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Interface mixing in [Fe/Cr/Al]x10 multilayer is studied under 120 MeV Ag9+swift heavy ions (SHIs) irradiation. The multilayers with different thicknesses were deposited using electron beam evaporation technique. The SHIs induced modifications in structural and magnetic properties were examined with X-ray reflectivity (XRR), magneto-optic Kerr effect (MOKE), and X-ray absorption fine structure (XAFS) to reveal interface diffusivity, including variation in magnetic coercivity, in-plane anisotropy, and local structure. The height of 1st order Bragg peak of XRR is used to determine the diffusion length as a function of ion fluence, and it is evident that the lower thickness of [Fe/Cr/Al]x10 multilayer possesses higher interface mixing as compared to samples with higher thickness. MOKE results confirm that both multilayers are soft magnetic in nature and show different behavior of in-plane anisotropy. With the SHIs irradiation, coercivity exhibits opposite trends for different thicknesses of Fe/Cr/Al multilayers due to different interface mixing. Fe K-edge XAFS is used for quantitative analysis of the Fe-Cr and Fe-Al phases as a function of multilayer thickness and ion fluence. The inelastic thermal spike (i-TS) model with size effect is used to explain the observed thickness-dependent intermixing due to the SHIs irradiation. The lattice temperature evaluation calculated by i-TS model shows longer spike duration in thinner film resulting in higher mixing.

The refining characteristics of the highly concentrated water-in-oil emulsion, which are used as ‘emulsion precursors’ for the preparation of emulsion explosives, were investigated to elucidate the manner in which the refining time influences its microstructure and rheological behaviour. The development of microstructure at various stages of the emulsification process has been studied in detail and an empirical correlation between the characteristic droplet size and refining time has been proposed. The evolution of rheological characteristics of the emulsion during the microstructure refinement has been investigated through different protocols of the dynamic and steady-state rheology. An extended refining led to a finer microstructure and resulted in an increase in the elastic modulus, yield stress and viscosity of the emulsion. The droplet size dependency of the elasticity and the yield stress during the refining have also been discussed. The network structure of the dispersed phase, the droplet size and the corresponding interdroplet interactions all govern the rheological characteristics of the final emulsion.

Thermotropic liquid crystalline polymer (LCP) was melt-mixed with multi-walled carbon nanotubes (MWCNTs) in a conical micro-compounder. The state of dispersion of MWCNTs in the LCP matrix was characterized using transmission electron microscopy. FIR spectroscopic analysis revealed the nature of interaction between the LCP phase and the MWCNTs. The rheological properties of the nanocomposites showed a significant dependence on the MWCNTs content. The 'network-like' structures could be assigned to 'nanotube-nanotube' and 'polymer-nanotube' interactions. Nanoindentation studies indicated an increase in Young's modulus and hardness of LCP/MWCNTs composites. DMTA studies showed an increase in the storage modulus in the composites as a function of nanotube content. (C) 2017 Elsevier Ltd. All rights reserved.

Heterogeneous catalyst design in environmental systems involve optimization of both the support and the active (nanoparticle-catalyst), impregnated within the support, in order to drive the reaction rate to be maximum for faster pollutant removal; of which, rhodamine B dye degradation has been used to illustrate the outcome of this work. In this regard, to first compare the role of pore-orientation in mesoporous silica support, we synthesized: (i) radial pore containing nano-spherical silica (RPNS) and (ii) axial pore containing cylindrical silica particles (of SBA-15). RPNS was found to give higher degradation rate, with simultaneously optimized 36.7 wt.% of TiO2 nano-catalyst in RPNS; thereby also addressing optimization of the loading amount of the active. This system achieved, as much as, 58% increased photocatalytic rate than SBA-15, with the same TiO2 content; with RPNS being also better than the commercial TiO2 catalyst (P25 Degussa). This is attributed to number of pores in RPNS being 4.6 times more than that in SBA-15, with all RPNS pores being aligned with the incident photon due to its radial orientation, compared to SBA-15, where in contrast, most part of the pores are hidden from incident photons. UV–-Vis powder spectroscopy ruled out the alternative possibility that, transmission of incident light in RPNS could be higher compared to light-absorption, which could have possibly favoured higher available photon-flux in RPNS. Therefore, it is the difference in pore orientation (namely radial pores being better than axial), which causes better photocatalysis by TiO2 containing RPNS. Thus, the right pore-orientation in substrate, coupled with optimum catalyst loading, can significantly improve performance in any diffusion, adsorption, reaction-driven system, which would play out similarly in heterogenous catalysis of any pollutant.

ZnO nanorod structures were deposited on micrometer interdigitated Au electrodes to function as three-dimensional matrixes for the immobilization of antibodies in a capacitive immunosensor format. As a proof of concept, anti-horseradish peroxidase (anti-HRP) antibodies were immobilized on the ZnO nanostructured surface by a crosslinking process. The ZnO nanorod layer allows distribution of antibodies across the entire region probed by the measuring electric field applied to the microelectrodes. This is an alternative approach to the use of more expensive nanometer electrodes necessary in the detection of smaller layers of antibodies. The new micrometer interdigitated capacitive immunosensor was able to discriminate between HRP antigen in buffer; a non-specific antigen in buffer; or buffer alone, as proven by capacitance measurements. Maximum response of the sensor was achieved in the 5–6 kHz frequency range, opening the possibility for a simplified single frequency detection system for direct antigen detection in complex biological samples.

