644 research outputs found
Magazine Hammer
No full textPatent for a new Magazine-Hammer. The new and improved Magazine-Hammer consists of a setting hammer head, carrying handle, feed device for nails, tacks, or like fasteners, discharge device, and mounted setting tube. This Magazine-Hammer improvement allows the operator to drive fasteners with one hand and manipulate an object with one free hand
An inexpensive DIY impact hammer for vibration analysis of buildings
No full textThe characterisation of vibration in buildings often involves exciting the building structure with a force and measuring the vibration response. The two common non-destructive force excitation methods are the use of an instrumented impact hammer or an electromagnetic vibration shaker. This paper contains a discussion on how to build a low cost instrumented hammer, and compares the performance of the hammer with a commercially available impact hammer and a commercially available electromagnetic shaker for vibrating buildings. The merits and disadvantages of each of these three instruments are discussed and it is the opinion of the author that for the vibration analyses often conducted in semiconductor manufacturing facilities, laboratories, and offices, the use of an instrumented impact hammer can provide higher quality measurements at a lower cost than the use of an electromagnetic shaker.http://www.mecheng.adelaide.edu.au/anvc/abstract.php?abstract=19
[Review of] Signe Hammer. Daugh ters and Mothers: Mothers and Daughters
No full textPoet, actress, and author ( Women: Body and Culture), Signe Hammer here attempts an exploration of the complex bonds and strains between women, their daughters, and their mothers. While it is written for a popular audience, the book\u27s credibility is strengthened by the inclusion of scholarly chapter notes following the final chapter
Prices and protocols in public health care
No full textThe author tries to derive price and rationing rules for public health facilities. He highlights the effect on these rules of different assumptions about the objectives of government (health versus welfare), the limits of available policy instruments, and the market environment in which the public system operates. One recurrent finding: policy reform must be assessed in relation to the changes it induces relative to the status quo before reform. This point may seem obvious, but it represents a distinct gap in the literature on resource allocation in health. To assess changes, the behavior of the private sector must be known in the type of care given in a system and on how this care will change in response to the policy. Substituting for a reasonably well-functioning private sector is not as valuable as providing services that the private sector cannot be expected to sustain. Research is needed to characterize market equilibrium for medical care and its response to policy measures. The author could not examine many issues - most important, those related to uncertainty and insurance. But if the research he calls for in this paper is pursued, those issues must figure prominently as major determinants in the demand for care. This need was originally identified by Arrow, and there is still a long way to go. The author's analysis is not done in terms of preventive or curative care, and he argues for assessing interventions on the basis of changes in the stated objectives of a public system. But there could well be a connection with the preventive-curative dichotomy if there were reason to believe that preventive care will systematically lose out to curative care in a market setting. Onthe basis of people's generally acknowledged undervaluation of preventive services, this may well be the case. Other prevention activities also have many public good features, with few private alternatives, and will look good when improvements over stauts quo are examined for all interventions. But all activities must be evaluated in their improvement over market provision. It is not necessary to prejudge the case for certain types of intervention.Economic Theory&Research,Health Monitoring&Evaluation,Health Economics&Finance,Health Systems Development&Reform,Environmental Economics&Policies
Do arbuscular mycorrhizal fungi stabilize litter-derived carbon in soil?
No full text1. Fine roots and mycorrhiza often represent the largest input of carbon (C) into soils and are therefore of primary relevance to the soil C balance. Arbuscular mycorrhizal (AM) fungi have previously been found to increase litter decomposition which may lead to reduced soil C stocks, but these studies have focused on immediate decomposition of relatively high amounts of high-quality litter and may therefore not hold in many ecological settings over longer terms. 2. Here, we assessed the effect of mycorrhizal fungi on the fate of C and nitrogen (N) contained within a realistic amount of highly C-13-/N-15-labelled root litter in soil. This litter was either added fresh or after a 3-month incubation period under field conditions to a hyphal in-growth core where mycorrhizal abundance was either reduced or not through rotation. After 3 months of incubation with a plant under glasshouse conditions, the effect of turning cores on residual C-13 and N-15 inside the cores was measured, as well as C-13 incorporation in microbial signature fatty acids and N-15 incorporation of plants. 3. Turning of cores increased the abundance of fungal decomposers and C-13 loss from cores, while N-15 content of cores and plants was unaffected. Despite the difference in disturbance that turning the cores could have caused, the results suggest that mycorrhizal fungi and field incubation of litter acted to additively increase the proportion of C-13 left in cores. 4. Synthesis. Apart from stimulating litter decomposition as previously shown, mycorrhizas can also stabilize C during litter decomposition and this effect is persistent through time
Nutrient balance and salinity stress in arbuscular mycorrhizal fungi
