Complete Inversion Research Articles

Effect of crosslinking on morphology and phase inversion of EPDM/PP blends

This study investigates the effect of cross-linking on morphology and phase inversion of EPDM/PP blends. Several EPDM/PP blends without and with cross-linking agent were prepared in a Haake batch mixer under constant conditions. The morphology was studied by electronic microscopy (SEM and TEM), and cross-linking was followed by EPDM gel content and swelling. The results showed that the position of the phase inversion region is essentially governed by composition, being independent of the viscosity ratio of the EPDM/PP blend. The TPVs’ morphology of the EPDM/PP blend, with 70 and 50wt% of PP, consists of EPDM cross-linked particles dispersed in the PP matrix. For EPDM-rich composition (30wt% of PP), the TPVs’ morphology appears to be co-continuous. Even though dynamic vulcanisation of the rubber phase always improves the dispersion of the EPDM phase, complete phase inversion (from fully dispersed PP in the EPDM matrix to EPDM fully dispersed in the PP matrix) was achieved only with low viscosity EPDM.The results suggest that phase inversion driven by cross-linking can occur at viscosity ratios lower than those estimated for the respective EPDM/PP blends at phase inversion.

Ultrasound diagnosis of complete uterine inversion in a nulliparous woman

Non-puerperal uterine inversion is an extremely rare event, and the diagnosis is made during vaginal examination or exploratory laparotomy. We report a case of complete uterine inversion which was diagnosed on abdominal ultrasound examination in a 50-year-old nulliparous virgin who was admitted to the hospital because of profuse vaginal bleeding, lower abdominal pain and anuria. The confirmatory diagnosis of complete uterine inversion secondary to a fundal fibroid was made at exploratory laparotomy. Total abdominal hysterectomy was performed, and the pathological examination confirmed its benign nature. Ultrasound evaluation is useful in the diagnosis of non-puerperal uterine inversion.

Influence of point mutations near the active site on the catalytic properties of fungal arylacetonitrilases from Aspergillus niger and Neurospora crassa

Arylacetonitrilases from Aspergillus niger CBS 513.88 and Neurospora crassa OR74A (NitAn and NicNc, respectively) were expressed in recombinant Escherichia coli JM109. The respective whole-cell catalysts preferentially hydrolyzed (R)-enantiomers of (R,S)-mandelonitrile and (R,S)-2-phenylpropionitrile. NitNc also formed significant amounts of mandelamide from (R,S)-mandelonitrile (40% of total product), mainly found as the (S)-enantiomer. At pH 4.5 and 5.0, the cells retained more than 40 and 60% of their nitrilase activity at pH 7, respectively. Nitrilase variants generated by site-directed mutagenesis carried amino acid replacements in the vicinity of the catalytically active cysteine residues (C162 and C167 in NitAn and NitNc, respectively). The conversions of (R,S)-mandelonitrile and (R,S)-2-phenylpropionitrile by the nitrilase variants were compared to the wild-type nitrilases in terms of activity, enantioselectivity, and acid/amide ratio of the products formed. Thus the W168A variant of NitNc was identified, which formed significantly increased amounts of mandelamide and 2-phenylpropionamide, and which demonstrated an almost complete inversion of enantioselectivity for the conversion of (R,S)-2-phenylpropionitrile (from R- to S-selectivity).

Noninvasive Characterization of the Effect of Varying PLGA Molecular Weight Blends on In Situ Forming Implant Behavior Using Ultrasound Imaging

