Rotational Phase Research Articles

Movement Mechanism Differences of Badminton Overhead Forehand and Backhand Smash Stroke Techniques during Teaching Learning in Human Movement Science

This study aims to analyze the movement of backhand and forehand smash stroke techniques in three dimen- sions using a kinematics approach in badminton. The results were analyzed using a descriptive and quantitative approach. Furthermore, 24 male badminton players from the University Student Activity Unit with an average age of 19.4±1.6 years, a height of 1.73±0.12m, and a weight of 62.8±3.7kg were used. The study was conducted using 3 Panasonic Handycams, a calibration set, 3D Frame DIAZ IV motion analysis software, and a speed radar gun. The data normalization from the kinematics values of the shoulder, elbow, and wrist joint motion was calculated using the inverse dynamics method. Also, the one-way Anova test was used to determine the differences in the kinematics of motion in the two different groups. The results showed that the speed of the shuttlecock during the forehand smash was greater than the backhand. In the maximal shoulder external rotation phase, two variables were found with the best results during the forehand smash, namely the velocity of shoulder external rotation and wrist palmar flexion. The velocity of shoulder internal rotation, elbow extension, and forearm supination in the maximum angu- lar velocity phase showed greater results when making a forehand smash.

Compact and High Gain 4 × 4 Circularly Polarized Microstrip Patch Antenna Array for Next Generation Small Satellite

In this article, a high gain and compact 4 × 4 circularly polarized microstrip patch antenna array is reported for the data transmission of the next-generation small satellite. The radiating element of the circularly polarized antenna array is realized by the conventional model of the patch with truncated corners. A compact two-stage sequential rotational phase feeding is adopted that broadens the operating bandwidth of the 4 × 4 array. A small stub is embedded in the sequential rotational feed, which results in better performance in terms of the S-parameters and sequential phases at the output ports than sequential rotational feed without open stub. A prototype of the array is fabricated and measured. Fulfilling the application requirements of the next-generation small satellites, the array has the left-handed circularly polarized gain of more than 12 dBic with the axial ratio level below 1.5 dB in the ±10∘ angular space with respect to the broadside direction for the whole bandwidth from 8.05 GHz to 8.25 GHz. Moreover, the left-handed circularly polarized gain varies from 15 to 15.5 dBic in the desired band. The radiation patterns are measured; both the co- and X-pol are validated.

New or Increased Cometary Activity in (2060) 95P/Chiron

Abstract Asteroid Terrestrial-impact Last Alert System (ATLAS) observations of Centaur (2060) 95P/Chiron show a brightening in the apparent magnitude not due rotational light curves or phase effects. This onset or enhancement of cometary activity started after 2021 February 8 UT and continued in later observations from 2021 June 18 UT onward. Recent ATLAS observations and deeper follow-up imaging obtained using the Las Cumbres Observatory 1.0 m robotic telescope network find no confirmed signature of coma or tail-like features.

Field Study on Wood Accumulation at a Bridge Pier

Transported large wood (LW) in rivers may block at river infrastructures such as bridge piers and pose an additional flood hazard. An improved process understanding of LW accumulations at bridge piers is essential for a flood risk assessment. Therefore, we conducted a field study at the River Glatt in Zurich (Switzerland) to analyze the LW accumulation process of single logs at a circular bridge pier and to evaluate the results of previous flume experiments with respect to potential scale effects. The field test demonstrated that the LW accumulation process can be described by an impact, rotation, and separation phase. The LW accumulation was described by combining two simplified equilibria of acting forces and moments, which are mainly a function of the pier diameter, pier roughness, and flow properties. We applied the resulting analytic criterion to the field data and demonstrated that the criterion can explain the behavior of 82% of the logs. In general, the field observations confirmed previous results on the LW accumulation probability in the laboratory, which supports the applicability of laboratory studies to investigate LW–structure interactions.

