1,326 research outputs found
An overview of tea research in Tanzania - with special reference to the Southern Highlands.
The history of tea development in Tanzania from the early part of this century
to the present is summarised. Average yields of made tea from well managed
estates in the Mufindi district have increased from around 600 kg ha-1 in the
late 1950s to 3000 kg ha-1 at the present time: by comparison, yields from
smallholder farms have remained much lower, averaging only 400-500 kg ha-1.
There have been a large number of technical, economic and other changes over the
last 30 to 40 years. The removal of shade trees, the use of herbicides, the
application of NPK compound fertilisers, the introduction of irrigation (on some
estates) and changes in harvesting policy have all contributed to the increases
in yield. Financial and infrastructural problems have contributed to the low
yields from many smallholders and others, and have limited the uptake of new
technology. The contribution of research is reviewed, from the start of the Tea
Research Institute of East Africa in Kenya in 1951, through to the development
of the Marikitanda Tea Research Centre in Amani in 1967; the Ngwazi Tea Research
Unit in Mufindi (1967 to 1970, and from 1986), and lastly the Kifyulilo Tea
Research Station, also in Mufindi in 1986. The yield potential of well
fertilized and irrigated clonal tea, grown at an altitude of 1800 m, is around
6000 kg ha-1. This potential is reduced by drought, lack of fertilizer, bush
vacancies and inefficient harvesting practices. The corresponding potential
yields at high (2200 m) and low (1200 m) altitude sites range from 3000-3500 kg
ha-1 up to 9000-10000 kg ha-1 and are largely a function of temperature. The
opportunities for increasing yields of existing tea, smallholder and estate, are
enormous. Tea production in the Southern Highlands of Tanzania is about to
expand rapidly. Good, appropriate research is needed to sustain this development
over the long term, and suggestions on how best this is done in order to assist
the large scale producers as well as the smallholders, are discussed
A comparison of the responses of mature and young clonal tea to drought.
To assist commercial producers with optimising the use of irrigation water, the
responses to drought of mature and young tea crops (22 and 5 years after field
planting respectively) were compared using data from two adjacent long-term
irrigation experiments in Southern Tanzania. Providing the maximum potential
soil water deficit was below about 400-500 mm for mature, and 200-250 mm for
young plants (clone 6/8), annual yields of dry tea from rainfed or partially
irrigated crops were similar to those from the corresponding well-watered crops.
At deficits greater than this, annual yields declined rapidly in young tea (up
to 22 kg (ha mm)-1) but relatively slowly in mature tea (up to 6.5 kg (ha mm)-
1). This apparent insensitivity of the mature crop to drought was due
principally to compensation that occurred during the rains for yield lost in the
dry season. Differences in dry matter distribution and shoot to root ratios
contributed to these contrasting responses. Thus, the total above ground dry
mass of well-irrigated, mature plants was about twice that for young plants.
