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1.
The need for rare resources, such as tungsten or cobalt, combined with the high energy requirements to produce cutting materials, is forcing research and development to work out environmentally friendly alternatives. Natural rocks could be an alternative since they are available in large quantities worldwide, have a potentially suitable property profile, and do not require energy-intensive processes to make them usable as cutting materials. However, there are only a few studies on the usability and suitability of natural rocks as cutting materials for machining processes. Therefore, in this article, inserts made of natural rocks were ground and used in turning operations. First, the properties of various natural rocks were determined, as were the tool properties after grinding. Then, the tool load and wear during the machining process were recorded and evaluated to assess the potential applications of this alternative cutting material more accurately. It is therefore becoming apparent that flint and quartz are suitable for use as alternative cutting materials and should be further researched.  相似文献   

2.
In order that the impact on the environment and human beings can be assessed, it may prove necessary for geochemical research work to entail determinations of concentrations of trace elements in building materials, and it is also likely that this will be a time-consuming and financially-demanding business. Additionally, once basic research has been carried out to determine the mineral composition and structural and textural features, it will then be important to determine concentrations of elements that affect the surrounding natural environment and the health of human beings. This paper thus describes mineralogical and geochemical analyses performed on the stone material that opoka rocks represent. Mineralogical studies have shown that the studied opoka rocks most often have cryptocrystalline silica dispersed among carbonate components. The texture of the rock is slightly porous. Silica in the form of type opal A and CT (cristobalite–tridymite) is the main mineral component of the opoka rocks. Carbonate minerals represented by calcite were an important component in the opoka rocks. Earlier geochemical studies focused on the concentration of Sr and Ba. However, the determination of the leachability of these elements as a function of time is a novelty in this study. Trace elements leached from the material matrix were made subject to determinations. The MATLAB program was used to assess leachability in the cases of both strontium and barium, by reference to the Mamdani–Assilian fuzzy algorithm. The presented work has thus sought to experiment with the use of statistical methods to monitor the effectiveness of geochemical processes taking place over time.  相似文献   

3.
Research into health systems all over the world has contributed to the development of new disease control strategies, modernized hospital and outpatient care, alternative financing mechanisms, cost-effective interventions and monitoring tools which resulted in improved delivery of care and public health services. But financing of such research is a problem in many European countries – particularly when the study is to be carried out outside the European Union – as it does not fall into the classical categories of basic science, medical science or development of drugs and vaccines and may not have an immediate impact on European health services. In view of this, a European programme for strengthening health systems research in developing countries (INCO-DEV) was set up by the European Commission in Brussels in 1983 which was integrated into the Science and Technology for Development programme on an increasing budget. For two decades it has facilitated high quality health systems research influencing health policies worldwide. Examples for INCO-funded projects are given below.  相似文献   

4.
The initial experience of several colonic and rectal surgeons with the EEA stapling device for low colorectal anastomoses is reviewed. It was found that the EEA gives a better anastomosis than is possible by hand and that a surgeon familiar with doing a low anterior resection can perform it on patients for whom it is not possible by hand. However, the results with the EEA are not perfect or guaranteed. The many complications associated with its use are reviewed, and ways to avoid them are discussed.  相似文献   

5.
Objectives: To determine GPs' reported use of written education materials with older patients and older patients' reported receipt of these materials. To determine GPs' and older patients' perceptions of written materials. Method: Using self‐report questionnaires, two populations were surveyed; a randomised sample of SO GPs (29 males and 21 females) practising in Brisbane's southern suburbs and a convenience sample of 188 older community‐dwelling people (aged over 64 years). Results: All GPs reported using written materials with patients, although 28% had not given any to the last 10 patients. This increased to 46% when patients were older. Twenty percent of patients wanted more written information from their GP, while some GPs believed that older patients preferred verbal information and gave out written information only when they perceived patient interest. All GPs reported giving written materials at the time of consultation and over two‐thirds discussed the content with patients. Just over 50% of patients reported receiving written information from GPs in the last six months and only half of these again discussed it directly with their GP. Overall, patients were more positive than GPs about the value of written education materials. Conclusions: Older patients' desire for written information may be better met if they are more assertive in requesting this of GPs and GPs may better serve their patients' needs if they make written information more readily available to them. Better access to materials and more financial incentives to give them out might also increase GPs' use of written materials.  相似文献   

