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We develop a framework for analysing the outcome of resource competition based on
bifurcation theory. We elaborate our methodology by readdressing the problem of
competition of two species for two resources in a chemostat environment. In the case of
perfect-essential resources it has been extensively discussed using Tilman’s
representation of resource quarter plane plots. Our mathematically rigorous analysis
yields bifurcation diagrams with a striking similarity to Tilman’s method including the
interpretation of the consumption vector and the resource supply vector. However, our
approach is not restricted to a particular class of models but also works with other
trophic interaction formulations. This is illustrated by the analysis of a model
considering interactively-essential or complementary resources instead of
prefect-essential resources. Additionally, our approach can also be used for other
ecosystem compositions: multiple resources–multiple species communities with equilibrium
or oscillatory dynamics. Hence, it gives not only a new interpretation of Tilman’s
graphical approach, but it constitutes an extension of competition analyses to communities
with many species as well as non-equilibrium dynamics.
Fusarium wilt caused by Fusarium oxysporum, Schlecht. emend. Snyd. & Hans. f. sp. ciceri is prevalent in most chickpea-growing countries and is a major devastating disease. Host plant resistance is the most practical method of disease management. Indigenous chickpea germplasm reveals a heterogeneous genetic make-up and the response of resistance to wilt is an unexplored potential source for disease resistance. There are 70 indigenous germplasm lines selected on the basis of their agronomic performance and diverse areas of collections in the country. Of these, four accessions had a highly resistant score of 1 and six had a score of 3 using a 1–9 rating scale, indicating their level of resistance to Fusarium wilt (race 4). Other germplasm accessions of chickpea were found to be moderately resistant to highly susceptible disease reaction. Likewise, the same set of germplasm was also screened for Meloidogyne incognita (race 1) using pot culture under controlled condition. Only one accession was found to be resistant to this pest. These resistant gene sources can be utilised effectively for race-specific chickpea wilt and root-knot resistance breeding programmes.
A temporal relationship of Japanese encephalitis virus (JEV) transmission in pigs, mosquitoes and humans revealed that sentinel pig seroconversions were significantly associated with human cases 4 weeks before (P = 0·04) their occurrence, highly correlated during the same time and 2 weeks before case occurrence (P < 0·001), and remained significantly correlated up to 2 weeks after human case occurrence (P < 0·01). JEV was detected in the same month in pigs and mosquitoes, and peaks of pig seroconversion were preceded by 1–2 months of peaks of infection in vectors. Kaplan–Meier analysis indicated that detection of JEV-positive mosquitoes was significantly associated with the median time to occurrence of seroconversion in pigs (P < 0·05). This study will not only help in predicting JEV activity but also accelerate timely vector control measures and vaccination programmes for pigs and humans to reduce the Japanese encephalitis risk in endemic areas.
The excess mortality following first-contact psychosis is well recognized. However, the causes of death in a complete incidence cohort and mortality patterns over time compared with the general population are unknown.
All 2723 patients who presented for the first time with psychosis in three defined catchment areas of the UK in London (1965–2004, n=2056), Nottingham (1997–1999, n=203) and Dumfries and Galloway (1979–1998, n=464) were traced after a mean of 11.5 years follow-up and death certificates were obtained. Data analysis was by indirect standardization.
The overall standardized mortality ratio (SMR) for first-contact psychosis was 184 [95% confidence interval (CI) 167–202]. Most deaths (84.2%, 374/444) were from natural causes, although suicide had the highest SMR (1165, 95% CI 873–1524). Diseases of the respiratory system and infectious diseases had the highest SMR of the natural causes of death (232, 95% CI 183–291). The risk of death from diseases of the circulatory system was also elevated compared with the general population (SMR 139, 95% CI 117–164) whereas there was no such difference for neoplasms (SMR 111, 95% CI 86–141). There was strong evidence that the mortality gap compared with the general population for all causes of death (p<0.001) and all natural causes (p=0.01) increased over the four decades of the study. There was weak evidence that cardiovascular deaths may be increasing relative to the general population (p=0.07).
