Method For Phase Determination Research Articles

Dispersive micro solid phase extraction of glibenclamide from plasma, urine, and wastewater using a magnetic molecularly imprinted polymer followed by its determination by a high-performance liquid chromatography-photodiode array detector.

The present study describes the development of a simple and selective analytical method for dispersive micro solid phase extraction and determination of glibenclamide (GLB) using magnetic molecularly imprinted polymer (MMIP) as a sorbent. MMIP was fabricated by the non-covalent method on the surface of silicated Fe3O4 and had a high affinity for glibenclamide; dual monomers, itaconic acid and allylamine, were used for this. Polymerization was achieved by the precipitation method in the presence of glibenclamide as the template and ethylene glycol dimethacrylate as the cross-linker. The morphology and structural properties of the MMIP were characterized by different analytical methods. To achieve maximum extraction efficiency, influencing parameters were optimized. The linearity range was 1-2000 and 12-2000 μg L-1 by high-performance liquid chromatography-photodiode array detector (HPLC-PDA) and UV-vis spectroscopy, respectively. The detection and quantification limits with UV-vis and HPLC-PDA analyses were 4 and 12 μg L-1 and 0.3 and 1 μg L-1, respectively. Under optimized conditions, recovery of glibenclamide spiked in plasma, human urine, and wastewater was between 89.4 and 102.9% at the concentration levels of 25, 250, and 500 μg L-1; relative standard deviations were below 3.7% by HPLC-PDA. The developed method has a favorable pre-concentration factor of 140.0. Equilibrium data and sorption isotherms fitted well with the Langmuir model. A maximum sorption capacity of 24.260 mg g-1 was acquired based on the Langmuir model. The synthesized sorbent with high selectivity was used to separate GLB from complex biological systems and wastewater before measurement with UV-vis or HPLC-PDA.

Determining menstrual cycle phase: An empirical examination of methodologies and recommendations for improvement in behavioral and brain sciences

The recent decade has brought an exciting proliferation of behavioral, psychological and neuroscientific research involving the menstrual cycle. However, the reliability and validity of many popular methodologies for determining menstrual cycle phase lack empirical examination. These under-investigated methods include: (1) predicting menstrual cycle phase using self-report information only (e.g., “count” methods), (2) utilizing ovarian hormone ranges to determine menstrual cycle phase, and (3) using ovarian hormone changes from limited measurements (e.g., two time points) to determine menstrual cycle phase. In the current study, we examine the accuracy of these methods for menstrual cycle phase determination using 35-day within-person assessments of circulating ovarian hormones from 96 females across the menstrual cycle. Findings indicate that all three common methods are error-prone, resulting in phases being incorrectly determined for many participants, with Cohen's kappa estimates ranging from −0.13 to 0.53 indicating disagreement to only moderate agreement depending on the comparison. Such methodological challenges are surmountable through careful study design, more frequent hormone assays (when possible), and utilization of sophisticated statistical methods. With increased methodological rigor in behavioral, psychological and neuroscientific research, the field will be poised to detect biobehavioral correlates of ovarian hormone fluctuations for the betterment of the mental health and wellbeing of millions of females.

The sensitivity of modeled snow accumulation and melt to precipitation phase methods across a climatic gradient

Abstract. A critical component of hydrologic modeling in cold and temperate regions is partitioning precipitation into snow and rain, yet little is known about how uncertainty in precipitation phase propagates into variability in simulated snow accumulation and melt. Given the wide variety of methods for distinguishing between snow and rain, it is imperative to evaluate the sensitivity of snowpack model output to precipitation phase determination methods, especially considering the potential of snow-to-rain shifts associated with climate warming to fundamentally change the hydrology of snow-dominated areas. To address these needs we quantified the sensitivity of simulated snow accumulation and melt to rain–snow partitioning methods at sites in the western United States using the SNOWPACK model without the canopy module activated. The methods in this study included different permutations of air, wet bulb and dew point temperature thresholds, air temperature ranges, and binary logistic regression models. Compared to observations of snow depth and snow water equivalent (SWE), the binary logistic regression models produced the lowest mean biases, while high and low air temperature thresholds tended to overpredict and underpredict snow accumulation, respectively. Relative differences between the minimum and maximum annual snowfall fractions predicted by the different methods sometimes exceeded 100 % at elevations less than 2000 m in the Oregon Cascades and California's Sierra Nevada. This led to ranges in annual peak SWE typically greater than 200 mm, exceeding 400 mm in certain years. At the warmer sites, ranges in snowmelt timing predicted by the different methods were generally larger than 2 weeks, while ranges in snow cover duration approached 1 month and greater. Conversely, the three coldest sites in this work were relatively insensitive to the choice of a precipitation phase method, with average ranges in annual snowfall fraction, peak SWE, snowmelt timing, and snow cover duration of less than 18 %, 62 mm, 10 d, and 15 d, respectively. Average ranges in snowmelt rate were typically less than 4 mm d−1 and exhibited a small relationship to seasonal climate. Overall, sites with a greater proportion of precipitation falling at air temperatures between 0 and 4 ∘C exhibited the greatest sensitivity to method selection, suggesting that the identification and use of an optimal precipitation phase method is most important at the warmer fringes of the seasonal snow zone.