6.
Six zeolite-bearing rocks, often used as building materials, were analyzed by thermodilatometry, together with a rock not bearing zeolites and a plaster covering a containing wall made of zeolite-bearing dimension stones, up to 250 °C. The main results obtained were the following: (i) the zeolite-bearing rocks exhibited very small, if any, positive variation of ΔL/Lo (%) up to about 100 °C, whereas they more or less shrank in the temperature range 100–250 °C (final values ranging from −0.21 to −0.92%); (ii) the rock not bearing zeolites regularly expanded through the whole temperature range, attaining a final value of 0.19%; (iii) the plaster showed a thermodilatometric behavior strongly affected by its water content. Obtained results were interpreted based on plain thermal expansion, shrinkage by dehydration, cation migration and thermal collapse of the zeolitic structure. The decay of the zeolite-bearing building materials was essentially related to: (i) the large differences recorded in the thermodilatometric behavior of the various rocks and the plaster; (ii) the different minerogenetic processes that resulted in the deposition of the various zeolite-bearing rocks.  相似文献   

7.
As one of the major materials used in construction, cement can be very resource-consuming and polluting to produce and use. Compared with traditional cement processing methods, dry-mix mortar is more environmentally friendly by reducing waste production or carbon emissions. Despite the continuous development and promotion of green construction materials, only a few of them are accepted or widely used in the market. In addition, the majority of existing research on green construction materials focuses more on their physical or chemical characteristics than on their promotion. Without effective promotion, their benefits cannot be fully appreciated and realized. Therefore, this study is conducted to explore the promotion of dry-mix mortars, one of the green materials. This study uses both qualitative and quantitative methods. First, through a case study, the potential of reducing carbon emission is verified. Then a path analysis is conducted to verify the validity and predictability of the samples based on the technology acceptance model (TAM) in this study. According to the findings of this research, to ensure better promotion results and wider application of dry-mix mortar, it is suggested that more systematic efforts be invested in promoting the usefulness and benefits of dry-mix mortar. The model developed in this study can provide helpful references for future research and promotion of other green materials.  相似文献   

8.
The paper deals with the possibility of using Phase Change Materials (PCM) in concretes and geopolymer composites. The article presents the most important properties of PCM materials, their types, and their characteristics. A review of the latest research results related to their use in geopolymer materials is presented. The benefits of using PCM in building materials include the improvement of thermal comfort inside the building, and also the fact that the additive in the form of PCM reduces thermal gradients and unifies the temperature inside the concrete mix, which can reduce the risk of cracking. The paper also presents a critical analysis related to the feasibility of mass scale implementations of such composites. It was found that the use of PCM in sustainable construction is necessary and inevitable, and will bring a number of benefits, but it still requires large financial resources and time for more comprehensive research. Despite the fact that PCM materials have been known for many years, it is necessary to refine their form to very stable phases that can be used in general construction as well as to develop them in a cost-effective form. The selection of these materials should also be based on the knowledge of the matrix material.  相似文献   

9.
The fenfluramines saga began in 1963 and ended in 1997. Fenfluramines are anorexigenic agents recommended, in April 1996, for the long-term treatment of obesity in USA, before being suddenly withdrawn from the market in September 1997. Over 34 years, about 60 million people were exposed to these drugs worldwide, mainly in Europe. The aim of this critical review is not to attempt to rehabilitate these appetite suppressants but to launch a plea for a more rational and rigorous approach to what might be called objective medical knowledge. Idiopathic primary pulmonary hypertension and cardiac valve disorders which have been both associated with fenfluramines have in common many puzzling features. The metamorphosis of facts into artifacts is only a hypothesis, but seems conceivable from a scientific point of view. Medicine is not only an art, it is also a science, which, like the others, implies adhesion to certain fundamental rules, such as refutation or verification of all experimental results by rigorous and standardized methods, before considering them as established facts. Firstly, a single study, moreover a case-control study like the International Primary Pulmonary Hypertension Study, is not sufficient to establish a causal relationship between exposure to appetite-suppressants and idiopathic pulmonary hypertension, because of the numerous biases which characterize even the best analytical research. Secondly, Doppler-echocardiography cannot be considered as a laboratory test, because of the poor interoperator reproducibility observed in obese patients. The use of this technique in pharmaco-epidemiology implies standardized procedures concerning not only reading data, but also their acquisition, because of possible uncontrolled interactions between sonographers, patients and sophisticated machines. In the case of the fenfluramines saga, numerous methodological artifacts concerning acquisition, processing and interpretation of epidemiologic and echocardiographic data might have contributed to distortion of reality. Let us recall how Webster's dictionary defines artifact: "a spurious observation or result arising from preparatory or investigative procedures or any feature that is not naturally present but is a product of an extrinsic agent, method, or the like".  相似文献   

