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Essential Requirement (essential + requirement)
Selected AbstractsMechanical Response Analysis and Power Generation by Single-Cell StretchingCHEMPHYSCHEM, Issue 4 2005Alexandre Micoulet Dr. Abstract To harvest useful information about cell response due to mechanical perturbations under physiological conditions, a cantilever-based technique was designed, which allowed precise application of arbitrary forces or deformation histories on a single cell in vitro. Essential requirements for these investigations are a mechanism for applying an automated cell force and an induced-deformation detection system based on fiber-optical force sensing and closed loop control. The required mechanical stability of the setup can persist for several hours since mechanical drifts due to thermal gradients can be eliminated sufficiently (these gradients are caused by local heating of the cell observation chamber to 37,°C). During mechanical characterization, the cell is visualized with an optical microscope, which enables the simultaneous observation of cell shape and intracellular morphological changes. Either the cell elongation is observed as a reaction against a constant load or the cell force is measured as a response to constant deformation. Passive viscoelastic deformation and active cell response can be discriminated. The active power generated during contraction is in the range of Pmax=10,16Watts, which corresponds to 2500 ATP molecules,s,1at 10 kBT/molecule. The ratio of contractive to dissipative power is estimated to be in the range of 10,2. The highest forces supported by the cell suggest that about 104molecular motors must be involved in contraction. This indicates an energy-conversion efficiency of approximately 0.5. Our findings propose that, in addition to the recruitment of cell-contractile elements upon mechanical stimulation, the cell cytoskeleton becomes increasingly crosslinked in response to a mechanical pull. Quantitative stress,strain data, such as those presented here, may be employed to test physical models that describe cellular responses to mechanical stimuli. [source] Scaling of water flow through porous media and soilsEUROPEAN JOURNAL OF SOIL SCIENCE, Issue 1 2008K. Roth Summary Scaling of fluid flow in general is outlined and contrasted to the scaling of water flow in porous media. It is then applied to deduce Darcy's law, thereby demonstrating that stationarity of the flow field at the scale of the representative elementary volume (REV) is a critical prerequisite. The focus is on the implications of the requirement of stationarity, or local equilibrium, in particular on the validity of the Richards equation for the description of water movement through soils. Failure to satisfy this essential requirement may occur at the scale of the REV or, particularly in numerical simulations, at the scale of the model discretization. The latter can be alleviated by allocation of more computational resources and by working on a finer-grained representation. In contrast, the former is fundamental and leads to an irrevocable failure of the Richards equation as is observed with infiltration instabilities that lead to fingered flow. [source] Nanomotors: Magnetic Control of Tubular Catalytic Microbots for the Transport, Assembly, and Delivery of Micro-objects (Adv. Funct.ADVANCED FUNCTIONAL MATERIALS, Issue 15 2010Mater. S. Sanchez, Y. F. Mei, and co-workers present the concept of a microfactory on page 2430, where micro-objects are mixed together with synthetic microbots in a fluid and fuel is added in order to power them, as shown in the image. The motion of these microbots is remotely controlled by magnetic field that is an essential requirement for specialized tasks such as transport and delivery of microscale loads. [source] Polyfluorene Light-Emitting Diodes: Understanding the Nature of the States Responsible for the Green Emission in Oxidized Poly(9,9-dialkylfluorene)s: Photophysics and Structural Studies of Linear Dialkylfluorene/Fluorenone Model Compounds (Adv. Funct.ADVANCED FUNCTIONAL MATERIALS, Issue 13 2009Mater. Polyfluorenes, whilst attractive candidates for polymer light-emitting diodes, are susceptible to oxidative degradation. This degradation results in significant green emission. Although it has been linked to the formation of fluorenones, the precise relationship between fluorenones and the observed color shift remains widely debated. On page 2147, Chan et al. report a study on this relationship with the use of a series of model compounds. Inter-molecular fluorenone,fluorenone interaction is reported to be an essential requirement for the color