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A new class of azole-derived hemiaminal ethers is designed as acetylcholinesterase (AChE) inhibitors. The synthesized compounds exhibited remarkable inhibitory activity against acetylcholine. Chiral hemiaminals (3d and 3i) based on (R)-menthoxymethyl group exhibit excellent inhibition with IC50 values of 0.983 ± 1.41 and 1.154 ± 0.89 µM. Similarly, butoxymethyl derivatives 3a, 3f and 3h, also showed promising inhibition comparable to the standard drug, Donepezil. In silico studies were performed to understand the mode of interactions with the target proteins, where menthoxymethyl azoles 3d and 3i demonstrated the highest docking scores. Molecular dynamics simulations displayed the stable ligand–protein complex of 3i with effective binding interactions. The bioavailability and pharmacokinetic parameterssupported the suitability of these small molecule inhibitors to develop cost-effective drug leads for Alzheimer’s disease (AD). MTT assay substantiated the non-cytotoxic nature of the compounds. The synthesized compounds are extensively characterized by 1H NMR, 13C NMR and mass spectral data and SC-XRD. Communicated by Ramaswamy H. Sarma

Gypsum is regarded as an environmentally friendly binding material and is widely used to enhance the engineering properties of soft fine-grained soils. However, the time-dependent strength and deformation characteristics of fine-grained soils stabilised with gypsum have not yet been thoroughly investigated and rational evaluation of these characteristics will assist in the formulation of cost-effective and reliable design approaches. In this study, the time-dependent mechanical behaviours of gypsum-mixed fine-grained soil (GMFS) specimens were investigated under unconfined monotonic loading conditions, considering ageing periods of 3–90 days and five different loading rates (LR = 0.0005–1.0%/min). The results revealed that the unconfined compressive strength and stiffness of the GMFS specimens initially decreased with ageing and finally became stable after 14 days and 28 days of ageing for water/gypsum ratios of 1.30 and 1.60, respectively. Furthermore, the strength and stiffness of the GMFS specimens increased with an increase in LR.

Abstract: The work describes a detailed account of the Lewis acid-catalyzed preparation of structurally variant alkoxymethyl halides. A series of Lewis acids with different halogenating agents are evaluated for the cleavage of bis-alkoxymethanes, where several readily available Lewis acids were found to exhibit high catalytic potential. SOCl2 with MgCl2 was found to be one of the best combinations for the facile and efficient preparation of structurally diverse alkoxymethyl halides under solvent-free conditions. The efficacy of the methodology was established to obtain a wide range of mixed acetals through alkoxymethylation of phosphorus, sulfur, nitrogen, and oxygen containing nucleophiles. The present procedure has significant advantages including simplicity, generality, rapidity, and availability of reagents.

The study of failure mechanisms from a microperspective demands a comprehensive understanding of the initiation and evolution of shear banding within granular materials. However, this topic is not fully understood due to the technical constraints in continuous quantification of the failure degree and visualization of particle interactions within soil specimens due to their inherent opacity. This paper reports the possibility of acoustic emission (AE) technique in characterizing the micromechanical behavior of saturated coral sands subjected to drained triaxial shearing. Results show that coral sand is less emissive than silica sands, while its AE rate forms concrete mathematic relations with soil mechanical parameters, which agrees with those revealed for silica sands. This allows soil mechanical parameters of coral sands that are difficult to be assessed in the field to be back-evaluated by acoustic measuring. The traced AE source locations confirm their spatiotemporal correspondence with the photographed appearance of deformed specimens, in which complex shear banding process, regarding the initiation and evolution, is traced. Three acoustic precursors are observed before the complete soil failure and are considered resulting from the structural variation that affects the emission and propagation of AEs, which hence could be used as indicators for early warning of soil’s instability.

With the development of deformation measuring technology at slope surfaces, prediction methods for rainfall-induced landslides based on the surface movements and tilting of slopes in the pre-failure stage have been recognized as a promising technique for risk reduction of slope failure triggered by rainfall. However, the correlation and possible mechanism for these prediction methods were rarely discussed. In this study, the comparison between the prediction methods of slope failure based on the time history of surface displacements and tilting in the acceleration stage was carried out by conducting a series of laboratory tests and field tests under rainfall, in which the movements and tilting behaviors at the slope surface were measured. The results show that the predicted failure time of tested slopes obtained by different prediction methods is consistent, and the correlation between these landslide prediction methods were also detected. A proportional relationship between the velocity of surface displacements and tilting rate was observed, and a possible mechanism for the sliding behavior was discussed based on this linear relationship as well. In addition, an expression for the linear relationship between the rate of the surface tilting and displacement was also established in this study, and the results could have significance for the understanding of the sliding behavior in the failure process in rainfall-induced landslides.