10.
Concrete production consumes enormous amounts of fossil fuels, raw materials, and is energy intensive. Therefore, scientific research is being conducted worldwide regarding the possibility of using by-products in the production of concrete. The objective is not only to identify substitutes for cement clinker, but also to identify materials that can be used as aggregate in mortar and concrete productions. Among the potential alternative materials that can be used in cement composite production is rock dust of different geological origin. However, some adversarial effects may be encountered when using rock dust regarding the properties and durability of mortars and concrete. Therefore, comprehensive research is needed to evaluate the adequacy of rock dust use in cementitious composite production. This paper presents a comprehensive review of the scientific findings from past studies concerning the use of various geological origins of rock dust in the production of mortars and concrete. The influence of rock dust as a replacement of fine aggregates on cementitious composites was analyzed and evaluated. In this assessment and review, fresh concrete and mortar properties, i.e., workability, segregation, and bleeding, mechanical properties, and the durability of hardened concrete and mortar were considered.  相似文献   

11.
Insufficient clinical results are yet available to determine the likely clinical role of NMR in gastroenterology. In some instances unique information is available from NMR imaging but ultrasound and CT also provide valuable information in a wide variety of diseases. Many of the organs and tissues within the abdomen are accessible to biopsy, and a variety of other biochemical tests have specific roles in assessing disease within the abdomen and pelvis. Virtually all NMR machines in current use are research prototypes rather than clinical instruments designed for routine use. Major questions about design are unresolved, such as whether resistive, permanent or cryogenic magnets should be used. There is also little agreement about the optimum field for imaging. The value of spectroscopy in research and clinical use is another unknown factor and it is probable that this will provide useful information in research applications at least. At the present time it is important to note the developments occurring in NMR imaging and the potential of this technique, although it is not yet possible to predict what value it may have in clinical practice. There are many current research developments, such as flow imaging and the imaging of 23Na which have been demonstrated in the laboratory but have not yet been applied in clinical practice. It is also possible that respiratory gating may result in considerable improvement in image quality. The use of paramagnetic contrast agents is another developing field. These agents, including molecular O2, iron, manganese and gadolinium, have the effect of decreasing T1 and T2. Gadolinium chelates have been used in animals and will soon be evaluated in humans. Not only do these materials act as contrast agents in their own right but they may be linked as markers to metabolites, antibodies and other compounds. Direct measurements of T1 and T2 may prove to be of value although initial results indicate that they are rather non-specific. Whether NMR will remain largely of research interest or will play a useful role in clinical practice remains to be seen but will certainly be the subject of intense investigation over the next few years.  相似文献   

12.
This article is an account of the birth and evolution of surface science as an interdisciplinary research area. Surface science emanated from the confluence of concepts and tools in physics and chemistry with technological innovations that made it possible to determine the structure and properties of surfaces and interfaces and the dynamics of chemical reactions at surfaces. The combination in the 1960s and 1970s of ultra-high-vacuum (i.e., P < 10(-7) Pascal or 10(-9) Torr) technology with the recognition that electrons in the energy range from 50 to 500 eV exhibited inelastic collision mean free paths of the order of a few angstroms fostered an explosion of activity. The results were a reformulation of the theory of electron solid scattering, the nearly universal use of electron spectroscopies for surface characterization, the rise of surface science as an independent interdisciplinary research area, and the emergence of the American Vacuum Society (AVS) as a major international scientific society. The rise of microelectronics in the 1970s and 1980s resulted in huge increases in computational power. These increases enabled more complex experiments and the utilization of density functional theory for the quantitative prediction of surface structure and dynamics. Development of scanning-probe microscopies in the 1990s led to atomic-resolution images of macroscopic surfaces and interfaces as well as videos of atoms moving about on surfaces during growth and diffusion. Scanning probes have since brought solid-liquid interfaces into the realm of atomic-level surface science, expanding its scope to more complex systems, including fragile biological materials and processes.  相似文献   