We have studied the optimal deposition conditions for the production of low-oxygen-content Zinc nitride films (ZnON) by Pulsed Laser Deposition (PLD). In particular, substrate temperature has been varied between 100 and 500 °C. The film properties, particularly its morphology, showed a strong dependence on substrate temperature. Substrate temperatures beyond 350 °C led to highly crystalline and smooth films with a band gap of 3.32 eV and with resistivities ranging from 10 -2 to 100 Ωcm. Film quality and surface oxygen content changed rapidly with exposure to air as evidenced by XPS analysis.

SBA-15 of high specific surface area (507 m2/g) and pore volume (1.05 cm3/g) [due to the presence of hexagonally arranged 8.26 nm pore diameter], was synthesized by sol-gel method and impregnated with different mole ratios of Sn to Ti, in order to prepare TiO2-SBA-15, Sn0.05Ti0.95O2-SBA-15, Sn0.08Ti0.92O2-SBA-15 and SnO2-SBA-15 photocatalysts. The average SBA-15 particle diameter was 740 nm. Impregnation of photocatalyst inside the SBA-15 pores were confirmed by electron microscopy and pore-size measurement. The anatase phase of TiO2-SBA-15 shifted to an anatase-rutile phase, after Sn-doping. A decrease of impregnated catalyst size (amongst the four catalysts), from 6.7 to 6.1 nm, due to lattice strain was confirmed by X-ray diffraction. From X-ray photoelectron spectroscopy, the oxidation states for TiO2-SBA-15 and SnO2-SBA-15 were found to be Ti4+ and Sn4+, respectively. It remained unchanged after Sn-doping of catalyst too. Subsequent UV-light based photocatalytic degradation of Rhodamine B, an organic pollutant, was conducted under various pH conditions. At pH 4.5, amongst these catalysts, Sn0.05Ti0.95O2-SBA-15 shows the highest activity (pseudo-first order kinetic rate constant of 1.36 h−1). The intermediate products during degradation were identified by HR-LC/MS and GC/MS. The temporal changes in Rhodamine B concentration both from UV-Vis absorbance and HR-LC/MS measurements were consistent too.

Anopheles (Cellia) maculatus is considered a group of at least nine formally named species. Faced with the difficulty of correct morphological identification due to overlapping characters, several member species of the An. maculatus group are known to play important role in malaria transmission in the Oriental region. Current assemblage, distribution and vectorial importance of the member species within the Maculatus group is far from clear in the north-eastern region of India. Our study encompassing 410 individuals, collected from 67 geo-referenced spots across the eight north-east Indian states, identified the presence of 6 member species of the Maculatus group using the molecular tools. Anopheles dravidicus and Anopheles rampae were documented for the first time in this part of India with latter forming the new country record. While Anopheles pseudowillmori (59.5%) and An. maculatus (32%) were widely available species in most of the north-eastern states, restricted distribution of Anopheles willmori to Nagaland and that of Anopheles sawadwongporni and An. rampae to Mizoram state was noted. None of the species was found positive for human malaria parasite. While no intraspecific differences existed in the sequences of second internal transcribed spacer (ITS2) region of ribosomal DNA (r-DNA) of the member species of the Maculatus group within north-east India, few differences were detected in the sequences of An. dravidicus, An. maculatus and An. pseudowillmori from north-east India with species from the neighbouring countries.

Stage-structured predator–prey models exhibit rich and interesting dynamics compared to homogeneous population models. The objective of this paper is to study the bifurcation behavior of stage-structured prey–predator models that admit stage-restricted predation. It is shown that the model with juvenile-only predation exhibits Hopf bifurcation with the growth rate of the adult prey as the bifurcation parameter; also, depending on parameter values, a stable limit cycle will emerge, that is, the bifurcation will be of supercritical nature. On the other hand, the analysis of the model with adult-stage predation shows that the system admits a fold-Hopf bifurcation with the adult growth rate and the predator mortality rate as the two bifurcation parameters. We also demonstrate the existence of a unique limit cycle arising from this codimension-2 bifurcation. These results reveal far richer dynamics compared to models without stage-structure. Numerical simulations are done to support analytical results.

Residual stress modulation in the diamond-like carbon coatings with incorporation of gold nanoparticles was studied critically. The films were deposited on glass and Si (1 0 0) substrates by using capacitatively coupled plasma chemical vapor deposition. Stresses in the films were determined from the broadening of the optical absorption tail and were found to decrease from 2.3 GPa to 0.48 GPa with increasing gold content (2–7 at.% Au) in the DLC matrix. Gold incorporation also made the films harder than the corresponding DLC coatings. Modulation of stress with nanocrystalline gold content in the DLC matrix was related to the relative amount of sp2/sp3 content in the DLC films.

In this paper, we study an eco-epidemiological model where prey disease is modeled by a Susceptible-Infected (SI) scheme. Saturation incidence kinetics is used to model the contact process. The predator population adapt switching technique among susceptible and infected prey. The prey species is supposed to be commercially viable and undergo constant non-selective harvesting. We study the stability aspects of the basic and the switching models around the infection-free state and the infected steady state from a local as well as a global perspective. Our aim is to study the role of harvesting and switching on the dynamics of disease propagation and/or eradication. A comparison of the local and global dynamical behavior in terms of important system parameters is obtained. Numerical simulations are done to illustrate the analytical results.

