Mapping Soil Erosion Sensitive Areas in Organic Matter Amended Soil Associations in the Ntabelanga area, Eastern Cape Province, South Africa

The study aims to map areas sensitive to erosion by water and rainfall erosivity after addition of organic matter (OM) in highly unstable soils. A soil association map was created using digital soil mapping methodology. Soil samples from six soil associations were incubated and analysed for several soil erodibility measures and inferred to the soil association map. Soil stabilization against soil erosion by use of OM was evaluated for 30 weeks under two simulated rainstorms, intermittent rainstorms (IR) and single rainstorm (SR). Rainfall erosivity (R-factor) was calculated from theduration of a rainstorm and the total amount of rainfall received under rainfall simulations. Erodibility factor (K-factor) was estimated using the soil OM content and texture. Largest area (40%) was covered by shallow soils and K-factor range of 0.0693-0.0778 t.ha.hha-1MJ-1mm-1. Largest (60.2%) area had a structural stability index of 0.8 and 42.7% of the area was covered by a dispersion ratio value range of 0.65-0.70. The area size with erosion rates of > 15 t/ha/yr was drastically reduced from 1 to 8 weeks after OM application thereafter gradually increased under both IR and SR.  Soil erosion rates of < 5 t-1 ha-1 yr-1 and > 15 t-1 ha-1 yr-1 were most and least observed respectively under both storms. R-factor was higher under IR than SR and the smallest areas with soil erosion rates of > 15 t-1 ha-1 yr-1 contributed most to the lost soil. Organic matter confers soil resistance to erosion up to a certain period before losing its effectiveness. The study provided first assessment of erosion dynamics, basis for identifying  conservation priorities which may be applicable in similar areas. Keywords: Erosivity, planning, rainstorm, soil conservation, soil degradatio

Sub-MHz Linewidth at 240 GHz from an Injection-Locked Free-Electron Laser

Radiation from an ultra-stable 240 GHz solid-state source has been injected, through an isolator, into the cavity of the University of California Santa Barbara (UCSB) MM-wave free-electron laser (FEL). High-power FEL emission, normally distributed among many of the cavity's longitudinal modes, is concentrated into the single mode to which the solid state source has been tuned. The linewidth of the FEL emission is 0.5 MHz, consistent with the Fourier transform limit for the 2 microsecond pulses. This demonstration of frequency-stable, ultra-narrow-band FEL emission is a critical milestone on the road to FEL-based pulsed electron paramagnetic resonance spectroscopy.Comment: 3 pages including 3 figure

Rabi oscillations of solitons in spin-chains: a new route to quantum computation and communication

We provide the first evidence for coherence and Rabi oscillations of spin-solitons pinned by the local breaking of translational symmetry in isotropic Heisenberg chains (simple antiferromagnetic-N\'{e}el or spin-Peierls).We show that these correlated spin systems made of hundreds of coupled spin bear an overall spin S=1/2 and can be manipulated as a single spin. This is clearly contrary to all known spin-qubits which are paramagnetic centres, highly diluted to prevent decoherence. These results offer an alternative approach for spin-qubits paving the way for the implementation of a new type of quantum computer

Quenching Spin Decoherence in Diamond through Spin Bath Polarization

We experimentally demonstrate that the decoherence of a spin by a spin bath can be completely eliminated by fully polarizing the spin bath. We use electron paramagnetic resonance at 240 gigahertz and 8 Tesla to study the spin coherence time $T_2$ of nitrogen-vacancy centers and nitrogen impurities in diamond from room temperature down to 1.3 K. A sharp increase of $T_2$ is observed below the Zeeman energy (11.5 K). The data are well described by a suppression of the flip-flop induced spin bath fluctuations due to thermal spin polarization. $T_2$ saturates at $\sim 250 \mu s$ below 2 K, where the spin bath polarization is 99.4 %.Comment: 5 pages and 3 figure

High-frequency electron paramagnetic resonance investigation of the Fe3+ impurity center in polycrystalline PbTiO3 in its ferroelectric phase

