447 research outputs found
Discussion - An empirical model of fatalities and injuries due to floods in Japan by Guofang Zhai, Teruki Fukuzono, and Saburo Ikeda
No full text[No abstract available]ASAAF H, 2002, P CAN DAM ASS CDA 20; ASSAF H, 2001, WORLD WAT ENV RES C; BROWN CA, 1988, WATER RESOUR BULL, V24, P1303; DEKAY ML, 1993, RISK ANAL, V13, P193, DOI 10.1111-j.1539-6924.1993.tb01069.x; JONKMAN SN, 2002, FLOOD DEFENCE 2002, P196; MILLER DM, 1984, AM STAT, V38, P124, DOI 10.2307-268324712
Chronaxie Measurements in Patterned Neuronal Cultures from Rat Hippocampus.
No full textExcitation of neurons by an externally induced electric field is a long standing question that has recently attracted attention due to its relevance in novel clinical intervention systems for the brain. Here we use patterned quasi one-dimensional neuronal cultures from rat hippocampus, exploiting the alignment of axons along the linear patterned culture to separate the contribution of dendrites to the excitation of the neuron from that of axons. Network disconnection by channel blockers, along with rotation of the electric field direction, allows the derivation of strength-duration (SD) curves that characterize the statistical ensemble of a population of cells. SD curves with the electric field aligned either parallel or perpendicular to the axons yield the chronaxie and rheobase of axons and dendrites respectively, and these differ considerably. Dendritic chronaxie is measured to be about 1 ms, while that of axons is on the order of 0.1 ms. Axons are thus more excitable at short time scales, but at longer time scales dendrites are more easily excited. We complement these studies with experiments on fully connected cultures. An explanation for the chronaxie of dendrites is found in the numerical simulations of passive, realistically structured dendritic trees under external stimulation. The much shorter chronaxie of axons is not captured in the passive model and may be related to active processes. The lower rheobase of dendrites at longer durations can improve brain stimulation protocols, since in the brain dendrites are less specifically oriented than axonal bundles, and the requirement for precise directional stimulation may be circumvented by using longer duration fields
Crisis and catastrophe: the motor of South African history?
No full textMP4 Video; Size: 3.34GB; Duration: 1:05Please cite as: Academy of Science of South Africa (ASSAf), (2021). Crisis and Catastrophe: The Motor of South African History?. [Online] Available at: http://hdl.handle.net/20.500.11911/201Annual Humanities Lecture Webinar hosted by the Academy of Science of South Africa (ASSAf) on 5 October 2021. Presented by Assistant Prof Jacob Dlamini, Princeton University, United States of America.
In 1977, R.W. Johnson published How Long will South Africa Survive?, a book that sought to examine the resilience of what the author called South Africa’s ‘White Establishment.’ Johnson challenged the tendency among left-wing thinkers and Afrikaner nationalists to see change in South Africa as being driven solely by the internal dynamics of the country’s history. As Johnson elaborated in a 2015 sequel to How Long will South Africa Survive?the ‘iron law’ of South African history was that international developments have always been more responsible for change in the country; that crises generated by South Africa’s position in the global economy have always been the key driver of political transformation in the country. In my presentation, the presenter built on Johnson’s claim that crisis (and catastrophe) is the motor of South African history. He used his claim to position South Africa as a vantage point from which to imagine a national history not burdened by race, and to tell a South African story that is at the same time a global history of the 20th-century. What happens to conventional accounts of South African history (not to mention global history) when we treat the country as the standpoint from which to examine some of the major crises and catastrophes of the 20th century? That is the question at the centre of this presentation.Academy of Science of South Africa (ASSAf
A hydro-economic model for managing groundwater resources in semi-arid regions
