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The Polarising Effects In Sintered Kaolin, Fm D'Ujanga, Y Kaahwa, L Atteraas
The Polarising Effects In Sintered Kaolin, Fm D'Ujanga, Y Kaahwa, L Atteraas
Tanzania Journal of Science
The polarizing effects in sintered kaolin samples were analysed in terms of the sample density (or porosity) using direct current (dc) techniques. More porous samples exhibited higher polarizing effects than the less porous ones. The conduction carriers in kaolin samples at room temperature were found to be mainly electrons, with ionic conduction being enhanced by the moisture content with the pores. The influence of the uniaxial pressure and particle-size on the compacted and sintered density of the ceramic have been studied, and a density-pressure relationship before- and after-sintering conditions obtained
Studies On Benthic Denitrification In The Chwaka Bay Mangrove Sediments, Zanzibar, Sm Mahommed, Rw Johnstone
Studies On Benthic Denitrification In The Chwaka Bay Mangrove Sediments, Zanzibar, Sm Mahommed, Rw Johnstone
Tanzania Journal of Science
Denitrification was measured at three sites in a narrow tidal creek in the Chwaka mangrove ecosystem. Denitrification arising from water column nitrate (Dw) was low (< 0.1μM Nm-2h-1) and there was little spatial and seasonal variation in Dw rates in the creek. Coupled nitrification-denitrification (Dn) was found to be low, but within the range measured in other mangrove sediments. Average values ranged from 0.01 to 0.45 μM Nm-2h-1 and showed strong spatial variations. The low denitrifcation rates observed in the creek were possibly as a result of the low availability of NO3 and high C:N values of the organic matter in the sediment. Spatial variations in denitrification rates were due to variations in concentration levels of organic matter and possibly to disproportionate competition for inorganic nitrogen between denitrifiers and benthic autotrophs among sites. There were no seasonal differences in denitrification rates. Results from the present study suggest that sediment denitrification does not play a major role as a sink for N in this ecosystem
Interpretation Of Refelction Seismic Data From The Usangu Basin, East African Rift System, Ei Mbede
Interpretation Of Refelction Seismic Data From The Usangu Basin, East African Rift System, Ei Mbede
Tanzania Journal of Science
Reflection seismic data collected by AMOCO Tanzania Oil Company in the 80s, are herin used to correlate the main Usangu Basin parameters to those estimated from outcrop, gravity and aeromagnetic data. The seismic data are further used to constrain the geometry of crustal extension in this south-western sector of the East African Rift System (EARS) in Tanzania. Three distinct sedimentary packages on top of the basement reflector are interpreted and correlated to the Permo-Carboniferous Karoo rocks, the Jurassic/Cretaceous and Miocene Red Sandstone Group and Miocene to recent Lake Beds in the adjacent Rukwa basin, where the ages of the sedimentary …
Tectonic Setting Of Gabbroic Rocks In The Western Part Of The Lupa Gold Field, South-West Tanzania, Sr Mnali
Tectonic Setting Of Gabbroic Rocks In The Western Part Of The Lupa Gold Field, South-West Tanzania, Sr Mnali
Tanzania Journal of Science
There is a pronounced occurrence of gabbroic rocks in the western part of the Lupa gold field, SW Tanzania. These rocks occur in the peripheral part around the Saza-Chuya granodiorite with which it makes a gradiational, unchilled contact. The rocks have been altered or metamorphosed to low-grade greenschist facies as indicated by the presence of secondary epidote, penninite, chlorite, sericite and calcite. The majority of major-element oxides show scattered variation trends against immobile elements such as Zr, indicating some degree of element mobility during post-crystallization processes of alteration or metamorphism. Major-trace-element data show that the gabbroic rocks in the study …
Identification Of Mushroom Mycelia Using Dna Techniques, Mhs Muruke, Ak Kivaisi, Fss Magingo, E Danell
Identification Of Mushroom Mycelia Using Dna Techniques, Mhs Muruke, Ak Kivaisi, Fss Magingo, E Danell
Tanzania Journal of Science
