Similar Linear Responses Research Articles

Comparing Performance of Spectral Image Analysis Approaches for Detection of Cellular Signals in Time-Lapse Hyperspectral Imaging Fluorescence Excitation-Scanning Microscopy.

Hyperspectral imaging (HSI) technology has been applied in a range of fields for target detection and mixture analysis. While HSI was originally developed for remote sensing applications, modern uses include agriculture, historical document authentication, and medicine. HSI has also shown great utility in fluorescence microscopy. However, traditional fluorescence microscopy HSI systems have suffered from limited signal strength due to the need to filter or disperse the emitted light across many spectral bands. We have previously demonstrated that sampling the fluorescence excitation spectrum may provide an alternative approach with improved signal strength. Here, we report on the use of excitation-scanning HSI for dynamic cell signaling studies-in this case, the study of the second messenger Ca2+. Time-lapse excitation-scanning HSI data of Ca2+ signals in human airway smooth muscle cells (HASMCs) were acquired and analyzed using four spectral analysis algorithms: linear unmixing (LU), spectral angle mapper (SAM), constrained energy minimization (CEM), and matched filter (MF), and the performances were compared. Results indicate that LU and MF provided similar linear responses to increasing Ca2+ and could both be effectively used for excitation-scanning HSI. A theoretical sensitivity framework was used to enable the filtering of analyzed images to reject pixels with signals below a minimum detectable limit. The results indicated that subtle kinetic features might be revealed through pixel filtering. Overall, the results suggest that excitation-scanning HSI can be employed for kinetic measurements of cell signals or other dynamic cellular events and that the selection of an appropriate analysis algorithm and pixel filtering may aid in the extraction of quantitative signal traces. These approaches may be especially helpful for cases where the signal of interest is masked by strong cellular autofluorescence or other competing signals.

Experimental study of the impact of electrospinning parameters on the electromechanical properties of strain sensitive electrospun multiwalled carbon nanotubes/ thermoplastic polyurethane nanofibers

Flexible strain sensitive electrospun fibrous layers have attracted widespread attention of researchers owing to their large surface area and exceptional flexibility. Herein, a detailed research on the impact of electrospinning parameters on the morphological and electromechanical properties of electrospun multiwalled carbon nanotubes (MWCNTs)/thermoplastic polyurethane (TPU) nanofibers is conducted. Besides the MWCNTs concentrations, electrospinning parameters have a significant effect on the morphology, electromechanical and sensory properties of electrospun MWCNTs/TPU nanofibrous membrane. Results show that at lower collector speeds, tip to collector distances, and higher electrospinning time lead to the formation of more homogeneously dispersed fibrous structures, which result in enhanced conductivity and strain sensitivity. Consequently, from the repeatability tests, all samples show quite similar linear responses under strain, indicating a highly repeatable fabrication process. Obtained results can help to gain a deeper understanding of the importance of controlling the electrospinning parameters, especially in the production of flexible strain sensors.

Use of Triangular Silver Nanoplates as Low Potential Redox Mediators for Electrochemical Sensing.

Redox mediators can facilitate the electrochemical communication between targets and electrodes for material characterization and investigation. To provide an alternative to the chemical-based redox mediators, herein, we present a nanoparticle-based redox mediator, i.e., the trisodium citrates (TSC)-capped triangular silver nanoplates (Tri-Ag-NPTSC), which demonstrates an efficient oxidative process at around 0.13 V (vs Ag/AgCl) with acceptable redox reversibility by exploiting the interaction between the carbonyl group of TSC and the Ag element of Tri-Ag-NPTSC. The TSC of Tri-Ag-NPs can be selectively replaced by thiols and enable the obtained Tri-Ag-NPTSC-thiol with changed electrochemical redox response, which could be utilized to determine various thiols at 0.13 V, a much lowered oxidative potential than traditional redox mediators, with a similar linear response range, response slope, and limit of detection (LOD). This work proposes a surface-engineering approach to design and develop electrochemical redox probes using Ag nanoparticles with particular morphology, indicating that the interaction between the carbonyl group and Ag nanoparticles might be extended to sensing application beyond the surface-enhanced Raman scattering.