Similarly, the total mass of structural roots (>1 mm diameter), to 3 m depth,
was four times greater in the mature crop than in the young crop and, for fine
roots (<1 mm diameter), eight times greater. The corresponding shoot to root
ratios (dry mass) were about 1:1 and 2:1 respectively. In addition, each unit
area of leaf in the canopy of a mature plant had six times more fine roots (by
weight) available to extract and supply water than did a young plant. Despite
the logistical benefits resulting from more even crop distribution during the
year when crops are fully irrigated, producers currently prefer to save water
and energy costs by allowing a substantial soil water deficit to develop prior
to the start of the rains, up to 250 mm in mature tea, knowing that yield
compensation will occur later
Bound and resonance states of the nonlinear Schroedinger equation in simple model systems
The stationary nonlinear Schroedinger equation, or Gross-Pitaevskii equation,
is studied for the cases of a single delta potential and a delta-shell
potential. These model systems allow analytical solutions, and thus provide
useful insight into the features of stationary bound, scattering and resonance
states of the nonlinear Schroedinger equation. For the single delta potential,
the influence of the potential strength and the nonlinearity is studied as well
as the transition from bound to scattering states. Furthermore, the properties
of resonance states for a repulsive delta-shell potential are discussed.Comment: 19 pages, 10 figure
Synthesis, X-ray structural characterization, and DFT calculations of binuclear mixed-ligand copper(II) complexes containing diamine, acetate and methacrylate ligands
The dinuclear Cu(II) complexes [Cu(en)(MAA)(µ-CH3COO)]2 (1) and [Cu(pn)(MAA)(µ-CH3COO)]2 (2) where MAA, en and pn are methacrylate, ethylendiamine and 1,3-propylendiamine, respectively, have been synthesized and characterized by elemental analysis, FT-IR and UV-Vis spectroscopy. The structures of the complexes have been determined by single-crystal X-ray diffraction analyses. In the dinuclear complexes 1 and 2 the two copper centers are five-coordinated and exhibit distorted square pyramidal geometries. The theoretical geometries of the studied compounds have been calculated by means of density functional theory (DFT) at the B3LYP/6-311+G(d,p)/LanL2DZ level considering effective core potential (ECP)
Quantitative single-molecule microscopy reveals that CENP-A(Cnp1) deposition occurs during G2 in fission yeast
The inheritance of the histone H3 variant CENP-A in nucleosomes at centromeres following DNA replication is mediated by an epigenetic mechanism. To understand the process of epigenetic inheritance, or propagation of histones and histone variants, as nucleosomes are disassembled and reassembled in living eukaryotic cells, we have explored the feasibility of exploiting photo-activated localization microscopy (PALM). PALM of single molecules in living cells has the potential to reveal new concepts in cell biology, providing insights into stochastic variation in cellular states. However, thus far, its use has been limited to studies in bacteria or to processes occurring near the surface of eukaryotic cells. With PALM, one literally observes and 'counts' individual molecules in cells one-by-one and this allows the recording of images with a resolution higher than that determined by the diffraction of light (the so-called super-resolution microscopy). Here, we investigate the use of different fluorophores and develop procedures to count the centromere-specific histone H3 variant CENP-A(Cnp1) with single-molecule sensitivity in fission yeast (Schizosaccharomyces pombe). The results obtained are validated by and compared with ChIP-seq analyses. Using this approach, CENP-A(Cnp1) levels at fission yeast (S. pombe) centromeres were followed as they change during the cell cycle. Our measurements show that CENP-A(Cnp1) is deposited solely during the G2 phase of the cell cycle
Synthesis, X-ray Structural Characterization, and DFT Calculations of Mononuclear Nickel(II) Complexes Containing Diamine and Methacrylate Ligands
The mononuclear Ni(II) complexes [Ni(en)2(H2O)2](MAA)2 (1) and [Ni(pn)2(MAA)2] (2), where MAA, en and pn are
methacrylate, ethylendiamine and 1,3-propylendiamine, respectively, have been synthesized and characterized by elemental
analysis, FT-IR and UV–Vis spectroskopy. Structures of the complexes have been determined by single-crystal
X-ray diffraction analyses. In the nickel(II) complexes 1 and 2 nickel(II) ion is six-coordinate and has a distorted octahedral
geometry. Ni(II) is bonded to four nitrogen atoms of the two diamines and additionally to two oxygen atoms of aqua
ligand in 1, and two oxygen atoms of methacrylate ligands in 2. The theoretical geometries of the studied compounds
have been calculated by means of density functional theory (DFT) at the B3LYP/6-311+G(d,p)/LanL2DZ level and considering
effective core potential (ECP). The comparison of the results indicates that the employed DFT method yields
good agreement with experimental data
Workshop on Mars Sample Return Science
Martian magnetic history; quarantine issues; surface modifying processes; climate and atmosphere; sampling sites and strategies; and life sciences were among the topics discussed
Manipulating the enone moiety of levoglucosenone: 1,3-Transposition reactions including ones leading to isolevoglucosenone
This research was part-funded by Circa Group Pty Ltd
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