Mean Peak Width Research Articles

Optimal Spectral Resolution for Infrared Studies of Solids and Liquids.

Due to a legacy originating in the limited capability of early computers, the spectroscopic resolution used in Fourier transform infrared spectroscopy and other systems has largely been implemented using only powers of two for more than 50 years. In this study, we investigate debunking the spectroscopic lore of, e.g., using only 2, 4, 8, or 16 cm-1 resolution and determine the optimal resolution in terms of both (i) a desired signal-to-noise ratio and (ii) efficient use of acquisition time. The study is facilitated by the availability of solids and liquids reference spectral data recorded at 2.0 cm-1 resolution and is based on an examination in the 4000-400 cm-1 range of 61 liquids and 70 solids spectra, with a total analysis of 4237 peaks, each of which was also examined for being singlet/multiplet in nature. Of the 1765 liquid bands examined, only 27 had widths <5 cm-1. Of the 2472 solid bands examined, only 39 peaks have widths <5 cm-1. For both the liquid and solid bands, a skewed distribution of peak widths was observed: For liquids, the mean peak width was 24.7 cm-1 but the median peak width was 13.7 cm-1, and, similarly, for solids, the mean peak width was 22.2 cm-1 but the median peak width was 11.2 cm-1. While recognizing other studies may differ in scope and limiting the analysis to only room temperature data, we have found that a resolution to resolve 95% of all bands is 5.7 cm-1 for liquids and 5.3 cm-1 for solids; such a resolution would capture the native linewidth (not accounting for instrumental broadening) for 95% of all the solids and liquid bands, respectively. After decades of measuring liquids and solids at 4, 8, or 16 cm-1 resolution, we suggest that, when accounting only for intrinsic linewidths, an optimized resolution of 6.0 cm-1 will capture 91% of all condensed-phase bands, i.e., broadening of only 9% of the narrowest of bands, but yielding a large gain in signal-to-noise with minimal loss of specificity.

Investigation into the Reciprocating Sealing Performance Based on an Optical Test Method

Reciprocating seals are essential elements for hydraulic cylinders. The status of the contact area between the seal and the counterpart directly determines the sealing performance. An optical test rig for the O-ring seal was constructed in this study to investigate the tribological characteristics among the contacting zone, where the cylinder was changed to be transparent and a microscope is employed to observe and record the sealing status. A numerical method coupling finite element analysis (FEA) and the mixed lubrication procedure is implemented for the theoretical analysis. A comparison between the simulation and the experiment for the sealing width, friction force, and leakage was conducted. During the reciprocating motion, it was found that the oil film thickness adhering onto the cylinder’s inner wall was not even along the axial direction and that the leakage oil would be accumulated at the stroke-end position because of the seal’s scraping effect. The topographic indicators for the contact mechanisms are discussed, and the results demonstrated that the implementation of the mean peak width (Rsm) for the asperity radius could obtain more reasonable results. The performance of the O-ring seal at different velocities was theoretically and experimentally investigated. With an increase in velocity, the leakage rate increased and the friction force decreased. The simulation results are consistent with the experimental results both in the overall trend and in the order of magnitude.

De novo NMR pulse sequence design using Monte-Carlo optimization techniques.

Separated Local Field (SLF) experiments have been routinely used for measuring 1H-15N heteronuclear dipolar couplings in oriented-sample solid-state NMR for structure determination of proteins. In the on-going pursuit of designing better-performing SLF pulse sequences (e.g. by increasing the number of subdwells, and varying the rf amplitudes and phases), analytical treatment of the relevant average Hamiltonian terms may become cumbersome and/or nearly impossible. Numerical simulations of NMR experiments using GPU processors can be employed to rapidly calculate spectra for moderately sized spin systems, which permit an efficient numeric optimization of pulse sequences by the Monte Carlo Simulated Annealing protocol. In this work, a computational strategy was developed to find the optimal phases and timings that substantially improve the 1H-15N dipolar linewidths over a broad range of dipolar couplings as compared to SAMPI4. More than 100 pulse sequences were developed de novo and tested on an N-acetyl Leucine crystal. Seventeen distinct pulse sequences were shown to produce sharper mean linewidths than SAMPI4. Overall, these pulse sequences have more variable parameters (involving non-quadrature phases) and do not involve symmetry between the odd and even dwells, which would likely preclude their rigorous analytical treatment. The top performing pulse sequence, termed ROULETTE-1, has 18% sharper mean linewidths than SAMPI4 when run on an N-acetyl Leucine crystal. This sequence was also shown to be robust over a broad range of 1H carrier frequencies and various crystal orientations. The performance of such an optimized pulse sequence was also illustrated on 15N Leucine-labeled Pf1 coat protein reconstituted in magnetically aligned bicelles. For the optimized pulse sequence the mean peak width was 14% sharper than SAMPI4, which in turn yielded a better signal to noise ratio, 20:1 vs. 17:1. This method is potentially extendable to de novo development of a variety of NMR experiments.