Two efficient pH sensors based on heteronuclear metal-organic frameworks

Two heteronuclear clusters-based MOFs, CoLi(HL)·4DMA (HNU-23) and CoLi2(L)(DMF)2·DMF·H2O (HNU-24) (H4L = 5- [bis(4-carboxybenzyl) amino] isophthalic acid) were successfully synthesized through a solvent-directed strategy. The luminescence sensing property investigations reveal that HNU-23 and HNU-24 exhibit turn-on luminescence towards the H+ concentration under strong acidic condition, and could be served as potential pH sensors. HNU-23 shows high linear H+ concentration response in the range of 0.02–0.2 M; HNU-24 exhibits similar linear response towards the H+ concentration from 0.1 to 0.2 M. The mechanism of this sensing behavior can be explained through disruption of the HNU-23 and HNU-24 structures under acidic condition to gradually release the fluorophore.

Large amplitude oscillatory shear of supramolecular materials

Large amplitude oscillatory shear [LAOS] helps to investigate non-linear rheology and the dynamic behaviour of materials when subjected to large deformations. Qualitative characterization of non-linear rheology can be easily done but quantification and physical interpretation of non-linear rheological characteristics is one of the most challenging aspects. In this work, LAOS tests are done on different materials generally known as ‘living polymers’, with similar linear response, in order to study their non-linear response using both quantitative and qualitative analysis. The effect of living polymer networks on LAOS was examined using different concentrations of 2,4 bis(2-ethyl hexyl ureido)toluene [EHUT] gels. Cetyl trimethyl ammonium bromide [CTAB] wormlike micellar solution is prepared to compare and contrast with EHUT gels since both these materials show similar linear viscoelastic response. Elastic loading/unloading and plastic deformations are identified as important processes that lead to the distinguishing behaviour for different materials. An equivalence is observed for Lissajous plots in the concentration frequency plane for EHUT. Giesekus model and Upper Convected Maxwell model coupled with transient network model [TNM], two well established models, are solved numerically for comparison with the experimental results. A modification of the Giesekus model to incorporate the network breakage/reformation as a linear function of strain amplitude, and nonlinear function of strain rate within an oscillation period is suggested. The proposed model is able to capture the competition between reptation, network breakage and reforming during LAOS. Moreover, the modified model suggests that the secondary loops during LAOS for EHUT gel occur soon after yielding due to competition between the network breaking and reforming at high shear rates and reptation at low shear rates within a cycle.

High performance liquid chromatography analysis of aliphatic thiols in alimentary supplements and pharmaceuticals using menadione as a new useful derivatization reagent

The use of menadione (MD) as a pre-column reagent for high performance liquid chromatography (HPLC) analysis of aliphatic thiols is proposed. The reaction was carried out for 5min at room temperature and pH 8.5. The developed method was applied to the N-acetylcysteine (NAC) analysis of alimentary supplements and pharmaceutical formulations. The effect of the complex matrix was evaluated by the study of the thiol derivatization reaction both in standard and in placebo solutions. The yield of NAC-MD adduct was found to be quantitative at a reagent to thiol molar ratio of about 4 in comparison with an authentic specimen of synthesized NAC adduct, which was characterized by 1H NMR, IR and UV. The routine chromatographic separations were performed on a Synergi MAX-RP column using a mobile phase consisting of methanol/triethylammonium (TEA) phosphate buffer (pH 3; 0.05molL−1) 70:30 (v/v) at a flow-rate of 0.4mLmin−1. UV-diode array detection was used setting the wavelength at λ=260nm. The validation parameters such as linearity, sensitivity, accuracy, precision, selectivity and ruggedness were found to be highly satisfactory. Similar linear responses were observed by standard and placebo solutions (determination coefficient: 0.9996). Limit of detection was about 0.019μgg−1. Intra-day precision (relative standard deviation, R.S.D.) was ≤0.81% for NAC to internal standard (IS) peak area ratio, ≤0.28% and ≤0.32%, respectively, for NAC and IS retention times (tR), without significant differences between intra- and inter-day data. NAC recovery studies gave good results (100.12%) with R.S.D.=1.05%.

