Net Strength Research Articles

Saccharomyces cerevisiae yeast immobilized on marrow stem sunflower and polyacrylamide hydrogels

Abstract Biocatalysts with microorganisms immobilized on solid carriers could provide the solution for development of continuous industrial processes for ethanol obtaining by fermentation of sugars. In this study, modified polyacrylamide hydrogels and marrow stem sunflower are used as supports for Saccharomyces cerevisiae yeast immobilization. The obtained structures are used for fermentation of molasses in batch systems. The free yeast cells are used as reference. The modification of polyacrilamide matrix with (2-hydroxyethyl)methacrylate has a positive effect on structure pore uniformity and fermentation performance. The mechanical properties of the obtained biocatalysts are compared. The novel natural matrix has net superior compression strength.

Trench Cutter Case Histories and Their Possible Application for Offshore Piles as Relieve Drilling

As of 30th June 2013, according to the European Wind Energy Association, there are 1,939 offshore wind turbines, with a combined capacity of 6,040 MW. They are fully grid connected in European waters in 58 wind farms across 10 countries. About 70 % of the foundations used for wind energy are monopiles with a diameter up to 6 m. The monopiles are installed by using hammers. However, there are situations where the piles cannot be installed without the “driving and drilling technique”, above all in the glacial areas, where glacial tills, boulders or cobbles can be encountered. A new technology for supporting the installation of monopiles is the monopile-trench cutter. The following paper describes four onshore trench cutter case histories in hard geology. Based on several projects, a correlation between net cut performance and uniaxial compressive strength (UCS) values of the in situ rock is briefly described. The variation of the cut performance decreases logarithmically with increasing UCS values. However, the data showed are only based on projects already performed, and it is not possible to extrapolate the data for future projects in similar geological conditions. The findings of this paper want to show how the trench cutter technology might be a suitable technology for supporting monopile installation in difficult sea beds. Besides, the information contained in this manuscript wants to be an aid for contractors involved in offshore pile installation.

Systematic Coarse-Graining of the Dynamics of Self-Attractive Semiflexible Polymers

We develop a coarse-graining procedure, using bead–rod chains with varying numbers of rods per Kuhn length (Nr,K), to model the conformational dynamics of polymer chains with bending stiffness and self-attraction. We find the conditions under which increased chain resolution leads to converged results for the effect of bending stiffness, attractive interaction strength (e), and shearing flow on the conformational dynamics. As chain stiffness increases, we find a collapse transition that becomes steeper as attractive strength increases. The collapsed state depends not only on the net dimensionless attractive strength e* = eNr,K between each Kuhn step of the chain but also on the ratio of bead diameter to Kuhn length (σ*). At high e* (>0.8/σ*), collapsed globules are produced at moderate chain diameter σ* = 1/4, while for fat chains with σ* = 1, helices are formed, and for thin ones with σ* = 1/16, tori, folded bundles, and finally globules are formed as e* increases.

A complete study of bearing stress in single bolt connections

The paper presents experiments on connections with one and two bolts made of mild steel grade S235. The results are compared with the tests on connections made of high strength steel. The test results are substantiated with numerical parametric analysis. The effect of bolt bearing is thoroughly analysed. The bearing strength at bolt holes according to standard EN 1993-1-8 is critically evaluated and a modified design check is proposed. The modified check is conceptually the same as the current one, but it is simpler, less conservative and it is in better correlation to the test results. The block shear strength and net cross-section strength are also discussed and modifications to the EN 1993 design rules are given.

Sleep and the price of plasticity: from synaptic and cellular homeostasis to memory consolidation and integration.