In situ forming implants (ISFIs) have shown promise in drug delivery applications due to their simple manufacturing and minimally invasive administration. Precise, reproducible control of drug release from ISFIs is essential to their successful clinical application. This study investigated the effect of varying the molar ratio of different molecular weight (Mw) poly(D,L-lactic-co-glycolic acid) (PLGA) polymers within a single implant on the release of a small Mw mock drug (sodium fluorescein) both in vitro and in vivo. Implants were formulated by dissolving three different PLGA Mw (15, 29, and 53kDa), as well as three 1:1 molar ratio combinations of each PLGA Mw in 1-methyl-2-pyrrolidinone (NMP) with the mock drug fluorescein. Since implant morphology and microstructure during ISFI formation and degradation is a crucial determinant of implant performance, and the rate of phase inversion has been shown to have an effect on the implant microstructure, diagnostic ultrasound was used to noninvasively quantify the extent of phase inversion and swelling behavior in both environments. Implant erosion, degradation, as well as the in vitro and in vivo release profiles were also measured using standard techniques. A non-linear mathematical model was used to correlate the drug release behavior with polymer phase inversion, with all formulations yielding an R2 value greater than 0.95. Ultrasound was also used to create a 3D image reconstruction of an implant over a 12 day span. In this study, swelling and phase inversion were shown to be inversely related to the polymer Mw with 53kDa polymer implants increasing at an average rate of 9.4%/day compared with 18.6%/day in the case of the 15 kDa PLGA. Additionally the onset of erosion, complete phase inversion, and degradation facilitated release required 9 d for 53 kDa implants, while these same processes began 3 d after injection into PBS with the 15 kDa implants. It was also observed that PLGA blends generally had intermediate properties when compared to pure polymer formulations. However, release profiles from the blend formulations were governed by a more complex set of processes and were not simply averages of release profiles from the pure polymers preparations. This study demonstrated that implant properties such as phase inversion, swelling and drug release could be tailored to by altering the molar ratio of the polymers used in the depot formulation.

PH-Triggered reversible morphological inversion of orthogonally-addressable poly(3-acrylamidophenylboronic acid)-block-poly(acrylamidoethylamine) micelles and their shell crosslinked nanoparticles.

Functionally-responsive amphiphilic core-shell nanoscopic objects, capable of either complete or partial inversion processes, were produced by the supramolecular assembly of pH-responsive block copolymers, without or with covalent crosslinking of the shell layer, respectively. A new type of well-defined, dual-functionalized boronic acid- and amino-based diblock copolymer poly(3-acrylamidophenylboronic acid)(30)-block-poly(acrylamidoethylamine)(25) (PAPBA(30)-b-PAEA(25)) was synthesized by sequential reversible addition-fragmentation chain transfer (RAFT) polymerization and then assembled into cationic micelles in aqueous solution at pH 5.5. The micelles were further cross-linked throughout the shell domain comprised of poly(acrylamidoethylamine) by reaction with a bis-activated ester of 4,15-dioxo-8,11-dioxa-5,14-diazaoctadecane-1,18-dioic acid, upon increase of the pH to 7, to different cross-linking densities (2%, 5% and 10%), forming well-defined shell cross-linked nanoparticles (SCKs) with hydrodynamic diameters of ca. 50 nm. These smart micelles and SCKs presented switchable cationic, zwitterionic and anionic properties, and existed as stable nanoparticles with high positive surface charge at low pH (pH = 2, zeta potential ~ +40 mV) and strong negative surface charge at high pH (pH = 12, zeta potential ~ -35 mV). (1)H NMR spectroscopy, X-ray photoelectron spectroscopy (XPS), dynamic light scattering (DLS), transmission electron microscopy (TEM), atomic force microscopy (AFM), and zeta potential, were used to characterize the chemical compositions, particle sizes, morphologies and surface charges. Precipitation occurred near the isoelectric points (IEP) of the polymer/particle solutions, and the IEP values could be tuned by changing the shell cross-linking density. The block copolymer micelles were capable of full reversible morphological inversion as a function of pH, by orthogonal protonation of the PAEA and hydroxide association with the PAPBA units, whereas the SCKs underwent only reptation of the PAPBA chain segments through the crosslinked shell of PAEA as the pH was elevated. Further, these nanomaterials also showed D-glucose-responsive properties.