Digital method of the harmonic signal initial phase determination at a sampling below the Nyquist frequency

Digital method of the harmonic signal initial phase determination at a sampling below the Nyquist frequency

Femtosecond Timekeeping: Slip-Free Clockwork for Optical Timescales

Using an optical frequency comb to directly convert a frequency reference to a useable time output will enable tight synchronization of tomorrow's optical-clock networks. Previous frequency-comb systems experienced cycle slips too often to provide true optical timescales. This study combines innovative fiber-comb designs, digital phase locking, and precise phase-determination methods to demonstrate optical clockwork with no phase slips for over a $m\phantom{\rule{0}{0ex}}o\phantom{\rule{0}{0ex}}n\phantom{\rule{0}{0ex}}t\phantom{\rule{0}{0ex}}h$. Fault-free timekeeping at the femtosecond level over months is a vital step in supplanting the current microwave time standard with an optical standard, and could improve $e.g.$ gravitational geodesy and GPS technology.

Towards 3D crystal orientation reconstruction using automated crystal orientation mapping transmission electron microscopy (ACOM-TEM).

To relate the internal structure of a volume (crystallite and phase boundaries) to properties (electrical, magnetic, mechanical, thermal), a full 3D reconstruction in combination with in situ testing is desirable. In situ testing allows the crystallographic changes in a material to be followed by tracking and comparing the individual crystals and phases. Standard transmission electron microscopy (TEM) delivers a projection image through the 3D volume of an electron-transparent TEM sample lamella. Only with the help of a dedicated TEM tomography sample holder is an accurate 3D reconstruction of the TEM lamella currently possible. 2D crystal orientation mapping has become a standard method for crystal orientation and phase determination while 3D crystal orientation mapping have been reported only a few times. The combination of in situ testing with 3D crystal orientation mapping remains a challenge in terms of stability and accuracy. Here, we outline a method to 3D reconstruct the crystal orientation from a superimposed diffraction pattern of overlapping crystals without sample tilt. Avoiding the typically required tilt series for 3D reconstruction enables not only faster in situ tests but also opens the possibility for more stable and more accurate in situ mechanical testing. The approach laid out here should serve as an inspiration for further research and does not make a claim to be complete.

Universal optical setup for phase-shifting and spatial-carrier digital speckle pattern interferometry

Digital speckle pattern interferometry (DSPI) is a competitive optical tool for full-field deformation measurement. The two main types of DSPI, phase-shifting DSPI (PS-DSPI) and spatial-carrier DSPI (SC-DSPI), are distinguished by their unique optical setups and methods of phase determination. Each DSPI type has its limited ability in practical applications. We designed a universal optical setup that is suitable for both PS-DSPI and SC-DSPI, with the aim of integrating their respective advantages, including PS-DSPI’s precise measurement and SC-DSPI’s synchronous measurement, improving DSPI's measuring capacity in engineering. The proposed setup also has several other advantages, including a simple and robust structure, easy adjustment and operation, and versatility of measuring approach.

Ab initio phasing by molecular averaging in real space with new criteria: application to structure determination of a betanodavirus.