The suitability of using DNA techniques in the determination of relatedness of mushroom fruiting bodies to isolated mycelia was examined. Nine isolates of edible mushroom mycelia of general Oudemansiella, Coprinus and Pleurotus were identified using fruiting bodies as references. Polymerase Chain Reaction (PCR) in conbination with Restriction Fragment Length Polymorphism (RLFP) analyses were carried out on fruiting bodies and mycelia of the isolates. The internally transcribed spacer region (ITS) and ribosomal RNA gene (rDNA) was amplified using ITS1 and ITS4 primers. The RLFP analysis was carried out on the regions amplified by PCR from fruiting bodies and the mycelia was …
Mobility And Immobility Of Mid-Ocean Ridges And Their Implications To Mantle Dynamics, Me Kamwaya
Mobility And Immobility Of Mid-Ocean Ridges And Their Implications To Mantle Dynamics, Me Kamwaya
Tanzania Journal of Science
In the past two decades, the mobility of mid-ocean ridges relative to the mantle (absolute migration) have been correlated with major observable features, such as, spreading asymmetry and asymmetry in the abundance of seamounts. The mobility of mid-ocean ridges is also thought to be an important factor that influences the diversity of ridge-crest basalts. However, the mobility of mid-ocean ridges have not yet been defined and mapped. The absolute migration of global mid-ocean ridges since 85 Ma has been computed and mapped. Global mid-ocean ridges have migrated extensively at varying velocities during that period. Presently, the fast-migrating ridges are the …
Assessment Of Heavy Metal Pollution In The Lupa Gold Field, Sw Tanzania, S. R. Mnali
Assessment Of Heavy Metal Pollution In The Lupa Gold Field, Sw Tanzania, S. R. Mnali
Tanzania Journal of Science
The concentrations of AS, Cd, Cr, Cu, Hg and Pb were determined in water, stream sediments, soil, and mine tailings from Lupa Gold Field (LGF), SW Tanzania, in order to assess their pollution levels. As, Cd and Cr were determined by automated Graphite Furnace Absorption Spectrophotometry. Cu and Pb were analysed by Air-Acetylene Flame, while Hg was analysed by Cold Vapour Atomic Absorption Spectrophotometry. The mean concentrations obtained were: As: 0.44 ppb (water), 1.2 ppm (sediments), 0.44 ppm (soil) and 5.2 ppm (tailings); Cd: 0.03 ppb (water), 0.03 ppm (sediments), 0.03 ppm (soil) and 0.50 ppm (tailings); Cr: 1.4 ppb …
Tectonic Setting And Uplift Analysis Of The Pangani Rift Basin In Northern Tanzania Using Apatite Fission Track Thermochronology, E. I. Mbede
Tanzania Journal of Science
Thirty four new Apatite Fission Track (AFT) ages and 32 track length distributions from samples of basement rocks flanking the Pangani rift, East African Rift System (EARS) are presented, in an attempt to elucidate the uplift and erosion of the rift flanks. The ages fall in the range of 207±15 to 48±4 Ma, spanning from Early Jurassic to Early Tertiary. These ages are much younger than the last termal event in the Mozambique belt that form the basement complex and are interpreted to represent the most recent tectonic events. Track length (TL) distributions suggest that uplift and erosion of the …
Sources And Diagenetic Alteration Of Organic Matter In Coastal Waters At The Vicinity Of Dar Es Salaam, Tanzania, Ann Muzuka
Tanzania Journal of Science
The stable isotope compositions of organic carbon (OC) and nitrogen, contents of OC and nitrogen, and C/N ratios for four short cores, which were recovered from Msansani Bay (WO 57), off Msimbazi River (WO 76) and Dar es Salaam harbour (WO 62 and WO 74), are used to document temporal variation in the sources and diagenetic alteration of organic matter (OM). The δ15N and δ13C values at sites WO 57, WO 62 and WO 74 show a trend of down-core decrease to the base of the core, and such a down-core trend could be related to diagenetic loss of compounds …
The Occurrence Of Digenean Larvae In Freshwater Snails At Mbezi-Temboni Pond, Dar Es Salaam, Esp Esp Kigadye, G. Nkwengulila
The Occurrence Of Digenean Larvae In Freshwater Snails At Mbezi-Temboni Pond, Dar Es Salaam, Esp Esp Kigadye, G. Nkwengulila
Tanzania Journal of Science
The abundance of digenean larvae in snails at a pond in Mbezi-Temboni, Dar es Salaam, was investigated from July 1996 to June 1997. A total of 2,112 snails belonging to three species, Bulinus globosus Morelet 1866, Bulinus forskalii Ehrenberg 1869, and Melanoides tuberculata Müller 1774 were examined, and 28 (1.3%) were found infected by four species of digenean trematodes. Trematodes were recovered only from Bulinus species; none of the examined M. tuberculata was infected. B. globosus was infected by Schistosoma haematobium Bilharz 1852 (1.14%), unidentified furcocercous cercariae (0.4%), and echinostome cercariae (0.76%). B. forskalii was infected by echinostome cercariae (0.25%) …
