Ecosystem services of urban green spaces in African countries—perspectives and challenges

The concept of ecosystem goods and services is increasingly used to describe how biodiversity and ecosystems are linked to human well-being and that it should be placed at the core of sustainable urban development. Predictions of a tremendous future increase of urbanization in Africa necessitate an investigation into the research on ecosystem goods and services in the urban green infrastructure of Africa. Ecosystem goods and services (ES) are described as the benefits humans derive directly or indirectly from ecosystem functions and are classified as supporting, provisioning, regulating and cultural services. A literature study focusing on journal papers was conducted. Additionally a case study based on two masters studies was further refined. ES studies in African cities are biased towards South Africa and include assessments and economic valuations in which several different methods were used to determine direct consumptive and non-consumptive and indirect use values. Emphasis was placed on the multifunctional nature of ES. The main objectives of these studies were to sensitize policy makers, planners and the general public about the importance of biodiversity and ES. Ecosystem-based adaptation is discussed as the most appropriate approach in terms of applying knowledge about ES and their values in African cities as many residents still rely on ES from natural areas, but the major ecological, economic and political challenges are acknowledged. A case study focusing on domestic gardens (private green spaces) have indicated that the demand and supply of certain ES differ along a socio-economic gradient due to poor service delivery and smaller plots in the poorer areas mainly due to the legacy of separate development of the past. Where provisioning services are mainly outsourced in cities, it was found that plant species useful as food, medicine, etc. were more frequent in the gardens of poorer residents than in those of more affluent areas. The tendency to pay more for residential properties close to public open spaces, as in Europe, could not be statistically proven in the more affluent areas of a South African city, although the property values in proximity of public open spaces in some of the areas studied were lower than further away.     

Regularized Gaussian belief propagation

Belief propagation (BP) has been applied in a variety of inference problems as an approximation tool. BP does not necessarily converge in loopy graphs, and even if it does, is not guaranteed to provide exact inference. Even so, BP is useful in many applications due to its computational tractability. In this article, we investigate a regularized BP scheme by focusing on loopy Markov graphs (MGs) induced by a multivariate Gaussian distribution in canonical form. There is a rich literature surrounding BP on Gaussian MGs (labelled Gaussian belief propagation or GaBP), and this is known to experience the same problems as general BP on graphs. GaBP is known to provide the correct marginal means if it converges (this is not guaranteed), but it does not provide the exact marginal precisions. We show that our adjusted BP will always converge, with sufficient tuning, while maintaining the exact marginal means. As a further contribution we show, in an empirical study, that our GaBP variant can accelerate GaBP and compares well with other GaBP-type competitors in terms of convergence speed and accuracy of approximate marginal precisions. These improvements suggest that the principle of regularized BP should be investigated in other inference problems. The selection of the degree of regularization is addressed through the use of two heuristics. A by-product of GaBP is that it can be used to solve linear systems of equations; the same is true for our variant and we make an empirical comparison with the conjugate gradient method.     

Variable Selection for Support Vector Machines

Consider using values of variables X ₁, X ₂,…, X _p to classify entities into one of two classes. Kernel-based procedures such as support vector machines (SVMs) are well suited for this task. In general, the classification accuracy of SVMs can be substantially improved if instead of all p candidate variables, a smaller subset of (say m) variables is used. A new two-step approach to variable selection for SVMs is therefore proposed: best variable subsets of size k = 1,2,…, p are first identified, and then a new data-dependent criterion is used to determine a value for m. The new approach is evaluated in a Monte Carlo simulation study, and on a sample of data sets.     

Perioperative morbidity and mortality in 80 years and older undergoing elective urology surgery – A prospective study

Background and purpose. The number of octogenarians requiring surgery increases constantly. Data regarding perioperative morbidity and mortality in octogenarians is limited. Our aim was to assess surgery-related complications in octogenarians, undergoing urological surgery.

Patients and methods. We prospectively collected data from octogenarians and a control group of younger patients undergoing an elective urological surgery in our institution. Recorded data included: age, gender, American Society of Anesthesiologists (ASA) score, co-morbidities, number of medications, operation extent, anaesthesia type, surgery duration and perioperative morbidity and mortality.

Results. Forty-seven octogenarians and 80 patients with a median age of 59 years (range 19–75) enrolled prospectively. Gender ratio, surgeries extent and median operative time were similar among groups. General anaesthesia was more prevalent in the control group. ASA classification and duration of hospitalization were significantly higher in octogenarians. The rate of intra-operative complications was significantly higher in the octogenarians group 6.38% versus 3.75% (p = 0.007), there was no significant difference in immediate post-operative and post-discharge complications among groups. One octogenarian patient died 2 days post-surgery, no death occurred in the control group.

Conclusions. Octogenarians have higher rate of intra-operative morbidity, leading to longer hospital stay. More experienced surgeons and anaesthetists should be involved in the operation; and careful surgical technique, tapered anaesthesia and higher level of post-operative monitoring should be applied for patients in this age.     

Shock wave lithotripsy for ureteral stones in elderly male patients

Introduction.?Age has never been considered as a factor in the treatment of ureteral stones, but elderly male patients may suffer from concomitant illnesses that may affect SWL results, such as voiding difficulties and musculo-skeletal and cardio-vascular disorders. The aim of this study was to assess the success rate and complications of shock wave lithotripsy (SWL) for all size and location ureteral stones in patients older than 70 years of age.

Patients and Methods.?We retrospectively reviewed the charts and radiology films of all patients who had undergone SWL for ureteral stones with the HM3 lithotriptor and compared the results of patients younger than 70 years to those older than 70 years.

Results.?During 2000–2003, 238 consecutive male patients (23 older than 70 years) underwent SWL under regional anesthesia for all size and locations ureteral stones. Stone sizes, locations, opacity, and pre-operative drainage procedures matched in both groups. The overall stone-free rate was 91% for both groups. Complications were recorded in 1% of the older patients and 3.7% of the younger ones. No treatment-related mortality was recorded.

Conclusions.?Age itself has no effect on the success rate of SWL with the HM3 lithotripter for ureteral stones. In general, SWL treatment showed a high success rate with minimal morbidity and no treatment-related mortality.