Molecular averaging, including noncrystallographic symmetry (NCS) averaging, is a powerful method for ab initio phase determination and phase improvement. Applications of the cross-crystal averaging (CCA) method have been shown to be effective for phase improvement after initial phasing by molecular replacement, isomorphous replacement, anomalous dispersion or combinations of these methods. Here, a two-step process for phase determination in the X-ray structural analysis of a new coat protein from a betanodavirus, Grouper nervous necrosis virus, is described in detail. The first step is ab initio structure determination of the T = 3 icosahedral virus-like particle using NCS averaging (NCSA). The second step involves structure determination of the protrusion domain of the viral molecule using cross-crystal averaging. In this method, molecular averaging and solvent flattening constrain the electron density in real space. To quantify these constraints, a new, simple and general indicator, free fraction (ff), is introduced, where ff is defined as the ratio of the volume of the electron density that is freely changed to the total volume of the crystal unit cell. This indicator is useful and effective to evaluate the strengths of both NCSA and CCA. Under the condition that a mask (envelope) covers the target molecule well, an ff value of less than 0.1, as a new rule of thumb, gives sufficient phasing power for the successful construction of new structures.

Direct decomposition X-ray diffraction method for amorphous phase quantification and glassy phase determination in binary blends of siliceous fly ash and hydrated cement

A direct decomposition method of X-ray diffraction pattern associated with amorphous phases in a binary blend containing hydrated cement and siliceous fly ash is developed. The method relies on identifying patterns associated with individual components within the overall intensity pattern produced by the total amorphous phase. The intensity pattern associated with the total amorphous phase in a binary blend of siliceous fly ash and hydrated cement is obtained using the Pawley intensity refinement method. The features of the intensity patterns associated with the amorphous reaction products in hydrated cement and the glassy content of siliceous fly ash extracted by decomposition of the overall intensity pattern produced by the combined amorphous phase are shown to match the features obtained directly from the pure phases. The direct decomposition method allows for quantification of amorphous components, which can be applied to study the evolving phases in a hydrating binary system.

Estimation of thermomagnetometry method sensitivity for magnetic phase determination

In this article, the sensitivity of thermomagnetometry method for magnetic phase determination in lithium substituted ferrites was estimated by thermogravimetric analysis in magnetic field of lithium-zinc ferrite and iron dioxide (Li0.4Fe2.4Zn0.2O4+α-Fe2O3) components mixture with different mass proportions: 2, 4, 6, and 100 mass% Li0.4Fe2.4Zn0.2O4 phase in total mixture. Thereby, analyzed samples are mixture of magnetic and nonmagnetic phases. Results of thermomagnetometric analysis were supplemented with the X-Ray diffraction analysis data. It was shown that the thermomagnetometry method allows to determine a magnetic phases with mass content not less than 2 mass% in analyzed mixture. In this case, we can clearly estimate the position and intensity of the peak on derivative thermogravimetric curve, which connected with a magnetic phase transition in ferrite at Curie temperature.

A novel method for quantitative phase determination of cristobalite in ceramic cores using differential scanning calorimeter

The present research aims at developing a new quantitative thermal analysis method based on differential scanning calorimeter for determination of cristobalite phase content in ceramic cores. For this purpose, various control samples with different amounts of cristobalite phase were made based on the chemical composition of silica-based ceramic cores and analyzed via differential scanning calorimetry (DSC) technique. The surface area under the α → β cristobalite transition peak in the DSC curves was calculated via numerical integral of the peaks area, and the ratio of this area to the samples weight (A/W) was calibrated by cristobalite content of the samples. Afterward, for determining the cristobalite content of some industrial samples, the DSC patterns were plotted, and the A/W ratio of these samples was determined by the same method. Then the A/W ratios of the industrial samples were fitted on the calibration line, and the cristobalite content was derived using the equation of the calibration line. The method showed good accuracy, and the error values of the estimated cristobalite content of the industrial samples were below 2 %.