The Mean Overabundance of Manganese over the Surface of 21 Com from its Midultraviolet Spectra Recorded by IUE

Abstract The coaddition of 21 mid ultraviolet spectra of 21 Com taken over the International Ultraviolet Explorer (IUE) mission reveals three strong lines of Mn ii at 2576.10, 2593.72 and 2605.68 Å. The synthesis of these lines consistently yields a sizable overabundance of manganese about 10 times the solar manganese abundance. Inspection of the 10 individual spectra taken over the 24 hr monitoring of 21 Com with IUE on 1991 April 17 does not reveal convincing variations of these lines between rotational phases 0.18 and 0.65 of the 2 days period.

Dynamics features of a resonant vibromachine with self-synchronizing inertial vibroexciters in the presence of vibration limiter

The work is devoted to the problem of ensuring the near-resonance vibration modes stability of the technological vibromachines at fluctuating mass of processed material. Vibrations of the machine are excited by two self-synchronizing inertial vibroexciters driven by asynchronous electric motors rotating in opposite directions. A planar model of a vibromachine on a linear elastic suspension is considered. The interaction of the machine working element with the processed material is described using the added mass and viscous friction forces proportional to the material mass. To expand the frequency range of vibration exciter self-synchronization the possibility of using an additional elastic limiter is considered. The limiter is mounted between the working element and the machine foundation with a predetermined initial clearance. The modes of the working element vibrations and vibroexciter self-synchronization are analyzed depending on the change in the material mass and the initial clearance. It is found that the introduction of the elastic limiter allows to significantly reduce the sensitivity of the vibration amplitudes to material mass changes in the resonant frequency range, and also leads to stabilization of the mutual phase of vibration exciters rotation. A decrease in the initial clearance leads to an expansion of the stable operating modes frequency range, at the same time the vibration amplitudes decrease.

КИНЕМАТИКА ГАЗОРАСПРЕДЕЛИТЕЛЬНОГО МЕХАНИЗМА ДВИГАТЕЛЯ HYUNDAI С РЕГУЛИРУЕМЫМ ВРЕМЕНЕМ РАБОТЫ КЛАПАНОВ

Increasing the efficiency of modern internal combustion engines is going in the direction of optimizing the gas distribution phases in order to adjust them to the operating conditions of motor vehicles. Hyundai has announced the development of the first production engine with continuously variable valve operation time – Continuously Variable Valve Duration. (Research purpose) The research purpose is in conducting a kinematic analysis of the gas distribution mechanism with an adjustable valve operating time, identifying the theoretical possibilities of this mechanism in comparison with the information provided in the prospects. (Materials and methods) The methods of kinematic analysis of lever mechanisms were used in the work. (Results and discussion) The analysis of the design of the gas distribution mechanism with an adjustable valve operating time made it possible to choose a suitable structural scheme that is equivalent to the original mechanism. The article presents the most effective method of kinematic analysis of this mechanism and developed on its basis a program for calculating the angles of rotation of the cam and the shaft of the gas distribution mechanism. (Conclusions) An engine with a valve operating time control system allows you to more effectively adjust the cylinder filling depending on the operating conditions due to the variable phase of rotation of the camshaft. The valve timing control system offered by Hyundai should only work with the valve timing control mechanism, since when the cam rotation speed changes, it starts working in the wrong phase that should be at a given time. With a slow rotation of the cam, it lags behind in phase from the shaft of the gas distribution mechanism, and with a fast rotation of the cam, on the contrary, the phase advance of the shaft of the gas distribution mechanism occurs.

