD and CAPP, namely feature recognition and feature-based design, are discussed and compared with the problem of either integrating or interfacing design and process planning activities. Results from a literature survey on feature-based design and feature definitions are described with the conclusion that feature definitions used are very different. A design-oriented manufacturing process database (MADED) and a feature-based CAD and CAPP system (DEPF), which currently are being developed at the Technical University, are presented.

The Stroke Prevention Patient Outcomes Research Team. Goals and methods.

Abstract: The aim of the present study, based at Duke University and involving 14 other institutions, is to identify the most appropriate and cost-effective clinical strategies for prevention of ischemic (thrombotic or embolic) stroke in high-risk individuals and to design and test an intervention to disseminate this information to providers and the public. The study uses (1) secondary data from literature review, Medicare claims, and population-based data from three epidemiological studies and (2) primary data generated in national physician and patient surveys and in demonstration trials. Phases I through III involve data collection and analysis using a decision/cost-effectiveness model and consensus development methods. Phase IV includes intervention in physicians9 practice patterns. Data is collected by literature survey and abstraction, review of medical records, claims analysis, and patient and physician surveys. A structured decision model and a well-defined clinical focus provide a successful organization for a PORT on stroke prevention.

Mathematical modelling of the human cervical spine: a survey of the literature

Abstract: This paper summarizes the results of a literature survey concerning the aspects relevant for mathematical modelling of the human cervical spine. Both relatively simple two pivot models and the more detailed discrete parameter and finite element models describing head-neck dynamics are reviewed. Attention is also given to data on the physical properties of cervical spine components, and to experiments which can be used to validate a cervical spine model. It is concluded that a number of sophisticated models are available in the literature. However, these models do not simulate the relative head motion better than two pivot models do. It is also concluded that both data on the material characteristics of cervical components and data for a detailed validation of local vertebral movements are incomplete. Recommendations for additional experimental research are given. (A) For the covering abstract of the conference see IRRD 860654.