Study of 1,4-naphthoquinone as a new useful derivatization reagent for LC analysis of aliphatic thiols in dietary supplements and pharmaceuticals

The use of 1,4-naphthoquinone as an advantageous pre-column reagent for liquid chromatography analysis of aliphatic thiol compounds is proposed. The compound reacts selectively in mild conditions (5 min at room temperature; pH 7.5) with thiol function. The resulting adducts were separated under isocratic conditions by using a reversed-phase column (C-12n) with a mobile phase corresponding to methanol/triethylammonium phosphate buffer (pH 3; 0.05 mol L(-1)) 65:35, v/v, at a flow rate of 0.4 mL min(-1) in presence of quercetin as internal standard. Detection was set at a wavelength of 420 nm. The effect of the derivatization reaction conditions on the N-acetylcysteine (NAC) reaction yield was investigated by a series of experiments. The yield of NAC derivative was found to be quantitative at a reagent thiol molar ratio of about 3 by comparison with an authentic specimen of synthesized NAC adduct, which was characterized by (1) H NMR, IR, and UV. Similar linear responses were observed by standard and placebo solutions (determination coefficient, 0.9998). The within- and between-day standard deviations (RSD) were ≤0.47 %. Recovery studies showed good results (100.03 %) with RSD 0.76 %. The limit of detection was about 20 pmol. The utility of the validated method for the determination of NAC in a new dietary supplement and commercial formulations is demonstrated.

Evaluation of a DNA Vaccine for Immunocontraceptive Potential Against Zona Pellucida Glycoproteins in Cattle

Holstein cows were administered zona pellucida (ZP) DNA vaccine and used to determine the potential of recombinant rabbit ZP glycoproteins (rZP) as immunocontraceptive antigens. Zona pellucida proteins were purified and quantified. Cows were assigned to one of four treatment groups in which plasmids encoding rabbit ZP proteins were administered, i.d., using a gene gun (ZP55, n=2; ZP75, n=2; Hep55, n=2; and Control, n=3). Blood samples were taken before initial vaccination, once weekly for 5 wk and at 148 wk post-immunization. An ELISA was developed to assess anti-ZP titer levels in cow serum and ovarian function in cows was monitored using trans-rectal ultrasonography. Four of the six cows in ZP treatment groups developed antibody titer levels with similar linear responses over time. These cows also experienced reduced ovarian function as indicated by decreases in follicular and luteal activity. Estrous activity was observed in all cows and decreased in ZP treatment cows in comparison to Controls. Further research is needed to determine the relationship between ZP immunocontraception and ovarian function. Still, this study provides a basis for future researchers to use in developing a contraceptive vaccine for cattle.

A method for early determination of meat ultimate pH

A patented method of rapidly determining the ultimate pH from approximate glycolytic potential of muscles of slaughtered animals has been devised. The method is based on the rapid hydrolysis of muscle glycogen to glucose by the enzyme amyloglucosidase and subsequent measurement of the liberated glucose. In acetate buffer at pH 4.5, glucose concentration can be determined in 30 s with domestic meters for diabetes control. The meter response differed from that of glucose in blood, but was linear with concentration. In slurries comprising homogenised meat in acetate buffer and added glucose, a similar linear response was obtained. Amyloglucosidase was capable of rapidly hydrolysing glycogen to glucose in such slurries. In the 24 h following slaughter, a decrease in glycogen, as determined by glucose, occurred in parallel with the decline in pH. At the same time, lactate progressively accumulated as expected. Values for the approximate glycolytic potential and (by calibration) ultimate pH, were obtained on prerigor muscle within 7 min of muscle sampling in an industrial environment. The method is suitable for on-line application in beef abattoirs particularly those employing hot boning where ultimate must be known at the grading point.