shift. [source] Comparing alternative models: log vs Cox proportional hazard?HEALTH ECONOMICS, Issue 8 2004Anirban Basu Abstract Health economists often use log models (based on OLS or generalized linear models) to deal with skewed outcomes such as those found in health expenditures and inpatient length of stay. Some recent studies have employed Cox proportional hazard regression as a less parametric alternative to OLS and GLM models, even when there was no need to correct for censoring. This study examines how well the alternative estimators behave econometrically in terms of bias when the data are skewed to the right. Specifically we provide evidence on the performance of the Cox model under a variety of data generating mechanisms and compare it to the estimators studied recently in Manning and Mullahy (2001). No single alternative is best under all of the conditions examined here. However, the gamma regression model with a log link seems to be more robust to alternative data generating mechanisms than either OLS on ln(y) or Cox proportional hazards regression. We find that the proportional hazard assumption is an essential requirement to obtain consistent estimate of the E(y,x) using the Cox model. Copyright © 2004 John Wiley & Sons, Ltd. [source] Characterization of Arginine Transport in Helicobacter pyloriHELICOBACTER, Issue 4 2003George L. Mendz ABSTRACT Background. The amino acid L-arginine is an essential requirement for growth of Helicobacter pylori. Several physiological roles of this amino acid have been identified in the bacterium, but very little is known about the transport of L-arginine and of other amino acids into H. pylori. Methods. Radioactive tracer techniques using L-(U- 14C) arginine and the centrifugation through oil method were employed to measure the kinetic parameters, temperature dependence, substrate specificity, and effects of analogues and inhibitors on L-arginine transport. Results. The transport of arginine at millimolar concentrations was saturable with a Km of 2.4 ± 0.3 mM and Vmax of 1.3 ± 0.2 pmole min,1 (µl cell water),1 or 31 ± 3 nmole per minute (mg protein),1 at 20°C, depended on temperature between 4 and 40°C, and was susceptible to inhibitors. These characteristics suggested the presence of one or more arginine carriers. The substrate specificity of the transport system was studied by measuring the effects of L-arginine analogues and amino acids on the rates of transport of L-arginine. The absence of inhibition in competition experiments with L-lysine and L-ornithine indicated that the transport system was not of the Lysine-Arginine-Ornithine or Arginine-Ornithine types. The presence of different monovalent cations did not affect the transport rates. Several properties of L-arginine transport were elucidated by investigating the effects of potential inhibitors. Conclusions. The results provided evidence that the transport of L-arginine into H. pylori cells was carrier-mediated transport with the driving force supplied by the chemical gradient of the amino acid. [source] Techniques for oxygen transfer measurement in bioreactors: a reviewJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 8 2009S Suresh Abstract Oxygen is the most essential requirement for aerobic bioprocesses. The microbial growth in a bioreactor depends upon the oxygen transfer rate (OTR). The OTR is widely used to study the growth behavior of microbial and plant cell cultures. The mass transfer coefficient (kLa) determines the magnitude of the OTR. There are many techniques for measuring oxygen concentration and OTR in bioreactors. Zirconia, electrochemical, infrared, ultrasonic and laser cells are used to measure oxygen concentration in the liquid medium. Optical sensors are better alternatives to measure oxygen concentration in small bioreactors. Sulfite oxidation and gassing-out methods with a Clark-type electrode have been used for OTR measurements in bioreactors. Many new novel techniques have evolved recently for intermittent and continuous online measurement of OTR/kLa in various types of bioreactors. The present paper gives an overview of various measurement techniques and their limitations and/or suitability for measurement of OTR/kLa in various kinds of bioreactors, especially small bioreactors. Copyright © 2009 Society of Chemical Industry [source] Health interventions and satisfaction with services: a comparative study of urinary incontinence sufferers living in two health authorities in EnglandJOURNAL OF CLINICAL NURSING, Issue 5 2000Brenda Roe PhD, FRSH ,,This comparative study found that significantly more people with severe incontinence had contacted a health professional than had those