Diverse rotations impact microbial processes, seasonality and overall nitrous oxide emissions from soils

AbstractMany studies haveexamined soil‐borne nitrous oxide (N2O) emissions from crops, but little effort has gone into determining the N2O emissions from each phase of a crop rotation. A 4‐yr study on a long‐term field experiment compared growing season N2O emissions from continuous corn (CC; Zea mays L.) and a 4‐yr crop rotation involving corn (RC), oat (Avena Sativa L.) underseeded to alfalfa (Medicago sativa L.) (RO), and 2 yr of alfalfa (RA1, RA2). Molecular microbial biomass (DNA yield), as well as N‐cycling functioning genes (mineralization, nitrification, and denitrification), were also evaluated. Although 4‐yr cumulative N2O emissions from RC (9.25 kg N ha–1) were significantly greater than from CC (7.94 kg N ha–1), cumulative emissions from the entire rotation were 54% lower (3.69 kg N ha–1) than CC because of low emissions from RO (3.1 kg N ha–1), RA1, and RA2 (1.11–1.27 kg N ha–1). Years that had substantial early‐season precipitation combined with high soil inorganic N from alfalfa plow‐down contributed to elevated N2O emissions from RC. Improved soil conditions and fertility under rotation increased RC grain yields by 35% (9.45 Mg ha–1) compared with CC (7.01 Mg ha–1). Microbial biomass was 73% greater in RC compared with CC. Nitrogen mineralization genes were 19% greater in RC but they were not correlated to N2O emissions, whereas bacterial nitrifiers were positively correlated. Denitrification was likely responsible for N2O emissions under CC, while nitrifier‐denitrification appeared to be the primary pathway under RC. The N2O emissions and microbial processes from all phases of a rotation should be considered for environmental modeling and policy decisions.

Dynamics of the Vibration System Driven by Three Homodromy Eccentric Rotors Using Control Synchronization

To solve the limitation of vibration synchronization, this paper investigates the dynamics of a vibration system driven by three homodromy eccentric rotors (ERs) using control synchronization. According to the synchronous condition and the stability condition, the changes of the phase differences of the three-ERs system and the two-third ERs system are obtained. Based on the electromechanical mathematic model of the vibration system and the master-slave control strategy, the synchronous target that three ERs achieve the same phase motion is converted into velocity and phase tracking of ERs. Considering the coupling characteristic of the self-adjusting of the system in the state of vibration synchronization, the velocity and phase controllers are designed by employing discrete-time sliding mode control. An experimental system for control synchronization is designed, including hardware composition and software programming. For the feedback signal used to match control targets, a method of calculating velocity and the phase difference is proposed from engineering. Recording the rotational velocities, phase differences, and system response, three group experiments with different control schemes are achieved. According to the experimental data, the coupling characteristic of the vibration system adopting control synchronization is analyzed, which can provide the basis for designing vibration machines using control synchronization.

Hidden Markov model tracking of continuous gravitational waves from a binary neutron star with wandering spin. III. Rotational phase tracking

A hidden Markov model (HMM) solved recursively by the Viterbi algorithm can be configured to search for persistent, quasimonochromatic gravitational radiation from an isolated or accreting neutron star, whose rotational frequency is unknown and wanders stochastically. Here an existing HMM analysis pipeline is generalized to track rotational phase and frequency simultaneously, by modeling the intra-step rotational evolution according to a phase-wrapped Ornstein-Uhlenbeck process, and by calculating the emission probability using a phase-sensitive version of the Bayesian matched filter known as the $\mathcal{B}$-statistic. The generalized algorithm tracks signals from isolated and binary sources with characteristic wave strain $h_0 \geq 1.3\times 10^{-26}$ in Gaussian noise with amplitude spectral density $4\times 10^{-24}\,{\rm Hz^{-1/2}}$, for a simulated observation composed of $N_T=37$ data segments, each $T_{\rm drift}=10\,{\rm days}$ long, the typical duration of a search for the low-mass X-ray binary (LMXB) Sco X$-$1 with the Laser Interferometer Gravitational Wave Observatory (LIGO). It is equally sensitive to isolated and binary sources and $\approx 1.5$ times more sensitive than the previous pipeline. Receiver operating characteristic curves and errors in the recovered parameters are presented for a range of practical $h_0$ and $N_T$ values. The generalized algorithm successfully detects every available synthetic signal in Stage I of the Sco X$-$1 Mock Data Challenge convened by the LIGO Scientific Collaboration, recovering the frequency and orbital semimajor axis with accuracies of better than $9.5\times 10^{-7}\,{\rm Hz}$ and $1.6\times 10^{-3}\,{\rm lt\,s}$ respectively. The Viterbi solver runs in $\approx 2\times 10^3$ CPU-hr for an isolated source and $\sim 10^5$ CPU-hr for a LMXB source in a typical, broadband ($0.5$-${\rm kHz}$) search.

