Spectrum of Sizes for Perfect Deletion-Correcting Codes

One peculiarity with deletion-correcting codes is that perfect $t$-deletion-correcting codes of the same length over the same alphabet can have different numbers of codewords, because the balls of radius $t$ with respect to the Levenshte\u{\i}n distance may be of different sizes. There is interest, therefore, in determining all possible sizes of a perfect $t$-deletion-correcting code, given the length $n$ and the alphabet size~$q$. In this paper, we determine completely the spectrum of possible sizes for perfect $q$-ary 1-deletion-correcting codes of length three for all $q$, and perfect $q$-ary 2-deletion-correcting codes of length four for almost all $q$, leaving only a small finite number of cases in doubt.Comment: 23 page

Acne Vulgaris: The Influence of Marriage, Pregnancy and Childbirth

SUMMARY. 1). It is difficult, time consuming, and in many cases impossible to get the co-operation of a large group of patients in a large industrial town, where movement of population is bound to be great, particularly in the 15-25 age group. Many of the questionnaires, though very simply worded were inadequately filled in. 827 addresses were collected, over 1100 letters were sent out and almost 100 homes visited personally, yet only 415 forms were finally collected. 2). The treatment given by a skin department, where only relatively stubborn and rather severely affected cases are treated would seem to shorten the duration of acne vulgaris, an important consideration in reassuring young women of marriageable age. See Table I. 3). Disfiguring scarring would appear to lessen a girl's chance of marriage. See Table II. 4). Marriage has an undeniable influence on the course of acne vulgaris. 43.4% in the series improved, 53%, however, noted no change in their skin condition, only 3.6% deteriorated following matrimony. The widely held belief of a universally beneficial influence of marriage on this complaint, while certainly true in a considerable percentage of women, has not been confirmed by this survey. See Table III. 5), Pregnancy, on the other hand, has a markedly beneficial influence on acne vulgaris according to this survey. See Table IV, This isthought to be due to an increase in secretion of oestrogens, progesterone and gonadotrophins during gestation, all of which have a beneficial effect on acne by suppressing the activity of the pilosebacecus apparatus. Androgen, the hormone which stimulates sebaceous gland activity is at a lower level than normal during gestation. The psychological, possibly hypothalamic influence of pregnancy leading to a happier, better balanced out-look would all appear to bring about an amelioration and often a permanent remission of acne vulgaris. 6). The largest percentage of patients improved after the birth of their baby. See table VI. Lactation appeared not to have further influenced the course of events. See Table VII. An analogy can be drawn between dysmenorrhoea and acne vulgaris, both conditions of varied aetiology, commonest in adolescents and both in many instances finally cured by child-birth. It is postulated that this final cure of acne vulgaris is due to a finally established ideal hormonal balance, only achieved by the hormonal stimuli of pregnancy and parturition. Other aetiological factors would appear to be only of secondary importance. A suggestion is made to qualify Plenck's dictum "Matrimonium varos curat" to "Non matrimonium sed infantes varos in feminas curant". 7). From experience in this and other skin departments the results of hormonal therapy are often disappointing and unpredictable and may give rise to unpleasant, though rarely dangerous side-effects. More, and if at all possible, controlled trials are necessary in this field, to find a more satisfactory and safer approach to the internal and external treatment of acne vulgaris with hormonal substances. 8). It is stressed that acne vulgaris must not be taken lightly, the presence of a disfiguring and usually all too obvious skin condition in a susceptible adolescent not only leads to psychological upset and trauma, but also may interfere with a young person's work and career, as well as jeopardizing a girl's chances in marriage

