Transition Metal Complexes with Reactive Trimethylsilylchalcogenolate Ligands: Precursors for the Preparation of Ternary Nanoclusters

The Co2+ and Mn2+ complexes (N,N´-tmeda)Co(ESiMe3)2 (E = S, 1a; E = Se, 1b), (3,5-Me2C5H3N)2Co(ESiMe3)2 (E = S, 2a; E = Se, 2b), [Li(N,N´-tmeda)]2[(N,N´-tmeda)Mn5(μ-ESiMe3)2(ESiMe3)4(μ4-E)(μ3-E)2] (E = S, 3a; E = Se, 3b), [Li(N,N´-tmeda)]2[Mn(SSiMe3)4] (4), [Li(N,N´-tmeda)]4[Mn4(SeSiMe3)4(μ3-Se)4] (5), and [Li(N,N´-tmeda)]4[Mn(Se4)3] (6) have been isolated from reactions of Li[ESiMe3] and the chloride salts of these metals. The treatment of (N,N´-tmeda)CoCl2 with two equivalents of Li[ESiMe3] (E = S, Se) yields 1a and 1b, respectively, whereas similar reactions with MnCl2 yield the polynuclear complexes 3a (E = S) and 3b (E = Se). The selective preparation of the mononuclear complex 4 is achieved by increasing the reaction ratios of Li[SSiMe3] to MnCl2 to 4:1. Single crystal X-ray analysis of complexes 1−5, confirms the presence of potentially reactive trimethylsilylchalcogenolate moieties and distorted tetrahedral geometry around the metal centers in each of these complexes. These compounds could potentially be utilized as a convenient source of paramagnetic ions into a semiconductor matrix for the synthesis of ternary clusters. The ternary clusters (N,N´-tmeda)6Zn14-xMnxS13Cl2 (7a-d) and (N,N´-tmeda)6Zn14-xMnxSe13Cl2 (8a-d) and the binary clusters (N,N´-tmeda)6Zn14E13Cl2 (E= S, 9a; Se, 9b) have been synthesized by reacting (N,N´-tmeda)Zn(ESiMe3)2 with Mn2+ and Zn2+ salts. Single crystal X-ray analysis of the complexes confirms the presence of the six ‘(N,N´-tmeda)ZnE2’ units as capping ligands that stabilize the clusters, and distorted tetrahedral geometry around the metal centers. Mn2+ is incorporated into the ZnE matrix by substitution of Zn2+ ions in the cluster core. Complexes 7a, 8a and 8d represent the first examples of ‘Mn/ZnE’ clusters with structural characterization and indications of the local chemical environment of the Mn2+ ions. DFT calculations indicate that replacement of Zn with Mn is perfectly feasible and at least partly allows for the identification of some sites preferred by the Mn2+ metals. These calculations, combined with luminescence studies suggest a distribution of the Mn2+ in the clusters. The room temperature emission spectra of clusters 7c-d display a significant red shift relative to the all zinc cluster 9a, with a peak maximum centered at 730 nm. Clusters 8c-d have a peak maximum at 640 nm in their emission spectra. The chalcogenolate complexes 3a and 4 have been utilized as molecular precursors for the isolation of ternary nanoclusters, with approximate formulae [Mn35/36Ag118/116S94(PnPr3)30], 10 and [Mn19/20Ag150/148S94(PnPr3)30], 11 respectively. Mn2+ is incorporated into the Ag2S matrix by substitution of two Ag+ ions in the cluster core

Screening of Potential Plant Growth Promoting Properties of Bacillus Species Isolated from Different Regions of Nepal

The deleterious effects of intensive use of chemical fertilizers and pesticides in agriculture has led to the substantial research efforts on finding the alternatives to these agrochemicals. This study was aimed to isolate Bacillus species from soil of different regions of Nepal and screen for their ability to promote plant growth directly or indirectly by testing their ability to produce plant growth hormone indole acetic acid, hydrogen cyanide, ammonia and protease as well as phosphate solubilization. Thirty nine Bacillus strains were isolated from 25 soil samples of different regions of Kathmandu and Chitwan districts of Nepal. These isolates were tested for plant growth promoting traits in vitro. Among the total isolates, about 48.7% were indole acetic acid producers, 38.4% of the isolates showed the ability to solubilize the phosphate, 71.8% were able to produce ammonia and all the isolates had the ability to produce hydrogen cyanide and protease. The isolated strains showed positive results to maximum PGPR traits and exhibited a potential to be used as alternatives to chemical fertilizers and pesticides and could be used as low-cost bio-based technology to promote plant growth in the agricultural sector