People with first-contact psychosis have an overall mortality risk that is nearly double that of the general population. Most excess deaths are from natural causes. The widening of the mortality gap over the last four decades should be of concern to all clinicians involved in delivering healthcare.
In the work presented here atomic force microscopy (AFM) based mechanical mapping techniques - HarmoniX imaging and Peak Force Tapping - were applied to determine the surface elastic modulus of phase separated polyurethanes and silica reinforced rubbers across the length scales. Segmented polyether polyurethanes (PUs) were prepared with varying stoichiometric ratio of the isocyanate and hydroxyl groups. The effect of molar mass, as well as the type and number of end-groups on their morphology was investigated. Smooth PU samples for AFM imaging were prepared by ultramicrotonomy. The micro phase separated morphology of the phase separated PUs showed characteristic “fingerprint” AFM phase images. Surface modulus values obtained by AFM were compared to bulk modulus values obtained by tensile testing. The moduli were mapped quantitatively with nanoscale resolution and were in excellent agreement for both AFM modes. Surface mean moduli values do not coincide with bulk values obtained via tensile testing which is attributed to fundamentally different averaging procedures and effects that lead to the respective modulus values obtained via surface and volume averaging. EPDM and SBR rubbers and rubber blends thereof were prepared with varying concentrations of silica nanoparticles and studied in order to investigate the effect of different composition on the resulting morphology (filler distribution) and elastic moduli on a specific rubber or rubber blend sample. Elastic moduli of the rubber and rubber blend samples were first measured by bulk tensile testing. The morphology of the rubber samples was visualized by height and phase imaging. Surface elastic moduli of silica reinforced rubbers and rubber blends were mapped quantitatively and compared with bulk tensile test results. AFM allowed the determination of modulus distributions at the sections imaged. As potential reasons for the observed differences between bulk and surface modulus different averaging procedures like surface and bulk averaging of AFM vs. tensile testing, different filler distributions in SBR and EPDM and the AFM modulus calibration procedures can be named.
Following earlier work of Huggins and Nix [Ionics6, 57 (2000)], several recent theoretical studies have used the shrinking core model to predict intraparticle Li concentration profiles and associated stress fields. A goal of such efforts is to understand and predict particle fracture, which is sometimes observed in degraded electrodes. In this paper we present experimental data on LiCoO2 and graphite active particles, consistent with previously published data, showing the presence of numerous internal pores or cracks in both positive and negative active electrode particles. New calculations presented here show that the presence of free surfaces, from even small internal cracks or pores, both quantitatively and qualitatively alters the internal stress distributions such that particles are prone to internal cracking rather than to the surface cracking that had been predicted previously. Thus, the fracture strength of particles depends largely on the internal microstructure of particles, about which little is known, rather than on the intrinsic mechanical properties of the particle materials. The validity of the shrinking core model for explaining either stress maps or transport is questioned for particles with internal structure, which includes most, if not all, secondary electrode particles.
Going from a small scale laboratory invention or discovery to a large scale application is not a trivial task and incorporating them into a product for a viable business is even more difficult. As technologies approach final products and applications, the number of criteria it must meet increases exponentially. Economics of the manufacturing process, environmental issues, intellectual property management, etc. needs to be assessed and monitored carefully. Bridging the gap from research to business not only needs multi-disciplinary understanding of the various aspects of the technology, but also how and what it could potentially enable or replace in current technologies and how to go about it through partnerships with global business entities. Especially with new materials, such as nano-scale materials, technology push needs to be rigorous and often the end results are uncertain. One needs to start from a large number of end user applications and narrow down to 1-2 high value-add or high volume opportunities. This process also requires constant development of the existing products to meet the exact needs for the high opportunity end markets. Timing for such efforts is crucial and the resources needed for such activities are often under-estimated by small start-up firms. Even for materials with well understood end products and established markets, significant market pull requires huge investments in product reliability demonstrations, cost of manufacturing, etc. Innovation, flexibility, change, educated risk, adaptability, focus and excellence are all key drivers and necessary ingredients for a successful and sustainable start-up venture. While scientific and engineering innovations are absolutely necessary, the metric for success for any business is revenue generation. Finding the right mechanisms for closing this gap (so-called the valley of death) is where the innovations of entrepreneurs lies. In this paper, I will share some of my personal learning experiences through the start-up company Applied Nanoworks Inc., (now Auterra Inc.).