Soil organic matter in physical fractions after intensification of irrigated rice-pasture rotation systems

Crop-pasture systems improve soil quality, but their intensification through the increase of the frequency of annual crops may reduce it. We evaluated the impacts of six no-till rice rotations systems on soil quality after five years in a field scale long term experiment established on a site with a 30 years old stabilized rice-pasture rotation. Rotations included: continuous rice (ContRc); rice-soybean (Rc-Sy); rice-soybean-rice-sorghum (Rc-Sy-Sg); rice-soybean-pasture (Rc-Sy-Past); and rice-pasture, with short (Rc-SPast) and long-term pastures (Rc-LPast). Cover crops were included in winter between cash crops. All rotation phases coexisted and were replicated three times in space. Soil quality indicators included: soil organic carbon and total nitrogen contents in bulk soil (TSOC and TN, respectively) and in particulate (>53 μm, POM-C and POM-N) and mineral associated soil organic matter fractions (<53 μm, MAOM-C and MAOM-N). Soil cores were collected at 0−5 cm and 5−15 cm soils depths (results presented at 0−5 and 0−15 cm depths). Additionally, soil samples were taken up to 60 cm soil depth every 15 cm for TSOC and TN. After five years, no differences were observed in TSOC (29.3 Mg C ha−1) or TN (3.16 Mg N ha−1) between rotations in the first 0−15 cm as well as for each layer and in the aggregated 0−60 cm of soil. Neither POM-C nor POM-N contents were different between treatments that had perennial pastures in the rotation. However, Rc-LPast had 18 and 19 % greater POM-C and POM-N respectively than the average of Rc-Sy and Rc-Sy-Sg, (6.06 Mg C ha−1 and 0.48 Mg N ha−1, 0−15 cm depth). Meanwhile, the POM-C represented 23.6 % of TSOC in Rc-LPast, but in rotations that replaced pastures (Rc-Sy and Rc-Sy-Sg) represented only 20 %. For soils in temperate zones, under a stable rice-pasture rotation, there are intensification alternatives which preserved TSOC in the midterm. However, the reduction in the particulate fractions observed in the rice rotations that substituted perennial pastures with other crops, suggests that TSOC may be more vulnerable to losses in the long term.

Physical characterization of the active asteroid (6478) Gault

ABSTRACT We report dense light-curve photometry, BVRc colours and phase–mag curve of (6478) Gault, an active asteroid with sporadic comet-like ejection of dust. We collected optical observations along the 2020 July–November months during which the asteroid appear always star-like, without any form of perceptible activity. We found complex light curves, with low amplitude around opposition and a bit higher amplitude far opposition, with a mean best rotation period of 2.46±0.02 h. Shape changes were observed in the phased light curves after opposition, a probable indication of concavities and surface irregularities. We suspect the existence of an Amplitude–Phase Relationship in C band. The mean colours are B − V = +0.84±0.04, V − Rc = +0.43±0.03, and B − Rc = +1.27±0.02, compatible with an S-type asteroid, but variables with the rotational phase index of a non-homogeneous surface composition. From our phase–mag curve and Shevchenko’s empirical photometric system, the geometric albedo result pV = 0.13±0.04, lower than the average value of the S-class. We estimate an absolute mag in V band of about + 14.9 and this, together with the albedo value, allows us to estimate a diameter of about 3–4 km, so Gault may be smaller than previously thought.