The Emplacement Age Of Gabbroic Rocks And Associated Granitoids Of The Liganga-Msanyo Complex, South Eastern Tanzania, M. A. H. Maboko
The Emplacement Age Of Gabbroic Rocks And Associated Granitoids Of The Liganga-Msanyo Complex, South Eastern Tanzania, M. A. H. Maboko
Tanzania Journal of Science
The Msanyo Gabbro and the associated Mdando granitoids, which intrude Paleoproterozoic high-grade metamorphic rocks of the Ubendian Belt in southern Tanzania, yield imprecise Sm-Nd whole rock isochron ages of 1608±134 Ma (ε (Nd) = 2.1) and 1642±100 Ma (ε (Nd) = 1.6), respectively. These ages are indistinguishable at the 95% confidence level, indicating that the two rock suites were intruded at the same time. A more precise estimate of the time of emplacement is provided by a 5-point mineral isochron age of 1505±42 obtained from one of the gabbro samples. Calculated initial ε (Nd) values and mean crustal residence ages …
The Geochemistry Of Banded Iron Formations In The Sukumaland Greenstone Belt Of Geita, Northern Tanzania: Evidence For Mixing Of Hydrothermal And Clastic Sources Of The Chemical Elements, M A H Maboko
Tanzania Journal of Science
Major and trace element compositions of samples of Banded Iron Formations (BIF) from the Neoarchaean Sukumaland Greenstone Belt of Geita in northern Tanzania reveal that the BIF precipitated from hydrothermal solutions. Fe-Ti-Al-Mn systematics suggest that the hydrothermal deposits have been contaminated, by up to 20% by weight, with detrital material having a composition similar to modern deep-sea pelagic clays. SiO2 and Fe2O3 contents are 48.2 to 88.5% and 8.9 to 49.1% respectively. Al2O3 contents lie between 0.33 and 2.1% and show no correlation with either Fe2O3 or SiO2. Al2O3 is, however, positively correlated with Ti, Ga, Hf, Rb,Th, Zr and …
Physicochemical Characteristics Of Some Locally Manufactured Edible Vegetable Oils Marketed In Dar Es Salaam, F N Ngassapa, O C Othman
Physicochemical Characteristics Of Some Locally Manufactured Edible Vegetable Oils Marketed In Dar Es Salaam, F N Ngassapa, O C Othman
Tanzania Journal of Science
The physicochemical properties (refractive index, saponification value, Free Fatty Acid (FFA) value, iodine value, acid value, peroxide value and tocopherol content) of seven edible vegetable oils manufactured in Tanzania, were assessed using standard procedures of the Association of Official Analytical Chemists (AOAC). Also determined were the levels of these properties with respect to shelf storage of the products. When compared with standard values recommended by the Codex Alimentarius Commission of FAO/WHO and with other published results, the locally produced vegetable oils were found to be of fair quality but of poor storage stability.
Comparison Of Direct Return And Birth-Death Return Receivers, H N Kundaeli
Comparison Of Direct Return And Birth-Death Return Receivers, H N Kundaeli
Tanzania Journal of Science
The performance of frame synchronized communication systems is governed largely by the design chosen for the receiver. Some systems employ a structure in which the receiver returns directly to the sync phase when a valid marker is encountered while in the loss verify state. These have been greatly studied. In some systems, the return path in the loss verify phase is implemented as a birth-death process. These systems have not received much attention. In this report, a receiver which employs a birth-death like structure in the loss path is investigated. Expressions for the performance parameters are derived and compared with …
Production Of Biogas From Water Hyacinth: Effect Of Subtrate Concentration, Particle Size And Incubation Period, J H Y Katima
Production Of Biogas From Water Hyacinth: Effect Of Subtrate Concentration, Particle Size And Incubation Period, J H Y Katima
Tanzania Journal of Science
A study was conducted, at constant temperature, to determine the effect of substrate concentration, particle size and incubation time on biogas production from water hyacinth. Substrate concentration was varied between 5-30 g/l of water, particle size between <1 mm - 3 mm and incubation period between 1-6 days. The maximum methane prodction of 72.53% v/v at substrate concentration of 25 g/1 and particle size less than 1 mm for water hyacinth shoots was achieved after five days of incubation. However, for the whole water hyacinth plant, methane content was 65.67% v/v at the same conditions.