No full textAccess to fresh water resources is a limiting factor in the socio-economical development of countries located in semi-arid regions. Water scarcity in these regions, particularly the North Africa and Middle East (MENA) region, is expected to intensify not only due to projected decline in effective precipitation due to climate change and variability, but also due to excessive growth in demand driven by explosive growth in population and improvement in living standards. The meager surface water resources in these regions have already been exploited and significantly polluted leading many governments to deplete their fossil and poorly recharged aquifers mostly to support inefficient and unsustainable agricultural policies and heavy subsidy of municipal water demand. The paper presents an interactive decision support model developed based on economic principles and simple aquifer representation using the STELLA system dynamics development environment. The model is designed to help water policy makers and managers and other stakeholders formulate and assess alternative water allocation policies among the municipal, industrial and agriculture sectors. Model users will be able to set and interactively manipulate key parameters that influence economic values and sustainability of alternative water policies. These parameters are associated with energy prices, discount rates, planning horizon, demographic factors, willingness-to-pay, hydro-meteorological conditions, aquifer characteristics, and industrial water productivities cropping patterns and agricultural water productivities. Long-term projections of economic value, withdrawals, and remaining water stocks in addition to water demand are presented in tabular and graphical forms. The paper presents a case application of the model for managing the Amman-Zarqa aquifer in Jordan. The aquifer is considered a crucial water resource in water poor Jordan. © 2009 WIT Press.ABDULLA F, 2008, WATER RESOURCES MANA; Assaf H, 2008, ENVIRON MODELL SOFTW, V23, P1327, DOI 10.1016-j.envsoft.2008.03.006; Chebaane M, 2004, HYDROGEOL J, V12, P14, DOI 10.1007-s10040-003-0313-1; GISSER M, 1983, J POLIT ECON, V91, P1001, DOI 10.1086-261197; Griffin R.C., 2006, WATER RESOURCE EC; *ISEE SYST, STELLA SYST THINK ED; Schiffler M., 1998, EC GROUNDWATER MANAG; Winz I, 2007, P 25 INT C SYST DYN1
Solving the Orientation Specific Constraints in Transcranial Magnetic Stimulation by Rotating Fields
No full textTranscranial Magnetic Stimulation (TMS) is a promising technology for both neurology and psychiatry. Positive treatment outcome has been reported, for instance in double blind, multi-center studies on depression. Nonetheless, the application of TMS towards studying and treating brain disorders is still limited by inter-subject variability and lack of model systems accessible to TMS. The latter are required to obtain a deeper understanding of the biophysical foundations of TMS so that the stimulus protocol can be optimized for maximal brain response, while inter-subject variability hinders precise and reliable delivery of stimuli across subjects. Recent studies showed that both of these limitations are in part due to the angular sensitivity of TMS. Thus, a technique that would eradicate the need for precise angular orientation of the coil would improve both the inter-subject reliability of TMS and its effectiveness in model systems. We show here how rotation of the stimulating field relieves the angular sensitivity of TMS and provides improvements in both issues. Field rotation is attained by superposing the fields of two coils positioned orthogonal to each other and operated with a relative phase shift in time. Rotating field TMS (rfTMS) efficiently stimulates both cultured hippocampal networks and rat motor cortex, two neuronal systems that are notoriously difficult to excite magnetically. This opens the possibility of pharmacological and invasive TMS experiments in these model systems. Application of rfTMS to human subjects overcomes the orientation dependence of standard TMS. Thus, rfTMS yields optimal targeting of brain regions where correct orientation cannot be determined (e.g., via motor feedback) and will enable stimulation in brain regions where a preferred axonal orientation does not exist.Version of Recor
‘Twelve Years Later: Second ASSAf report on Research Publishing in and from South Africa (2018)’: Some issues arising