Peak bordering for ultrafast single particle analysis using ICP-MS

The characterisation of inorganic nanoparticles (NPs) by single particle inductively coupled plasma mass spectroscopy is possible only if the spectrometer is capable of measurement with high time-signal resolution. The latest generation of spectrometers allow for measurements with dwell times (dt) shorter than the 100 μs gold standard, i.e. as low as 10 μs. The statistical behaviours of signals obtained with dt values of 10, 20, 50, and 100 μs were tested for 40, 60, and 100 nm silver NPs. Very low measured signals (units of counts) led to the occurrence of zero signal values inside the peaks corresponding to individual NPs. The probability of the occurrence of a zero signal inside the peak increased with decreasing dt and decreasing NP size. The standard approach to the bordering of the beginning and end of the peak by one zero signal point failed here and lead to the false detection of a larger number of smaller peaks. For example, in the case of 40 nm NPs a quadruple number of peaks were detected for a dt value of 10 μs compared to the 100 μs dt value; the mean peak width at 10 μs dt was approximately 220 μs, while at 100 μs dt it was 550 μs. The results tended to be less distorted when dt was longer and the NP size was larger. Low dt values also led to a distortion of the peak area distribution. For 40 nm NPs and 10 μs, the most frequent peak area and the width of the peak area distribution were not evaluated due to a non-Gaussian course; 20 μs dt caused (compared to 100 μs) a decrease in the most frequent peak area by approximately 35% (33 counts for 100 μs dt vs. 22 counts for 20 μs dt) and an increase in the width of the peak area distribution by 70% (10 counts for 100 μs dt vs. 17 counts for 20 μs dt). Therefore, new approaches to bordering peaks were tested, which consisted of searching for an uninterrupted zero signal point sequence with a total length of 50 μs or 100 μs. Only the criterion of a 100 μs delay between the two adjacent peaks resulted in values of the number of detected peaks, the most frequent peak areas, and the width of peak area distribution virtually independent of dt.

Alpha particle irradiation of bulk and exfoliated MoS2 and WS2 membranes

The properties of two-dimensional transition metal dichalcogenide (TMDC) nanosheets have been intensively studied in recent years as these compounds have emerged as promising materials for future electronic, photonic and sensor applications. Some of these applications may require the nanosheets to be exposed to radiation fields; therefore, an understanding of their interaction mechanisms with ionising radiation is required.In our experiment, we administer 1.66 MeV helium nuclei to bulk and liquid phase exfoliated MoS2 and WS2 membranes to two total absorbed doses. Raman spectroscopy shows small changes, within the spectrometer resolution, in all samples. Although small, some reproducible changes are observed such as a blueshift of the E2g1 and A1g modes in the bulk MoS2 membrane irradiated to a high total absorbed dose; these shifts are accompanied by a small broadening of both peaks. In bulk WS2 membranes, He2+ irradiation induces a blueshift and monotonic mean peak width decrease of the 2LA(M) phonon mode with increasing fluence. The structural changes associated to these peak shifts are currently unknown. Raman spectroscopy, in agreement with energy dispersive x-ray spectroscopy, shows that amorphous carbon is present in the exfoliated MoS2 and WS2 membranes after irradiation. It is suggested that this amorphous carbon could be formed by radiolytic amorphisation of residual solvent, retained within the ripplocations of the exfoliated nanosheets.Due to the morphology of the liquid phase exfoliated nanosheets, they exhibit greater radiation stability than bulk TMDCs when exposed to heavy charged particle radiation. These results differ from those previously reported for monolayer and bulk MoS2 produced by mechanical exfoliation. The relative radiation stability of the liquid phase exfoliated nanosheets is expected to arise from attenuation and dissipation of the ion beam energy by the residual solvent and the amorphous carbon subsequently produced.

Energy calibration and gain correction of pixelated spectroscopic x-ray detectors using correlation optimised warping

We describe the implementation of a reliable, robust and flexible gain correction and energy calibration algorithm for pixelated spectroscopic x-ray detectors. This algorithm uses a data processing method known as correlation optimised warping which aligns shifted datasets by means of a segmental linear stretching and compression of the spectral data in order to best correlate with a reference spectrum. We found the algorithm to be very robust against low-count spectroscopy, and was reliable in a range of different spectroscopic applications. Analysis of the integrated spectrum over all pixels for a Cerium K-alpha x-ray emission (at 34.72 keV) yielded a peak width of 2.45 keV before alignment and 1.11 keV after alignment. This compares favourably with the best in class pixel peak width of 0.76 keV and the mean peak width for all pixels of 1.00 keV. We also found the algorithm to be more user friendly than other peak-search algorithms because there is less external input. A key advantage of this algorithm is that it requires no prior knowledge of the input spectral characteristics, shape or quality of the data. This therefore lends itself to being useful for in-line processing and potentially removes the need for a separate calibration standard (e.g. a radioactive source). This algorithm can be used for any system that simultaneously collects large numbers of spectral data—including multi-element detectors.