Following numerous applications of Wittig reaction now functionalized phosphonium salts are gaining attention due to their characteristic properties and diverse reactivity. This review is focused on α-alkoxyalkyl triphenylphosphonium salts: an important class of functionalized phosphonium salts. Alkoxymethyltriphenylphosphonium salts are majorly employed in the carbon homologation of carbonyl compounds and preparation of enol ethers. Their methylene insertion strategy is extensively demonstrated in the total synthesis of a wide range of natural products and other important organic molecules. Similarly enol ethers prepared thereof are important precursors for different organic transformations like Diels-Alder reaction, Claisen rearrangement, Coupling reactions, Olefin metathesis and Nazarov cyclization. Reactivity of these α-alkoxyalkylphosphonium salts have also been studied in the nucleophilic substitution reactions. A distinctive application of this class of phosphonium salts was recently reported in the phenylation of carbonyl compounds under very mild conditions. Synthesis of structurally diverse alkoxymethyltriphenylphosphonium salts with variation in alkoxy groups as well as counter anions are reported in literature. Here we present a detailed account of different synthetic methodologies for the preparation of this unique class of quaternary phosphonium salts and their applications in organic synthesis.

In recent decades, early warning systems using tilt sensors to predict the occurrence of landslides have been developed and employed in slope monitoring due to the simple installation and low cost of these systems. However, few studies were carried out to investigate the tilting behaviors of landslides, and the prediction methods for the occurrence of slope failure based on tilting measurements also demand detailed investigations. In this paper, pre-failure tilting behaviors of slopes were investigated by performing a series of model tests as well as a field test. The test results reveal a linear relationship between the reciprocal tilting rate and time during the acceleration stage of tilting before slope failure. Furthermore, an equation for this linear relation was also proposed. By approximating the reciprocal tilting rate to be 0/o, the slope failure time can be forecasted using the proposed equation, and the predicted failure time is consistent with the actual slope failure time recorded in this study. Additionally, the correlation between the tilting rate and remaining time before slope failure in logarithmic space was also studied, and most of the data is situated in a region with boundaries. Based on this region, it is possible to anticipate the remaining time before slope failure at an arbitrary tilting rate in the acceleration stage. Conclusively, this paper provides comprehensive investigations on the correlation between the pre-failure tilting behaviors and duration time before landslides, and also introduces a method to potentially predict the occurrence of slope failure based on the slope tilting measurement.

An efficient solvent free method is developed for the preparation of structurally diverse 1-alkoxymethylphosphonium chlorides in high yield. One of the prepared salts derived from (1 R,2S,5R)-(−)-Menthol auxiliary was further employed for the synthesis of vinyl ethers, where up to 99% stereoselectivity was achieved.

A facile, efficient and general synthesis of a broad range of structurally variant alkoxymethylphosphonium tetrafluoroborates (2a–e) is described. The reaction involves the triphenylphosphination of bis-alkoxy methanes in the presence of ethereal boron trifluoride at room temperature. Application of these new salts to carbon homologation of aldehydes is also studied.

Gypsum is among the widely used construction materials, and is nowadays been considered for a variety of applications including soil stabilization, foundation works, grouting and brick manufacturing etc. Considering this prevalent utilization of gypsum in construction industry, a comprehensive study was conducted to examine the time-dependent strength and deformation characteristics of Gypsum Mixed Sand (GMS) by examining the hardening characteristics (up to nine months) and loading rate (up to five folds); under unconfined monotonic loading conditions. Effects of different factors including gypsum content, hemihydrate batches and interaction between ageing and loading rate were considered to rationally comprehend the time-dependent mechanical behaviour of GMS. The results revealed an obvious reduction in the peak strength of GMS during the initial month of ageing, and no further effects of ageing were witnessed afterwards. Moreover, a unique and significant dependency of strength and deformation on the loading rate was observed for GMS, and this behaviour was categorized into three different zones of loading rates.