No full textAbstract:Responding to the extraordinary challenges facing publication in the digital age is the holistic view taken by the Academy of Science of South Africa (ASSAf) on threats and opportunities that characterise this conjuncture. Twelve Years Later, researched by Wieland Gevers, Robin Crewe and Susan Veldsman on national publishing strategies, provides the ‘nuts ’n bolts’ that every researcher should know in order to navigate the changing environment.1 The Report examines both past and present. The first chapter reviews ASSAf’s 2006 report.2 Chapter 2 revisits the 2009 report on books. Chapter 3 details ASSAf’s Scholarly Publishing Programme between 2007 and 2018. How to enhance access of South African authors to global commercial publishers is discussed in Chapter 4. Chapter 5 deals with journal and book publishing, and Chapter 6 examines pitfalls and threats to good publishing practices. Outstanding problems are highlighted in Chapter 7. Chapter 8 offers recommendations. Appendices (45 pp) tabulate the hard data on which the study draws. These data showcase close correlations between the ASSAf qualitative evaluations and Department of Higher Education and Training (DHET) decisions. Significantly, ASSAf ratings and reviews of publishers closely align with the international Socio-economic and Natural Sciences of the Environment (SENSE) and the Norwegian Register for Scientific Journals, Series and Publishers ratings. The 2018 Report offers a detailed history useful for individual university policy planning, and implementation of monitoring mechanisms, and explains accreditation decisions. A basic cost–benefit analysis of the publication incentive system administered by DHET identifies residual problems. Notwithstanding these (see below), the statistics tabulated in Appendices by the Centre for Research, Evaluation, Science and Technology (CREST) at Stellenbosch University reveals that DHET has been very effective in encouraging publication. It has also acted as an inhibiting factor in author choice of predatory journals, although many thousands of articles still slipped through...
Geostatistical assessment of groundwater nitrate contamination with reflection on DRASTIC vulnerability assessment: The case of the upper litani basin, Lebanon
No full textGroundwater constitutes the largest single source of fresh water in many parts of the world and provides a risk buffer to sustain critical water demands during cyclic and prolonged dry periods, especially in semi-arid and arid regions. However, unprecedented socio-economical growths are threatening the viability of these precious resources through fast depletion of already critically low stocks accompanied by persistent degradation of water quality due to salinization, and contamination by pesticides and fertilizers, urban sewage and industrial waste. These circumstances are particularly true of the Upper Litani Basin (ULB), which houses over 500,000 of Lebanon's 4 million population and provides the bulk of the country's agricultural output. Uncontrolled urban, agricultural and industrial growths following a prolonged civil strife and foreign occupation have resulted in the deterioration of the quality of the basin's surface water and potentially its groundwater resources. An assessment study of groundwater quality conditions in the ULB was conducted in support of efforts to manage water quality in the basin. Geostatistical analysis of groundwater nitrate levels was conducted using data collected through an extensive basin-wide water quality survey sponsored by the USAID and covered two periods representing the summer and winter periods. The results of analysis include maps of nitrate contamination and probability of exceedance of drinking-water nitrate regulatory limit. The results indicate a significant, widespread and persistent nitrates contamination of groundwater in the ULB. Nitrate levels in groundwater exceed standard limits for drinking water in many parts of the basin. These findings were examined with respect to those of a DRASTIC groundwater vulnerability assessment conducted by the USAID BAMAS project. Comparative analysis of the two assessments shed the light on several issues related to the application and interpretation of DRASTIC scores and the groundwater nitrate contamination process. © Springer Science+Business Media B.V. 2008.ASSAF H, 2006, P IEMSS 3 