The legislative framework regarding bullying in South African schools

Bullying in schools is a global phenomenon that has the potential to impact on children not only physically but also psychologically. In South Africa countless children fall victim to bullying, harassment and abuse at schools. A myriad of constitutional rights are infringed upon when bullying occurs, and the problem is escalating. The Protection from Harassment Act 71 of 2011 was signed and accepted into law on the 27th of April 2013. This new Act may grant relief to victims of bullying inter alia by providing for  protection orders, and therefore adds to the legislative framework available to victims. However, in terms of bullying in schools, the parties to these incidents are minors and therefore a critical analysis is necessary with regard to the rights of the victim and the offender. In this context the relationship and interaction between the Protection from Harassment Act 71 of 2011, the Child Justice Act 75 of 2008, the Children's Act 38 of 2005 and the South African Schools Act 84 of 1996 call for critical analysis

Design and applications of a secure and decentralized DHT

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2011.Cataloged from PDF version of thesis.Includes bibliographical references (p. 105-114).Distributed Hash Tables (DHTs) are a powerful building block for highly scalable decentralized systems. They route requests over a structured overlay network to the node responsible for a given key. DHTs are subject to the well-known Sybil attack, in which an adversary creates many false identities in order to increase its influence and deny service to honest participants. Defending against this attack is challenging because (1) in an open network, creating many fake identities is cheap; (2) an attacker can subvert periodic routing table maintenance to increase its influence over time; and (3) specific keys can be targeted by clustering attacks. As a result, without centralized admission control, previously existing DHTs could not provide strong availability guarantees. This dissertation describes Whanau, a novel DHT routing protocol which is both efficient and strongly resistant to the Sybil attack. Whanau solves this long-standing problem by using the social connections between users to build routing tables that enable Sybilresistant one-hop lookups. The number of Sybils in the social network does not affect the protocol's performance, but links between honest users and Sybils do. With a social network of n well-connected honest nodes, Whanau provably tolerates up to O(n/ log n) such "attack edges". This means that an attacker must convince a large fraction of the honest users to make a social connection with the adversary's Sybils before any lookups will fail. Whanau uses techniques from structured DHTs to build routing tables that contain O(Vf log n) entries per node. It introduces the idea of layered identifiers to counter clustering attacks, which have proven particularly challenging for previous DHTs to handle. Using the constructed tables, lookups provably take constant time. Simulation results, using large-scale social network graphs from LiveJournal, Flickr, YouTube, and DBLP, confirm the analytic prediction that Whanau provides high availability in the face of powerful Sybil attacks. Experimental results using PlanetLab demonstrate that an implementation of the Whanau protocol can handle reasonable levels of churn.by Christopher T. Lesniewski-Laas.Ph.D

Rotational and high-resolution infrared spectrum of HC3_3N: global ro-vibrational analysis and improved line catalogue for astrophysical observations

HC$_3$N is an ubiquitous molecule in interstellar environments, from external galaxies, to Galactic interstellar clouds, star forming regions, and planetary atmospheres. Observations of its rotational and vibrational transitions provide important information on the physical and chemical structure of the above environments. We present the most complete global analysis of the spectroscopic data of HC$_3$N. We have recorded the high-resolution infrared spectrum from 450 to 1350 cm$^{-1}$, a region dominated by the intense $\nu_5$ and $\nu_6$ fundamental bands, located at 660 and 500 cm$^{-1}$, respectively, and their associated hot bands. Pure rotational transitions in the ground and vibrationally excited states have been recorded in the millimetre and sub-millimetre regions in order to extend the frequency range so far considered in previous investigations. All the transitions from the literature and from this work involving energy levels lower than 1000 cm$^{-1}$ have been fitted together to an effective Hamiltonian. Because of the presence of various anharmonic resonances, the Hamiltonian includes a number of interaction constants, in addition to the conventional rotational and vibrational l-type resonance terms. The data set contains about 3400 ro-vibrational lines of 13 bands and some 1500 pure rotational lines belonging to 12 vibrational states. More than 120 spectroscopic constants have been determined directly from the fit, without any assumption deduced from theoretical calculations or comparisons with similar molecules. An extensive list of highly accurate rest frequencies has been produced to assist astronomical searches and data interpretation. These improved data, have enabled a refined analysis of the ALMA observations towards Sgr B2(N2).Comment: 35 pages, 14 figures, accepted for pubblication in ApJ Supplemen