Rational evaluation of the long-term performance of large-scale foundations, tunnels and natural slopes located in seismically active areas necessitates accurate assessment of the strength and deformation characteristics of bounded geomaterials, such as natural rocks and cemented soils, under creep and cyclic loading conditions. In the present study, a unique approach for examining the induced instantaneous loading/strain rates during unconfined creep and cyclic loading was adopted to unveil the effects of creep and cyclic loading on the mechanical behaviour of laboratory-produced bounded geomaterial, namely Gypsum Mixed Sand (GMS). At first, a series of unconfined monotonic tests at six different strain rates ranging from 5.3E+0 to 2.1E-5%/min were conducted on GMS. Subsequently, the mechanical behaviour of the GMS was examined under unconfined creep/sustained loading at four different stress levels. Further, these results were compared with a number of unconfined cyclic loading tests performed at different stress amplitudes. Identical patterns of the variations of axial strain accumulation and instantaneous strain rates were observed during the creep and cyclic loading. Based on the relationships between the failure stress/strain and the corresponding instantaneous strain rate, the mechanical behaviour of the GMS specimens subjected to creep and cyclic loading was found to be similar to each other, and was distinctively different than those under monotonic loading condition.

The surface displacements of slopes have been considered as a significant indicator in landslide investigations in last several decades, while in recent years the tilting of slope surfaces is also being recognized as an important index in landslide monitoring. However, the slope surface tilting has been rarely examined so far, and requires detailed investigations. In this paper, a series of laboratory tests and a field test were performed to investigate the surface tilting in rotational landslides, as well as the correlation between tilt angles and displacements of slope surfaces. In the laboratory tests, slope models were constructed with different shapes of pre-designed slip surfaces, and tested under varying test conditions. The tilting behavior of the slope surfaces in laboratory tests was measured using tilt sensors embedded into the slopes, while the surface displacement was obtained by tracing the movement of marked points set on the slope surfaces near to the tilt sensors. The test results revealed a linear relationship between the tilt angles and displacements of slope surfaces in the process of slope failure, and this linear relationship was validated by a field test in which the slope failure was triggered by artificial rainfall. The test results also indicated that the coefficient of the linear relation is consistent with the value of real distance between the locations of tilt sensors and the centers of slip surfaces. An equation that relates the slope surface tilting and displacements was proposed in this study. Furthermore, a method to estimate the geometry of the slip surface was also developed, which was deduced from the observation that the path of the sliding masses was parallel to the slip surface according to the results of laboratory tests. Additionally, an acceleration stage of surface tilting was observed in slope failure induced by artificial rainfall, which implies that the surface tilting measurement can be used to predict the potential development of a rotational landslide or its reactivation.

An efficient one pot method for the synthesis of α-alkoxymethylphosphonium iodides is developed by using PPh3/I2 combination at room temperature. Reaction conditions are found general to synthesize wide range of structurally variant alkoxymethylphosphonium iodides in high yield (70–91%). These new functionalized phosphonium salts are further used in stereoselective synthesis of vinyl ethers as well as in carbon homologation of aldehydes. Electronic supplementary material The online version of this article (10.1186/s13065-018-0421-6) contains supplementary material, which is available to authorized users.

It has been unanimously acknowledged that the strength and deformation characteristics of bounded geomaterials, viz. cemented soils and natural rocks, are predominantly governed by the rate of loading/deformation. Rational evaluation of these time-dependent characteristics due to viscosity and ageing are vital for the reliable constitutive modelling. In order to study the effects of ageing and loading/strain rate (viscosity) on the behaviour of bounded geomaterials, a number of unconfined monotonic loading tests were performed on Gypsum Mixed Sand (GMS) specimens at a wide range of axial strain rates; ranging from 1.9E-05 to 5.3E+00 %/min (27,000 folds), and at different curing periods. The results indicate shifts in the viscous behaviour of GMS at critical strain rates of 2.0E-03 and 5.0E-01 %/min. In the light of this finding, the results are categorized into three discrete zones of strain rates, and the behaviour of GMS in each of these zones is discussed. A significant dependency of peak strength and stress-strain responses on strain rate was witnessed for specimens subjected to strain rates lesser than 2.0E-03 %/min, and the effects of viscosity/strain rate was found to be insignificant at strain rate higher than 5.0E-01%/min.