In the present work, a mathematical model of predator–prey ecological interaction with infected prey is investigated. A saturation incidence function is used to model the behavioral change of the susceptible individuals when their number increases or due to the crowding effect of the infected individuals [V. Capasso, G. Serio, A generalization of the Kermack–McKendrick deterministic epidemic model, Math. Biosci. 42 (1978) 41–61]. Stability criteria for the infection-free and the endemic equilibria are deduced in terms of system parameters. The basic model is then modified to incorporate a time delay, describing a latency period. Stability and bifurcation analysis of the resulting delay differential equation model is carried out and ranges of the delay inducing stability and as well as instability for the system are found. Finally, a stability analysis of the bifurcating solutions is performed and the criteria for subcritical and supercritical Hopf bifurcation derived. The existence of a delay interval that preserves the stability of periodic orbits is demonstrated. The analysis emphasizes the importance of differential predation and a latency period in controlling disease dynamics.

A proportion of acute coronary syndromes (ACS) are thought to be triggered acutely by physical exertion, emotional stress and other stimuli. We assessed the consequences of triggering for long-term adaptation following ACS.We assessed mental and physical health status in 150 male and 44 female ACS survivors 12 and 36 months after cardiac events using standardised questionnaire measures. Triggers were assessed by interview an average of 2.56 days after hospital admission. Emotional triggers were defined as moderate or intense anger, stress or sadness/depressed mood in the 2 h before symptom onset, while vigorous physical exertion was defined as activity/=6 metabolic equivalents in the hour before symptom onset. Clinical characteristics, psychiatric history, health behaviours and the Global Registry of Acute Coronary Events (Grace) risk algorithm were also assessed.Emotional triggers predicted elevated anxiety and poor mental health status at 12 months independently of age, gender, socioeconomic status, ACS presentation, Grace risk scores, pre-admission medication, anxiety in hospital, depression history and symptom recurrence (p0.001). Effects persisted at 36 months. Emotional triggers were not related to physical health status at follow up. By contrast, impaired physical health status was predicted by vigorous exertion during the trigger period independently of covariates (p=0.019).ACS triggering has a long-term impact on adaptation and quality of life, with differential effects of physical and emotional triggers.

Objective: Evidence suggests that emotional stress can trigger acute coronary syndromes in patients with advanced coronary artery disease (CAD), although the mechanisms involved remain unclear. Hostility is associated with heightened reactivity to stress in healthy individuals, and with an elevated risk of adverse cardiac events in CAD patients. This study set out to test whether hostile individuals with advanced CAD were also more stress responsive. Methods: Thirty-four men (aged 55.9 +/- 9.3 years) who had recently survived an acute coronary syndrome took part in laboratory testing. Trait hostility was assessed by the Cook Medley Hostility Scale, and cardiovascular activity, salivary cortisol, and plasma concentrations of interleukin-6 were assessed at baseline, during performance of two mental tasks, and during a 2-h recovery. Results: Participants with higher hostility scores had heightened systolic and diastolic blood pressure (BP) reactivity to tasks (both P

The Bay of Bengal (BOB) sedimentary basin is one of the largest offshore sedimentary basins of the world having the thickest accumulation of sediments which mask the underlying crust and it is the Geopotential data that offers the unique opportunity of seeing below the thick sediments. Satellite derived Free Air Gravity (FAG) data, marine magnetic data, bathymetry, available seismic profiles and isopach maps over the Bay of Bengal are utilized in the present paper to throw light on the nature and tectonics of the BOB with particular emphasis on the 85°E Ridge. Combined analysis of gravity and magnetic data along six EW profiles of length varying from 325 to 440 km is undertaken, incorporating seafloor spreading anomalies in the model. Of the several theories put forth for the evolution of the 85°E Ridge, the present study supports the sagging of the crust and rules out the hotspot trace and magmatic under-plating theories. The crustal model derived from the magnetic profile analysis suggests that the 85°E Ridge does not extend to the North of 15°N latitude and this is supported by the Euler solutions of the FAG and the long wavelength filtered FAG. However, the intermediate wavelength filtered FAG suggests that the 85°E Ridge extends up to the Ocean Continent Boundary thereby suggesting that the 85°E Ridge thins out dramatically to the North of 15°N latitude. Analysis of gravity data along 17°N latitude profile predicts that in the northern segment the 85°E Ridge is a geo-morphological feature within the sediments above the basement whereas to the South of 15°N latitude it is a feature within the oceanic crust (below the basement). Further the reverse magnetization associated with the seafloor spreading anomalies lying on the 85°E Ridge belongs either to the Albian period or the anomaly A34/A33. The 85°E Ridge would be younger than these seafloor spreading anomalies and would have formed due to horizontal compressional forces of the lithosphere preceding development of the subduction zone at the Andaman trench.

A simple method is depicted in this communication to determine the optical constants of transparent thin films from transmittance versus wavelength traces, showing no fringes, for evaluating thickness. The strength of this technique is apparent when applied to Zn 1 − x Mg x O films.

In the present paper we propose a modification of a basic eco-epidemiological model by incorporating predator switching among susceptible and infected prey population. A local and global study of the basic model is performed around the disease-free boundary equilibrium and the interior equilibrium to estimate important parameter thresholds that control disease eradication and species coexistence. Next we analyze the switching model from the same perspective in order to elucidate the role of switching on disease dynamics. Numerical simulations are carried out to justify analytical results.