Heavy Metals In Green Vegetables And Soils From Vegetable Gardens In Dar Es Salaam, Tanzania, O C Othman
Heavy Metals In Green Vegetables And Soils From Vegetable Gardens In Dar Es Salaam, Tanzania, O C Othman
Tanzania Journal of Science
Edible portions of five varieties of green vegetables, namely amaranth, chinese cabbage, cowpea leaves, leafy cabbage and pumpkin leaves, collected from several areas in Dar es Salaam, were analyzed for lead, cadmium, chromium, zinc, nickel and copper. Except for zinc, the levels of heavy metals in the vegetables grown at Tabata area were much higher than in the vegetables from Ukonga and Kiwalani. Amaranth and pumpkin leaves had more than 60% higher content of heavy metals, especially copper, chromium and lead, than the other vegetables. All vegetables from Tabata, Buguruni and Sinza had lead-levels higher then the FAO/WHO recommended permissible …
Influence Of Endocrine Activity On Larval Development In Busseola Fusca (Fuller) (Lepidoptera:Noctudine), M Njau
Tanzania Journal of Science
The present study investigated the role of juvenile and moulting hormones in development of Busseola fusca. Morphometric measurements were used to distinguish differences in endocrine activity between non-diapause and diapause development with regard to the prothoracic glands and the corpora allata. The corpora allata of non-diapause larvae were similar in size to those of diapause larvae. The critical period for the prothoracic glands to produce the required titer of ecdysone for further development was by the third day after ecdysis to the last larval instar. Juvenile hormone extracts from haemolymph of Busseola fusca larvae in non-diapause and diapause development had …
Subsidence History Of The Rukwa Rift In South West Tanzania Analysed From Ivuna Well, E I Mbede
Subsidence History Of The Rukwa Rift In South West Tanzania Analysed From Ivuna Well, E I Mbede
Tanzania Journal of Science
The variation in subsidence rate during rift basin development is a good indication for the Geodynamic history of a sedimentary basin. The sedimentary section of Ivuna Well is herein used to explain the structural evolution of Rukwa Basin within the Western Rift of the East African Rift System. The sedimentary record of Ivuna Well is extracted from published information. The effects of sedimentary load, corrected for compaction and variation in water depth, and lake-level have been removed to obtain the "tectonic subsidence." Curves show two phases of accelerated subsidence related to the fault controlled rifting phases: The Karoo rifting and …
Preliminary Evidence For A Second -525-545 Ma Old Event Of Granilate Facies Metamorphism In The Mozambique Belt Of Tanzania And Its Implication For A Two-Stage Model For Gondwana Assembly, M A H Maboko
Tanzania Journal of Science
Garnets from two samples of the Kitumbi granulites in the Mozambique Belt of north eastern Tanzania yield Sm-Nd ages of 525±15 Ma and 545±15 Ma. At the 95% confidence level, these ages are younger than the 576 ±15 to 634±16 Ma (Mean 606±12 Ma) ages previously reported from the more extensive Eastern Granulites. The Kitumbi garnets are therefore interpreted as dating cooling from a granulite facies event that is distinctly younger than the 630-700 Ma event that produced the Eastern Granulites. Unlike the Eastern Granulites, the Kitumbi rocks occur as small enclaves not separated from the surrounding amphibolite facies gneisses …
Thermogravimetric Study Of Gadolinium Chlorotungstate In Air Between 25 And 1500°C., F N Ngassapa, N U Venskovskii
Thermogravimetric Study Of Gadolinium Chlorotungstate In Air Between 25 And 1500°C., F N Ngassapa, N U Venskovskii
Tanzania Journal of Science
Using DTA, X-ray powder diffraction, chemical and optical methods, the thermostability of Gd3WO6Cl3 was investigated. The compound was relatively stable on heating in air up to 710oC. Above this temperature it exhibited two decomposition temperature ranges (710-900oC and 900-1130oC). The final product consisted of a mixture of gadolinium tungstate of different composition. This suggests the decomposition scheme of polyphase products
Tidally Induced Flow In Chwaka Bay Zanzibar, O U. Mwaipopo
Tidally Induced Flow In Chwaka Bay Zanzibar, O U. Mwaipopo
Tanzania Journal of Science
Time series data of currents and sea current levels recorded by current meter and tide gauges, respectively from Chwaka Bay, Zanzibar were obtained from the entrance near to Mapopwe Creek and at the middle of the bay. The analysis of the data reveals that the tidal currents had an asymmetry near the entrance to Mapopwe Creek where the ebb currents were stronger than flood currents although the ebb periods were considerably longer than flood periods.