Sleep is universal, tightly regulated, and its loss impairs cognition. But why does the brain need to disconnect from the environment for hours every day? The synaptic homeostasis hypothesis (SHY) proposes that sleep is the price the brain pays for plasticity. During a waking episode, learning statistical regularities about the current environment requires strengthening connections throughout the brain. This increases cellular needs for energy and supplies, decreases signal-to-noise ratios, and saturates learning. During sleep, spontaneous activity renormalizes net synaptic strength and restores cellular homeostasis. Activity-dependent down-selection of synapses can also explain the benefits of sleep on memory acquisition, consolidation, and integration. This happens through the offline, comprehensive sampling of statistical regularities incorporated in neuronal circuits over a lifetime. This Perspective considers the rationale and evidence for SHY and points to open issues related to sleep and plasticity.

Slow Oscillation Amplitudes and Up-State Lengths Relate to Memory Improvement

There is growing evidence of the active involvement of sleep in memory consolidation. Besides hippocampal sharp wave-ripple complexes and sleep spindles, slow oscillations appear to play a key role in the process of sleep-associated memory consolidation. Furthermore, slow oscillation amplitude and spectral power increase during the night after learning declarative and procedural memory tasks. However, it is unresolved whether learning-induced changes specifically alter characteristics of individual slow oscillations, such as the slow oscillation up-state length and amplitude, which are believed to be important for neuronal replay. 24 subjects (12 men) aged between 20 and 30 years participated in a randomized, within-subject, multicenter study. Subjects slept on three occasions for a whole night in the sleep laboratory with full polysomnography. Whereas the first night only served for adaptation purposes, the two remaining nights were preceded by a declarative word-pair task or by a non-learning control task. Slow oscillations were detected in non-rapid eye movement sleep over electrode Fz. Results indicate positive correlations between the length of the up-state as well as the amplitude of both slow oscillation phases and changes in memory performance from pre to post sleep. We speculate that the prolonged slow oscillation up-state length might extend the timeframe for the transfer of initial hippocampal to long-term cortical memory representations, whereas the increase in slow oscillation amplitudes possibly reflects changes in the net synaptic strength of cortical networks.

Growing season and spatial variations of carbon fluxes of Arctic and boreal ecosystems in Alaska (USA)

To better understand the spatial and temporal dynamics of CO2 exchange between Arctic ecosystems and the atmosphere, we synthesized CO2 flux data, measured in eight Arctic tundra and five boreal ecosystems across Alaska (USA) and identified growing season and spatial variations of the fluxes and environmental controlling factors. For the period examined, all of the boreal and seven of the eight Arctic tundra ecosystems acted as CO2 sinks during the growing season. Seasonal patterns of the CO2 fluxes were mostly determined by air temperature, except ecosystem respiration (RE) of tundra. For the tundra ecosystems, the spatial variation of gross primary productivity (GPP) and net CO2 sink strength were explained by growing season length, whereas RE increased with growing degree days. For boreal ecosystems, the spatial variation of net CO2 sink strength was mostly determined by recovery of GPP from fire disturbance. Satellite-derived leaf area index (LAI) was a better index to explain the spatial variations of GPP and NEE of the ecosystems in Alaska than were the normalized difference vegetation index (NDVI) and enhanced vegetation index (EVI). Multiple regression models using growing degree days, growing season length, and satellite-derived LAI explained much of the spatial variation in GPP and net CO2 exchange among the tundra and boreal ecosystems. The high sensitivity of the sink strength to growing season length indicated that the tundra ecosystem could increase CO2 sink strength under expected future warming, whereas ecosystem compositions associated with fire disturbance could play a major role in carbon release from boreal ecosystems.

Pathologist Workforce in the United States: I. Development of a Predictive Model to Examine Factors Influencing Supply