Feasibility of continuous action unit parameters for road underlay formation

Introduction.Russia has a large spatial disunity of settlements and other objects. Therefore, it is irrational to use low-productivity technical means of cyclical action in the construction of roads. To increase the pace of road construction, improve quality, reduce energy costs for road construction, where relief allows, it is economically feasible to use a set of units of continuous action. Continuous action units, moving one after another, will consistently perform a set of works, carrying out the full construction of the road by flow method. The complex should have a continuous action unit to form a underlying layer. To create complex units, their theoretical justification is necessary. In order to determine the geometric and dynamic parameters of the loading part of the unit to form the underlying layer, the process of moving the bucket filled with soil before it is unloaded is considered.The method of research. Based on the constructive layout of the loading part of the unit, the process of moving the bucket filled with soil before it is unloaded is divided into the stages: vertical ascent, moving in the direction of the leading star of the upper drive, two phases of the bucket rotation on the leading stars of the upper drive, moving from the moment of the end of the turn on the leading star of the upper drive to the start of the turn on the lower turn. When the bucket moves vertically up, the ground is no for dumped. Graphically, this angle of the bucket is chosen when it moves in the direction of the leading star of the upper drive, at which the ground will not fall out of the bucket. Two phases of the bucket rotation on the leading stars of the upper drive and moving the bucket from the moment of the end of the turn on the leading star of the upper drive to the moment of the turn on the lower turning roller are considered. The necessary parameters dependencies have been deduced.Results.Based on the developed methodology, the geometric and dynamic parameters of the loading part of the unit are defined. In particular, the torque of the top drive, the angular velocity of the drive sprockets, the power required for the top drive, the transmission ratio from the hydraulic motor to the sprockets are calculated. Based on the power transferred, a hydromotor was selected for the upper drive of the unit.Conclusion.The calculations reveal the maximum traction force of all buckets during their travel to discharge the soil, the torque of the top drive, the angular velocity of the top drive sprockets and the power required for the top drive. It is advisable to use for the upper drive of the unit gerotor hydromotor MT-160 and two-stage planetary gearbox. The calculations made it possible to develop the design of the elements of the loading part of the continuous action unit to form the underlying layer of roads.

Fallow replacement cover crops in a semi‐arid High Plains cropping system

AbstractReplacing portions of fallow between sorghum [Sorghum bicolor (L.) Moench] harvest and wheat (Triticum aestivum) planting with cover crops provides opportunity to increase productivity and profitability in dryland winter wheat–sorghum–fallow (WSF) cropping systems. The objective of this study was to identify potential spring fallow replacement cover crops and management to optimize productivity and resource use efficiency of a WSF system. The study was conducted 2013–2018 at Garden City, KS. Three crop rotation phases (WSF, SFW, and FWS) were the main plot, and fallow replacement cover crops were the sub plot. Cover crop treatments were further split into hayed and cover crop left standing groups to estimate forage potential. Results showed precipitation utilization and storage efficiency (PUtSE) increased by 146% for grain cover crop, 50% for cover crop hayed, and 38% for cover crop left standing compared with fallow. Available soil water at wheat planting (ASWPww) was not different between cover crop left standing and fallow. Spring triticale [×Triticosecale Wittm. ex A. Camus (Secale × Triticum)] had up to 182% more forage accumulation over other forage cover crops and a 108% grain yield advantage over other grain cover crops. Our findings showed fallow replacement, forage‐hayed, and grain cover crops have a greater PUtSE than fallow which may increase economic returns if subsequent crop yields are not reduced. Cover crops left standing had a moderate PUtSE advantage and similar ASWPww compared to fallow, and cover crop left standing, or fallow would be the best choice if the production goal is to maximize ASWPww and subsequent crop yields.

