An overview of the British Aerospace HOTOL transatmospheric vehicle

British Aerospace's space-going aircraft and economical launcher Hotol, so named for its horizontal take-off and landing ability, is described. The craft uses Rolls Royce's new Swallow engine, the principle behind which is still secret, which burns atmospheric oxygen until it leaves the atmosphere and then switches to liquid oxygen. This lightens the craft's fuel load tremendously, so that it can carry significant payloads and still take off and land like a normal airplane. A typical future mission for the craft is described

Asymmetry of Information within Family Networks

This paper studies asymmetry of information and transfers within 712 extended family networks from Tanzania. Using cross-reports on asset holdings, we construct measures of mis-perception of living standards among households within the same network. We contrast altruism, pressure, exchange and risk sharing as motives to transfer in simple models with asymmetric information. Testing the model predictions in the data uncovers the active role played by recipients of transfers. Our findings suggest that recipients set the terms of the transfers, either by exerting pressure on donors or because they hold substantial bargaining power in their exchange relationships

Ethnic parity in labour market outcomes for benefit claimants

A significant gap exists in the UK between the employment rate for Ethnic Minorities and that for Whites. From a policy perspective, it is important to know whether this gap is due to differences in the characteristics of White and Ethnic Minority groups (which reduce the employability of Ethnic Minority groups relative to Whites) or whether it results from some form of discriminatory behaviour in the labour market. In this paper, we use administrative data to estimate ethnic differences in employment and benefit receipt amongst individuals who began claiming a Jobcentre Plus benefit in 2003. In contrast to much of the previous UK literature, we use a number of different quantitative techniques to estimate this gap, and show that in a lot of cases the estimates obtained are very sensitive to the techniques used. We argue that for the questions we are interested in and the data we have, propensity score matching methods are the most robust approach to estimating ethnic parity. We compare this preferred approach with estimates derived using alternative approaches commonly used in the literature (generally regression-based techniques) to determine the extent to which more straightforward methods are able to replicate those produced by matching. In many cases, it turns out not to be possible to calculate satisfactory quantitative estimates even with matching techniques: the characteristics of Whites and Ethnic Minorities are simply too different before the Jobcentre Plus intervention to reliably estimate the parameters of interest. Moreover, for a number of the groups, results seem to be very sensitive to the methodology used. This calls into question previous results based on simple regression techniques, which are likely to hide the fact that observationally different ethnic groups are de facto being compared on the basis of parametric extrapolations. Two groups for which it was possible to calculate reasonably reliable results are incapacity benefit (IB) and income support (IS). For these groups we find that large and significant raw penalties almost always disappear once we appropriately control for pre-inflow background and labour market characteristics. There is also a good degree of consistency across methodologies

Some conceptual difficulties regarding "net" multipliers

Multipliers are routinely used for impact evaluation of private projects and public policies at the national and subnational levels. Oosterhaven and Stelder (2002) correctly pointed out the misuse of standard 'gross' multipliers and proposed the concept of 'net' multiplier as a solution to this bad practice. We prove their proposal is not well founded. We do so by showing that supporting theorems are faulty in enunciation and demonstration. The proofs are flawed due to an analytical error but the theorems themselves cannot be salvaged as generic, non-curiosum counterexamples demonstrate. We also provide a general analytical framework for multipliers and, using it, we show that standard 'gross' multipliers are all that is needed within the interindustry model since they follow the causal logic of the economic model, are well defined and independent of exogenous shocks, and are interpretable as predictors for change

Asymmetry of Information within Family Networks

This paper studies asymmetry of information and transfers within a unique data set of 712 extended family networks from Tanzania. Using cross-reports on asset holdings, we construct measures of misperception of income among all pairs of households belonging to the same network. We show that there is significant asymmetry of information and no evidence of major systematic over-evaluation or under-evaluation of income in our data, although there is a slight over-evaluation on the part of migrants regarding non-migrants. We develop a static model of asymmetric information that contrasts altruism, pressure and exchange as motives to transfer. The model makes predictions about the correlations between misperceptions and transfers under these competing explanations. Testing these predictions in the data uncovers the active role played by the recipient. Our findings suggest that the recipient sets the terms of the transfers, either by exerting pressure to give on the donor or by holding the bargaining power during the exchange of services with the donor

A Discrete Choice Experiment to Elicit the Willingness to Pay for Health Insurance by the Informal Sector Workers in Sierra Leone