13.
Disease biomarkers would aim at a more specific definition of diagnosis or subtype of a certain disease, as well as prognosis definition, including efficacy and side effects of certain therapeutics. Biomarkers could lead to a prognostically optimized definition of remission in the individual patient and thus to a more objective definition of therapeutic efficacy. Is this possible and does it make sense? Or would an extensive analysis of biomarkers to date lead to a costly overestimation of as yet not well established biologic parameters? Although we are currently unable to answer this question, many colleagues argue in favour of more in depth research for a better evaluation of biomarkers in many diseases. This could save money if we were able to predict the efficacy of expensive drugs such as immunobiologics. Biomarkers comprise cytometric information, data on protein expression and secretion, mRNA, microRNA or DNA, including epigenetic variants. Although much of these data already exist in the scientific literature, it is associated with problems in terms of feasibility (for cytometry and RNA analysis only on-site analysis is possible, while for DNA analysis central testing is also possible), costs and reproducibility (ethnic variability!). To date all biomarkers have only limited value in terms of the above-mentioned aims. The present review compiles “PROs and CONs” in a subjective way in order to provoke a discussion on the meaningfulness of biomarkers, while at the same time supporting and encouraging further research in this field.  相似文献   

14.
Nanotechnology is the creation, manipulation and use of materials at the nanometre size scale (1 to 100 nm). At this size scale there are significant differences in many material properties that are normally not seen in the same materials at larger scales. Although nanoscale materials can be produced using a variety of traditional physical and chemical processes, it is now possible to biologically synthesize materials via environment-friendly green chemistry based techniques. In recent years, the convergence between nanotechnology and biology has created the new field of nanobiotechnology that incorporates the use of biological entities such as actinomycetes algae, bacteria, fungi, viruses, yeasts, and plants in a number of biochemical and biophysical processes. The biological synthesis via nanobiotechnology processes have a significant potential to boost nanoparticles production without the use of harsh, toxic, and expensive chemicals commonly used in conventional physical and chemical processes. The aim of this review is to provide an overview of recent trends in synthesizing nanoparticles via biological entities and their potential applications.  相似文献   

15.
Proteomics, a new branch of science studying proteins, only emerged in the postgenomic period. What makes so it important is that fact even the exciting recent insights into the genome have not furnished sufficient information about proteins, which are the main agents behind cellular, subcellular, and supracellular functions. The center of attention of proteomics is identification of proteins in complex protein mixtures with an emphasis on the identification of a large number of proteins at a time, search for interrelations between identified proteins, their more exact characterization, determination of quantity, and better understanding of their function. Proteomics in nephrology is still in its infancy. Although it makes use, like in other fields, of various methodological procedures, the principal techniques are two-dimensional gel electrophoresis and MALDI-TOF (matrix-assisted laser desorption/ionization-time of flight) mass spectrometry. Nephrology-related proteomic findings made to date inform about normal protein composition of renal parenchyma, urine and plasma, and on their alterations under the influence of physiological or pathological stimuli. Search is under way for uremic toxins in uremic infiltrate, and their elimination from the body of patients with renal failure using various dialysis membranes is being investigated. Findings have made it possible to formulate hypotheses regarding renal physiology and pathology. Current nephrology-related proteomics raises more questions than it answers. Its potential for improving the understanding of physiological processes, pathological states, non-invasive diagnosis, monitoring of therapy, development of drugs and therapeutic procedures is a major promise for future.  相似文献   

16.
This article provides evidence that basic science research and education should be key priorities for global health training, capacity building, and practice. Currently, there are tremendous gaps between strong science education and research in developed countries (the North) as compared to developing countries (the South). In addition, science research and education appear as low priorities in many developing countries. The need to stress basic science research beyond the typical investment of infectious disease basic service and research laboratories in developing areas is significant in terms of the benefits, not only to education, but also for economic strengthening and development of human resources. There are some indications that appreciation of basic science research education and training is increasing, but this still needs to be applied more rigorously and strengthened systematically in developing countries.  相似文献   