Results of prior pathology workforce surveys have varied between a state of equilibrium and predictions of shortage. To assess the current and future supply of pathologists, and apply a dynamic modeling tool for assessing the effects of changing market forces and emerging technologies on the supply of pathologists' services through 2030. Data came from various sources, including the literature, College of American Pathologists' internal data, and primary research through custom-developed surveys for the membership and for pathology practice managers Through 2010, there were approximately 18 000 actively practicing pathologists in the United States (5.7 per 100 000 population), approximately 93% of whom were board certified. Our model projects that the absolute and per capita numbers of practicing pathologists will decrease to approximately 14 000 full-time equivalent (FTE) pathologists or 3.7 per 100 000 in the coming 2 decades. This projection reflects that beginning in 2015, the numbers of pathologists retiring will increase precipitously, and is anticipated to peak by 2021. Including all types of separation, the net pathologist strength will begin falling by year 2015. Unless workforce entry or exit rates change, this trend will continue at least through 2030. These changes reflect the closure of many training programs 2 to 4 decades ago and the substantially decreased number of graduating residents. This comprehensive analysis predicts that pathologist numbers will decline steadily beginning in 2015. Anticipated population growth in general and increases in disease incidence owing to the aging population, to be presented in a companion article on demand, will lead to a net deficit in excess of more than 5700 FTE pathologists. To reach the projected need in pathologist numbers of nearly 20 000 FTE by 2030 will require an increase from today of approximately 8.1% more residency positions. We believe a pathologist shortage will negatively impact both patient access to laboratory services and health care providers' abilities to deliver more effective health care to their patient populations.

Various ways to strengthen the fiber‐matrix interface for enhanced composite performance

Surface treatment (ST) of carbon fibers (CF) leads to an enhancement in fiber‐matrix adhesion. However, it deteriorates the strength of a fiber which makes its reinforcing action less effective in a composite. These effects in opposite directions control the net strength of a composite, and hence, the treatment has to be judiciously applied, which would enhance the first factor and minimize the second one. Authors have recently reported on four effective techniques (using various doses) such as treatments with nanoparticles of Ytterbium fluoride (YbF3), cold remote nitrogen–oxygen plasma (CRNOP), γ‐ray irradiation and nitric acid oxidation. Amongst these methods, nitric acid oxidation is studied in depth in the literature, and γ‐ray irradiation is sparingly studied. However, nano‐YbF3 and CRNOP were first time reported in the literature by the authors. However, comparative aspects of all these methods were not addressed. In this paper, these aspects in details are discussed to lay down the right criteria for selection of a ST technique of CF to design the desired performance of a composite. The composites with polyetherimide and treated CF (including untreated) were developed and evaluated for various properties including tribological one. Treated CF based composites exhibited excellent mechanical and tribological properties (under harsh operative conditions with wear rates ≈ 1 × 10−15 m3/Nm and μ ≈ 0.09). It was concluded that for strength and tribo‐performance, different treatments and doses are to be employed. Overall nanosized‐YbF3 treatment of CF proved to be the most promising ST method. Copyright © 2013 John Wiley & Sons, Ltd.

Influence of fiber–matrix interface on abrasive wear performance of polymer composites

* Present address: MED, Shri G S Institute of Technology & Science, 23, Park Road, Indore, Madhya Pradesh 452003, India. Surface treatment of carbon fibers (CFs) is an excellent way to enhance the fiber–matrix adhesion. However, this is generally at a cost of deterioration in the strength of a fiber. The two effects in opposite directions control the net strength of a composite. The weightage of each factor depends on the selected method and dose. Authors have recently reported on three fiber-treatment techniques (using various doses) such as that with nano-YbF3 (new method); cold remote nitrogen–oxygen plasma (newer one) and γ rays apart from one traditional method of acid oxidation of a fiber. In the present paper, comparative aspects (benefits and limitations) of all these four methods are discussed to enable a right selection of a surface treatment technique of CF to design the composite with a right combination of strength and wear resistance in abrasive wear mode. The composites with these surface treated fabrics and polyetherimide matrix were developed and evaluated for various properties including abrasive wear performance. Specific wear rate of HNO3 treated composite was lowest among these composites while plasma treated composites showed least improvement. Scanning electron microscope (SEM) analysis of worn surfaces showed mechanisms responsible for improved performance of treated composites and high wear rate of untreated composites.