Gaussian fluctuations and linear response in an electron transfer protein.

In response to charge separation or transfer, polar liquids respond in a simple linear fashion. A similar linear response for proteins might be expected from the central limit theorem and is postulated in widely used theories of protein electrostatics, including the Marcus electron transfer theory and dielectric continuum theories. Although these theories are supported by a variety of experimental data, the exact validity of a linear protein dielectric response has been difficult to determine. Molecular dynamics simulations are presented that establish a linear dielectric response of both protein and surrounding solvent over the course of a biologically relevant electron transfer reaction: oxido-reduction of yeast cytochrome c in solution. Using an umbrella-sampling free energy approach with long simulations, an accurate treatment of long-range electrostatics and both classical and quantum models of the heme, good agreement is obtained with experiment for the redox potential relative to a heme-octapeptide complex. We obtain a reorganization free energy that is only half that for heme-octapeptide and is reproduced with a dielectric continuum model where the heme vicinity has a dielectric constant of only 1.1. This value implies that the contribution of protein reorganization to the electron transfer free energy barrier is reduced almost to the theoretical limit (a dielectric of one), and that the fluctuations of the electrostatic potential on the heme have a simple harmonic form, in accord with Marcus theory, even though the fluctuations of many individual protein groups (especially at the protein surface) are anharmonic.

Measurement of biodegradable substances with a mycelia-sensor based on the salt tolerant yeast Arxula adeninivorans LS3

The microbial sensor based on budding cells of the dimorphic yeast Arxula adeninivorans LS3 is one of the best suitable sensors for rapid measurement of biodegradable substances. However, Arxula is able to change its morphology (budding cells ⇔ mycelia) in response to the cultivation temperature. The suitability of such mycelia was tested as microbial sensor component. The mycelia-based sensor possess a similar linear response, stability, limit of determination and detection compared with the conventional budding cell-based sensor. However, differences exist in the storage capacity and substrate specificity: the mycelia-sensor has with six months a better storage stability as the conventional sensor, achieves a higher sensitivity for specific amino acids or sugars, shows a better correlation between sensorBOD and the BOD 5-value with yeast extract as model wastewater and is more suitable for measurement of salt water.

Photosynthetic Response to Chilling in Peanut

Recent evidence suggests peanut (Arachis hypogaea L.) may be sensitive to relatively mild night temperature in terms of both dry matter accumulation and yield. The objective of this research was to quantify the effects of a range of night temperatures (9–20 °C) on leaf CO2 exchange rate (CER) of unhardened plants and to study the mechanisms involved in the contrasting response of peanut cultivars to differing night temperature. Four peanut cultivars (Ontario Agricultural College [OAC] Ruby, OAC Garroy, Chico, and Early Bunch) were grown in either controlled‐environment cabinets or outdoors during August and September at Guelph, Ontario. Results of the outdoor study indicated a linear decline in CER as ambient night temperature fell from 20 to 13 °C for all cultivars except OAC Garroy, with OAC Ruby less sensitive to low night temperature than Chico or Early Bunch. Limitations to CER after chilling at 10 °C in the dark were greater for Chico and Early Bunch (CER reduced by ≈35%) than for OAC Ruby and OAC Garroy (CER reduced ≈15%). All cultivars showed the ability to recover CER within 24 to 48 h of alleviation of chilling conditions. Cultivars grown indoors showed differing responses to one or two successive chilling nights (Chico was more affected than all others), but after four successive chilling nights, all cultivars showed a similar linear response to night temperature (i.e., CER = 0.693 × Train + 11.8 ; r2 = 0.90). An analysis of the relative contribution of stomatal and mesophyll constraints to CER in indoor studies (chilled at 9 °C) indicated significant limitations due to each component, with the relative importance dependent on cultivar and chilling period duration. Results suggest that night temperatures may be an important factor in determining relative cultivar performance in cool production environments.