A new approach to electromagnetic wave tails on a curved spacetime

We present an alternative method for constructing the exact and approximate solutions of electromagnetic wave equations whose source terms are arbitrary order multipoles on a curved spacetime. The developed method is based on the higher-order Green's functions for wave equations which are defined as distributions that satisfy wave equations with the corresponding order covariant derivatives of the Dirac delta function as the source terms. The constructed solution is applied to the study of various geometric effects on the generation and propagation of electromagnetic wave tails to first order in the Riemann tensor. Generally the received radiation tail occurs after a time delay which represents geometrical backscattering by the central gravitational source. It is shown that the truly nonlocal wave-propagation correction (the tail term) takes a universal form which is independent of multipole order. In a particular case, if the radiation pulse is generated by the source during a finite time interval, the tail term after the primary pulse is entirely determined by the energy-momentum vector of the gravitational field source: the form of the tail term is independent of the multipole structure of the gravitational source. We apply the results to a compact binary system and conclude that under certain conditions the tail energy can be a noticeable fraction of the primary pulse energy. We argue that the wave tails should be carefully considered in energy calculations of such systems.Comment: RevTex, 28 pages, 5 eps figures, http://www.tpu.ee/~tony/texdocs/, 4 changes made (pp. 2, 4, 22, 24), 2 references adde

Estimation of tungsten and ODS tungsten damages after dense plasma exposure in PF-12 and PF-1000

The paper presents experimental investigations of damages in pure tungsten and ODS (oxide dispersed strengthened) tungsten under dense plasma shots. The experiments were performed with plasma focus devices PF-12 and PF-1000 with a power flux density of 10⁶…10¹² W/cm² using deuterium. The surface morphology of the targets exposed to plasma streams is analyzed using electron and optical microscopy. Due to the plasma effect, different surface structures, such as wave-like structures, a melted layer, a mesh of microcracks, droplets, craters, crevices and holes appear. Both the original and irradiated samples were investigated by local X-ray spectroscopic analysis and by X-ray phase-shift analysis.Представлены результаты исследований повреждений в чистом вольфраме и вольфраме, легированном дисперсными, оксидами под воздействием плотной плазмы. Эксперименты были проведены на установках плазменный фокус ПФ-12 и ПФ-1000 в дейтериевой плазме с плотностью мощности 10⁶…10¹² W/cm². Морфология поверхностей мишеней, облученных плазменными потоками, была исследована с помощью сканирующего электронного микроскопа и оптического микроскопа. На поверхности материала были обнаружены различные дефекты, такие как расплавленный слой, волнообразные структуры, сеть микротрещин, брызги, кратеры, наплывы и поры. Оба материала до и после облучения также исследовались с помощью рентгеноспектрального и рентгеновского фазового анализов.Представлені результати досліджень пошкоджень у чистому вольфрамі та вольфрамі, легованому дисперсними, оксидами під впливом густої плазми. Експерименти були проведені на установках плазмовий фокус ПФ-12 та ПФ-1000 на дейтерієвій плазмі з густиною потужності 10⁶…10¹² W/cm². Морфологія поверхонь мішеней, опромінених плазмовими потоками, була досліджена за допомогою скануючого електронного мікроскопа та оптичного мікроскопа. На поверхні матеріалу були виявлені різні дефекти, такі як розплавлений шар, хвилеподібні структури, сітка мікротріщин, бризки, кратери, напливи і пори. Обидва матеріали до і після опромінення також досліджувалися за допомогою рентгеноспектрального й рентгенівського фазового аналізів

Toward an optimal search strategy of optical and gravitational wave emissions from binary neutron star coalescence