Stable Isotope Compositions Of Sedimentary Organic Matter Off Zanzibar Town, Ann Muzuka
Stable Isotope Compositions Of Sedimentary Organic Matter Off Zanzibar Town, Ann Muzuka
Tanzania Journal of Science
Stable isotope compositions of sedimentary organic carbon for sediments collected off the Zanzibar Town averaged -17.9%. Low isotope values of organic carbon, which were associated with high C/N ratios, were observed within Zanzibar harbour suggesting a significant contribution of terrestrial organic matter to the harbour. Sediments collected outside the Zanzibar harbour were richer in 13C than those collected within the harbour area. This 13 enrichment in 13C can be attributed to a decrease in the influence of terrestrial organic matter (0M) and high contribution of' sea grasses. A decrease in the influence of terrestrial OM is further supported …
A Simple Method For Indexing Powder Diffraction Patterns Of Cubic Materials (11): Using The D-Values Of Reference, Me Kamwaya
Tanzania Journal of Science
From the d-values (in decreasing order) taken from powder diffraction patterns of the cubic material a variable constant, KQ, which is a multiple of Ʃh12 where Q = l/d2 can be determined. The smallest values of Q give rise to multiples of ones, twos and threes, which correspond to the smallest values of Ʃh12 for the primitive, bcc, and fcc/diamond Type structures, respectively. Cognance of the lattice types is best accomplished by the ΔQ-criterion, where ΔQ denotes the difference between successive values of Q. Indexing is greatly simplified and the use of rigorous tables is …
Bis(4-Carboxylato-5-Methyl-Oxazolidine) Nickel(Ii)Dihydrate, Its Preparation And Crystal Structure, Me Kamwaya
Bis(4-Carboxylato-5-Methyl-Oxazolidine) Nickel(Ii)Dihydrate, Its Preparation And Crystal Structure, Me Kamwaya
Tanzania Journal of Science
An aqueous solution of nickel (Il) acetate tetrahydrate was added to warm solution of L-threonine and sodium bicarbonate. The mixture was subsequently treated with aqueous solution of formaldehyde and stirred until the blue solution turned green. The reaction consists in a base catalysed condensation of formaldehyde with L-threonine-nickel (Il) – complex followed by formation of an oxazolidine ring. A single crystal X-ray investigation was carried out at 120(1) oC. The X-ray structure analysis showed an octahedral nickel comp/ex containing two water molecules. The oxazolidine rings were connected to the Ni by nitrogen and one of the carboxylato oxygen atoms. …
Heavy Metal Content In Water Hyacinth (Eichhornia Crassipes (Mart) Solms.) From Lake Victoria Shore, Tanzania, Nk Mohammed, In Makundi
Heavy Metal Content In Water Hyacinth (Eichhornia Crassipes (Mart) Solms.) From Lake Victoria Shore, Tanzania, Nk Mohammed, In Makundi
Tanzania Journal of Science
Water hyacinth (Eichhornia crassipes (Mart) Solms,) samples from Lake Victoria shore were analysed for heavy metal pollution using Energy Dispersive X-ray Fluorescence Spectroscopy (EDXRF). The roots of the water hyacinth samples were collected from areas influenced by industrial and domestic sewage and little influenced area. Water hyacinth from industrial area and those from sewage discharge points had higher concentrations of heavy metals than that from the little disturbed area.