Multiwall carbon nanotubes (MWNT) were incorporated in melt-mixed co-continuous blends of polyamide 6 (PA6) and acrylonitrile–butadiene–styrene (ABS) using a conical twin-screw microcompounder. The state of dispersion of MWNT in the blends was assessed through AC electrical conductivity measurements and melt-rheological investigations. The electrical and rheological percolation threshold in PA6/ABS blends was ∼3–4 and ∼1–2 wt% MWNT, respectively. A unique reactive modifier (sodium salt of 6-amino hexanoic acid, Na–AHA) was employed to facilitate ‘network-like’ structure of MWNT and to confine them in a specific phase. This was achieved by establishing specific interactions with the delocalized ‘π-electron’ clouds of MWNT and melt-interfacial reaction during melt-mixing. The electrical percolation threshold was significantly reduced in the blends (∼0.25 wt%) in the presence of Na–AHA modified MWNT and even coincided with the rheological percolation threshold. Significant refinement in the co-continuous structure was also observed in the presence of Na–AHA modified MWNT.

Objective Poor social support is associated with recurrent cardiac events following acute coronary syndrome (ACS). Interventions have largely targeted emotional support, but practical support may be particularly important in encouraging recovery behaviors. We assessed whether practical and emotional support differentially predicted medication adherence and rehabilitation attendance following ACS. Methods This prospective observational clinical cohort study involved 262 survivors of verified ACS, recruited from four coronary care units in the London area. Practical and emotional support were measured in hospital, and depression, 7–10 days after discharge. Medication adherence and rehabilitation attendance were assessed by telephone interview 12 months after hospitalization. Results Nearly one third of patients (29.8%) had no practical supports, 16% had one, and 54.2% had two or more sources of practical support. Patients with greater practical support were more likely to adhere to medication ( P= .034) independently of age, gender, marital status, clinical risk profile, and depression. There was also an association with rehabilitation attendance ( P =.034), but this was no longer significant after depression had been taken into account. Emotional support was unrelated to medication adherence and rehabilitation attendance. Conclusions Cardiac patients with greater practical support may receive more prompts about medications, help with filling prescriptions and assistance with cardiac rehabilitation attendance. These behaviors can influence long-term recovery.

Objective Depression is associated with coronary heart disease, but the underlying mechanisms are not fully understood. Cortisol is involved in the development of coronary artery disease (CAD), but evidence directly linking depression with cortisol in patients with CAD is limited. This study evaluated cortisol output over the day in patients with suspected CAD in relation to depressive symptoms. Methods Eighty-eight patients who were being investigated for suspected CAD (defined by clinical symptoms plus positive exercise tests or myocardial perfusion scans) took eight saliva samples over the day and evening. Depressed mood was assessed with the Beck Depression Inventory. Actigraphy was used to define time of waking objectively. Results The cortisol awakening response and cortisol rhythm over the remainder of the day and evening were analyzed separately. Fifty-two (61.9%) patients were later found to have definite CAD on angiography, while the remainder did not. The cortisol slope over the day was flatter in more depressed patients with CAD ( P P =.68). This effect was due to the combination of lower cortisol early in the day and higher cortisol in the evening in more depressed CAD patients, independent of age, gender, medication, and times of waking and sleeping ( P =.003). Additionally, cortisol measured on waking and 15 and 30 min after waking was greater in CAD than in non-CAD patients ( P =.04), but was not related to depression. Conclusions The flatter cortisol rhythms of more depressed CAD patients may contribute to the progression of coronary atherosclerosis.

In the present paper we study a three-component mathematical model of tumor–immune system interaction. A number of solid tumors contain a high proportion of macrophages and these immune cells are known to have a remarkable impact on the progression and dormancy of such tumors. We assume these macrophages as the main immune system component facilitating tumor destruction. Stability criteria of the basic model around the steady state of coexistence are derived. Next, we consider the process of macrophage activation as non-instantaneous by using a distributed delay with a weak kernel and obtain a range for the macrophage death rate that ensures system stability. Finally, we incorporate the spatial irregularity of solid tumors by making the delay nonlocal. Analysis of the resulting spatiotemporal model gives a number of thresholds in terms of different system parameters that guarantee tumor stability. Numerical simulations are performed to justify analytical findings.

We present a nonlinear SEIS epidemic model which incorporates distinct incidence rates for the exposed and the infected populations. The model is analyzed for stability and bifurcation behavior. To account for the realistic phenomenon of non-homogeneous mixing, the effect of diffusion on different population subclasses is considered. The diffusive model is analyzed using matrix stability theory and conditions for Turing bifurcation derived. Numerical simulations are performed to justify analytical findings.

The application of a sufficiently high negative substrate bias, during the growth of tetrahedral amorphous carbon (ta-C), is usually associated with low sp3 bonding configuration and stressed films. However, in an effort to understand and utilize the higher pseudo thermo dynamical conditions during the film growth, at high negative substrate bias (− 300 V), reported here is a study on ta-C films grown under different hydrogen and nitrogen concentration. As grown ta-C films were studied under different negative substrate bias conditions. The variation of the sp3 content and sp3/sp2 ratio in the ta-C films exhibits a trend similar to those reported in literature, with a subtle variation in this report being the substrate bias voltage, which was observed to be around − 200 V, for obtaining the highest sp3 (80%) bonding and sp3/sp2 (3.95) ratio. The hydrogen and nitrogen incorporated ta-C films studied, at a bias of − 300 V, show an increase in sp3 (87–91%) bonding and sp3/sp2 (7–10) ratio in the range of studies reported. The inference is drawn on the basis of the set of data obtained from measurements carried out using X-ray photoelectron spectroscopy, X-ray induced Auger electron spectroscopy and Raman spectroscopy of as grown and hydrogen and nitrogen incorporated ta-C films deposited using an S bend filtered cathodic vacuum arc system. The study indicates the possibility of further tailoring ta-C film properties and also extending capabilities of the cathodic arc system for developing carbon based films for electronics and tribological applications.