Hydrogeochemistry of Two Major Mid-hill Lentic Water Bodies for Irrigation of the Central Himalaya, Nepal

The concentration and composition of different salts in natural water bodies determine the water quality for various purposes. This study assesses the water quality of two mid-mountain lentic water bodies, Lake Phewa and Kulekhani Reservoir. For this purpose, selected physico-chemical parameters along with major ions such as HCO3-, SO42-, PO43-, NO3-, Cl-, Ca2+, Mg2+, Na+, K+, and NH4+ were analyzed. Major ions were analyzed using ion chromatography, anions by DX-600 and cations by Dionex ISC-2500 ion chromatographs. The sources of major ions were determined by using the Gibbs diagram, Piper plot, and Scatter plots. Dissolved oxygen, ammonia and phosphate showed seasonal variations in both lakes. The concentrations of cations are in the order of Ca2+ > Na+ > Mg2+ > K+ in both water bodies. However the trend of anions had small variations for Cl- and SO42- in Lake Phewa (HCO3- > Cl- > SO42- > NO3-) and Kulekhani Reservoir (HCO3- > SO42- > Cl- > NO3-). The Piper plot and equiline plots indicated that the water chemistry is dominantly controlled by the dissolution of carbonate minerals and to a limited extent by weathering of silicate minerals. This is further supported by the Gibbs plot showing bedrock geology as the main source of major ions. The overall study indicates that the hydrogeochemistry of these water bodies is controlled by local geology and is suitable for irrigation purposes

Applicability of Unlined/Shotcrete Lined Pressure Tunnels for Hydropower Projects in the Himalaya

Nowadays, unlined or shotcrete lined pressure tunnels and shafts are used in hydropower projects worldwide. The prime requirements for these tunnels and shafts are that they should be economically attractive and should be able to operate without any significant problems in the long run. The concepts and design principles behind these conduits developed from the Norwegian planning, design, construction and operational experiences have been crucial for their successful implementation. However, by virtue of the different topographical, geological and tectonic environment of the Himalaya than that of the Scandinavia, the implementation of unlined pressure tunnels in the Himalaya has been emerging as a challenging issue. As a matter of fact, it was realized that a clear gap exists between the success of the unlined pressure tunnel concept in Norway and the challenge of its implementation in the Himalaya. To fulfill this gap, this PhD research project was formulated to study the possibility of implementing the unlined or shotcrete lined pressure tunnels in the Himalaya. First of all, the economical attractiveness of the shotcrete lined pressure tunnel of the Himalayan hydropower projects was evaluated. Since the tunnel roughness is one of the decisive parameters for cost effectiveness, a methodology was developed to estimate the roughness of shotcrete lined tunnel based on the study of two tunnel cases from Nepal Himalaya. The tunnel cases were taken from Modi Khola Hydroelectric Project (MKHP) and Chilime Hydroelectric Project (CHP). It was found that the shotcrete lined tunnels are one of the economically attractive solutions in the waterway system of hydropower projects. In addition, the roughness of shotcrete lined tunnel of Upper Tamakoshi Hydroelectric Project (UTHP), which is also located in Nepal and is under construction, was predicted by using the developed methodology. More importantly, the shotcrete lined tunnels in all cases were provided with the concrete lining in the invert. The PhD work further reviewed the Norwegian design principles for unlined pressure tunnel and their applicability in different topographical, geological and tectonic environments. In doing so, ten Norwegian hydropower projects including both failure and successful cases of unlined pressure shafts and tunnels were studied in detail. The review process revealed that the hydrostatic head gives water pressure to the rock mass surrounding the tunnel periphery. In an unlined tunnel, the confining pressure from the rock mass should be able to counteract the water pressure for the safety of unlined tunnel against hydraulic jacking. The attempt of all design criteria is then to define the confining pressure as accurate as possible. The Norwegian confinement criteria use both vertical and lateral rock covers to estimate the confining pressure. On the other hand, the magnitude of minimum principal stress in the rock mass is considered as a limiting confining pressure to counteract the water pressure. This criterion came out as a stress criterion and is the state-of-the-are design principle for unlined pressure shaft and tunnel. However, some discrepancies were noticed between the confining pressures given by these different criteria. The Norwegian design concepts and criteria were then applied to the UTHP. The fact is that the pressure tunnel of the UTHP was designed as a shotcrete lined tunnel with concrete lining in the invert. This tunnel is different from the one which is normally fully unlined in Norwegian Hydropower projects. However, same design criteria as for the unlined pressure tunnel were used in the shotcrete lined pressure tunnel as well by virtue of the permeable nature of shotcrete lining. The extensive assessments carried at the UTHP concluded that the good quality rock mass with tight joints is suitable for unlined or shotcrete lined tunnel provided that the stress requirement is fulfilled. However, the presence of weakness zones, local shear bands, unfavorable jointing, and destressed area makes the use of unlined or shotcrete lined tunnel more challenging. Even though the Norwegian confinement criteria show headrace tunnel alignment is safe for unlined tunnel concept at the UTHP, the detailed rock engineering assessment, stress state analysis, fluid flow and leakage analyses indicates that some critical locations along the headrace tunnel alignment are vulnerable for the unlined or shotcrete lined tunnel concept. More importantly, the weakness zone considerably attenuates the in-situ stress state. In addition, the open joints and the joints filled with silt and clay having low stiffness are vulnerable for hydraulic jacking and water leakages even the stress conditions are fulfilled. Considering these facts, this thesis finally argues that there is a need for the modification of the Norwegian confinement criteria in order to successfully apply in the Himalayan rock mass conditions. This is mainly due to the presence of complex topography, geology and tectonic environment of this region