BIENN M SU; *BAMAS, 2005, FIN REP; *BAMAS, 2005, TECHN SURV REP SUMM; *BAMAS, 2005, RAP REV REP; *BAMAS, 2005, GROUNDW FLOW MOD VUL; Basistha A, 2008, WATER RESOUR MANAG, V22, P1325, DOI 10.1007-s11269-007-9228-2; BELLER H, 2005, CALIFORNIA GAMA PROG; Canter LW, 1997, NITRATES GROUNDWATER; COOPER RM, 1988, J ENVIRON ENG-ASCE, V114, P270; Edmunds WM, 1997, J ENVIRON QUAL, V26, P1231; *FAO, 1997, REP DER LAND US MAP; Fritch TG, 2000, ENVIRON MANAGE, V25, P337, DOI 10.1007-s002679910026; Hamza MH, 2006, J ENVIRON MANAGE, V84, P12; Hossain F, 2007, WATER RESOUR MANAG, V21, P1245, DOI 10.1007-s11269-006-9079-2; Hussain I, 2001, 26 IWMI; Journel A. G., 1978, MINING GEOSTATISTICS; Kass A, 2005, J HYDROL, V300, P314, DOI 10.1016-j.jhydrol.2004.06.013; Li FM, 2001, AGR WATER MANAGE, V49, P173, DOI 10.1016-S0378-3774(01)00087-7; Mardikis MG, 2005, WATER RESOUR MANAG, V19, P251, DOI 10.1007-s11269-005-3179-2; ROSSI RE, 1992, ECOL MONOGR, V62, P277, DOI 10.2307-2937096; Tang C, 2004, HYDROL PROCESS, V18, P2303, DOI 10.1002-hyp.5531; VANGRINSVEN HJM, 2006, ENV HLTH, V5, P1; Vazquez JCG, 2005, WATER RESOUR MANAG, V19, P1, DOI 10.1007-s11269-005-0129-y; Ward MH, 2005, ENVIRON HEALTH PERSP, V113, P1607, DOI 10.1289-ehp.8043; Zizhen L., 1998, ECOL MODEL, V107, P279, DOI 10.1016-S0304-3800(98)00004-021191
The Philistines and Aegean Migration at the End of the Late Bronze Age
No full textIn this study, Assaf Yasur-Landau examines the early history of the biblical Philistines who were among the 'Sea Peoples' who migrated from the Aegean area to the Levant during the early twelfth century BC. Creating an archaeological narrative of the migration of the Philistines, he combines an innovative theoretical framework on the archaeology of migration with new data from excavations in Greece, Turkey, Cyprus, Syria, Lebanon, and Israel and thereby reconstructs the social history of the Aegean migration to the southern Levant. The author follows the story of the migrants from the conditions that caused the Philistines to leave their Aegean homes, to their movement eastward along the sea and land routes, to their formation of a migrant society in Philistia and their interaction with local populations in the Levant. Based on the most up-to-date evidence, this book offers a new and fresh understanding of the arrival of the Philistines in the Levant.</jats:p
Framework for Modeling Mass Disasters
No full textThis paper introduces a generic mass Disaster Modeling Framework (DMF) to support integrated sociophysical risk assessment and management of disasters. The DMF draws on the principles that disasters have many common features regardless of their instigating hazards and are the outcome of interaction between a hazard and society. The modular architecture of the DMF weakly couples three key applications: the Community Simulation Model (CSM), the Hazard Simulation Model (HSM), and the Evacuation Simulation Model (ESM). The CSM utilizes census, cadastral, and other data to construct an individual-based representation of the potentially impacted community. The CSM estimates people and built environment at risk at any given time of the day, week, and year. The CSM assessment along with the hazard simulation of the HSM feed into the ESM to simulate the progression of fatalities throughout the event. Dam failures, for which vivid and detailed accounts of human interaction with the incoming flood exist, served as case studies
DISentangled Counterfactual Visual interpretER (DISCOVER) generalizes to natural images
No full textWe recently presented DISentangled COunterfactual Visual interpretER (DISCOVER), a method toward systematic visual interpretability of image-based classification models and demonstrated its applicability to two biomedical domains. Here we demonstrate that DISCOVER can be applied to the domain of natural images. First, DISCOVER visually interpreted the nose size, the muzzle area, and the face size as semantic discriminative visual traits discriminating between facial images of dogs versus cats. Second, DISCOVER visually interpreted the cheeks and jawline, eyebrows and hair, and the eyes, as discriminative facial characteristics. These successful visual interpretations across two natural images domains indicate that DISCOVER is a generalized interpretability method
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