Further Study on the Net Shear Strain Energy Density Theory

The net shear strain energy density strength theory was systematically explained. Firstly, the composition of elastic strain energy and the roles of their own were analyzed, and it is pointed out that the distortion strain energy is the energy driving failure and the volumetric strain energy can help improve the material strength. Therefore, ultimate energy driving material damage should be the shear strain energy after deducting the friction effect, namely the net shear strain energy, which indicates rationality of the assumption adopted by the net shear strain energy strength theory. Secondly, the empirical laws of geomaterial strength were summarized and explained by using the net shear strain energy theory, which verifies the new theory is appropriate.

Intraoperative hypercoagulability during liver transplantation as demonstrated by thromboelastography

Thrombotic complications are more common in liver disease than might be expected because of the coagulopathy described by conventional coagulation tests. Some of these complications may be life-threatening. The phenomenon of hypercoagulation is associated with complications in many populations, but the incidence in liver transplant recipients is unclear. We performed a retrospective database review of intraoperative thromboelastography (TEG) for 124 liver transplant recipients. We assessed the prevalence of hypercoagulation in this group and investigated the relative frequency of both shortened TEG reaction times (R times) and increased net clot strength (G) values. These findings were correlated with thrombotic complications. At the baseline, the prevalence of high G values was 15.53% on native TEG, and the prevalence of shortened R times was 6.80% on native-heparinase TEG. Patients with cholestatic pathologies had particularly high rates of hypercoagulation (42.9% with primary biliary cirrhosis and 85.7% with primary sclerosing cholangitis), but hypercoagulation was also common in patients with fulminant hepatic failure (50%) and nonalcoholic steatohepatitis (37.5%). There was a poor correlation between the TEG R time and the international normalized (INR), with 37.7% of TEG analyses demonstrating a short R time with an INR > 2. Six of the patients developed early hepatic artery thrombosis (5%); 3 of these patients had TEG evidence of high G values (P = 0.25), and 4 had short R times (not significant). In conclusion, intraoperative TEG evidence of high G values and short R times is relatively common in liver transplantation. It is unclear what bearing this condition has on thrombotic complications. Conventional coagulation tests have no ability to diagnose this condition. It is conceivable that such patients may come to harm if hypercoagulability is unrecognized and, therefore, inappropriately managed.

Dynamics of a vortex pair interacting with a fixed point vortex

The dynamics of a vortex pair consisting of two counter-rotating point vortices encountering a fixed point vortex in a uniform medium is addressed. This problem is of interest in part because such an interaction occurs frequently in geophysical flows. The vortex pair is shown to exhibit two different regimes of motion. First, the localized motion (entrapping of the vortex pair), when the pair moves periodically in the vicinity of the fixed vortex. Second, the unrestricted motion, when the pair moves unrestrictedly to infinity. The realization of one of the regimes is demonstrated to be conditional on parameters determined by the asymmetry in the initial positions of the pair's vortices, and the ratio of the fixed vortex's strength and the pair's strength. We show, that unlike the classical three-vortex problem, the regime of unrestricted motion appears even if the net strength of the vortex system is not equal to zero.

High-spin resonant states in 16O

α+12C elastic scattering in the energy range Ec.m. = 21.15–26.625 MeV is analyzed by the optical model with parity-dependent potential. The characteristic features enhanced by Coulomb scattering appear to be reproduced. The volume integral of the potential, which indicates the net strength of interactions between nuclei, seems to be consistent with those from other studies and it gives a smooth energy variation from high to low energies. The 9− state is found to occur at Ec.m. ≈ 23.0 MeV, corresponding to the excitation energy Ex ≈ 30.2 MeV. It is possible that the 8+ resonance was observed at Ex ≈ 29 MeV with a large width. The α+12C rotational band can survive even at high excitation energies. The rotational band starting from the 0+2 state (Ex = 6.05 MeV) is confirmed to have N = 8; the odd-parity band, N = 9.