Evaluation on the Squeezing Phenomenon at the Headrace Tunnel of Chameliya Hydroelectric Project, Nepal

Growing demand of electricity in Nepal can be fulfilled by hydropower generation. The huge potentiality of hydropower generation in Nepal is mainly due to abundant water resources and available geographical head due to steep Rivers. In medium and large hydropower projects, huge amount of water discharge has to be handled form intake to power station and ultimately back to river again. Also, because of steep topography, the construction of pipe and canal on the surface of terrain could be very difficult and expensive for larger discharges. Hence, underground construction such as tunnels or shafts could only be the feasible options of water conveyance system for large discharges and in case of steep terrains. But, at the same time, there are higher risks and uncertainties associated with the underground works like tunnels and shafts or caverns.The main risks and uncertainties associated with the underground works are stress induced instability, water leakage, mud flows and finally the cost overrun during construction. When there is overstressing of rock mass that means rock stresses exceed the strength of rock mass, there will be stress induced instability in the tunnel. If the rock mass is very weak, schistose and deformable, squeezing phenomenon will occur with the development of plastic zone around the tunnel which causes excessive deformation of tunnel. In the Himalayan region, due to the high degree of schistocity, fracturing and shearing, weak rocks such as mudstone, shale, slate, phyllite, schist, highly schistose gneiss and the rock mass of the tectonic fault zones are not capable to withstand the high stresses. Basically, squeezing has been common phenomenon in the tunnels in these weak and deformable rock masses. In this thesis, Chameliya Hydroelectric Project (CHEP), located in far western region of Nepal, has been taken as the case study. In this project, huge squeezing problem occurred in about 800m stretch of headrace tunnel from chainage 3+100m to 3+900m. The most affected section is about 550m in between these chainages. At several locations in squeezing section, the tunnel wall closure (deformation) has been recorded well over 1.0 m in an average and the maximum above 2.0 m where the original tunnel diameter is 5.2m. Hence, the thesis basically deals with squeezing analysis of the case using different approaches. Rock types along the headrace tunnel alignment are dolomite, slate, talcosic phyllite and dolomite intercalated with phyllite. Mostly, talcosic phylite has been found in the squeezed section. The rock mass quality in the squeezed section is extremely poor to exceptionally poor.The main objectives of this thesis are the assessment of squeezing phenomenon, evaluation of stability of the tunnel and support pressure estimation. In this thesis, four main methods have been used to evaluate the squeezing phenomenon viz.; empirical methods such as Singh et al (1992) and Q-system (Grimstad and Barton, 1993), semi-analytical method such as Hoek and Marinos (2000), analytical method such as Convergence Confinement Method (Carranza-Torres and Fairhurst, 2000) and numerical program Phase2. Initially, seventeen tunnel sections at different chainages have been taken into consideration. The squeezing prediction criteria, such as Singh et al (1992), Q-system and Hoek and Marinos (2000) approach, show that there is severe squeezing in last ten sections. Hence more detail squeezing analysis has been done for these ten sections using Hoek and Marinos (2000) and Convergence Confinement Method, and support pressure has also been estimated using these two approaches and Barton et al. (1974) approach. Hoek and Marinos (2000) and Convergence Confinement Method analysis show that there is significant amount of tunnel deformation to cause squeezing problems. The main factors that control the squeezing phenomenon are the rock mass parameters and rock stresses. Therefore, quality of squeezing analysis largely depends upon the correct estimation of these input parameters. The main components of rock stresses are gravity and tectonic stresses. The rock stresses in the project area were not measured, so Phase2 program has been used to estimate the tectonic stress value from measured deformation. The tectonic stress value has been found to be equal to 3.5MPa in this area, but stress measurement will be necessary to verify this value. Uniaxial unconfined strength of intact rock in four tunnel sections has been back calculated from measured deformations using Phase2 program and found to be in the range of 10 to 15Mpa in the squeezed section. Later, the deformation has been calculated using Hoek and Marinos (2000) and Convergence Confinement Method for improved intact rock strength and compared with Phase2 result. All analyses show that there is significant deformation to cause squeezing problem. In CHEP, tunnel cross section has reduced considerably in several stretches of tunnel. Due to the excessive deformation, temporary supports were provided at several locations, steel ribs and lattice girders are buckled at several locations and shotcrete lining is also cracked. All these have to be removed before application of final lining. Finally, two different possible solutions have been studied using Phase2 program to address the existing problems in squeezed section of the headrace tunnel