17.
A critical analysis of the basic hypotheses of psychosomatic research and the sometimes hasty assertions drawn from the previous works makes it possible to better discern the data confirmed by the most recent works or the most rigorous meta-analyses and to highlight the emerging tracks. If the hypothesis of behavioral patterns specifically related to the risk of certain pathologies seems abandoned, the predictive value of depression in the cardiovascular field, more than in that of oncology, becomes clearer. Negative affect and impaired emotional awareness emerge as two complementary factors of somatic vulnerability. Several vulnerability factors seem all the more effective as they affect individuals of lower socio-economic status. Social exclusion feeling and its links with the inflammatory response appear to be a possible common denominator, both for depression and for many somatic conditions. A series of studies on the cerebral regulation of emotions and stress, as well as on bidirectional brain-bowel relations and on the mediating role of the gut microbiota, complements the available epidemiological data. The same is true for certain advances in behavioral neuro-economics, which inform the decision-making processes of patients facing preventive health choices. Lastly, it appears that a significant part of the excess mortality associated with the existence of severe mental disorders is not due to factors inherent to the patients themselves, but to disparities in the quality of the care provided to them.  相似文献   

18.
Acoustic emissions (AE) due to microcracking in solid materials permit the monitoring of fracture processes and the study of failure dynamics. As an alternative method of integrity assessment, measurements of electrical resistance can be used as well. In the literature, however, many studies connect the notion of criticality with AE originating from the fracture, but not with the changes in the electrical properties of materials. In order to further investigate the possible critical behavior of fracture processes in rocks and cement-based materials, we apply natural time (NT) analysis to the time series of AE and resistance measurements, recorded during fracture experiments on cement mortar (CM) and Luserna stone (LS) specimens. The NT analysis indicates that criticality in terms of electrical resistance changes systematically precedes AE criticality for all investigated specimens. The observed greater unpredictability of the CM fracture behavior with respect to LS could be ascribed to the different degree of material homogeneity, since LS (heterogeneous material) expectedly offers more abundant and more easily identifiable fracture precursors than CM (homogenous material). Non-uniqueness of the critical point by varying the detection threshold of cracking events is apparently due to finite size effects which introduce deviations from the self-similarity.  相似文献   

19.
Ceramics are advanced engineering materials in which have been broadly used in numerous industries due to their superior mechanical and physical properties. For application, the industries require that the ceramic products have high-quality surface finishes, high dimensional accuracy, and clean surfaces to prevent and minimize thermal contact, adhesion, friction, and wear. Ceramics have been classified as difficult-to-machine materials owing to their high hardness, and brittleness. Thus, it is extremely difficult to process them with conventional finishing processes. In this review, trends in the development of non-conventional finishing processes for the surface finishing of difficult-to-machine ceramics are discussed and compared to better comprehend the key finishing capabilities and limitations of each process on improvements in terms of surface roughness. In addition, the future direction of non-conventional finishing processes is introduced. This review will be helpful to many researchers and academicians for carrying out additional research related to the surface finishing techniques of ceramics for applications in various fields.  相似文献   

20.
Changjie Zhang 《Platelets》2017,28(5):434-440
Due to the importance of fluid flow during thrombotic episodes, it is quite appropriate to study clotting and bleeding processes in devices that have well-defined fluid shear environments. Two common devices for applying these defined shear stresses include the cone-and-plate viscometer and parallel-plate flow chamber. While such tools have many salient features, they require large amounts of blood or other protein components. With growth in the area of microfluidics over the last two decades, it has become feasible to miniaturize such flow devices. Such miniaturization not only enables saving of precious samples but also increases the throughput of fluid shear devices, thus enabling the design of combinatorial experiments and making the technique more accessible to the larger scientific community. In addition to simple flows that are common in traditional flow apparatus, more complex geometries that mimic stenosed arteries and the human microvasculature can also be generated. The composition of the microfluidics cell substrate can also be varied for diverse basic science investigations, and clinical investigations that aim to assay either individual patient coagulopathy or response to anti-coagulation treatment. This review summarizes the current state of the art for such microfluidic devices and their applications in the field of thrombosis and hemostasis.  相似文献   

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