Studies of the salivary cortisol awakening response (CAR) may be confounded by delays between waking in the morning and obtaining the 'waking' salivary sample. We used wrist actigraphy to provide objective information about waking time, and studied the influence of delays in taking the waking sample on the CAR. Eighty-three men and women (mean age 61.30 years) who were referred to hospital with suspected coronary artery disease were studied. Saliva samples were obtained on waking and 15 and 30 min later. The mean interval between waking defined by actigraphy and reported waking time was 6.12+/-(S.D.) 14.8 min, with 55.4% having no delay. The waking saliva sample was obtained an average 5.78+/-15.0 min after self-reported waking, and 12.24+/-20.3 min after objective waking. The waking cortisol value was significantly higher in participants who had a delay between waking and sampling >15 min (mean 14.46+/-6.34 nmol/l) than in those with zero (mean 10.45+/-6.41 nmol/l) or 1-15 min delays (mean 11.51+/-5.99 nmol/l, p=0.043). Cortisol did not increase between 15 and 30 min after waking in those who delayed >15 min. There were no differences in CAR between participants with zero and 1-15 min delays from objectively defined waking to reported sample times. A small proportion (14.7%) of participants who did not delay saliva sampling showed no increase in cortisol over the 30 min after waking. These CAR nonresponders did not differ from the remainder on sleep patterns, waking time, clinical or medication characteristics, but were more likely to be of higher socioeconomic status (p=0.009). We conclude that long delays between waking and obtaining 'waking' cortisol samples will lead to misleading CAR results, but that delays up to 15 min may not be problematic. A small minority of individuals do not show a positive CAR despite not delaying saliva sampling after waking.

ENVISAT AATSR data over the Indian subcontinent have been procured from ESA and preprocessed with DESCW and BEAM 2.2 software for extraction of our area of interest. Two intensive test sites have been chosen, including a part of the Himalayan region and the Sundarban Delta. Calibration of AATSR thermal IR data for surface temperature modelling has been attempted over the Sundarban Delta region. Later, the surface temperature maps have been utilized to generate the momentary and daily evapotranspiration patterns over the area of interest which have been further used for broad land use/crop classifications. A simplified model suggested by Soer [Estimation of regional evapotranspiration and soil moisture conditions using remotely sensed crop surface temperatures, Remote Sensing of Environment 9 (1980) 27–45] has been used to estimate evapotranspiration over the area of interest. The results match with the earlier observation in this region. Further processing of AATSR data has been performed over the Himalayan region to extract two minor faults across the main thrust belts.

Emotional triggers of acute coronary syndromes include population-level events such as earthquakes and terrorist attacks, and individual experiences of acute anger, stress and depression. The methodology of studying emotional triggers has developed markedly over recent years, though limitations remain. The biological processes underlying triggering include acute autonomic dysregulation, neuroendocrine activation, hemostatic and inflammatory responses which, when associated with plaque disruption, promote myocardial ischemia, cardiac dysrhythmia and thrombosis formation. Prevention and management strategies for ameliorating emotional triggering remain to be effectively developed.

The 20/80 blends of polyamide 6 (PA6) and acrylonitrile–butadiene–styrene copolymer (ABS) in the presence of styrene–maleic anhydride copolymer (SMA) and multiwall carbon nanotubes (MWNT) were prepared using melt-mixing technique. Crystallization behavior of the PA6 phase in the blends was studied using DSC, WAXD and SAXS techniques. Blends' morphology was characterized by SEM. We observed fractionated crystallization of PA6 phase in 20/80 PA6/ABS blends. It was also observed that the phenomenon of fractionated crystallization was influenced by the presence of both SMA and MWNT. Blends' morphology revealed the presence of wide domain size distribution of PA6 droplets in the amorphous ABS matrix. On incorporation of either SMA or SMA modified MWNT, the average domain size of PA6 droplets was found to be finer up to 1 wt% SMA modified MWNT. Encapsulation of SMA copolymer layer on the MWNT surface was also evident from SEM micrographs. SAXS analysis revealed the formation of multiple lamellae stacking of PA6 phase in the presence or absence of SMA and MWNT in 20/80 PA6/ABS blends. This was attributed to the formation of less perfect crystallites formed during the cooling of melt at higher degree of supercooling., © Elsevier

Copyright to Elsevier Publishers, The homogeneous dispersion of carbon nanotubes (CNT) remains a hindrance in exploiting the exceptional properties associated with CNT in polymer/CNT composites. Here we present for the first time the key role of sodium salt of 6-aminohexanoic acid (Na-AHA) in assisting debundling the multiwall carbon nanotubes (MWNT) through specific interactions leading to homogeneous dispersion within polyamide6 (PA6) matrix during melt-mixing. The composite fabricated via this route exhibits low electrical percolation threshold of 0.5 wt% at room temperature, the lowest reported value in this system so far. FTIR and Raman spectroscopy reveal the existence of 'cation-π' interaction between Na-AHA and MWNT. The phenomenon of reactive coupling between amine functionality of Na-AHA and acid end group of PA6 during melt-mixing is also established.