The multilayers of ferroelectric (FE) Pb(Zr, Ti)O3 (PZT) and ferromagnetic (FM) CoFe2O4 (CFO) thin films with 3, 5, and 9 layers having configurations PZT/CFO (PC) and CFO/PZT (CP) were fabricated by pulsed laser deposition technique. We have investigated the effect of inter-diffusion at the interface of multilayers (MLs) and reversing the order of FE and FM layers in the multilayers configuration on the electrical/magnetic properties. The TEM of the films showed that the layer structure was not maintained and the inter-diffusion of the CFO into PZT and vice verse were observed at the interface of MLs. Both the PC and CP configurations of multilayer films exhibited pseudo FE hysteresis loop and proper FM hysteresis loops at room temperature. Reversing the multilayer configuration from CP to PC resulted in increasing the pseudo remanent polarization, however this behavior was not observed in magnetic properties. The frequency and temperature dependences of the impedance and modulus spectroscopy of the multilayer PC and CP films were studied in the ranges of 102 to 106 Hz and 200 to 650 K respectively. The electrical response of all multilayer films investigated could be resolved into two contributions. We attributed these to the grain and grain boundary effects in impedance and modulus formalism. We found that the difference between the grain and grain boundary capacitive effect decreased due to increase of the number of layers.
Recent developments in our laboratory related to polymer-based light sensors are reviewed. The inherent processibility of the active polymer medium is utilized in the implementation of different designs for the opto-electronic applications. The utility of these devices as sensitive photodetectors, image sensors and position sensitive detectors is demonstrated. The schottky-type layer formation at interfaces of polymers such as polyalkylthiophenes and aluminum accompanied by the enhanced photo-induced charge separation due to high local electric field is tapped for some of these device structures. The sensitivity of polymer-based field effect transistors to light also provides a convenient lateral geometry for efficient optical-coupling and control of the transistor state. The range of these polymer-detectors available with the option of operating in the diode and transistor modes should be an attractive feature for many potential applications.
The main aim of this paper is to obtain optimality conditions for a constrained set-valued optimization problem. The concept of Clarke epiderivative is introduced and is used to derive necessary optimality conditions. In order to establish sufficient optimality criteria we introduce a new class of set-valued maps which extends the class of convex set-valued maps and is different from the class of invex set-valued maps.
Radio-frequency (RF) photoreflectance measurements and one-dimensional device simulations have been used to evaluate bulk recombination parameters and surface recombination velocity (SRV) in doubly-capped 0.55-eV p-InGaAsSb epitaxial layers, doped at 2 × 1017 cm-3, for thermophotovoltaic (TPV) applications. Bulk lifetimes of 90 to 100 ns and SRVs of 680 cm/s to 3200 cm/s (depending on the capping layer) are obtained, with higher doping and higher bandgap capping layers most effective in reducing SRV. RF photoreflectance measurements and one-dimensional device simulations are compatible with a radiative recombination coefficient (B) of 3 × 10-11 cm3/s and Auger coefficient (C) of 1 × 10-28 cm6/s.
Back-end interconnect structures (BEIS) of micro-electronic devices are susceptible to several deformation phenomena during thermal excursions, because of large differences in thermal expansion coefficients (CTE) between Si, interlayer dielectric (ILD) and metal lines. Here we use atomic force microscopy (AFM) to study plastic deformation and interfacial sliding of Cu interconnect lines on embedded in a low K dielectric (LKD). Following thermal cycling, changes were observed in both inplane Cu line dimensions, as well as out-of plane step height between Cu and LKD in single layer structures. The results of AFM measurements following both ex-situ and in-situ thermal cycling presented. A shear-lag based model is utilized to simulate the thermal cycling response, and rationalize the observed interfacial sliding behavior. Results of in-situ AFM experiments to observe the deformation of Cu-low K interconnect structures under far-field (i.e., package-level) stresses are also presented.