The current health care financing system in Sierra Leone is unsustainable and poses challenges ranging from increased in out of pocket health care expenditure to accessibility problems, particularly in rural areas where living standards are low and health care facilities are scarce. This paper investigates whether privately financed health Insurance can improve the accessibility to formal health care in Sierra Leone and mitigate the effects of OOPs on poor households. To do so, we estimate the Willingness To Pay (WTP) for health insurance among informal sector workers in Sierra Leone using a Discrete Choice Experiment approach. Eight informal sector activities were selected namely – petty trading, subsistence farming, commercial bike riding, cattle rearing, fishing, tailoring, mining and quarrying. A random effect logit model is used to estimate households’ WTP for an improvement in coverage, choice of health care provider and a reduction in waiting time. Our study reveals that households were WTP more to have better attributes (better coverage, less waiting time) and to go to a faith - based provider. Our findings also suggest that location – rural versus urban – matters in determining the WTP since urban households were WTP more for health insurance than their rural counterparts, (SLL 54,348 or $7.34) and (SLL 37,250.5 or$5.03), respectively

Orbit Assembly Of Unmanned Spacecraft

In future, the mission demands on unmanned spacecraft, (whether they be Earth orbiters or deep space probes) , will be so great and so complex as to preclude their being small enough to be launched from Earth by chemical rocket. Such spacecraft can be assembled in Earth orbit by suited astronauts, using pre-fabricated modules specifically designed for such orbital assembly. These modules could be standardized, so that any number of spacecraft and mission requirements could be accommodated without extensive need for specialized hardware

An SMT-Based Concolic Testing Tool for Logic Programs

[EN] Concolic testing combines symbolic and concrete execution to generate test cases that achieve a good program coverage. Its benefits have been demonstrated for more than 15 years in the case of imperative programs. In this work, we present a concolic-based test generation tool for logic programs which exploits SMT-solving for constraint resolutionThird author is a research associate at FNRS that also supports this work (O05518FRG03). The last author is partially supported by the EU (FEDER) and the Spanish MCI/AEI under grants TIN2016-76843-C4-1-R/PID2019-104735RB-C41 and by the Generalitat Valenciana under grant Prometeo/2019/098 (DeepTrust)Fortz, S.; Mesnard, F.; Payet, E.; Perrouin, G.; Vanhoof, W.; Vidal, G. (2020). An SMT-Based Concolic Testing Tool for Logic Programs. Springer Nature. 215-219. https://doi.org/10.1007/978-3-030-59025-3_13S215219de Moura, L., Bjørner, N.: Z3: an efficient SMT solver. In: Ramakrishnan, C.R., Rehof, J. (eds.) TACAS 2008. LNCS, vol. 4963, pp. 337–340. Springer, Heidelberg (2008). https://doi.org/10.1007/978-3-540-78800-3_24Giantsios, A., Papaspyrou, N., Sagonas, K.: Concolic testing for functional languages. Sci. Comput. Program. 147, 109–134 (2017)Godefroid, P., Klarlund, N., Sen, K.: DART: directed automated random testing. In: Proceedings of PLDI 2005, pp. 213–223. ACM (2005)Mesnard, F., Payet, É., Vidal, G.: Concolic testing in logic programming. TPLP 15(4–5), 711–725 (2015). https://doi.org/10.1017/S1471068415000332Mesnard, F., Payet, É., Vidal, G.: On the completeness of selective unification in concolic testing of logic programs. In: Hermenegildo, M.V., Lopez-Garcia, P. (eds.) LOPSTR 2016. LNCS, vol. 10184, pp. 205–221. Springer, Cham (2017). https://doi.org/10.1007/978-3-319-63139-4_12Mesnard, F., Payet, É., Vidal, G.: Selective unification in constraint logic programming. In: Vanhoof, W., Pientka, B. (eds.) PPDP, pp. 115–126. ACM (2017)Mesnard, F., Payet, É., Vidal, G.: Concolic Testing in CLP. CoRR abs/2008.00421 (2020). https://arxiv.org/abs/2008.00421Sen, K., Marinov, D., Agha, G.: CUTE: a concolic unit testing engine for C. In: ESEC/ FSE, pp. 263–272. ACM (2005)Ströder, T., Emmes, F., Schneider-Kamp, P., Giesl, J., Fuhs, C.: A linear operational semantics for termination and complexity analysis of ISO Prolog. In: Vidal, G. (ed.) LOPSTR 2011. LNCS, vol. 7225, pp. 237–252. Springer, Heidelberg (2012). https://doi.org/10.1007/978-3-642-32211-2_16Tikovsky, J.R.: Concolic testing of functional logic programs. In: Seipel, D., Hanus, M., Abreu, S. (eds.) WFLP/WLP/INAP -2017. LNCS (LNAI), vol. 10997, pp. 169–186. Springer, Cham (2018). https://doi.org/10.1007/978-3-030-00801-7_11Vidal, G.: Concolic execution and test case generation in prolog. In: Proietti, M., Seki, H. (eds.) LOPSTR 2014. LNCS, vol. 8981, pp. 167–181. Springer, Cham (2015). https://doi.org/10.1007/978-3-319-17822-6_10Wielemaker, J., Schrijvers, T., Triska, M., Lager, T.: SWI-prolog. TPLP 12(1–2), 67–96 (2012). https://doi.org/10.1017/S147106841100049