Crystal Structure of BRP39 protein expressed during Mammary Gland Apoptosis

Breast regression protein (BRP39) from mice is a 39 kDa protein which is a member of chitolectin class of GH18 family. High levels of expression of BRP39 have been detected in breast carcinoma. It has been proposed that this may act as a protecting signalling factor and also help in proliferation of cells during breast cancer. It can act as a potential candidate for rational structure based drug design against breast cancer. Here, we report the crystal structure of recombinant BRP39 in a deglycosylated form which was expressed in a heterologous system i.e E.Coli. To understand the role of sugar moiety, crystal structure of a deglycosylated chitolectin is an essential requirement. The structure was solved by molecular replacement method of phase determination and refined to a 2.6 A0resolution. The overall structure of BRP39 consists of two globular domains: a large (β/α)8 TIM barrel domain and a small (α+β) domain. The most striking observation from BRP39 structure is the conformation of critical Trp 100 residue into the β-barrel of carbohydrate binding groove of BRP39. The structure reveals that the glycan moiety plays an important role in the orientation of critical Trp100 in the β-barrel. In deglycosylated BRP39, it orients away from the barrel and resembles the conformation as seen in non-glycosylated chitinases. In contrast to this, the corresponding Trp is oriented into the barrel in case of other glycosylated homologues of BRP39 which may have its implications in sugar binding. Furthermore, in MGP-40, the altered conformation of loop is stabilized by H-bonding and stacking interactions whereas in BRP39, no hydrogen bond was observed between any of the residues of this loop except for Trp100 which interacts with a water molecule may be to stabilize its conformation. Another important observation in the sugar binding groove of BRP39 structure is the mutation of two important residues, one in TIM barrel domain and another in a part of α+β domain which is also involved in sugar binding. Asn100 and Arg263 in Hcgp39 and other chitinase- like proteins (SPX-40 structures) are replaced by Lys101 and Lys264 in BRP39. Both of these residues i.e. Asn100 and Arg 263 in HCgp39 have been reported to be involved in stabilizing the binding of GlcNAc inside the groove. Possibly, there is a significant distortion in the shape of sugar binding groove due to these mutations in BRP39.

Estrus Cycle Status Defined by Vaginal Cytology Does Not Correspond to Fluctuations of Circulating Estrogens in Female Mice

Gender-oriented studies in shock, trauma, and/or sepsis require accurate monitoring of hormonal fluctuations as estrogens may influence various end points. Yet, monitoring is challenging in small laboratory animals: e.g., despite its subjectivity, vaginal smears are the major method for determination of estrus cycle phases in mice. Using female mice of different age, we aimed to (a) characterize general age-related changes in systemic estrogens and (b) examine the utility of determination of the estrus cycle by vaginal smears and/or impedance simultaneously comparing them with oscillation of systemic estrogens. In this study, 3-, 15-, and 20-month-old mice underwent vaginal smear and impedance examination each morning for 22 days. Ten hours after each morning checkup, feces were collected, and a second vaginal smear performed. Blood was collected on days 15 and 22. In 3-month-old females, estrus (by smears) was three times more frequent than in older mice, but mean concentrations of plasma and fecal estrogens never decreased with age. Collectively (not individually) plotted fecal estrogens values increased in the proestrus/estrus interphase (by smears) in 3-month-old mice only. Impedance typically peaked (4.5 Ω in 3-month-old mice) in the estrus phase, and only the prediction of estrus (highest area under the curve = 0.87 in 3-month-old) but not of other phases was possible. Regardless of age, individual cycle phase (by smears) never correlated with corresponding fecal estrogens, and estrus could not be predicted. In conclusion, while the fecal estrogens oscillation and frequency of estrus phase were affected by age, the systemic hormone release persisted. In mice, vaginal cytology did not reflect changes of systemic (fecal) estrogens, whereas impedance accurately identified estrus. The flaws and advantages of the examined monitoring methods should be considered in the design of future shock studies.

A new structure determination method of lectins using a selenium-containing sugar ligand.

Phase determination is essential for solving X-ray crystal structures of proteins and their complexes. Conventional phase-determination methods using heavy atoms (Pt, Au, Hg, etc.) or the selenium (Se) atom are routinely utilized in structure determination of protein crystals. Here, we describe an alternative phase-determination method for proteins such as lectins in which a Se-containing glycan is used as a ligand. In this technique, the Se atoms are simply introduced into the protein crystal as a complex, and the phase of the protein can be determined using anomalous signals from the Se-containing sugar.

IDENTIFYING PHASE SYNCHRONOUS REGIMES IN NON-COHERENT AND MULTIPLE SCROLL ATTRACTOR SYSTEMS

This work discusses the applicability of a method for phase determination of scalar time series from nonlinear systems. We apply the method to detect phase synchronization in different scenarios, and use the phase diffusion coefficient, the Lyapunov spectrum, and the similarity function to characterize synchronization transition in nonidentical coupled Rössler oscillators, both in coherent and non-coherent regimes. We also apply the method to detect phase synchronous regimes in systems with multiple scroll attractors as well as in experimental time series from coupled Chua circuits. The method is of easy implementation, requires no attractor reconstruction, and is particularly convenient in the case of experimental setups with a single time series data output.