Multifrequency study of the peculiar pulsars PSR B0919+06 and PSR B1859+07

ABSTRACT Since their discovery more than 50 years ago, broad-band radio studies of pulsars have generated a wealth of information about the underlying physics of radio emission. In order to gain some further insights into this elusive emission mechanism, we performed a multifrequency study of two very well-known pulsars, PSR B0919+06 and PSR B1859+07. These pulsars show peculiar radio emission properties whereby the emission shifts to an earlier rotation phase before returning to the nominal emission phase in a few tens of pulsar rotations (also known as ‘swooshes’). We confirm the previous claim that the emission during the swoosh is not necessarily absent at low frequencies and the single pulses during a swoosh show varied behaviour at 220 MHz. We also confirm that in PSR B0919+06, the pulses during the swoosh show a chromatic dependence of the maximum offset from the normal emission phase with the offset following a consistent relationship with observing frequency. We also observe that the flux density spectrum of the radio profile during the swoosh is inverted compared to the normal emission. For PSR B1859+07, we have discovered a new mode of emission in the pulsar that is potentially quasi-periodic with a different periodicity than is seen in its swooshes. We invoke an emission model previously proposed in the literature and show that this simple model can explain the macroscopic observed characteristics in both pulsars. We also argue that pulsars that exhibit similar variability on short time-scales may have the same underlying emission mechanism.

Statistical properties of a controllable rotating elliptical Gaussian Schell-model vortex optical coherence lattice

A new source for a controllable rotating elliptical Gaussian Schell-model vortex optical coherence lattice with both spiral phase and rotation phase is introduced. It is shown that both the irradiance distribution of lattice and the degree of coherence (DOC) rotate synchronously in the same direction within a certain propagation, whose rotation velocity, direction and maximum angle all are controllable. Specifically, the rotation parameters broaden the transverse diffusion of the beam mean-squared width. Both the intensity lattice with solid or hollow beamlets and the splitting direction of the partially coherent vortex sub-beams can be controlled by adjusting the coherence widths in the source plane. Meanwhile, the lattice constant can flexibly control the distance and number of beamlets and the lattice periodicity of the source DOC profile. The effects of atmosphere turbulence parameters on the vortex beam array structure and the variation trend of the DOC are analyzed. Our results manifest such beam may be applied in particles trapping and rotating, and be beneficial for robust optical communications in turbulence.

Residual stress fluctuates periodically via the workpiece rotation phase during low frequency vibration cutting

The turning process is a standard machining process employed in diverse sectors. However, it produces long continuous chips that can affect the efficiency of the process, accelerate the tooling's wear, or damage the machined surface. As a solution, low frequency vibration cutting synchronizing with the spindle rotation has recently been developed as a new machining method in turning operation. It applies vibrations in the tool feed direction and can synchronously control the applied vibrations and the spindle rotation. It can also effectively divide the long continuous chips generated by the turning process and has the potential to reduce thermo-mechanical load on the tool by periodically enabling the tool to leave the workpiece due to the vibrations. Low frequency vibration cutting, the cutting characteristics of which differ from those of conventional turning, induces residual stresses in the machined surface; however, the properties of these stresses have not yet been studied. Residual stress can have both beneficial and negative effects on the fatigue life of products. While compressive residual stress increases the fatigue life of the product, tensile residual stress facilitates the growth of fine cracks on the product's surface and reduces fatigue life. Therefore, it is important to understand the characteristics of the residual stress developed on a machined surface. In this study, an annealed 0.45% C steel bar was machined via straight turning of the vibration cutting process synchronizing with the spindle rotation, and the residual stress on the finished surface was measured. Particular focus was placed on analyzing the effects of the spindle phase on the characteristics of the residual stress inside the machined surface, especially the effects of the number of vibrations per spindle rotation, D, which is a unique parameter defining the vibration condition. Our results revealed that the residual stress varied depending on the position of the finished surface owing to the change in feed with the spindle phase during the process. Furthermore, D was observed to heavily influence the distribution of the residual stress on the finished surface. By means of adjusting its value, the residual stress value could either fluctuate periodically according to the phase of the workpiece or not fluctuate.