The study of reflectance and photoluminescence (PL) spectra of as grown and also hydrogen and nitrogen incorporated tetrahedral amorphous carbon (ta-C) films, deposited using an S bend filtered cathodic vacuum arc process is reported here. First the effect of negative substrate bias on the properties of as grown ta-C films and next the effect of varying hydrogen and nitrogen partial pressure at a high substrate bias of − 300 V on the properties of hydrogen and nitrogen incorporated ta-C (ta-C:H and ta-C:N) films are reported for the first time. The values of the optical band gap ( E g ) evaluated using the reflectance spectra were found to decrease with the increase of the substrate bias in the as grown ta-C films. Hydrogen incorporation up to 1.9 × 10 − 2 Pa partial pressure in as grown ta-C films increased the values of E g and beyond which the values of E g decreased while the nitrogen incorporation up to 3.0 × 10 − 1 Pa partial pressure has no effect on the E g values. The PL spectra indicated a strong peak at ∼2.66 eV in as grown ta-C films deposited at − 20 V substrate bias. This main peak was found to shift to higher energy with the increase of the substrate bias up to − 200 V and thereafter the PL peak shifted towards the lower energy. Other peak at 3.135 eV starts appearing and this is found to start shifting to higher energy for films deposited at higher substrate bias. The intensity of the main PL peak was enhanced at low temperature and several other peaks started appearing in place of the broad peak at ∼3.16 eV. The peak width and area of both the main peak were found to decrease with the increase of substrate bias in as grown ta-C films and with the increase of the hydrogen and nitrogen partial pressure used in depositing ta-C:H and ta-C:N films. The current models on the source of luminescence in amorphous carbon have been discussed.

The sibling species composition of the Anopheles minimus and Anopheles dirus complexes is poorly known in the highly malarious north-eastern region of India where these two vector taxa are accountable for most of the malaria transmission among 30.7 million inhabitants. Prevalent members of these two complexes in this part of India were identified using sequences for the second internal transcribed spacer (ITS2) of ribosomal DNA. Anopheles baimaii (species D) of the An. dirus complex and An. minimus s.s. (species A) of the An. minimus complex were detected in Arunachal Pradesh, Assam, Meghalaya and Nagaland states. No intraspecific variation was observed in the ITS2 sequence (479 bp) of An. baimaii whereas a single substitution was detected in the ITS2 sequence (372 bp) of An. minimus from Nagaland state. © 2006 Published by Elsevier B.V.

The present paper deals with a nutrient-plankton model in an aquatic environment in the context of phytoplankton bloom. Toxin producing phytoplanktons are assumed to play the key role. To account for the toxication effect of the allelopathic phytoplankton, a type-IV functional response is used to model zooplankton grazing. The main aim of the study is to analyze the role, zooplankton grazing plays, in determining the dynamics of the system. Stability and bifurcation behavior of the different equilibrium points of the ODE model is studied. It has been observed that under certain parameter restrictions, extinction of one or both plankton population can occur. The model system is seen to exhibit oscillatory behavior around the equilibrium point of co-existence for a critical value of zooplankton grazing rate. A spatial extension of the model is considered and analyzed for diffusion-driven instability as well as stability. For the diffusive model also, it is found that diffusion-driven instability takes place when the grazing rate of zooplankton lies within an interval. The analysis also revealed that for sufficiently low diffusivity of phytoplankton and high value of half-saturation constant in zooplankton predation function, the diffusive system exhibit asymptotically stable behavior which signifies disappearance of the phenomenon of bloom formation for the diffusive model. Cross-diffusion of zooplankton under the influence of allelopathic phytoplankton is incorporated into the spatial model. Using matrix stability approach, the cross-diffusive model is analyzed and criteria for Turing bifurcation derived. Numerical simulations are performed to justify analytical findings.

The present paper deals with two prey–predator models, one with prey group defence and the other without it. The prey species is assumed to live in two distinct habitats and the predator species has the tendency of switching between the habitats. The models are analyzed regarding stability and bifurcation aspects for the cases where the switching index has the values n = 1 and 2. To model prey dispersal between the habitats, a spatial extension of both the models are considered using physical diffusion of the concerned species. Criteria for diffusion-driven instability are derived and interpreted ecologically. A comparative study of the spatial models are carried out. Numerical simulations are carried out to support analytical findings.

Nanocrystalline GaN films with different crystallite sizes were deposited onto quartz and NaCl substrates by magnetron sputtering of a GaN target in argon plasma. All the films showed predominant hexagonal phase. The band gap values were always found to be higher than that of the bulk. This blue shift in band gap could be attributed to the quantum confinement effect. The optical absorption in these films could be explained by the combined effects of phonon and inhomogeneity broadening along with optical loss due to light scattering at the nanocrystallites. Band edge luminescence is absent in these GaN nanocrystalline films. The line shapes of the photoluminescence (PL) spectra are asymmetric and broad. The film deposited at lower substrate temperature showed broader PL peak. It may be observed that no significant energy shift in the peak positions was observed with reduction in crystallite size but the intensity of the peak decreased for films with the reduction in crystallite size. Below band gap emission observed in this study may also originate due to the presence of polarization-induced electric field present in wurtzite GaN deposited here.

In the present investigation, DLC films were grown by saddle-field fast atom beam (FAB) source using acetylene as source gas. The as-deposited films are having properties like low stress (0.1–0.3 GPa), relatively high hardness (9–21 GPa) values and low amount of unbound hydrogen (0.12–2.9 at.%). Stress per unit hardness (SPUH) has been found to be the “figure-of-merit” to describe the film property. A correlation between unbound hydrogen in the DLC films and compressive stress has been established. The effect of nitrogen doping on the properties of DLC films is also investigated. While exploring the conditions for deposition of stress relieved DLC films, many patterns of stress relief behaviour in these films are observed and studied carefully. Surprisingly, we came across new patterns of stress relief behaviour in the case of nitrogen-doped DLC films. This new pattern of the stress relief behaviour, termed as “hexagonal buckling network”, has been found for the first time and claimed here. The detailed observations of this type of stress relief pattern have been presented.