No full textEarth’s primary production depends to a considerable extent on the mycorrhizal symbiosis, since mycorrhizal fungi supply their host plant with important mineral nutrients. I examined the influence of different nutrient regimes on the fungal partner in the arbuscular mycorrhizal symbiosis. I especially focused on salinity problems, as they occur in southern Tunisia, where I performed several field studies. The following main results were obtained: • The spores of arbuscular mycorrhizal fungi (AMF) may contain high amounts of mineral nutrients. Therefore, our results indicate that AM fungal spores do not only serve for carbon storage, but also as mineral nutrient reservoirs. Both high environmental P concentrations and low C status of the plant partner led to an accumulation of P and other mineral nutrients in the fungus. We suggest that AMF can control the transfer of P and hold it back if not provided with sufficient C from the host, and that there must be a feed-back mechanism in the symbiotic C-P exchange. • I found AMF in saline ecosystems in southern Tunisia with at least 17 morphospecies per 40 g soil. The AMF biomass in soil declined with rising salinity Under elevated salinity, AM fungal hyphae and spores contained high amounts of Ca, Cl and K, while Na was found at low levels. The same findings hold true for a salinity stressed G. intraradices grown in in vitro cultures. This led us to suggest that AMF could act as an ion filter for the plant under high salinity, which could explain the high K/Na rates that are often reported in mycorrhized plants growing in saline soils. • Sole osmotic stress had different effects on G. intraradices than salinity stress, which includes both osmotic and toxic ion stress. Sole osmotic stress impaired the growth of the external mycelium and spores more than salinity stress, while the uptake of nutrients from the medium was more reduced by salinity stress caused by NaCl or KCl. This indicates that sole osmotic stress constitutes a high energetic cost in osmoregulation in AMF. • NaCl stress triggered a strong rise in production of glomalin, a protein important for soil structure, while sole osmotic stress did not. Thus, glomalin seems to be a stress response, but not a general one. • Growth of AM external mycelium was strongly stimulated by organic matter addition to the soil, and also the C flow from the plant to the mycelium was higher under organic matter addition. Mineral nutrient addition to the soil also stimulated AMF growth, though to a lesser extent than organic material. Organic matter addition to subtropical soils can therefore be an important soil remedy, since by stimulating AMF growth, it supports the symbiotically associated vegetation, improves soil structure and increases C storage in the soil. • In a revegetation project, double inoculation of Acacia saplings with AMF and Rhizobium in the desert border of the Sahara did not lead to measurable effects on the plants after five years, but the overall survival of the saplings in field after having been raised in a nursery was satisfactory. We suggest that the inoculum needs to be very carefully chosen in order to be compatible with the ecosystem, or that the native soil inoculum should be considered in management practices
Experimental identification of the dynamic behaviour of pile-soil system installed by means of three different pile-driving techniques
No full textA novel pile-driving technique, named Gentle Driving of Piles (GDP), that combines axial low-frequency and torsional high-frequency vibrations has been developed and tested recently. During the experimental campaign, several piles were installed onshore, making use of the GDP shaker. Besides those, a number of additional piles were installed using conventional pile-driving techniques, i.e. impact piling and axial vibratory driving. After the completion of the installation phase, the installed piles have been subjected to impact hammer tests with the following goals. First, the in-situ dynamic properties of the pile-soil system have been identified. Second, the post-installation soil state has been investigated, along with its evolution in time for each pile driving scenario. Preliminary analyses, of the data collected during the impact tests show dissimilar trends in the overall dynamic response between the piles installed with impact hammer and those installed with the axial and the GDP shakers.This observation suggests a difference in the post-installation dynamic behaviour of the pile-soil systems related to different pile-driving techniques. In this paper, a first attempt is made to identify the differences in the overall pile-soil dynamic behaviour of the piles installed by means of the three different pile-driving techniques.Dynamics of StructuresOffshore EngineeringEMSD CE&GGeo-engineeringBusiness RelationsEngineering Structure
‘Cyborg soil’ reveals the secret microbial metropolis beneath our feet
No full textDig a teaspoon into your nearest clump of soil, and what you’ll emerge with will contain more microorganisms than there are people on Earth. We know this from lab studies that analyse samples of earth scooped from the microbial wild to determine which forms of microscopic life exist in the world beneath our feet
A Novel Method for Railway Crossing Monitoring Based on Ambient Vibration Caused by Train-Track Interaction
No full textRailway crossings are critical components in the rail network. They usually degrade faster than the other components. It is therefore vital to monitor their conditions using appropriate methods. This paper proposes to use the ambient vibration caused by the train-track interaction from a distance to monitor the condition of railway crossings. Both impact tests and pass-by measurements were performed on an instrumented crossing. The eigenfrequencies and mode shapes in the frequency range of 10–2000 Hz are first identified by impact tests using three different devices, i.e. a falling weight device, a big hammer and a small hammer. For the pass-by measurement, the dynamic features of both the wheel-crossing impact and ambient vibration are analyzed using time-frequency representations. It is shown that the ambient vibration signals are stationary and contain several characteristic frequencies. Then a method based on the frequency domain decomposition is applied to the ambient vibration signals to further identify the frequency components. It is found that the frequencies identified from the pass-by measurement agree well with the eigenfrequencies identified from the impact test. The proposed method can be further developed to continuously monitor the condition of railway crossings without interrupting train operations.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Railway Engineerin
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