Comparison Of Synchronization Strategies For Systems Employing Multiple-Code Markers, Hn Kundaeli
Comparison Of Synchronization Strategies For Systems Employing Multiple-Code Markers, Hn Kundaeli
Tanzania Journal of Science
Frame synchronization strategies based on single-code markers have been widely researched and reported. On the other hand, frame synchronization strategies based on multiple-code markers have not been so well reported although they have become quite popular in systems operating at high transmission rates. In this paper, the performance of various synchronization strategies for systems employing multiple-code markers is compared. It is shown that, systems employing contiguous multiple-code markers have better performance than those employing distributed multiple-code markers. It is also shown that, systems in which the individual codewords of the markers are checked during loss of synchronization hare better performance …
Facies Analysis Of Limestones At Songo Songo Island In South East Tanzania, S Kapilima, Ka Msindai
Facies Analysis Of Limestones At Songo Songo Island In South East Tanzania, S Kapilima, Ka Msindai
Tanzania Journal of Science
Songo Songo Island is situated at close proximity of the continental slope of the coastal sedimentary basin of Tanzania. Its rich varieties of marine organisms and carbonate sediments provide a classic example of island emergence with the development of successive detrital and organic reefs as well as lime sand. Facies analysis at the Island was done through mapping, logging, faces and microfacies analysis. Results show that Songo Songo Island can be classified into three faces; the detrital reefs, organic reef and lime sand. The fossil assemblage reveals that most of the fauna and flora are frame-building organisms in organic reef. …
Turbulent Heat Energy Exchange In A Tropical Bay, S B. Mahongo
Turbulent Heat Energy Exchange In A Tropical Bay, S B. Mahongo
Tanzania Journal of Science
Atmospheric and Sea surface temperature data were used to describe the magnitude of turbulent heat energy processes Chwaka Bay, Zanzibar, Bulk aerodynamic formulae were applied in the investigation for data collected over a 23-day period in 1996. These were those Smith (1988), Friehe and Schmitt (1976), Mohanty and Mohan Kumar (1990) and Bunker (1976). The computed fluxes of moisture were 156 Wm-2 (Smith), 158 Wm-2 (Friehe and Schmitt), 160 Wm-2 (Mohanty and Mohan Kumar) and 188 Wm-2 (Bunker), respectively. The corresponding fluxes of sensible heat were 15 Wm-2, 13 Wm-2, 18 Wm …
Status Of Heavy Metals Pollution In The Nile Around Khartoum Area, F I. Habbani, S E. Salih
Status Of Heavy Metals Pollution In The Nile Around Khartoum Area, F I. Habbani, S E. Salih
Tanzania Journal of Science
Investigations for heavy metals pollution in the Nile around Khartoum area were carried Out using the technique of x-ray fluorescence (XRF). Samples were collected from various locations around Khartoum area before and after the flood. The results indicated that there was no heavy metals pollution in the Nile in Khartoum area resulting from industrial activities. The origin for the observed heavy metals concentrations, except for Pb, was considered to be soil erosion caused by the river on its journey from the Ethiopian Highlands and Lake Victoria. However, there are indications that some Pb pollution could be due to emissions of …
Synthesis Of Bis-(3-Carbethoxy-6-Methoxy-4-Methyl-2-Quinolyl) Selenide, Rr Malisa, G L. Mhehe, Sjm Mdachi
Synthesis Of Bis-(3-Carbethoxy-6-Methoxy-4-Methyl-2-Quinolyl) Selenide, Rr Malisa, G L. Mhehe, Sjm Mdachi
Tanzania Journal of Science
In the execution of a synthetic strategy aiming at 3-acetyl-2,4-dichloro-6-methoxyquinoline, a precursor to a 4-methoyselenolo[2,3-b]quinolone, we have instead obtained 2-chloro-3-carbethoxy-6-methoxy-4-methylquinoline. These results strongly suggest that the compound claimed to be 3-acetyl-2,4-dihydroxy-6-methoxyquinoline in the literature and a precursor to 3-actyl-2,4-dichloro-6-methoxyquinoline, is 3-carbethoxy-2-hydroxy-6-methoxy-4-methylquinoline, a precursor to 2-chlo-3-carbethoy-6-methoxy-4-methylquinoline. The reaction of the latter compound with sodium hydrogen selenide in ethanol yielded bis-(3-carbethoxy-6-methoxy-4-methyl-2-quinolyl) selenide.