with slight to moderate incontinence (P=0.00008). There was a significant linear trend towards people with severe incontinence seeing a health professional (P=0.00007). ,,The majority of people who were incontinent had not been asked to complete a bladder chart, which is an essential requirement for assessment and diagnosis of the type of incontinence and the subsequent health interventions that are offered. ,,Significantly more people in the health authority with an established continence advisory service had completed a bladder chart, had received physiotherapy and currently undertook pelvic floor muscle exercises than did those in the health authority without a continence service. ,,The majority of sufferers did not use any aids or appliances. Of those who did use incontinence aids, a majority bought their own. There was a significant linear trend for increased pad usage with increasing severity of incontinence (P=0.0003). ,,Significantly more people in the health authority with the continence service were satisfied with their healthcare and services, while more of those in the health authority without a service were unsatisfied (P=0.005). Significantly more people in the health authority without a service felt that healthcare and services could be improved (P=0.00001). ,,Significantly more people with severe incontinence were dissatisfied with services than were those with slight to moderate incontinence (P=0.01). [source] Recovery of transition metal complex by reverse flow adsorptionAICHE JOURNAL, Issue 1 2008Jeroen Dunnewijk Abstract Reverse flow adsorption (RFA) is a technique with a definite potential to prevent the leaching of a homogenous catalyst. In this work, we model an RFA-process for a continuous ideally stirred tank reactor with an adsorption bed upstream and another one downstream from the reactor. The model parameters concerning adsorption equilibrium and kinetics are taken from previous experimental studies on CoCl2 adsorption on polymer-bound trifenylfosfine. We use this model to study the concentration profiles of CoCl2 in the adsorption beds during consecutive adsorption,desorption cycles. The model calculations show that the concentration profile eventually reaches a fixed position after a number of adsorption,desorption cycles, even though internal mass transfer was a limiting factor. Hence, the transition metal is kept within the system boundaries, which is an essential requirement for the application of RFA. © 2007 American Institute of Chemical Engineers AIChE J, 2008 [source] Cigarette smoking is associated with an increased incidence of vascular complications after liver transplantationLIVER TRANSPLANTATION, Issue 7 2002Surakit Pungpapong Hepatic artery thrombosis (HAT) and other vascular complications are significant causes of morbidity after liver transplantation. Although cigarette smoking increases the risk of vascular complications after renal transplantation, its impact after liver transplantation remains unknown. Between May 1995 and April 2001, 288 liver transplantations were performed in 263 patients. Vascular complications developed in 39 patients (13.5%) (arterial complications, 28 patients [9.7%]; venous complications, 11 patients [3.8%]). Patient demographics, comorbid illnesses, and risk factors were analyzed using the Mann-Whitney U test, Chi-squared test, and Fisher's exact test. In patients with a history of cigarette smoking, incidence of vascular complications was higher than in those without history of cigarette smoking (17.8% v 8%, P = .02). Having quit cigarette smoking 2 years before liver transplantation reduced the incidence of vascular complications by 58.6% (24.4% v 11.8%, P = .04). The incidence of arterial complications was also higher in patients with a history of cigarette smoking compared with those without such history (13.5% v 4.8%, P = .015). Cigarette smoking cessation for 2 years also reduced the risk of arterial complications by 77.6% (21.8% v 5.9%, P =.005). However, the incidence of venous complications was not associated with cigarette smoking. Furthermore, there was no significant association between development of vascular complications and all other characteristics studied. Cigarette smoking is associated with a higher risk for developing vascular complications, especially arterial complications after liver transplantation. Cigarette smoking cessation at least 2 years before liver transplantation can significantly reduce the risk for vascular complications. Cigarette smoking cessation should be an essential requirement for liver transplantation candidates to decrease the morbidity arising from vascular complication after liver