Characterizing Neuronal Network Burst Synchrony by Using Burst Signal

Characterizing Neuronal Network Burst Synchrony by Using Burst Signal

Influence of pumpkin seed oil in continuous phase on droplet size and stability of water-in-oil emulsions

The aim of this work was to contribute to the optimized production of water-in-oil emulsions with pumpkin seed oil in the oil phase using a high-speed homogenizer. Pumpkin seed oil is a valuable natural source of essential fatty acids and biologically active micronutrients that contribute to its nutritive value and medical uses, and reduce interfacial tension between water and the oil phases. Therefore, pumpkin seed oil can be considered as a prosperous oil phase whose use can possibly decrease the amount of some emulsifier that is normally involved in every emulsification process. A central composite rotatable experimental design was implemented to analyze the impact of the contents of polyglycerol polyricinoleate and pumpkin seed oil in the continuous phase, as well as water phase content in the emulsion on droplet size distribution and the response surface methodology was used to obtain optimal conditions for water-in-oil emulsion preparation. Mean size diameter of water droplets was in a range from 400 to 850 nm, with mean peak width of 100 to 220 nm, respectively. The influence of all three investigated factors on the emulsification was determined. Additionally, the emulsions prepared with pumpkin seed oil showed a higher stability during the storage time compared to the emulsions with sunflower oil.

Peak capacity estimation in isocratic elution

Peak capacity (i.e. maximal number of resolved peaks that fit in a chromatographic window) is a theoretical concept with growing interest, but based on a situation rarely met in practice. Real chromatograms tend to have uneven distributions, with overlapped peaks and large gaps. The number of resolved compounds should, therefore, be known from estimations. Several equations have been reported for this purpose based on three perspectives, namely, the intuitive approach (peak capacity as the size of the retention time window measured in peak width units), which assumes peaks with the same width, and the outlines of Giddings and Grushka, which consider changes in peak width with retention time. In this work, the peak capacity concept is discussed and three new approaches are derived based on realistic descriptions of peak shape. The first one is based on the Grushka's approach and considers the contributions of column and extra-column peak variances. The second one relies on Giddings’ and assumes asymmetrical peaks where left and right peak half-widths depend linearly on retention time. The third equation, based on the intuitive approach, uses a mean peak width obtained by integration, instead of a mean value from several representative peaks. The accuracy of the classical Giddings’ approach for ideal peaks, a modification of the Grushka's approach that considers variation of peak width at half-height, and the three new approaches were checked on combined chromatograms built by adding real peaks. The results demonstrate that the change in efficiency (and not in skewness) is the relevant factor, at least in the studied examples. Also, peak width should be measured at low peak height ratios (i.e. 10%) to better account peak deformation.

Relationship Between Interstitial And Blood Glucose in Type 1 Diabetes Patients: Delay And The Push-Pull Phenomenon Revisited

Interpretation of glucose sensor results requires clarification of the relationship between interstitial (IG) and blood (BG) glucose. We examined the delay of IG upon BG change and reinvestigated the push-pull phenomenon in type 1 diabetes patients. The push-pull phenomenon postulates that IG shows a delayed increase but earlier decrease compared to BG. If so, postprandial sensor curves should have narrower peak widths than BG curves. For both sensors a two-point calibration procedure was used. Delay was assessed by shifting combined fitted postprandial glucose sensor curves horizontally. The sensor and BG peak widths of the separately fitted curves were assessed and compared. Peak width was re-assessed for the microdialysis sensor using raw current values to rule out any calibration effect on the shape of the curve. The contribution of instrumental delay to the earlier reported 7.1-min delay of the microdialysis sensor was calculated. No delay [-2.2 +/- 6.2 (SD) min] was seen for the needle-type sensor. Instrumental delay was >6.2 min for the microdialysis sensor, accounting for more than 87% of the total reported delay of 7.1 +/- 5.5 min. Mean peak width for the BG curves was 100.8 +/- 25.0 min, for the needle-type sensor curves 110.0 +/- 20.5 min, and for the microdialysis sensor curves 104.6 +/- 21.7 min (P = 0.052 and P = 0.11 vs. BG, respectively). Mean peak width for the uncalibrated microdialysis current values was 105.0 +/- 23.1 min, which was not different from the peak width of the BG curves (P = 0.347). IG-BG delay may be smaller than previously postulated. The sensor curves tended to have broader peaks than the BG curves, in contrast to the expected narrower peaks predicted by the push-pull phenomenon. This argues against the existence of the push-pull phenomenon.

