Land degradation in the Limpopo Province, South Africa

Student Number : 9511039F - MSc Dissertation - School of Animal, Plant and Environmental Sciences - Faculty of ScienceAn estimated 91 % of South Africa’s total land area is considered dryland and susceptible to desertification. In response, South Africa has prepared a National Action Programme to combat land degradation, and this requires assessment and monitoring to be conducted in a systematic, cost effective, objective, timely and geographically-accurate way. Despite a perception-based assessment of land degradation conducted in 1999, and a land-cover mapping exercise conducted for 2000/2001, there are few national scientifically rigorous degradation monitoring activities being undertaken, due largely to a lack of objective, quantitative methods for use in large-scale assessments. This study therefore tests a satellitederived index of degradation for the Limpopo Province in South Africa, which is perceived to be one of the most degraded provinces in the country. The long-term average maximum normalized difference vegetation index (NDVI), calculated from a time series (1985-2004) of NOAA AVHRR satellite images, as a proxy for vegetation productivity, was related to water balance datasets of mean annual precipitation (MAP) and growth days index (GDI), using both linear and non-linear functions. Although the linear regressions were highly significant (p<0.005), a non-linear four parameter Gompertz curve was shown to fit the data more accurately. The curve explained only a little of the variance in the data in the relationship between NDVI and GDI, and so GDI was excluded from further analysis. All pixels that fell below a range of threshold standard deviations less than the fitted curve were deemed to represent degraded areas, where productivity was less than the predicted value. The results were compared qualitatively to existing spatial datasets. A large proportion of the degraded areas that were mapped using the approach outlined above occurred on areas of untransformed savanna and dryland cultivation. However the optical properties of dark igneous derived soils with high proportions of smectitic minerals and therefore low reflectance, were shown to lower NDVI values substantially. Overall, there was an acceptable agreement between the mapped degradation and the validation datasets. While further refinement of the methodology is necessary, including a rigorous field-based resource condition assessment for validation purposes, and research into the biophysical effects on the NDVI values, the methodology shows promise for regional assessment in South Africa

Vascular access survival and incidence of revisions: A comparison of prosthetic grafts, simple autogenous fistulas, and venous transposition fistulas from the United States Renal Data System Dialysis Morbidity and Mortality Study

AbstractObjective: The study's aim was to evaluate access patency and incidence of revisions in patients initiating hemodialysis and to determine differences in access performance by type of access among patient subgroups. Methods: The study used data from the United States Renal Data System Dialysis Morbidity and Mortality Study Wave 2, which contained a random sample of dialysis patients initiating dialysis in 1996 and early 1997. Failures and revisions were evaluated among 2247 newly placed hemodialysis accesses by using Cox proportional hazards regression model and Poisson regression. Primary and secondary patency rates were estimated using the Kaplan-Meier method. Results: Fifteen hundred seventy-four prosthetic grafts, 492 simple autogenous fistulas, and 181 venous transposition fistulas were available for evaluation. Prosthetic grafts had a 41% greater risk of primary failure compared with simple fistulas (relative risk, 1.41; 95% CI, 1.22-1.64; P <.001) and a 91% higher incidence of revision (relative risk, 1.91; 95% CI, 1.60-2.28; P <.001). At 2 years, autogenous fistulas demonstrated superior primary patency (39.8% versus 24.6%, P <.001) and equivalent secondary patency (64.3% versus 59.5%, P =.24) compared with prosthetic grafts. When compared with simple fistulas, vein transpositions demonstrated equivalent secondary patency at 2 years (61.5% versus 64.3%, P =.43) but inferior primary patency (27.7% versus 39.8%, P =.008) and had a 32% increased incidence of revision (P =.04). Autogenous fistulas had superior primary patency compared with prosthetic grafts in all patient subgroups except for patients with previously failed access. Vein transpositions showed the greatest benefit in terms of patency and incidence of revision in women and in patients with previously failed access. Conclusions: The preferential placement of autogenous fistulas may increase primary patency and decrease the incidence of revisions. Vein transpositions had similar secondary patency compared with simple fistulas, but required more revisions. The greatest benefit of a vein transposition fistula was seen in women and in patients with a history of access failure. (J Vasc Surg 2001;34:694-700.

A Population of X-ray Weak Quasars: PHL 1811 Analogs at High Redshift

We report the results from Chandra and XMM-Newton observations of a sample of 10 type 1 quasars selected to have unusual UV emission-line properties (weak and blueshifted high-ionization lines; strong UV Fe emission) similar to those of PHL 1811, a confirmed intrinsically X-ray weak quasar. These quasars were identified by the Sloan Digital Sky Survey at high redshift (z~2.2); eight are radio quiet while two are radio intermediate. All of the radio-quiet PHL 1811 analogs are notably X-ray weak by a mean factor of ~13. These sources lack broad absorption lines and have blue UV/optical continua, suggesting they are intrinsically X-ray weak. However, their average X-ray spectrum appears to be harder than those of typical quasars, which may indicate the presence of heavy intrinsic X-ray absorption. Our radio-quiet PHL 1811 analogs support a connection between an X-ray weak spectral energy distribution and PHL 1811-like UV emission lines; this connection provides an economical way to identify X-ray weak type 1 quasars. The fraction of radio-quiet PHL 1811 analogs in the radio-quiet quasar population is estimated to be < 1.2%. We have investigated correlations between relative X-ray brightness and UV emission-line properties for a sample combining radio-quiet PHL 1811 analogs, PHL 1811, and typical type 1 quasars. These correlation analyses suggest that PHL 1811 analogs may have extreme wind-dominated broad emission-line regions. Observationally, radio-quiet PHL 1811 analogs appear to be a subset (~30%) of radio-quiet weak-line quasars. The existence of a subset of quasars in which high-ionization "shielding gas" covers most of the BELR, but little more than the BELR, could potentially unify the PHL 1811 analogs and WLQs. The two radio-intermediate PHL 1811 analogs are X-ray bright. One of them appears to have jet-dominated X-ray emission, while the nature of the other remains unclear.Comment: ApJ accepted; 25 pages, 11 figures and 8 table