Observations of an optical source coincident with gravitational wave emission detected from a binary neutron star coalescence will improve the confidence of detection, provide host galaxy localisation, and test models for the progenitors of short gamma ray bursts. We employ optical observations of three short gamma ray bursts, 050724, 050709, 051221, to estimate the detection rate of a coordinated optical and gravitational wave search of neutron star mergers. Model R-band optical afterglow light curves of these bursts that include a jet-break are extrapolated for these sources at the sensitivity horizon of an Advanced LIGO/Virgo network. Using optical sensitivity limits of three telescopes, namely TAROT (m=18), Zadko (m=21) and an (8-10) meter class telescope (m=26), we approximate detection rates and cadence times for imaging. We find a median coincident detection rate of 4 yr^{-1} for the three bursts. GRB 050724 like bursts, with wide opening jet angles, offer the most optimistic rate of 13 coincident detections yr^{-1}, and would be detectable by Zadko up to five days after the trigger. Late time imaging to m=26 could detect off-axis afterglows for GRB 051221 like bursts several months after the trigger. For a broad distribution of beaming angles, the optimal strategy for identifying the optical emissions triggered by gravitational wave detectors is rapid response searches with robotic telescopes followed by deeper imaging at later times if an afterglow is not detected within several days of the trigger.Comment: 6 pages, 1 figure, Accepted for publication in MNRAS Letters (2011 April 22

Laboratory and tentative interstellar detection of trans-methyl formate using the publicly available Green Bank Telescope PRIMOS survey

The rotational spectrum of the higher-energy trans conformational isomer of methyl formate has been assigned for the first time using several pulsed-jet Fourier transform microwave spectrometers in the 6-60 GHz frequency range. This species has also been sought toward the Sagittarius B2(N) molecular cloud using the publicly available PRIMOS survey from the Green Bank Telescope. We detect seven absorption features in the survey that coincide with laboratory transitions of trans-methyl formate, from which we derive a column density of 3.1 (+2.6, -1.2) \times 10^13 cm-2 and a rotational temperature of 7.6 \pm 1.5 K. This excitation temperature is significantly lower than that of the more stable cis conformer in the same source but is consistent with that of other complex molecular species recently detected in Sgr B2(N). The difference in the rotational temperatures of the two conformers suggests that they have different spatial distributions in this source. As the abundance of trans-methyl formate is far higher than would be expected if the cis and trans conformers are in thermodynamic equilibrium, processes that could preferentially form trans-methyl formate in this region are discussed. We also discuss measurements that could be performed to make this detection more certain. This manuscript demonstrates how publicly available broadband radio astronomical surveys of chemically rich molecular clouds can be used in conjunction with laboratory rotational spectroscopy to search for new molecules in the interstellar medium.Comment: 40 pages, 7 figures, 4 tables; accepted for publication in Ap

Efficient production of S8 in interstellar ices: the effects of cosmic-ray-driven radiation chemistry and nondiffusive bulk reactions

Theoretical Chemistr

Cost–utility of different treatment strategies after the failure of tumour necrosis factor inhibitor in rheumatoid arthritis in the Finnish setting

Objective. To evaluate the cost–utility of different treatment strategies in severe RA after TNF-inhibitor failure

Atmospheric stilling leads to prolonged thermal stratification in a large shallow polymictic lake

To quantify the effects of recent and potential future decreases in surface wind speeds on lake thermal stratification, we apply the one-dimensional process-based model MyLake to a large, shallow, polymictic lake, Võrtsjärv. The model is validated for a 3-year period and run separately for 28 years using long-term daily atmospheric forcing data from a nearby meteorological station. Model simulations show exceptionally good agreement with observed surface and bottom water temperatures during the 3-year period. Similarly, simulated surface water temperatures for 28 years show remarkably good agreement with long-term in situ water temperatures. Sensitivity analysis demonstrates that decreasing wind speeds has resulted in substantial changes in stratification dynamics since 1982, while increasing air temperatures during the same period had a negligible effect. Atmospheric stilling is a phenomenon observed globally, and in addition to recent increases in surface air temperature, needs to be considered when evaluating the influence of climate change on lake ecosystems