transplantation. [source] Testing the role of genetic factors across multiple independent invasions of the shrub Scotch broom (Cytisus scoparius)MOLECULAR ECOLOGY, Issue 22 2007MING KANG Abstract Knowledge of the introduction history of invasive plants informs on theories of invasiveness and assists in the invasives management. For the highly successful invasive shrub Scotch broom, Cytisus scoparius, we analysed a combination of nuclear and chloroplast microsatellites for eight native source regions and eight independent invasion events in four countries across three continents. We found that two exotic Australian populations came from different sources, one of which was derived from multiple native populations, as was an invasive sample from California. An invasive population from New Zealand appeared to be predominantly sourced from a single population, either from the native or exotic ranges. Four invasive populations from Chile were genetically differentiated from the native range samples analysed here and so their source of introduction could not be confirmed, but high levels of differentiation between the Chilean populations suggested a combination of different sources. This extensive global data set of replicated introductions also enabled tests of key theories of invasiveness in relation to genetic diversity. We conclude that invasive populations have similar levels of high genetic diversity to native ranges; levels of admixture may vary across invasive populations so admixture does not appear to have been an essential requirement for invasion; invasive and native populations exhibit similar level of genetic structure indicating similar gene flow dynamics for both types of populations. High levels of diversity and multiple source populations for invasive populations observed here discount founder effects or drift as likely explanations for previously observed seed size differences between ranges. The high levels of genetic diversity, differential and source admixture identified for most exotic populations are likely to limit the ability to source biocontrol agents from the native region of origin of invasive populations. [source] Serotonin 5-HT2 receptor activation induces a long-lasting amplification of spinal reflex actions in the ratTHE JOURNAL OF PHYSIOLOGY, Issue 1 2001D. W. Machacek 1C-fibre activation induces a long-term potentiation (LTP) in the spinal flexion reflex in mammals, presumably to provide enhanced reflexive protection of damaged tissue from further injury. Descending monoaminergic pathways are thought to depress sensory input but may also amplify spinal reflexes; the mechanisms of this modulation within the spinal cord remain to be elucidated. 2We used electrical stimulation of primary afferents and recordings of motor output, in the rat lumbar spinal cord maintained in vitro, to demonstrate that serotonin is capable of inducing a long-lasting increase in reflex strength at all ages examined (postnatal days 2,12). 3Pharmacological analyses indicated an essential requirement for activation of 5-HT2C receptors while 5-HT1A/1B, 5-HT7 and 5-HT2A receptor activation was not required. In addition, primary afferent-evoked synaptic potentials recorded in a subpopulation of laminae III-VI spinal neurons were similarly facilitated by 5-HT. Thus, serotonin receptor-evoked facilitatory actions are complex, and may involve alterations in neuronal properties at both motoneuronal and pre-motoneuronal levels. 4This study provides the first demonstration of a descending transmitter producing a long-lasting amplification in reflex strength, accomplished by activating a specific serotonin receptor subtype. It is suggested that brain modulatory systems regulate reflex pathways to function within an appropriate range of sensori-motor gain, facilitating reflexes in behavioural situations requiring increased sensory responsiveness. [source] Frequent monitoring of temperature: an essential requirement for site selection in bivalve aquaculture in tropical,temperate transition zonesAQUACULTURE RESEARCH, Issue 10 2006María Teresa Sicard Abstract Frequent monitoring of temperature (FMT) for over 1 year at two aquaculture sites in the western Baja California peninsula was analysed in terms of hourly, daily and monthly variability, and with this information, temperature-change indices were calculated. These data were contrasted against a long-term series from a global database (Extended Reconstruction of Sea Surface Temperature (ERSST)) to evaluate whether these could substitute for FMT. The compatibility of species requirements with the thermal conditions was evaluated by comparing the temperature frequency distributions