Stabilization of Memory States by Stochastic Facilitating Synapses

Bistability within a small neural circuit can arise through an appropriate strength of excitatory recurrent feedback. The stability of a state of neural activity, measured by the mean dwelling time before a noise-induced transition to another state, depends on the neural firing-rate curves, the net strength of excitatory feedback, the statistics of spike times, and increases exponentially with the number of equivalent neurons in the circuit. Here, we show that such stability is greatly enhanced by synaptic facilitation and reduced by synaptic depression. We take into account the alteration in times of synaptic vesicle release, by calculating distributions of inter-release intervals of a synapse, which differ from the distribution of its incoming interspike intervals when the synapse is dynamic. In particular, release intervals produced by a Poisson spike train have a coefficient of variation greater than one when synapses are probabilistic and facilitating, whereas the coefficient of variation is less than one when synapses are depressing. However, in spite of the increased variability in postsynaptic input produced by facilitating synapses, their dominant effect is reduced synaptic efficacy at low input rates compared to high rates, which increases the curvature of neural input-output functions, leading to wider regions of bistability in parameter space and enhanced lifetimes of memory states. Our results are based on analytic methods with approximate formulae and bolstered by simulations of both Poisson processes and of circuits of noisy spiking model neurons.

Evaluation on net strength and arresting performance of aircraft arresting system by FE method

PurposeThe purpose of this paper is to provide an effective way to evaluate structure strength margin of AAS (aircraft arresting system) barrier net and efficiency of its control scheme.Design/methodology/approachA numerical method to deal with barrier net strength design of AAS by means of nonlinear finite element (FE) has been used in this paper. The key of the simulation is that a special technique is proposed to cope with the arresting forces exerted on the tapes as boundary conditions, so the time history of stress/force distribution of AAS key components can be obtained. Also some techniques measures are taken to ensure good numerical convergence for this complex nonlinear system.FindingsThe simulation results cannot only provide the general important performance indexes of AAS, such as run‐out distance and the maximum deceleration of the arrested aircraft, but also present stress or force contours of barrier net, tapes and aircraft, etc. therefore it is easy to evaluate the component's strength when a specific control scheme is adopted.Practical implicationsFrom component/structure strength perspective, this paper gives a practical engineering design method to evaluate performance of AAS.Originality/valueThe paper is probably the first to give a method which can evaluate AAS components strength considering their 3D geometry, and also its control scheme. The method has been validated through experimental results.

Temperature Dependence of Water Interactions with the Amide Carbonyls of α-Helices

Hydration is a key determinant of the folding, dynamics, and function of proteins. In this study, temperature-dependent Fourier transform infrared (FTIR) spectroscopy combined with singular value decomposition (SVD) and global fitting were used to investigate both the interaction of water with α-helical proteins and the cooperative thermal unfolding of these proteins. This methodology has been applied to an isolated α-helix (Fs peptide) and to globular α-helical proteins including the helical subdomain and full-length villin headpiece (HP36 and HP67). The results suggest a unique IR signature for the interaction of water with the helical amide carbonyl groups of the peptide backbone. The IR spectra indicate a weakening of the net hydrogen bond strength of water to the backbone carbonyls with increasing temperature. This weakening of the backbone solvation occurs as a discrete transition near the maximum of the temperature-dependent hydrophobic effect, not a continuous change with increasing temperature. Possible molecular origins of this effect are discussed with respect to previous molecular dynamics simulations of the temperature-dependent solvation of the helix backbone.

RbxBayMn[3-(x + 2y)]/2[Fe(CN)6]·zH2O prussian blue analogues: Controlling magnetic ordering by alkaline earth metal cation substitution and magnetic field