Prediction of conception rate in extensive beef herds in north-western Australia. 2. Continuous mating and minimal management

Data from a continuously mated, unweaned and unsupplemented herd of 400 Bos indicus cross cows at 'Kidman Springs', from 1981-85, were used to develop statistical models for conception rate and pattern. At the annual muster in June, an average of 49% of cows were rearing a calf; 15% of these and 75% of those not rearing a calf were pregnant; and 54% conceived within the next 12 months. Cows non-pregnant in June had higher conception rates than pregnant ones (75 v. 33%), and among pregnant cows, those which had reared a calf had higher conception rates than those which had not (40 v. 26%). Cows that had not reared a calf were much heavier and in better condition in June than those that had, while pregnant cows were slightly heavier and better conditioned than non-pregnant ones. The effect of liveweight or condition score in June on subsequent conception rate was consistent across years, reproductive classes and cow ages. Conception rates responded linearly to increases in liveweight, in the range 250-400 kg, by 11 percentage points up to October and by 24 points up to June. Similar linear responses to condition score in the range poor-good condition were 8 points by October and 15 points by June. Reproductive wastage was high, with 20% of cows diagnosed pregnant in June failing to rear their calf to branding. Low-cost management options to improve reproductive efficiency should be aimed at reducing nutritional stress and improving seasonal nutrition. To improve on the norm of a calf every second year in this environment, the class of cows not rearing a calf but pregnant and expected to calve by December has the greatest potential to conceive in consecutive years and should be segregated for preferential management. Conversely, aged cows not rearing a calf have comparatively low fertility and non-pregnant younger cows not rearing a calf are likely to be a survival risk following an out-ofseason conception. Both groups should be culled.

Effects of selection criteria on yield stability in chickpea (Cicer arietinum L.)

Selection in the F3 generation for seed yield, fruiting branches/plant, effective pods/plant, and seed index (100-seed weight) was carried out in two chickpea crosses. Sixty F5 lines (15 lines/selection criterion) along with check variety were evaluated for seed yield in three distinct environments. The effects of selection criteria on yield stability was examined using linear regression approach and genotype-grouping technique. There were no differences between selection criteria for linear yield responses of F5 lines to different environments. Within all four selection criteria the lines showed similar linear responses. The non-linear component was relatively higher for lines selected for effective pods and seed index than lines selected for yield and fruiting branches. On the basis of mean yield and coefficient of variation across environments, the seed index was the least effective selection criterion for developing high yielding and stable lines. When the results of stability parameters and genotype-grouping technique were considered together, selection for yield and fruiting branches was highly effective for isolating stable and high yielding lines.

Injury and Yield Response of Soybean to Chronic Doses of Ozone and Soil Moisture Deficit1

A 2‐yr field study was performed near Raleigh, NC, to determine injury and yield response of soybean [Glycine max (L.) Merr. ‘Davis’] to long‐term O3 exposure and soil moisture deficit. Two levels of soil moisture [well‐watered (WW) and water‐stressed (WS)] were tained by differential irrigating during periods of low precipitation. Open‐top field chambers were used to expose plants to different levels of O3 for 109 days. The 1983 season was drier and hotter than the 1984 season. In 1983, plants in the WS plots were under moderate to severe moisture stress from shortly after planting (V2) until midway through flowering (R3) and they yielded approximately half as much as those in the WW plots. In 1984, plants in the WS plots were under moderate moisture stress during flowering and pod‐fill stages and they yielded 20% less than those in the WW plots. In 1983, there was a significant relationship between O3 concentration and yield in the WW plots, but not in the WS plots. In 1984, similar linear responses to O3 occurred at both levels of soil moisture. Compared to yield in the charcoal‐filtered‐air (control) treatment (2‐yr 7 h day−1 mean O3 concentration of 0.027 μL L−1), predicted yield loss for WW plots at ambient O3 levels (2‐yr 7 h day−1 mean of 0.054 μL L−1) was 12% in 1983 and 14% in 1984. The predicted loss value for the WS plants in 1984 was 12%.