Stereochemical Inversion of Phosphonothioate Methanolysis by La(III) and Zn(II): Mechanistic Implications for the Degradation of Organophosphate Neurotoxins

The utility of phosphonothioate methanolysis to degrade organophosphate neurotoxins has prompted the stereochemical investigation of this useful transformation. The methanolysis of enantiomerically pure O,S-diethyl phenylphosphonothioate (5) was studied both in the presence and in the absence of metal ions known to catalyze the phosphonothioate → phosphonate transformation. This report outlines the syntheses of enantiomerically pure 5 and its methanolysis product O-ethyl O-methyl phenylphosphonate (7). Compound 7 results from exclusive P-S scission of 5, which is the desired mode of phosphonothioate methanolysis (E(a) = 14.5 ± 0.5 kcal/mol). The stereochemical analysis of the phosphonothioate methanolysis was done for the first time with β-cyclodextrin, and it shows complete inversion on the phosphorus center upon methoxide displacement of ethanethiolate. The presence of La(III) or Zn(II) complexes do not alter this S(N)2-like substitution which sheds new light on the mechanism of methanolysis of phosphonothioates.

Reconfiguration of spectral absorption features using a frequency-chirped laser pulse

A technique is proposed to manipulate atomic population in an inhomogeneously broadened medium, which can set an arbitrary absorption spectrum to a uniform transparency (erasure) or to a nearly complete inversion. These reconfigurations of atomic spectral distribution are achieved through excitation of electronic transitions using a laser pulse with chirped frequency, which precisely affects selected spectral regions while leaving the rest of the spectrum unperturbed. An erasure operation sets the final atomic population inversion to zero and the inversion operation flips the population between the ground and the excited states, regardless of the previously existing population distribution. This technique finds important applications both in optical signal processing, where fast, recursive processing and high dynamic range are desirable and in quantum memory and quantum computing, which both require high efficiency and high fidelity in quantum state preparation of atomic ensembles. Proof-of-concept demonstrations were performed in a rare-earth doped crystal.

Palladium-catalyzed cross-coupling reactions of organogold(i) phosphanes with allylic electrophiles

Aryl and alkenylgold(I) phosphanes react regioselectively with allylic electrophiles such as cinnamyl and geranyl halides (bromide, chloride and acetates) under palladium catalysis in THF at 80 °C to afford the α-substitution product with moderate to high yields. When the reaction is performed with a chiral enantiopure secondary acetate, the α-substituted cross-coupling product is obtained with complete inversion of the stereochemistry.

A Rare Case of Occult Uterine Inversion at an Army Community Hospital: A Case Report

Uterine inversion is a rare occurrence in obstetrics, but it is a life-threatening complication. Most cases of inversion are caused by excessive cord traction during management of the third stage of labor. We describe a rare case of a complete uterine inversion in a 19-year-old G1P0 dependent spouse of a deployed active duty soldier. After failure of manual correction of the inversion, the patient was taken emergently to the operating room, where the inversion was successfully corrected using surgical methods. The patient required 3 units of packed red blood cells over the next 24 hours, but was discharged home in good condition on postoperative day 3. This case demonstrates the importance of a rapid diagnosis and management of uterine inversion, as it is a rare but serious complication of vaginal delivery.

Myomectomy for Reversion of a Nonpueperal Uterine Inversion

Background: Puerperal uterine inversion is rare. Nonpuerperal uterine inversion occurs even more infrequently. Usually associated with cancerous growths, nonpuerperal uterine inversion often necessitates hysterectomy. Case: This article presents the case of a 37‐year‐old woman with worsening pelvic pain and vaginal discharge, who was found to have a fundal myoma causing complete uterine inversion. Because of her desire for fertility preservation, the surgical approach involved abdominal hysterotomy and myomectomy. Results: Postoperative imaging showed restoration of normal anatomy. Conclusions: The uncommon nonpuerperal uterine inversion often has a chronic presentation, and diagnosis can be aided by a combination of clinical examination and imaging. Careful surgical repair may spare fertility in cases with benign pathology. (J GYNECOL SURG 27:261)