We have controlled the nature of magnetic ordering in RbxBayMn[3-(x + 2y)]/2[Fe(CN)6]·zH2O prussian blue analogues by alkaline earth metal cation (Ba2+) substitution and application of an external magnetic field. Structural analysis, by employing Rietveld refinement of X-ray and neutron diffraction patterns, reveals a tetragonal crystal structure for all these compounds. The presence of Fe3+-C ≡ N-Mn2+ chains in the structure, and absence of both cyanide flipping (Mn2+-C ≡ N-Fe3+) and charge transfer from Mn2+ to Fe3+ (Fe2+-C ≡ N-Mn3+) have been confirmed by infrared and Mössbauer studies. The analysis of the low temperature neutron powder diffraction data reveals a long-range antiferromagnetic ordering in these compounds. The magnetic structure is layered, consisting of an antiparallel stacking of ferromagnetic sheets along the crystallographic c-direction. Within each sheet in the ab plane, the ordered moments of Mn2+ [5.04(1) μB for (x = 0.84, y = 0) and 4.99(7) μB for (x = 0.19, y = 0.3) sample at 1.5 K] and Fe3+ [0.98(3) μB for (x = 0.84, y = 0) and 0.99(3) μB for (x = 0.19, y = 0.3) sample at 1.5 K] are aligned ferromagnetically along the c-axis. Interestingly, dc magnetization study indicates that on application of an external magnetic field, an antiferromagnetic to ferrimagnetic-like phase transition occurs below ∼5 K. This phase transition becomes more and more prominent with increasing magnetic field as well as for higher Ba substitution. The role of a number of factors (such as ionic radius of Ba2+ ion and change in net ligand strength around Mn due to chemical insertion of Ba2+ ions) on the affecting nature of magnetic ordering has been discussed. The observed magnetism in these compounds is seen in light of the orbital model of superexchange interaction between magnetic ions (Mn2+ and Fe3+) mediated by cyanide ligands.

Tensile failure of two-dimensional quasi-brittle foams

Stress redistribution caused by damage onset and the subsequent local softening plays an important role in determining the ultimate tensile strength of a cellular structure. The formation of damage process zones with struts dissipating a finite amount of fracture energy will require the macroscopic stress to be increased in order to continue structural damage. The goal of this paper is to investigate the influence of the fracture energy of the solid on the tensile fracture strength and the strain to fracture in quasi-brittle two-dimensional foams using a microstructural model. We analyze the mesoscopic damage and failure mechanisms in uniaxial tension. Relative density, strut cross-sectional profile, solid’s fracture strain, and fracture energy are varied systematically. The effect of the specific fracture energy on the peak behavior has been shown to be captured by the ratio of the fracture energy to the stored elastic energy. We have also explored the net section strength variation in the presence of a central crack at two different fracture energies. Comparison is made between two structurally identical quasi-brittle and ductile strain hardening foams to identify the differences in the damage mechanisms.

Climate Sensitivity of the Community Climate System Model, Version 4

Equilibrium climate sensitivity of the Community Climate System Model, version 4 (CCSM4) is 3.20°C for 1° horizontal resolution in each component. This is about a half degree Celsius higher than in the previous version (CCSM3). The transient climate sensitivity of CCSM4 at 1° resolution is 1.72°C, which is about 0.2°C higher than in CCSM3. These higher climate sensitivities in CCSM4 cannot be explained by the change to a preindustrial baseline climate. This study uses the radiative kernel technique to show that, from CCSM3 to CCSM4, the global mean lapse-rate feedback declines in magnitude and the shortwave cloud feedback increases. These two warming effects are partially canceled by cooling because of slight decreases in the global mean water vapor feedback and longwave cloud feedback from CCSM3 to CCSM4. A new formulation of the mixed layer, slab-ocean model in CCSM4 attempts to reproduce the SST and sea ice climatology from an integration with a full-depth ocean, and it is integrated with a dynamic sea ice model. These new features allow an isolation of the influence of ocean dynamical changes on the climate response when comparing integrations with the slab ocean and full-depth ocean. The transient climate response of the full-depth ocean version is 0.54 of the equilibrium climate sensitivity when estimated with the new slab-ocean model version for both CCSM3 and CCSM4. The authors argue the ratio is the same in both versions because they have about the same zonal mean pattern of change in ocean surface heat flux, which broadly resembles the zonal mean pattern of net feedback strength.