Regression and Cluster Analysis of Environmental Responses of Hybrid and Pureline Winter Wheat Cultivars1

The commercial development and release of F1 hybrid wheat (Triticum aestivum L.) cultivars should enable wheat producers to achieve higher levels of grain production. Despite increased interest in hybrid wheat, planting of hybrid cultivars at the presentime is limited to areas traditionally having high yield potential or receiving intensive management. This study was conducted to compare yield responses of hybrid and pureline cultivars across a wide range of environments. Regression and cluster analyses were applied to data obtained from four winter wheat performance trials from 1982 to 1985. A different set of either 30 or 40 genotypes, approximately half of which were hybrids, was evaluated each year in Oklahoma. Because the environmental responses of all genotypes were highly correlated in each year, environment means were employed as the index in the regression analysis. In 1982, the average regression coefficient (b) for hybrids (1.12) was significantly greater than that for either semidwarf purelines (0.99) or tall pnrelines (0.79), indicatingreater responsiveness of hybrids to improving production conditions. For the remaining years (1983–1985), similar linear responses of hybrids and semidwarf pnrelines indicated that the hybrid yield advantage did not increase in environments with higher index values. In addition, classification of genotypes into homogeneous‐response clusters according to actual responses indicated high similarity between environmental responses of hybrids and semidwarf pnrelines. Responses of hybrids and tall purelines, however, were dissimilar. The similar environmental response patterns of the most recently developed hybrid and semidwarf pureline winter wheat cultivars does not support the recommendation of either cultivar type when considering overall production potential of the environment.

X-ray experiments on dormant seeds of six-rowed barley.

In this expenment the vanety chosen was Sekitori Sai No.1, a six-rowed barley, now widely cultivated in Kanto area in Japan. Dormant seeds which had been stored under laboratory conditions since the previous harvest were used for irradiation. The seeds were placed in open petri dishes at about 9 cm. from target of a 60 kVp X-ray plant, run at 4 mA., where the dose rate was 235 r. per minute. After doses of 435 r. to 25, 000 r. were given, the seeds were sown in the field together with unirradiated seeds from the same sources. Contrary to expectation, even with higher X-ray doses maOrity of barley seeds produced plants up to maturity. The plant growth determined by measurements of the total height of the 18-day seedling after was sowing inhibited with the higher dose of X-rays. As regards the shape of the grbwth / dose curve, the X-rays gave a sigmoid curve (Fig. 1). The average spike fertility, as evidenced by seed set of the irradiated generation, decreased due to X-irradiation. The average spike fertility is the function of X-ray dose as illustrated by Fig. 2. Regression analysis indicated that relationship was linear. Three to five spikes were removed from each plant, and the seeds were sown for seedling mutation studies. The mutations observed resulted from chlorophyll deficiencies, and a linear relation between dose and frequency of mutations was obtained (Fig. 3). While at low doses the frequency of mutations per spike proge'ny and per dose unit was almost constant, at higher dcse there was a drop in the amount of effect produced per dose unit (Table 1). Also, in this experiment, the phenotypic effects, differed in response to varying doses, i.e., tlle mutation freqliency of viridis increased linearly with dose, while that of albilea showed a similar linear response to lower doses but somewhat decrement in the frequency of mutation at high doses. Most of the mutants were produced in the same relative frequencies as observed by earlier workers (Table 2).