A mathematical model of nutrient recycling in an autotroph–herbivore ecosystem is analysed. The analysis consists of stability and bifurcation behaviour of model ecosystem with and without time delay in the growth equation of the nutrient. An estimation of stability preserving delay has been performed.

Melt processing of SWCNT/Ultem nanocomposite fibers was demonstrated for fibers containing up to 1 wt% SWCNTs. High-resolution electron microscopy and Raman spectroscopy were used to evaluate the quality of SWCNT dispersion. SWCNT alignment in the fiber direction was induced by shear forces present during the melt extrusion and fiber drawing processes. This alignment resulted in significantly higher tensile moduli and yield stress in SWCNT/Ultem nanocomposite fibers relative to unoriented nanocomposite films having the same SWCNT concentration.

This paper reports the space charge limited conduction (SCLC) and electron paramagnetic resonance (EPR) studies of as grown and nitrogen incorporated tetrahedral amorphous carbon (ta-C) films deposited by pulsed unfiltered cathodic vacuum arc process. The effect of varying substrate bias and nitrogen content on the properties of as grown and nitrogen incorporated ta-C films have been studied. The values of density of states (N(EF)) evaluated from SCLC measurements and spin density (Ns) evaluated from EPR studies of as grown ta-C films deposited at 5 V substrate bias are found to be 1.6×1019 cm−3 eV−1 and 6.7×1019 cm−3, respectively, which decrease to 8.7×1018 cm−3 eV−1 and 4.6×1019 cm−3, respectively, with the increase of substrate bias up to 80 V and beyond 80 V substrate bias these values are found to increase. A small amount of nitrogen incorporation up to 3.6 at.% nitrogen content in nitrogen incorporated ta-C films reduces the values of N(EF) and Ns to 1.4×1019 cm−3 eV−1 and 4.3×1019 cm−3, respectively. Beyond 3.6 at.% nitrogen content, the values of N(EF) and Ns are found to increase monotonically to 2.6×1019 cm−3 eV−1 and 1.0×1020 cm−3, respectively, in nitrogen incorporated ta-C films with further increase of nitrogen content up to 15.6 at.%. The local minimum in the values of N(EF) and Ns in as grown ta-C films deposited at 80 V substrate bias arises due to the ability of sp2 sites to pair up. Nitrogen incorporation up to 3.6 at.% in nitrogen incorporated ta-C films seems to compensate the p-type nature and beyond 3.6 at.% nitrogen content the donor electron increases the values of N(EF) and Ns in the films.

The focus of the paper is to investigate several issues related to the state of dispersion of multiwalled carbon nanotubes (MWNTs) in a polycarbonate (PC) matrix. A masterbatch of PC–MWNT (15 wt.%) was diluted with different amounts of PC in a small scale conical twin screw extruder (DACA Micro Compounder) to obtain different compositions of MWNT. In this system, electrical measurements indicated percolation of MWNT between 1.0 and 1.5 wt.%. We report TEM and AFM investigations of the state of dispersion of MWNT, in the entire volume of the matrix, in selected composites with compositions below (1 wt.% MWNT) and above the percolation threshold (2 and 5 wt.% MWNT). In addition, it was investigated if surface segregation of MWNT and flow induced orientation of nanotubes within the extruded strands had been occurred. It is found that the nanotubes dispersed uniformly through the matrix showing no significant agglomeration in the compositions studied. TEM micrographs seem to be able to detect the percolated structure of the carbon nanotubes. Furthermore, by comparing AFM micrographs from the core region and near to surface region no evidence of segregation or depletion of MWNT at the surface of the extruded strand was found. Comparison of TEM and AFM micrographs on surfaces cut along and perpendicular to the strand direction led to the conclusion that no preferred alignment had occurred as a result of extrusion. Aside from TEM technique, AFM is shown to be suitable to characterize the state of nanotube dispersion along with the issue of surface segregation and orientation of the nanotubes.

This paper presents composites of polycarbonate (PC) having different amounts of multiwalled carbon nanotubes (MWNT). The composites were prepared by diluting a masterbatch of PC with 15 wt% MWNT using melt mixing in a DACA-Micro Compounder. Electrical resistivity measurements indicated percolation of MWNT between 1 and 1.5 wt%. Transmission electron microscopy (TEM) showed excellent dispersion of the MWNT and indicated no preferred orientation of MWNT in extrusion direction. In addition, a conductive PC-2 wt% MWNT composite was melt mixed with polyethylene in order to get co-continuous blends exhibiting double percolation. Significant reduction in electrical resistivity of the blends could be achieved in compositions down to 30 vol% filled PC in which the total MWNT content was only 0.41 vol%. These blends exhibited co-continuous structures.

