Search

The effective seepage force on cohesionless interfacial bed particles that comprise a plane bed was determined from the results of slope instability tests and from extrapolation of the results of erosion tests. The seepage flow was perpendicular to the bed and either into or out of the bed for the slope instability tests. Tests were conducted using two columns, one square and the other circular, in cross-section. For uniform sand particles ranging from 0.46 mm diam. to 0.72 mm diam., the seepage force on the interfacial sand grains was determined from slope instability tests to be one-half that on particles well within the bed. Subsequent to the condition of instability for seepage flow vertically upward and into a bed, erosion of the sand bed was measured. From an extrapolation of the results of the erosion tests to a condition of no erosion (which was assumed to correspond to the condition of incipient instability), it is concluded that the seepage force on the interfacial grains is approximately 35% to 40% of that on grains well within the bed.

When people [at the National Democratic Alliance conference in Asmara in 1995] started talking about democratic laws, the issue of women was raised. Of course [a member of a sectarian party] jumped up and said “so women’s [issues] have come here as well? Just like that from the start? So what do women have to do with that issue? Why do you want to mess up the story?” A party representative actually said that! (Interview with a former member of the NDA Executive Office and delegate to theAsmara 1995 Conference).

2-Acetyl, 2-cyano-, and 2-nitro-2-phenylazopropionic acid derivatives suffer cleavage of the phenylazo-grouping on treatment with boron trifluoride, giving benzenediazonium tetrafluoroborate and the corresponding difluoroboron propionic acid derivative; 2-cyano- or 2-nitro-2-phenylazoisobutyronitrile and the corresponding amides behave similarly, but 1-phenylazo-2-naphthol gives a difluoroboron salt, and 2-phenylazo(diphenylmethyl)acetate is cyclised to 1,3-diphenylindazole on treatment with boron trifluoride. Acyl-2-phenylazopropionates suffer loss of the acyl grouping during attempted ketonic carbonyl condensation reactions, with conversion into corresponding phenylhydrazones; new examples, broadening the scope of the Japp–Klingemann reaction, are described.

The CD of the anilides of α-halo-propionic acids depends on solvent and substitution of the aromatic ring. Changes of the CD with solvent can be explained by taking into account three conformers (G, A + and A − of Fig 1). The CD band around 250 nm is negative for derivatives of the l -acids in all solvents except hydrocarbons in which it is positive. The 1 L b band Cotton effects are very weak or not observed. The 1 L a —CD band is much stronger in the m - and o- substituted anilides than in-the p - or unsubstituted anilides.

The NMR spectra of a series of chiral propionamides have been determined in D(+)1-phenylethylamine solution. The α-methine protons of the propionic acid moiety in the propionamide enantiomers were found to be anisochronous in this solvent. The sense of non-equivalence of these protons was found to be the same for all members of a homochiral series. The chemical shift difference between their signals was demonstrated to be dependent upon the temperature and concentration of the solution. A method is described whereby the enantiomeric purity of the amides could be calculated from these signals in cases where the position of the baseline in their spectra was unknown.

Two promising routes towards synthesis of the hitherto unknown α-alkoxypropionanilides were explored with success. As expected, facile displacement of the bromide in l (−)α-bromopropionanilide by alkoxide lead to inversion of configuration with considerable racemization, whereas substitution of the chloride in l (−) α-alkoxypropionyl chloride by arylamine proceeded with little or no racemization. α-Ethoxypropionanilide and the higher alkoxy homologues appear as low-melting noncrystallizable gum. Optical properties and other physical data for few model compounds of this new anilide series are reported.

The Republic of the Sudan is predominantly a land of cultivators and nomads, importing mainly manufactured goods and exporting agricultural products of which long-staple cotton, cottonseeds, gum arabic, groundnuts, sesame, hides and skins, and livestock are the most important. The development of this commercial sector of the economy is post-nineteenth-century; seventy years ago a subsistence economy prevailed throughout the Sudan. Surpluses for export were few, and consisted of such items as gum arabic, ostrich feathers, and ivory. After the establishment of the Condominium Government in 1898, however, railway lines were built and a new port developed. These were among the main factors which led to the gradual increases in the production of both commercial and subsistence crops. At present the total area annually under long-staple cotton is about 333,000 hectares (800,000 acres), whilst that under dura (the main staple diet of the Sudanese) reaches 1 million hectares (2.5 million acres), partly as a result of new mechanised production. In recent years some light industries have been established, and mining developments have taken place. Among important industries are cotton textiles in Khartoum North, and sugar production in Guneid and Khashm el Girba. These, together with cement and food-processing industries, are meant to satisfy the home market.

l INTRODUCTION i Description and objectives i Location and accessibility 3 Geography and geomorphology 5 Previous investigations 7 Acknowledgements 3 PRESENT INVESTIGATIONS ^....... 9 Introduction 9 Geologic mapping 10 Diamond drilling 13 Topographic surveys 14 Analysis of drill cores 17 GEOLOGIC SETTING 17 STEUtf IG3AFHY -20 Older metavoIconic rocks 20 Metasedimentary rocks 23 Younger matavolcanlo -cooks 25 Intrusive rocks.. 27 Tertiary and younger rocks 29

Mean distance measurements between winterfat (Eurotia lanata) and saltsage (Atriplex nuttallii) plants in stands of different densities due to grazing history were used to determine adequate plot size to detect density and frequency differences. The plot size which best estimated the densities and frequencies of these two species was 21/2 to 22/3 times mean inter-plant distances. Distribution of these species, as reflected by the test used, was random for winterfat and regular for salt- sage. The common practice of using a standard plot to sample vegetation of the same size, growth form and stratum was not substantiated for this vegetation. Even the same species in areas alike except for different grazing histories gave significant differences in optimum plot size.