from the two FMTs, with the optimum and lethal temperature information available on five bivalve species of aquacultural interest. We concluded that there was no correlation between ERSST and FMT because the former underestimates the amplitude of real temperature fluctuations and exhibits a different pattern of variation during the year. Therefore, FMT was needed for a correct selection of an aquaculture site for bivalves. The FMT indicated high temperature variability at both sites studied on different time scales, with the site located at lower latitude (Rancho Bueno) warmer and with a higher variability than Laguna Manuela. Contrasting these results with optimum and lethal temperature values of bivalve species, it was possible to find the ideal site, for temperature, for culturing the species, taking into account the variability associated with large-scale phenomena. [source] Improvement of Metabolic Performance of Cultured Hepatocytes by High Oxygen Tension in the AtmosphereARTIFICIAL ORGANS, Issue 1 2001Kennichi Yanagi Abstract: Maintaining metabolic functions of cultured hepatocytes at higher levels is an essential requirement for the development of a bioartificial liver. We investigated the effect of oxygen tension (10,40%) of the medium on immobilization efficiency and metabolic functions of cultured hepatocytes obtained from a rat for up to 4 days. Immobilization efficiencies of cultures in 10% oxygen showed a significantly lower value from those for the other conditions. The ammonium metabolic rate and the albumin secretion rate were significantly improved with an increase of dissolved oxygen tension for up to 2 days. These values remained similar in the later stage of the culture. The urea secretion rate showed similar values in all conditions. In conclusion, higher oxygen tension improved immobilization efficiency and metabolic functions of cultured rat hepatocytes in the earlier stage of culture for up to 2 days. [source] GABAB receptor function in the ileum and urinary bladder of wildtype and GABAB1 subunit null miceAUTONOMIC & AUTACOID PHARMACOLOGY, Issue 3 2002G. J. Sanger Summary1 GABAB1 receptor subunit knockout mice were generated and the effects of the GABAB receptor agonist, baclofen, were evaluated within the peripheral nervous system (PNS) of wildtype (+/+), heterozygote (+/,) and knockout (,/,) animals. For this purpose, neuronally-mediated responses were evoked in both the isolated ileum and urinary bladder, using selective electrical field stimulation (EFS). 2 In ileum resected from 4,8-week-old-mice, low frequencies of EFS (0.5 Hz) evoked irregular muscle contractions which were prevented by atropine 1 ,M and reduced by baclofen (33.4 ± 5.6%, 100 ,m). The latter effect was antagonized by the GABAB receptor antagonist CGP54626 0.2 ,m. Baclofen 100 ,m did not affect contractions of similar amplitude induced by carbachol, indicating that the ability of baclofen to inhibit cholinergic function in mouse ileum may be due to an action at prejunctional GABAB receptors. 3 To avoid the development of grand mal seizure by GABAB1 (,/,) mice, a behaviour observed when the mice were greater than 3 weeks old, it was necessary to study the effects of this knockout in 1,3-week-old-animals. However, at this age, EFS at 0.5 Hz did not evoke robust muscle contractions. Consequently we used EFS at 5 Hz, which did evoke cholinergically mediated contractions, found to be of similar amplitude in (+/+) and (+/,) mice, of both 1,3 weeks and 4,8 weeks of age. At this frequency of EFS, baclofen reduced the amplitude of the evoked contractions [n=6 (+/+) and n=5 (+/,), IC50 19.2 ± 4.8 ,m) and this effect was greatly reduced in the presence of CGP54626 0.2 ,m. 4 In urinary bladder from 1,3-week-old-mice, using higher frequencies of EFS to evoke clear, nerve-mediated contractions (10 Hz), baclofen 10,300 ,m concentration-dependently inhibited contractions in (+/+) mice (IC50 9.6 ± 3.8 ,m). This effect was inhibited by CGP54626 (0.2 ,m, 46.2 ± 13.6% inhibition, 300 ,m baclofen n=7) a concentration which, by itself, had no effect on the EFS-evoked contractions. 