This paper reports the X-ray photoelectron spectroscopy (XPS) and X-ray induced Auger electron spectroscopy (XAES) studies of as grown and nitrogen incorporated tetrahedral amorphous carbon (ta-C) films deposited by pulsed unfiltered cathodic vacuum arc process. The effect of varying substrate bias and nitrogen content on the properties of the as grown and the nitrogen incorporated ta-C films has been studied. The XPS spectra indicate that in the as grown ta-C films the C 1s peak occurs at 285.15±0.08 eV and the binding energy (BE) marginally decreases with the increase of substrate bias. The nitrogen incorporated ta-C films show N 1s peak at 399.46±0.10 eV in addition to the C 1s peak. The peak position of C 1s remains unchanged with nitrogen incorporation, whereas the N 1s peak seems to marginally decrease in BE, with increasing nitrogen content. From the values of the parameter D, the energy width between the highest maximum and the lowest minimum value of the derivative of C (KLL) spectra, sp2, sp3 and sp3/sp2 ratio were evaluated. The values of D, sp2, sp3 and sp3/sp2 ratio for the as grown ta-C films are found to be 17.16 eV, 35.7%, 64.3% and 1.80, respectively. The values of D and sp2 fraction are found to decrease to 16.19 eV and 23.9% and those of sp3 and sp3/sp2 ratio are found to increase to 76.1% and 3.18 in the case of ta-C films deposited at an applied substrate bias of 40 V. In the case of applied substrate bias beyond 40 V, the values of these parameters show a reversal in the trend. The nitrogen incorporated ta-C films with 3.6 at.% nitrogen content do not show any change in the values of D, sp2, sp3 and sp3/sp2 ratio. With further increase in the nitrogen content up to 15.6 at.%, the values of D and sp2 fraction decrease continuously to 15.87 eV and 20.1% and the values of sp3 and sp3/sp2 ratio increase to 79.9% and 3.98, respectively. The study suggests that, at certain conditions of nitrogen incorporation in the case of ta-C films, there is an increase in sp3 fraction or the diamond like nature of the ta-C films.

This paper reports the effect of positive substrate bias ( V s ) varying from 0 to 180 V on the spectroscopic ellipsometry (SE), X-ray photoelectron spectroscopy (XPS) and X-ray Auger electron spectroscopy (XAES) studies of diamond-like carbon (DLC) films deposited using CH 4 gas as a feedstock into a saddle field fast atom beam (FAB) source. The values of optical constants like refractive index ( n ) and extinction coefficient ( k ) of the deposited DLC films were determined using a two phase model. The values of ‘ n ’ were found to fall in the range from 1.505 to 1.720 and ‘ k ’ from 0.03 to 0.125 by application of different values of V s . Value of these optical constants were found to decrease with the increase of substrate bias up to 90 V and then increase beyond this value. Position of C 1s peak evaluated from XPS data was found to occur at 286.09±0.18 eV in DLC films deposited by application of different values of V s . Observation of full width at half maximum (FWHM) ( τ ) value (1.928 eV at V s =0 V, 2.0 eV at V s =90 V and 1.89 eV at V s =180 V) clearly hinted the existence of a point of inflection in the properties of DLC films deposited using FAB source this way. A parameter ‘ D ’ defined as the distance between the maximum of positive going excursion and the minimum of negative going excursion was calculated in the derivative XAES spectra. The values of ‘ D ’ evaluated from XAES data for DLC films were found to be 14.8, 14.5 and 15.2 at V s =0, 90 and 180 V, respectively. The sp 2 percentage was calculated for samples deposited this way and was found to be low and lie approximately at 5.6, 2.8, 2.3, 5.7 and 11.5 for different values of V s =0, 50, 90, 150 and 180 V. The sp 3 content percentage and sp 3 /sp 2 ratio was found to be 94.4 and 16.7, 97.7 and 42.5 at V s =0 and 90 V, respectively. Beyond V s =90 V these values started decreasing. Mainly, a point of inflection in all the properties of DLC films studied over here at around 90 V of applied substrate bias has been observed, which has been explained on the basis of existing theories in the literature.

Blends were prepared from a high density polyethylene (PE) material and a conductive polycarbonate (PC) composite containing multiwalled carbon nanotubes (MWNT). The PC composite contained 2 wt% MWNT and was prepared by diluting a PC masterbatch consisting of 15 wt% MWNT by melt mixing in an extruder. The aim of blending a conductive PC composite with PE was to obtain a conductive blend at lower amounts of MWNT than required for the pure PC component. The blend morphology was found to be co-continuous over a broad composition range of 30–80 vol.% of the filled PC phase as verified by selective extraction of PC and morphological investigations. The co-continuous structure is very fine with ligaments in the range of 1 μm. Significantly reduced volume resistivity values, i.e. in the range of 10 7 Ω cm, could be achieved in the same composition range of that of the continuous PC phase, i.e. starting at compositions of 30 vol.% filled PC. Here, the total MWNT content in the blend was only 0.41 vol.%. Interestingly, even if the MWNT had been incorporated in the PC phase, the tubes are still visible in the blends after selective extraction of PC. Scanning electron microscopy investigations revealed that the MWNT bridge the PC and PE phases, at least with their ends. This can be understood by the length dimensions of the tubes, which is higher than the phase sizes in the blends.

In this paper, we report field-emission measurements from ∼0.5-μm-thick hydrogenated amorphous carbon (diamond-like carbon (DLC)) films. These films were grown by a variety of easily implementable plasma-enhanced chemical vapor deposition (PECVD) based techniques and also by a method that uses a saddle-field fast atom beam source. Field-emission behavior in these materials has been discussed in light of residual stress, hardness, optical band gap, and characteristic energy of band tails (Urbach energy). Onset emission-fields as low as ∼6 V/μm, together with low residual stress of 0.25 GPa, hardness of 17.5 GPa, optical band gap of 1.5 eV, and Urbach energy of 165 meV, have been obtained in DLC films grown by pulsed-PECVD at 13.56 MHz. DLC films of comparable quality could also be grown using a saddle-field fast atom beam source, which operates on modest dc power supply and with no heated filaments or magnets.