Singlet–triplet reactions of optical vortices in Gaussian beams

A general complex scalar wavefield in two dimensions contains singularities of phase,namely vortices, saddles and extrema. As an external control parameter is changed,reactions occur between the singularities. We examine here the reaction whereby a singlevortex splits into three, and several models that display this phenomenon are discussed.The reaction is essentially the same in all of them, but attention is focused on a model inwhich two coaxial Gaussian beams of different waist sizes and amplitudes are superposed inantiphase. The saddles are arranged in a pattern that has some interesting features. At themoment of triplet formation a saddle passes through the central vortex and twonew saddles are formed below the new flanking vortices. The vortices are nearlydegenerate, but not completely so. This property is associated with a factor of 2 intheir rate of circulation of phase that is in addition to the primary circulation of2π around a vortex. It suggests a new integer that characterizes such near-degenerate vortices,and it results in a factor of 2 in the vortex–saddle separations. As the waist of the narrowerbeam is reduced to less than a wavelength, an unusual reaction occurs in which a newpair of saddles is created apparently from nothing; however, the intervention ofphase extrema as catalysts ensures that the Poincaré index remains conserved. Thefinal result after this event is a complete inversion of the original triplet pattern,a feat that is accomplished without the saddles passing through the vortices.

Full-waveform based complete moment tensor inversion and source parameter estimation from downhole microseismic data for hydrofracture monitoring

Downhole microseismic monitoring is a valuable tool in understanding the efficacy of hydraulic fracturing. Inverting for the moment tensor has gained increasing popularity in recent years as a way to understand the fracturing process. Previous studies utilize only part of the information in the waveforms, such as direct P- and S-wave amplitudes, and make far-field assumptions to determine the source mechanisms. The method is hindered in downhole monitoring, when only limited azimuthal coverage is available. In this study, we develop an approach to invert for complete moment tensor using full-waveform data recorded at a vertical borehole. We use the discrete wavenumber integration method to calculate full wavefields in the layered medium. By using synthetic data, we find that, at the near-field range, a stable, complete moment tensor can be retrieved by matching the waveforms without additional constraints. At the far-field range, we discover that the off-plane moment tensor component is poorly constrained by waveforms recorded at one well. Therefore, additional constraints must be introduced to retrieve the complete moment tensor. We study the inversion with three different types of constraints. For each constraint, we investigate the influence of velocity model errors, event mislocations, and data noise on the extracted source parameters by a Monte Carlo study. We test our method using a single well microseismic data set obtained during the hydraulic fracturing of the Bonner sands in East Texas. By imposing constraints on the fracture strike and dip range, we are able to retrieve the complete moment tensor for events in the far-field. Field results suggest that most events have a dominant double-couple component. The results also indicate the existence of a volumetric component in the moment tensor. The derived fracture plane orientation generally agrees with that derived from the multiple event location.

Enantioselective Synthesis of Benzyl tert‐Butyl Sulfoxides

AbstractEnantiomerically pure benzyl sulfoxides are effective tools for the formation of new C–C bonds with control of configuration at new stereogenic centres. The reaction of enantioenriched tert‐butyl tert‐butanethiosulfinate with benzyllithium derivatives, obtained by deprotonation of the corresponding toluene derivatives, gave a wide variety of benzyl tert‐butyl sulfoxides with complete inversion of configuration. The benzyl sulfoxides were deprotonated in situ, and addition of the electrophiles gave α‐substituted products with good diastereoselectivity.

One channel spatio-temporal inversion of acoustic wave in reverberant cavities

It has been recently shown that it was possible to optimally recover the Green functions from a complex wave field despite of a non-isotropic distribution of the noise sources. The method used is based on a particular use of the inverse filter (IF) formalism which is called the passive IF. Based on this formalism, we have investigated the possibility to control the spatio-temporal degrees of freedom in a reverberant cavity for the focusing of waves (active processes). The understanding of this phenomenon can be very useful in a lot of different applications like in acoustical imaging, seismology, or telecommunications. In the present work, the spatio-temporal focalization of ultrasounds in reverberant cavities is studied using medical arrays and water tanks. Through experiments, a complete spatio-temporal inversion is realized to synthesize optimized emitting signals. The result generalizes the focalization control over a spatial vector and during an arbitrary time window.