5 The effects of baclofen in both ileum and urinary bladder were absent in the GABAB1 receptor subunit (,/,) mice; however, responses to EFS were unaffected in (,/,) when compared to the (+/+) mice. 6 Our data suggest that, as in the central nervous system (CNS), the GABAB1 receptor subunit is an essential requirement for GABAB receptor function in the enteric and PNS. As such, these data do not provide a structural explanation for the existence of putative subtypes of GABAB receptor, suggested by studies such as those in which different rank-orders of GABAB agonist affinity have been reported in different tissues. [source] Iron Absorption: Biochemical and Molecular Insights into the Importance of Iron Species for Intestinal UptakeBASIC AND CLINICAL PHARMACOLOGY & TOXICOLOGY, Issue 3 2002Piero Cremonesi Redox chemistry of iron is particularly important in iron metabolism, both as a potential source of toxic intermediates and as an essential requirement for efficient iron transport. The initial step in iron absorption (uptake from lumen to mucosa) is particularly important and several pathways involving Fe(III) reduction or transport and Fe(II) transport have been identified. Novel genes associated with iron uptake include Dcytb, a putative iron-regulated reductase and DMT1, a Fe(II) carrier in the brush border membrane. Other mechanisms may also operate, however. We review the recent findings and apply this to understanding the absorption of Fe(III) pharmaceuticals. [source] Verbund-Simulation , Strategic Planning and Optimization of Integrated Production NetworksCHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 4 2010T. Viere Abstract Strategic analysis and optimization of highly integrated production networks is an essential requirement for cost-effective and resource-efficient production. This paper presents a comprehensive software-based concept for modeling, simulation, optimization, and visualization of an integrated silicone production network of Wacker Chemie AG. A Verbund-Model was implemented in a step-by-step approach, starting with primary material streams in one business unit up to the modeling of all energy, waste, and cost streams in several business units. The system's flexibility enables different levels of detail for modeling processes and parts of the network: from simple input-output relations to complex, nonlinear equations and specifications. The proactive implementation of technical measures and projects based on the assessment of future scenarios is an important outcome of the Verbund-simulation. [source] Surveillance of antibiotic use in hospitals: methods, trends and targetsCLINICAL MICROBIOLOGY AND INFECTION, Issue 8 2006E. I. Kritsotakis Abstract A standardised antibiotic surveillance system is an essential requirement of all antibiotic control strategies. Antibiotic use can be quantified accurately using patient-level surveillance, although this is not feasible for most hospitals. Instead, population-level surveillance is a more realistic alternative for ongoing and systematic monitoring of antibiotic use. Monitoring of aggregate, ward-supply data on a monthly basis, stratification by patient care area, and analysis by the anatomical therapeutic chemical/defined daily dose (ATC/DDD) system, adjusting for bed-occupancy, provides a clear picture of antibiotic consumption density and time-trends within a hospital. When usage rates are supplemented and interpreted according to changes in hospital resource indicators, benchmarking is facilitated. This provides an efficient tool for triggering and targeting antibiotic control interventions. [source] High-level distribution for the rapid production of robust telecoms software: comparing C++ and ERLANGCONCURRENCY AND COMPUTATION: PRACTICE & EXPERIENCE, Issue 8 2008J. H. Nyström Abstract Currently most distributed telecoms software is engineered using low- and mid-level distributed technologies, but there is a drive to use high-level distribution. This paper reports the first systematic comparison of a high-level distributed programming language in the context of substantial commercial products. Our research strategy is to reengineer some C++/CORBA telecoms applications in ERLANG, a high-level distributed language, and make comparative measurements. Investigating the potential advantages of the high-level ERLANG technology shows that two significant benefits are realized. Firstly, robust configurable systems are easily developed using the high-level constructs for fault tolerance and distribution. The ERLANG code exhibits resilience: sustaining throughput at extreme loads and automatically recovering when load drops; availability: remaining available despite repeated and multiple failures; dynamic reconfigurability: with throughput scaling near-linearly when resources are added or removed. Secondly, ERLANG delivers significant productivity and maintainability benefits: the ERLANG components are less than one-third of the size of their C++ counterparts. The productivity gains are attributed to specific language features, for example, high-level communication saves 22%, and automatic memory management saves 11%,compared with the C++ implementation. Investigating the feasibility of the