Error-correction on non-standard communication channels

Many communication systems are poorly modelled by the standard channels assumed in the information theory literature, such as the binary symmetric channel or the additive white Gaussian noise channel. Real systems suffer from additional problems including time-varying noise, cross-talk, synchronization errors and latency constraints. In this thesis, low-density parity-check codes and codes related to them are applied to non-standard channels. First, we look at time-varying noise modelled by a Markov channel. A low-density parity-check code decoder is modified to give an improvement of over 1dB. Secondly, novel codes based on low-density parity-check codes are introduced which produce transmissions with Pr(bit = 1) ≠ Pr(bit = 0). These non-linear codes are shown to be good candidates for multi-user channels with crosstalk, such as optical channels. Thirdly, a channel with synchronization errors is modelled by random uncorrelated insertion or deletion events at unknown positions. Marker codes formed from low-density parity-check codewords with regular markers inserted within them are studied. It is shown that a marker code with iterative decoding has performance close to the bounds on the channel capacity, significantly outperforming other known codes. Finally, coding for a system with latency constraints is studied. For example, if a telemetry system involves a slow channel some error correction is often needed quickly whilst the code should be able to correct remaining errors later. A new code is formed from the intersection of a convolutional code with a high rate low-density parity-check code. The convolutional code has good early decoding performance and the high rate low-density parity-check code efficiently cleans up remaining errors after receiving the entire block. Simulations of the block code show a gain of 1.5dB over a standard NASA code

On Secure Workflow Decentralisation on the Internet

Decentralised workflow management systems are a new research area, where most work to-date has focused on the system's overall architecture. As little attention has been given to the security aspects in such systems, we follow a security driven approach, and consider, from the perspective of available security building blocks, how security can be implemented and what new opportunities are presented when empowering the decentralised environment with modern distributed security protocols. Our research is motivated by a more general question of how to combine the positive enablers that email exchange enjoys, with the general benefits of workflow systems, and more specifically with the benefits that can be introduced in a decentralised environment. This aims to equip email users with a set of tools to manage the semantics of a message exchange, contents, participants and their roles in the exchange in an environment that provides inherent assurances of security and privacy. This work is based on a survey of contemporary distributed security protocols, and considers how these protocols could be used in implementing a distributed workflow management system with decentralised control . We review a set of these protocols, focusing on the required message sequences in reviewing the protocols, and discuss how these security protocols provide the foundations for implementing core control-flow, data, and resource patterns in a distributed workflow environment

The Impact of the Hunga Tonga Volcanic Eruption on Earth\u27s Temperature

In January 2020, we published a paper [1] showing that the Intergovernmental Panel on Climate Change (IPCC) claimed that Earth’s temperature would reach 1.5 °C above pre-industrial days by 2030. At the same time, those who study the Sun, such as Valentina Zharkov, indicated that by 2030, the Earth\u27s temperature would be much lower and close to pre-industrial times. The satellite temperature measurements of the Earth’s temperature are the best because they cover the whole Earth and minimize the urban heat island effect. This record shows that from January 2019 to January 2023, the temperatures dropped by approximately 0.5 °C, which indicates that the Earth is cooling. On January 15, 2022, the Hunga Tonga submarine volcano violently erupted, sending approximately 146 million tonnes of water into the stratosphere. This water reduced the heat flow to space. It increased the Earth’s temperature to a peak in April 2024 of approximately 0.45 °C above the safe upper limit of 1.5 °C above pre-industrial levels, as promoted by the IPCC. There was no disastrous effect. We are halfway to 2030, and there are serious problems with the IPCC estimate. It is recommended that the IPCC consider revising its estimates of the impact of CO2 on warming the Earth’s atmosphere

A critical review on modelling formalisms and simulation tools in computational biosystems

Integration of different kinds of biological processes is an ultimate goal for whole-cell modelling. We briefly review modelling formalisms that have been used in Systems Biology and identify the criteria that must be addressed by an integrating framework capable of modelling, analysing and simulating different biological networks. Aware that no formalism can fit all purposes we realize Petri nets as a suitable model for Metabolic Engineering and take a deeper perspective on the role of this formalism as an integrating framework for regulatory and metabolic networks.Research supported by PhD grant SFRH/BD/35215/2007 from the Fundacao para a Ciencia e a Tecnologia (FCT) and the MIT-Portugal program

Successful GEP implementation depends on national frameworks: Institutional engagement alone is not enough

TARGET and GEECCO have both been funded within Horizon 2020 (Science with and for Society programme – SwafS). Both projects supported the development and implementation of GEPs in RPOs and RFOs in a total of 12 institutions from 11 countries. The policy brief is based on the results of the joint TARGET - GEECCO conference