Interaction between C/EBPβ and Tax down-regulates human T-cell leukemia virus type I transcription

AbstractThe human T-cell leukemia virus type I (HTLV-I) Tax protein trans-activates viral transcription through three imperfect tandem repeats of a 21-bp sequence called Tax-responsive element (TxRE). Tax regulates transcription via direct interaction with some members of the activating transcription factor/CRE-binding protein (ATF/CREB) family including CREM, CREB, and CREB-2. By interacting with their ZIP domain, Tax stimulates the binding of these cellular factors to the CRE-like sequence present in the TxREs. Recent observations have shown that CCAAT/enhancer binding protein β (C/EBPβ) forms stable complexes on the CRE site in the presence of CREB-2. Given that C/EBPβ has also been found to interact with Tax, we analyzed the effects of C/EBPβ on viral Tax-dependent transcription. We show here that C/EBPβ represses viral transcription and that Tax is no more able to form a stable complex with CREB-2 on the TxRE site in the presence of C/EBPβ. We also analyzed the physical interactions between Tax and C/EBPβ and found that the central region of C/EBPβ, excluding its ZIP domain, is required for direct interaction with Tax. It is the first time that Tax is described to interact with a basic leucine-zipper (bZIP) factor without recognizing its ZIP domain. Although unexpected, this result explains why C/EBPβ would be unable to form a stable complex with Tax on the TxRE site and could then down-regulate viral transcription. Lastly, we found that C/EBPβ was able to inhibit Tax expression in vivo from an infectious HTLV-I molecular clone. In conclusion, we propose that during cell activation events, which stimulate the Tax synthesis, C/EBPβ may down-regulate the level of HTLV-I expression to escape the cytotoxic-T-lymphocyte response

SOD1G93A transgenic mouse CD4+ T cells mediate neuroprotection after facial nerve axotomy when removed from a suppressive peripheral microenvironment

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease involving motoneuron (MN) axonal withdrawal and cell death. Previously, we established that facial MN (FMN) survival levels in the SOD1G93A transgenic mouse model of ALS are reduced and nerve regeneration is delayed, similar to immunodeficient RAG2-/- mice, after facial nerve axotomy. The objective of this study was to examine the functionality of SOD1G93A splenic microenvironment, focusing on CD4+ T cells, with regard to defects in immune-mediated neuroprotection of injured MN. We utilized the RAG2-/- and SOD1G93A mouse models, along with the facial nerve axotomy paradigm and a variety of cellular adoptive transfers, to assess immune-mediated neuroprotection of FMN survival levels. We determined that adoptively transferred SOD1G93A unfractionated splenocytes into RAG2-/- mice were unable to support FMN survival after axotomy, but that adoptive transfer of isolated SOD1G93A CD4+ T cells could. Although WT unfractionated splenocytes adoptively transferred into SOD1G93A mice were able to maintain FMN survival levels, WT CD4+ T cells alone could not. Importantly, these results suggest that SOD1G93A CD4+ T cells retain neuroprotective functionality when removed from a dysfunctional SOD1G93A peripheral splenic microenvironment. These results also indicate that the SOD1G93A central nervous system microenvironment is able to re-activate CD4+ T cells for immune-mediated neuroprotection when a permissive peripheral microenvironment exists. We hypothesize that dysfunctional SOD1G93A peripheral splenic microenvironment may compromise neuroprotective CD4+ T cell activation and/or differentiation, which, in turn, results in impaired immune-mediated neuroprotection for MN survival after peripheral axotomy in SOD1G93A mice