high-level ERLANG technology demonstrates that it fulfils several essential requirements. The requisite distributed functionality is readily specified, even although control of low-level distributed coordination aspects is abrogated to the ERLANG implementation. At the expense of additional memory residency, excellent time performance is achieved, e.g. three times faster than the C++ implementation, due to ERLANG's lightweight processes. ERLANG interoperates at low cost with conventional technologies, allowing incremental reengineering of large distributed systems. The technology is available on the required hardware/operating system platforms, and is well supported. Copyright © 2007 John Wiley & Sons, Ltd. [source] Erosion modelling approach to simulate the effect of land management options on soil loss by considering catenary soil development and farmers perceptionLAND DEGRADATION AND DEVELOPMENT, Issue 6 2008A. C. Brunner Abstract The prevention of soil erosion is one of the most essential requirements for sustainable agriculture in developing countries. In recent years it is widely recognized that more site-specific approaches are needed to assess variations in erosion susceptibility in order to select the most suitable land management methods for individual hillslope sections. This study quantifies the influence of different land management methods on soil erosion by modelling soil loss for individual soil-landscape units on a hillslope in Southern Uganda. The research combines a soil erosion modelling approach using the physically based Water Erosion Prediction Project (WEPP)-model with catenary soil development along hillslopes. Additionally, farmers' perceptions of soil erosion and sedimentation are considered in a hillslope mapping approach. The detailed soil survey confirmed a well-developed catenary soil sequence along the hillslope and the participatory hillslope mapping exercise proved that farmers can distinguish natural soil property changes using their local knowledge. WEPP-model simulations show that differences in soil properties, related to the topography along the hillslope, have a significant impact on total soil loss. Shoulder and backslope positions with steeper slope gradients were most sensitive to changes in land management. Furthermore, soil conservation techniques such as residue management and contouring could reduce soil erosion by up to 70 percent on erosion-sensitive slope sections compared to that under tillage practices presently used at the study site. The calibrated model may be used as a tool to provide quantitative information to farmers regarding more site-specific land management options. Copyright © 2008 John Wiley & Sons, Ltd. [source] Single-port laparoscopic surgery, the new evolution of endoscopic surgeryASIAN JOURNAL OF ENDOSCOPIC SURGERY, Issue 3 2009H. Rivas Abstract Introduction: Laparoscopic surgery through a single port is gaining great interest throughout the world. Our group has pioneered and been a leader on these novel techniques. Here we describe our experience based on a model of single-port laparoscopic cholecystectomy. Materials and Methods: From January 2008 until August 2009, over 200 patients have undergone single-port laparoscopic surgery at our institution. Here, we analyze a cohort of the initial 100 cholecystectomies in order to evaluate a proposed technique, common challenges, the learning curve and potential solutions. Results: Single-port laparoscopic surgery was feasible in all patients from this cohort. Patients were strictly selected. Operating times similar to those of conventional laparoscopy were only achieved after completing 50 cases. Common technical challenges included clashing instruments, deflection of laparoscope due to conflict with light source, and organ retraction. Acceptance by surgeons and lack of patience and time may become significant obstacles that prevent the procedure's widespread adoption. The excellent aesthetic results are superior to laparoscopy. Other benefits of laparoscopy are preserved and may prove to be superior on clinical trials. Discussion: Single-port laparoscopic surgery is becoming popular worldwide. Safe and successful adoption requires learning the basic concepts of this method, identifying challenges, and implementing solutions. Once these essentials are mastered, the learning curve may be shortened, especially for experienced laparoscopic surgeons, and this technique may then be used to replicate many abdominal operations. Transparency with patients and team building are essential requirements for a successful adoption. Clinical trials are ideal before universal adoption. [source] | |||||||||||||||||||