Assessment of Barriers to Providing Introductory Pharmacy Practice Experiences (IPPEs) in the Hospital Setting

Objectives: The primary objective of the study is to identify the barriers to providing Introductory Pharmacy Practice Experiences (IPPEs) in the hospital setting. Methods: Potential barriers to IPPEs were identified via literature review and interviews with current IPPE preceptors from various institutions. Based on this information, an electronic survey was developed and distributed to IPPE preceptors in order to assess student, preceptor, logistical and college or school of pharmacy related barriers that potentially exist for providing IPPE in the hospital setting. Results: Sixty-eight of the 287 eligible survey respondents (24%) completed the electronic survey. Seventy-six percent of respondents agreed or strongly agreed that available time was a barrier to precepting IPPE students even though a majority of respondents reported spending a third or more of their day with an IPPE student when on rotation. Seventy-three percent of respondents disagreed or strongly disagreed that all preceptors have consistent performance expectations for students, while just 46% agreed or strongly agreed that they had adequate training to precept IPPEs. Sixty-five percent of respondents agreed that IPPE students have the ability to be a participant in patient care and 70% of preceptors believe that IPPE students should be involved in patient care. Conclusions: Conducting IPPEs in the institutional setting comes with challenges. Based on the results of this study, experiential directors and colleges/schools of pharmacy could make a positive impact on the quality and consistency of IPPEs by setting student expectations and training preceptors on appropriate and consistent expectations for students. &nbsp; Type:&nbsp;Original Researc

Assessment of Barriers to Providing Introductory Pharmacy Practice Experiences (IPPEs) in the Hospital Setting

Objectives: The primary objective of the study is to identify the barriers to providing Introductory Pharmacy Practice Experiences (IPPEs) in the hospital setting. Methods: Potential barriers to IPPEs were identified via literature review and interviews with current IPPE preceptors from various institutions. Based on this information, an electronic survey was developed and distributed to IPPE preceptors in order to assess student, preceptor, logistical and college or school of pharmacy related barriers that potentially exist for providing IPPE in the hospital setting. Results: Sixty-eight of the 287 eligible survey respondents (24%) completed the electronic survey. Seventy-six percent of respondents agreed or strongly agreed that available time was a barrier to precepting IPPE students even though a majority of respondents reported spending a third or more of their day with an IPPE student when on rotation. Seventy-three percent of respondents disagreed or strongly disagreed that all preceptors have consistent performance expectations for students, while just 46% agreed or strongly agreed that they had adequate training to precept IPPEs. Sixty-five percent of respondents agreed that IPPE students have the ability to be a participant in patient care and 70% of preceptors believe that IPPE students should be involved in patient care. Conclusions: Conducting IPPEs in the institutional setting comes with challenges. Based on the results of this study, experiential directors and colleges/schools of pharmacy could make a positive impact on the quality and consistency of IPPEs by setting student expectations and training preceptors on appropriate and consistent expectations for students.   Type: Original Researc

Tuning of catalytic sites in Pt/TiO2 catalysts for chemoselective hydrogenation of 3-nitrostyrene

The catalytic activities of supported metal nanoparticles can be tuned by appropriate design of synthesis strategies. Each step in a catalyst synthesis method can play an important role in preparing the most efficient catalyst. Here we report the careful manipulation of the post-synthetic heat treatment procedure—together with control over the metal loading—to prepare a highly efficient 0.2 wt% Pt/TiO2 catalyst for the chemoselective hydrogenation of 3-nitrostyrene. For Pt/TiO2 catalysts with 0.2 and 0.5 wt% loading levels, reduction at 450 °C induces the coverage of TiOx over Pt nanoparticles through a strong metal–support interaction, which is detrimental to their catalytic activities. However, this can be avoided by following calcination treatment with reduction (both at 450 °C), allowing us to prepare an exceptionally active catalyst. Detailed characterization has revealed that the peripheral sites at the Pt/TiO2 interface are the most likely active sites for this hydrogenation reactio

Tuning of catalytic sites in Pt/TiO₂ catalysts for the chemoselective hydrogenation of 3-nitrostyrene

The catalytic activities of supported metal nanoparticles can be tuned by appropriate design of synthesis strategies. Each step in a catalyst synthesis method can play an important role in preparing the most efficient catalyst. Here we report the careful manipulation of the post-synthetic heat treatment procedure—together with control over the metal loading—to prepare a highly efficient 0.2 wt% Pt/TiO2 catalyst for the chemoselective hydrogenation of 3-nitrostyrene. For Pt/TiO2 catalysts with 0.2 and 0.5 wt% loading levels, reduction at 450 °C induces the coverage of TiOx over Pt nanoparticles through a strong metal–support interaction, which is detrimental to their catalytic activities. However, this can be avoided by following calcination treatment with reduction (both at 450 °C), allowing us to prepare an exceptionally active catalyst. Detailed characterization has revealed that the peripheral sites at the Pt/TiO2 interface are the most likely active sites for this hydrogenation reaction.</p