Population inversion by chirped pulses

In this paper, we analyze the condition for complete population inversion by a chirped pulse over a finite duration. The nonadiabatic transition probability is mapped in the two-dimensional parameter space of coupling strength and detuning amplitude. Asymptotic forms of the probability are derived by the interference of nonadiabatic transitions for sinusoidal and triangular pulses. The qualitative difference between the maps for the two types of pulses is accounted for. The map is used for the design of stable inversion pulses under specific accuracy thresholds.

A Foldamer-Based Chiroptical Molecular Switch That Displays Complete Inversion of the Helical Sense upon Anion Binding

Chiral indolocarbazole dimers fold into a helical conformation by virtue of intramolecular hydrogen bonds, as demonstrated by (1)H NMR and CD spectra and optical rotations. In particular, the optical properties of the dimers were found to be extremely sensitive to the nature of the solvent, depending on whether they are folded or not. The helical sense of the dimers can be reversibly switched by binding sulfate ion, which gives rise to complete inversion of the CD spectra. The binding mode and absolute stereochemistry of the sulfate complexes was unequivocally determined by single-crystal X-ray structures, which are all consistent with the CD and (1)H NMR spectra in solution.

Spin transport properties in an organic molecule in the presence of Rashba spin-orbit interaction

In the present letter, we study the spin-dependent electron transport in a 1,4-2-phenyl-dithiolate molecule using the Hückel method and equilibrium Green's function formalism. The effect of the contacts on spin transport is taken into account. It is shown that spin inversion can occur in the presence of the Rashba spin-orbit interaction. The necessary conditions for complete spin inversion are obtained by using contour maps. This study can provide a new route to design molecular spintronic devices.

Structural anatomy and dynamics of evolution of the Qikou Sag, Bohai Bay Basin: Implications for the destruction of North China craton

The Qikou Sag is a complex Cenozoic faulted basin at the center of the Bohai Bay Basin. The Paleogene sediments in the basin show a maximum thickness of 11,000m in Paleogene representing intense crustal extension. The sag has a typical dish-like structure in the upper part, with the central domain represented by a deep half graben, and surrounded by different types of gentle slopes and sub-sags linked with the basin-margin uplifts. The inner structure of the sag is jointly controlled by the basin-margin extensional faults, intrabasinal extensional tectonics and transfer tectonics. The sag is divided into four different extensional tectonic domains by the basement fault along the coastline, the Haihe–Xingang Fault and the Qidong Fault. These sub-sags are in turn controlled by different detachment systems. The listric Cangdong and Hangu faults mark the major boundary faults controlling the extensional structure of the basin.The structure and tectonics of the Qikou Sag provide a direct record of the late stages of rifting and destruction of the North China Craton. The Mesozoic basement structures of the sag determine the tectonic styles in different sub-sags. The complete inversion of the structures in Mesozoic profoundly influenced the development and evolution of the basin during Paleogene. We identify three main stages in the tectonic evolution of the Qikou: the Oligocene faulting stage, the Miocene–Pliocene thermal subsidence stage and the Pleistocene–Quaternary depression stage. In the Oligocene, fault activities and the basin architecture were mainly controlled by the listric boundary fault system of the basin and the secondary fault system in the hanging wall under the detachment and extension in the upper crust. Since Miocene, the boundary fault of the basin underwent weak extension. The upwelling of the upper mantle and the formation of corresponding shallow depressions contributed to the evolution and tectonic architecture of the Qikou Sag.

Mitsunobu Reaction of 1,2,3‐NH‐Triazoles: A Regio‐ and Stereoselective Approach to Functionalized Triazole Derivatives

Mitsunobu Reaction of 1,2,3‐NH‐Triazoles: A Regio‐ and Stereoselective Approach to Functionalized Triazole Derivatives

Complete population transfer induced by transient nonadiabatic effects in a strongly detuned micromaser

We show that complete population inversion can be obtained in a micromaser even in the presence of large detuning. This spectacular effect is due to nonadiabatic transitions induced in the atomic system when the atom crosses the cavity. This effect is shown to depend strongly on the shape of the cavity mode and the axial atomic position.