The intrinsic iron(III) impurity center in polycrystalline lead titanate was investigated by means of high-frequency electron paramagnetic resonance (EPR) spectroscopy in order to determine the local-environment sensitive fine structure parameter D. At a spectrometer frequency of 190 GHz, spectral analysis of a powder sample was unambiguously possible. The observed mean value D = +35.28 GHz can be rationalized if Fe3+ ions substitute for Ti4+ at the B-site of the perovskite ABO3 lattice forming a directly coordinated iron - oxygen vacancy defect associate. A consistent fit of the multi-frequency data necessitated use of a distribution of D values with a variance of about 1 GHz. This statistical distribution of values is probably related to more distant defects and vacancies.Comment: 6 pages, 3 figures, 1 table, to appear in J. App. Phys, 96 (2004

Mapping Soil Erosion Sensitive Areas in Organic Matter Amended Soil Associations in the Ntabelanga area, Eastern Cape Province, South Africa

The study aims to map areas sensitive to erosion by water and rainfall erosivity after addition of organic matter (OM) in highly unstable soils. A soil association map was created using digital soil mapping methodology. Soil samples from six soil associations were incubated and analysed for several soil erodibility measures and inferred to the soil association map. Soil stabilization against soil erosion by use of OM was evaluated for 30 weeks under two simulated rainstorms, intermittent rainstorms (IR) and single rainstorm (SR). Rainfall erosivity (R-factor) was calculated from the duration of a rainstorm and the total amount of rainfall received under rainfall simulations. Erodibility factor (K-factor) was estimated using the soil OM content and texture. Largest area (40%) was covered by shallow soils and K-factor range of 0.0693-0.0778 t.ha.hha-1MJ-1mm-1. Largest (60.2%) area had a structural stability index of 0.8 and 42.7% of the area was covered by a dispersion ratio value range of 0.65-0.70. The area size with erosion rates of > 15 t/ha/yr was drastically reduced from 1 to 8 weeks after OM application thereafter gradually increased under both IR and SR. Soil erosion rates of < 5 t-1 ha-1 yr-1 and > 15 t-1 ha-1 yr-1 were most and least observed respectively under both storms. R-factor was higher under IR than SR and the smallest areas with soil erosion rates of > 15 t-1 ha-1 yr-1 contributed most to the lost soil. Organic matter confers soil resistance to erosion up to a certain period before losing its effectiveness. The study provided first assessment of erosion dynamics, basis for identifying conservation priorities which may be applicable in similar areas

Monitoring Electron Spin Fluctuations with Paramagnetic Relaxation Enhancement

The magnetic interactions between the spin of an unpaired electron and the surrounding nuclear spins can be exploited to gain structural information, to reduce nuclear relaxation times as well as to create nuclear hyperpolarization via dynamic nuclear polarization (DNP). A central aspect that determines how these interactions manifest from the point of view of NMR is the timescale of the fluctuations of the magnetic moment of the electron spins. These fluctuations, however, are elusive, particularly when electron relaxation times are short or interactions among electronic spins are strong. Here we map the fluctuations by analyzing the ratio between longitudinal and transverse nuclear relaxation times T1 and T2, a quantity which depends uniquely on the rate of the electron fluctuations and the Larmor frequency of the involved nuclei. This analysis enables rationalizing the evolution of NMR lineshapes, signal quenching as well as DNP enhancements as a function of the concentration of the paramagnetic species and the temperature, demonstrated here for LiMgMnPO4 and Fe(3+) doped Li4Ti5O12, respectively. For the latter, we observe a linear dependence of the DNP enhancement and the electron relaxation time within a temperature range between 100 and 300K

Africa’s First Alpine and Transboundary Long-Term Socioecological Research Platform

The austrotemperate alpine system of southern Africa's Maloti–Drakensberg is the only alpine system south of Mount Kilimanjaro, making it unique on the continent. With a difference in elevation of only 300–600 m and characterized by an undulating Gondwanan mature erosional land surface plateau around 2865–3500 masl, it is threatened by unsustainable land uses and climate change. To better understand these challenges, the Afromontane Research Unit of the University of the Free State, South Africa, is setting up the 1200 km2 Mont-Aux-Sources Long-Term Socio-Ecological Research (LTSER) platform. It is the first alpine-focused, long-term monitoring protocol implemented in the Maloti–Drakensberg. Straddling the border between South Africa and Lesotho, it is also the only alpine and transboundary LTSER area in Africa