Deformation of interconnect structures at the back-end of microelectronic devices during processing or service can have a pronounced effect on component reliability. Here, we use atomic force microscopy (AFM) to study plastic deformation and interfacial sliding of Cu interconnects lines on Si. The behavior of both stand-alone Cu lines and lines embedded in a low K dielectric was studied. Following thermal cycling, changes were observed in the in-plane Cu line dimensions, as well as the out-of plane step height between Cu and dielectric in single layer structures. These were attributed to differential deformation of the Cu/Si and Cu/dielectric material pairs due to thermal expansion mismatch, accommodated by interfacial creep. These results are discussed in light of previous work on the mechanism of interfacial creep. Some preliminary results on the distortion of Cu lines due to package-level stresses are also presented.
We have studied the structural evolution in amorphous and microcrystalline silicon deposited from silane-argon mixture by radio frequency plasma enhanced chemical vapour deposition (PECVD) method. Sharp increase in small angle x-ray scattering (SAXS) intensity, in accordance with tilt measurements, indicates columnar morphology in the sample deposited in the amorphous-microcrystalline transition region. The variation of SAXS measured heterogeneity and a gradual shift of Si-H stretching vibrational frequency at 2000 cm-1 towards higher wave number with increase of power density indicate structural modifications in the films. Observation of sharp increase in the ratio of the intensity of Ar* to SiH* in the transition region may explain the surface modification assisted by Ar* and hence the structural changes in the material.
The aim of the present study was to investigate the effects of stearic acid-, oleic acid- and linoleic acid-rich meals on postprandial haemostasis in young healthy volunteers whose background diets had been controlled for 14 d in a residential study. Six healthy male volunteers were assigned randomly to consume diets rich in stearic acid, oleic acid or linoleic acid for 14 d. On day 15, plasma lipids and haematological variables were measured in the fasted state, and 3 and 7 h (factor VII and prothrombin activation peptide fragments, 1 and 2 only) after consumption of a test meal. Test meals provided 40 % of the subjects' daily energy requirement, with 41 % of the energy provided as fat, 17 % energy as protein and 42 % energy as carbohydrate. The mean fat content of the meal was 45 (SD 5) g. Significant alterations from fasted values were observed for activated factor VII (P<0·05 after 7 h), factor VII antigen (P<0·05 after 7 h), prothrombin activation peptide fragments 1 and 2 (P<0·05 after 7 h) and plasminogen activator inhibitor type 1 activity (P<0·01 after 3 h) after consumption of each of the three meals. No significant differences were observed in haemostatic values (factor VII coagulant activity, factor VII antigen, tissue plasminogen activator activity prothrombin activation peptide fragment and plasminogen activator inhibitor type-1) with regard to diet except for activated factor VII at 3 h; values were higher after the oleic acid- and linoleic acid-rich meals than after the stearic acid-rich meal (P<0·05). After consumption of each of the three meals, chylomicrons contained proportionately more palmitic acid than the lipids ingested. The present study shows that there are demonstrable changes in postprandial haemostasis when young healthy volunteers with controlled dietary backgrounds are challenged with a physiological fat load. These changes are independent of the fatty acid composition of the test meals.
Thin a-Si:H films, with a thickness of 1 µm, with different hydrogen concentrations, prepared by hot wire deposition were crystallized by 514.5 nm cw Ar ion laser radiation, with a power density between 150 and 270 kW/cm2. The crystallization was continuously monitored by Raman spectroscopy for exposures up to hours. The analysis of crystallization process using Johnson-Mehl phenomenological equations showed an apparent crystallization energy of around 0.5 eV and low dimensional crystal growth. The mean value of the crystal size decreases with increasing irradiation energy and initial hydrogen content and varies between 3 and 6 nm.