Periodicity, amplitude and width of synchronized cardiac sympathetic nerve activity in anaesthetized cats

Using a recently developed method, we studied periodicity, amplitude and width of synchronized cardiac sympathetic nerve activity (CSNA) at various intervals of periodic baroreceptor input in anaesthetized cats. ECG, aortic pressure and CSNA were recorded when cardiac interval was changed by artificial pacing, or when the aortic nerve was stimulated after baroreceptor denervation. The periodicity of synchronized CSNA showed mainly two modes: one was 8–14 Hz rhythmicity (Tc) and the other was related to cardiac cycle (Tb). The Tc mode was almost constant and independent of cardiac interval or stimulation. The probability of the Tc mode increased as pacing interval increased. The Tb mode reflected the interval of inhibition in CSNA due to pulsatile baroreceptor input. The mode of inhibitory rhythm (Ts) related to the stimulation of the aortic nerve was almost constant and independent of the stimulation interval. The probability of the Ts mode was highest at a 250-ms interval and decreased with increase in stimulus interval. The mean peak height or mean peak width did not changed significantly during pacing the heart at various intervals, nor after baroreceptor denervation. The peak height and peak width had a significant linear relationship at any cardiac interval or after baroreceptor denervation, whereas no relationship between the peak-to-peak interval and the peak height or peak width was found. These results indicate that the cardiac-related rhythm is produced by inhibition of transmission of the fundamental rhythm by periodic baroreceptor input. Our results suggest also that the amplitude and periodicity of synchronized CSNA are separately regulated.

Episodic and seasonal rhythms of cortisol secretion in male Eld's deer (Cervus eldi thamin).

Episodic and seasonal rhythms of cortisol secretion were evaluated in six adult Eld's deer (Cervus eldi thamin) stags. Plasma cortisol was measured in serial blood samples collected via remote catheterization every 10 min for 10 h within 2 weeks of the summer solstice (21 June), autumn equinox (22 September), winter solstice (21 December) and spring equinox (20 March), and in weekly blood samples collected from sedated stags. Cortisol was secreted episodically at a rate of approximately 0.6 peaks/h. Based on quantitative peak detection analyses of each 10-h data series, no overall seasonal differences (P > 0.05) were detected in the number of peaks (mean range, 5.7-6.2), maximal peak height (mean range, 30.1-40.8 nmol/l), mean peak height as per cent increase (mean range, 158-168%), mean interval between peaks (mean range, 80.1-88.6 min), mean peak width (mean range, 55.1-65.1 min) and mean peak area under the curve (mean range, 675-816 nmol/l min). Based on weekly blood sampling, spring cortisol concentrations were elevated (P < 0.05) compared with summer and autumn concentrations. However, when mean cortisol concentrations derived from the 10-h quarterly data sets were analysed, no seasonal differences (P > 0.05) were detected. The present study represents the first detailed confirmation of episodic cortisol secretion in any cervid. Results (1) indicate that Eld's deer stags lack a distinct seasonal rhythm of cortisol secretion and (2) clearly illustrate the need for frequent blood sampling in fully conscious individuals to ensure accurate assessment of adrenal status in cervids.

Verification of the uncertainty principle in neutron interferometry

A recent neutron interferometry experiment has been interpreted as an explicit verification of the uncertainty principle. Here the question is discussed which mathematical expression of the uncertainty principle is relevant to this experiment. It is shown that the experiment does not measure the standard deviation σ q in position independently of ad hoc assumptions on the shape of the wavefunction. Rather, it is the “mean peak width” that is measured directly. Therefore, the natural interpretation of this experiment is not as a verification of the Heisenberg relation σ pσ q ⩾ 1 2 ; but rather of a relation between mean peak width in position and the overall spread in momentum.

Overall width, mean peak width and the uncertainty principle

We define the overall width W and the mean peak width w of a normalized function ψ ( x). We show W ≤ 2 Δx and w > (2 Δp) −1, where Δx and Δp are standard deviations. Analogous relations hold for the Fourier transform. The uncertainty principle is expressed precisely by these relations, not by ΔxΔp ≥ 1 2 .

Advantages of a new ion-exchange resin for the liquid chromatography of biogenic amines: a methacrylic acid polymer cross-linked with butanedioldiacrylate

The synthesis of a methacrylic acid polymer, cross-linked with 11% 1,4-butane-dioldiacrylate is described. This was shown to be much more efficient than conventional carboxylic resins for the liquid chromatography of biogenic amines, at least in the pH range 7–9. The height equivalent to a theoretical plate was from 2–3 particle diameters for most of the amines tested. The peaks given by the remainder could often be sharpened by adding imidazole to the eluting buffer. A low-pressure system based on the new resin, giving a mean peak width of only 1.1 ml will separate 18 or more mono-, di- and polyamines simultaneously.