Academic Freedom for Faculty Members and Students: A Case Study of the Faculty of Education at Tribhuvan University in Nepal

ABSTRACT The aim of this study is to investigate the perceptions of faculty members, students and members of the academic leadership on academic freedom. Furthermore, the role of the Faculty of Education in relation to safeguarding academic freedom of faculty members and students is examined in the study. The study provides insights that help to understand the concept of academic freedom and offers valuable information for those who are particularly interested in the issue of academic freedom. The study uses a research strategy focusing on a qualitative case study in order to examine and collect comprehensive and detailed information on academic freedom. Semi- structured interviews are conducted to obtain faculty members , students and the academic leadership s views regarding academic freedom. Additionally, relevant official documents are analysed for the study. The results indicate that the meaning of academic freedom is perceived as something, which is essential for both faculty members and students to conduct academic activities. However, the rights of faculty members and students to conduct academic activities and participate in the governance of the university are limited to some extent by the rules and regulations of the university as well as a lack of financial resources. The results also reveal that both faculty members and students enjoy the right to form and join associations on the basis of their interests. Political instability is the major threat for academic freedom of faculty members and students at Tribhuvan University insofar as political parties directly interfere in the management and the operation of the university. The results of this study indicate that there is a lack of higher education policy regarding academic freedom due to the negligence of both the government and the university. There is also no particular internal policy to safeguard academic freedom at the Faculty of Education. Furthermore, the study reveals that the Faculty of Education has not paid significant attention to the protection of academic freedom to its members

Evaluation of earthquake impact on magnitude of the minimum principal stress along a shotcrete lined pressure tunnel in Nepal

In situ stress condition in rock mass is influenced by both tectonic activity and geological environment such as faulting and shearing in the rock mass. This influence is of significance in the Himalayan region, where the tectonic movement is active, resulting in periodic dynamic earthquakes. Each large-scale earthquake causes both accumulation and sudden release of strain energy, instigating changes in the in situ stress environment in the rock mass. This paper first highlights the importance of the magnitude of the minimum principal stress in the design of unlined or shotcrete lined pressure tunnel as water conveyance system used for hydropower schemes. Then we evaluated the influence of local shear faults on the magnitude of the minimum principal stress along the shotcrete lined high pressure tunnel of Upper Tamakoshi Hydroelectric Project (UTHP) in Nepal. A detailed assessment of the in situ stress state is carried out using both measured data and three-dimensional (3D) numerical analyses with FLAC3D. Finally, analysis is carried out on the possible changes in the magnitude of the minimum principal stress in the rock mass caused by seismic movement (dynamic loading). A permanent change in the stress state at and nearby the area of shear zones along the tunnel alignment is found to be an eminent process

Review on the Major Failure Cases of Unlined Pressure Shafts/Tunnels of Norwegian Hydropower Projects

The Norwegian hydropower industry has more than 100 years of experience in constructing the unlined pressure shafts and tunnels. Most of the hydropower projects have long waterway systems consisting unlined high pressure shafts, underground powerhouse cavern, headrace and tailrace tunnels. The maximum static head reached with unlined pressure shaft and pressure tunnel concept is 1047 meter, which is equivalent to almost 10.5 MPa. It is obvious that the rock mass in the periphery of unlined shafts and tunnels experience high hydrostatic pressure exerted by the flowing water discharge. Experienced gained from the construction and operation of these unlined pressure shafts and tunnels were useful to develop design criterion and principles applied here in the Scandinavia. This paper reviews some of the first attempts of the use of unlined pressure shaft and tunnel concepts, highlights major failure cases, reviews and evaluates the triggering factors for the failure and also discusses about the gradual development of design criterion for the unlined pressure shafts and tunnels. The authors consider this review is a first step in the upgrade on this innovative concept, which could be used in other geological and tectonic environment than of the Scandinavia, such as in the Himalaya