The distribution of mutual inclinations arising from the stellar quadrupole moment

ABSTRACT A large proportion of transiting planetary systems appear to possess only a single planet as opposed to multiple transiting planets. This excess of singles is indicative of significant mutual inclinations existing within a large number of planetary systems, but the origin of these misalignments is unclear. Moreover, recent observational characterization reveals that mutual inclinations tend to increase with proximity to the host star. These trends are both consistent with the dynamical influence of a strong quadrupolar potential arising from the host star during its early phase of rapid rotation, coupled with a non-zero stellar obliquity. Here, we simulate a population of planetary systems subject to the secular perturbation arising from a tilted, oblate host star as it contracts and spins down subsequent to planet formation. We demonstrate that this mechanism can reproduce the general increase in planet-planet mutual inclinations with proximity to the host star, and delineate a parameter space wherein the host star can drive dynamical instabilities. We suggest that approximately 5–10 per cent of low-mass Kepler systems are susceptible to this instability mechanism, suggesting that a significant number of single-transiting planets may truly be intrinsically single. We also report a novel connection between instability and stellar obliquity reduction and make predictions that can be tested within upcoming TESS observations.

The influence of long-term N and P fertilization on soil P forms and cycling in a wheat/fallow cropping system

Efficient phosphorus (P) management is important for crop production and environmental sustainability of cropping systems. The effects of the agricultural management practices of crop rotation and fertilization on soil P forms and cycling were investigated in plots in Swift Current, SK, Canada, under three crop rotation phases [fallow (F), wheat after fallow (WF), and wheat after wheat (WW)], with four nitrogen (N) and/or P fertilizer treatments (+N+P, -N+P, +N-P, and -N-P), using techniques including sequential fractionation, 31P nuclear magnetic resonance (P-NMR), and P K-edge X-ray absorption near-edge (P-XANES). Soil total P (TP) and organic P (Po) concentrations were significantly reduced in F and WW phases compared to WF regardless of fertilization practice. Compared to WW, WF had the highest grain yield and nutrient uptake. Fertilization with N and P significantly influenced soil total carbon (C), total N, TP, and Mehlich 3-P concentrations and acid phosphatase activities, as well as the concentration of some P pools by sequential fractionation and stable P determined by P-XANES. Stopping P fertilization significantly increased the proportions, but not concentrations, of soil Po determined by P-NMR compared to plots still receiving P fertilizers, while the concentration of total diesters increased in plots fertilized with N. Redundancy analysis showed that soil pH and organic C were the significant predictors of P forms in these soils, suggesting that long-term N and P fertilization altered soil P forms by changing soil chemical properties.

Rotator phases in hexadecane emulsion drops revealed by X-ray synchrotron techniques

HypothesisMicrometer sized alkane-in-water emulsion drops, stabilized by appropriate long-chain surfactants, spontaneously break symmetry upon cooling and transform consecutively into series of regular shapes (Denkov et al., Nature 2015, 528, 392). Two mechanisms were proposed to explain this phenomenon of drop “self-shaping”. One of these mechanisms assumes that thin layers of plastic rotator phase form at the drop surface around the freezing temperature of the oil. This mechanism has been supported by several indirect experimental findings but direct structural characterization has not been reported so far. ExperimentsWe combine small- and wide-angle X-ray scattering (SAXS/WAXS) with optical microscopy and DSC measurements of self-shaping drops in emulsions. FindingsIn the emulsions exhibiting drop self-shaping, the scattering spectra reveal the formation of intermediate, metastable rotator phases in the alkane drops before their crystallization. In addition, shells of rotator phase were observed to form in hexadecane drops, stabilized by C16EO10 surfactant. This rotator phase melts at ca. 16.6 °C which is significantly lower than the melting temperature of crystalline hexadecane, 18 °C. The scattering results are in a very good agreement with the complementary optical observations and DSC measurements.