An Echo-Based Gait Phase Determination Method of Lower Limb Prosthesis

The gait phase determination is the basis of the control of intelligent prosthesis. The prosthetic usually determines the gait phase according to its own motion parameters, which will cause the asymmetry gait of the prosthesis wearer during level walking due to the lack of contralateral motion information. By using of a variety of sensors installed in the healthy leg and prosthesis, the gait phase determination method based on echo control can achieve good symmetry, but at the same time also made calculation difficult. Based on the existing echo method, a gait phase determination method by utilize of the contralateral motion parameters is proposed. According to gait test data collected from healthy subjects, motion parameters and their relation can be obtained. Then the proposed method can determine its gait phase and contralateral phase. Preliminary experiment is conducted and verified the effective of the method.

Phase determination method in statistical generalized phase-shifting digital holography

A simple estimation method of the relative phase shift for generalized phase-shifting digital holography based on a statistical method is proposed. This method consists of a selection procedure of an optimum cost function and a simple root-finding procedure. The value and sign of the relative phase shift are determined using the coefficient and the solution of the optimum cost function. The complex field of an object wave is obtained using the estimated relative phase shift. The proposed method lifts the typical restriction on the range of the phase shift due to the phase ambiguity problem. Computer simulations and optical experiments are performed to verify the proposed method.

Surface-based precipitation phase determination methods in hydrological models

We compared solid and liquid precipitation mass output from three categories of common model precipitation phase determination schemes (PPDS) to the recorded precipitation phase in a set of 45 years of 3-hour manual meteorological observations from 19 Swedish meteorological stations. In the first category of rain/snow thresholds, it was found that rain/snow air temperature threshold (ATT) is a better precipitation phase indicator than a rain/snow dew point temperature threshold. When a rain/snow ATT of 0.0 °C (a default value used in some recent models) was replaced by 1.0 °C, misclassified precipitation was reduced by almost one half. A second category of PPDS use two ATTs, one snow and one rain, with a linear decrease in snow fraction between. This category identified precipitation phase better than a rain/snow ATT at 17 stations. Using all observations from all the meteorological stations, a final category using an air-temperature-dependent snow probability curve resulted in slightly lower misclassified precipitation mass at 13 of the 19 stations. However, schemes from the linear decrease in snow fraction category had the lowest misclassified precipitation mass at four meteorological stations.

Application of Neutron Scattering in Earth Sciences

The unique properties of neutron interaction with materials have long been applied to the study of geological materials, with Shull and Smart using them in 1949 to determine the antiferromagnetic structure of manganosite (MnO). Neutron diffraction provides an accurate method for crystal structure determination of hydrous phases, particularly ices, and investigations of cation ordering of elements that are adjacent in the Periodic Table, such as Al–Si in feldspars and zeolites. Both elastic and inelastic scattering have been used to determine the properties of fluids that are present in many sedimentary rocks, including shales that are often saturated with brines or hydrocarbons. Due to minimal absorption and deep sample penetration, neutron scattering has become a favorite tool for crystallographic preferred orientation (texture) analysis of rocks as well as destruction-free three-dimensional (3D) tomographic characterization of microstructures.

A Simple PCR–RFLP Method for Genetic Phase Determination in Compound Heterozygotes

When susceptibility to diseases is caused by cis-effects of multiple alleles at adjacent polymorphic sites, it may be difficult to assess with confidence the genetic phase and identify individuals carrying the risk haplotype. Experimental assessment of genetic phase is still challenging and most population studies use statistical approaches to infer haplotypes given the observed genotypes. While these statistical approaches are powerful and have been proven very useful in large scale genetic population studies, they may be prone to errors in studies with small sample size, especially in the presence of compound heterozygotes. Here, we describe a simple and novel approach using the popular PCR–RFLP based strategy to assess the genetic phase in compound heterozygotes. We apply this method to two extensively studied SNPs in two clustered immune-related genes: The −308 (G > A) and the +252 (A > G) SNPs of the tumor necrosis factor (TNF) alpha and the lymphotoxin alpha (LTA) genes, respectively. Using this method, we successfully determined the genetic phase of these two SNPs in known compound heterozygous individuals and in every sample tested. We show that the A allele of TNF −308 is carried on the same chromosome as the LTA +252(G) allele.