161 research outputs found
Human factors and missed solutions to Enigma design weaknesses
The German World War II Enigma suffered from design weaknesses that facilitated its large-scale decryption by the British throughout the war. The author shows that the main technical weaknesses (self-coding and reciprocal coding) could have been avoided using simple contemporary technology, and therefore the true cause of the weaknesses is not technological but must be sought elsewhere. Specifically, human factors issues resulted in the persistent failure to seek out more effective designs. Similar limitations seem to beset the literature on the period, which misunderstands the Enigma weaknesses and therefore inhibits broader thinking about design or realising the critical role of human factors engineering in cryptography
Controlling passively-quenched single photon detectors by bright light
Single photon detectors based on passively-quenched avalanche photodiodes can
be temporarily blinded by relatively bright light, of intensity less than a
nanowatt. I describe a bright-light regime suitable for attacking a quantum key
distribution system containing such detectors. In this regime, all single
photon detectors in the receiver Bob are uniformly blinded by continuous
illumination coming from the eavesdropper Eve. When Eve needs a certain
detector in Bob to produce a click, she modifies polarization (or other
parameter used to encode quantum states) of the light she sends to Bob such
that the target detector stops receiving light while the other detector(s)
continue to be illuminated. The target detector regains single photon
sensitivity and, when Eve modifies the polarization again, produces a single
click. Thus, Eve has full control of Bob and can do a successful
intercept-resend attack. To check the feasibility of the attack, 3 different
models of passively-quenched detectors have been tested. In the experiment, I
have simulated the intensity diagrams the detectors would receive in a real
quantum key distribution system under attack. Control parameters and side
effects are considered. It appears that the attack could be practically
possible.Comment: Experimental results from a third detector model added. Minor
corrections and edits made. 11 pages, 10 figure
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Diallyl disulfide-induced apoptosis in a breast-cancer cell line (MCF-7) may be caused by inhibition of histone de-acetylation
The health benefits of garlic have been proven by epidemiological and experimental studies. Diallyl disulphide (DADS), the major organosulfur compound found in garlic oil, is known to lower the incidence of breast cancer both in vitro and in vivo. The studies reported here demonstrate that DADS induces apoptosis in the MCF-7 breast-cancer cell line through interfering with cell-cycle growth phases in a way that increases the sub-G0 population and substantially halts DNA synthesis. DADS also induces phosphatidylserine (PS) translocation from the inner to the outer leaflet of the plasma membrane and activates caspase-3. Further studies revealed that DADS modulates the cellular levels of Bax, Bcl-2, Bcl-xL and Bcl-w in a dose-dependent manner, suggesting the involvement of Bcl-2 family proteins in DADS induced apoptosis. Histone deacetylation inhibitors (HDACi) are known to suppress cancer growth and induce apoptosis in cancer cells. Here it is shown that DADS has HDACi properties in MCF-7 cells as it lowers the removal of an acetyl group from an acetylated substrate and induces histone-4 (H4) hyper-acetylation. The data thus indicate that the HDACi properties of DADS may be responsible for the induction of apoptosis in breast cancer cells
Mapping the internal recognition surface of an octanuclear coordination cage using guest libraries
Size and shape criteria for guest binding inside the cavity of an octanuclear cubic coordination cage in water have been established using a new fluorescence displacement assay to quantify guest binding. For aliphatic cyclic ketones of increasing size (from C5 to C11), there is a linear relationship between ΔG for guest binding and the guest’s surface area: the change in ΔG for binding is 0.3 kJ mol–1 Å–2, corresponding to 5 kJ mol–1 for each additional CH2 group in the guest, in good agreement with expectations based on hydrophobic desolvation. The highest association constant is K = 1.2 × 106 M–1 for cycloundecanone, whose volume is approximately 50% of the cavity volume; for larger C12 and C13 cyclic ketones, the association constant progressively decreases as the guests become too large. For a series of C10 aliphatic ketones differing in shape but not size, ΔG for guest binding showed no correlation with surface area. These guests are close to the volume limit of the cavity (cf. Rebek’s 55% rule), so the association constant is sensitive to shape complementarity, with small changes in guest structure resulting in large changes in binding affinity. The most flexible members of this series (linear aliphatic ketones) did not bind, whereas the more preorganized cyclic ketones all have association constants of 104–105 M–1. A crystal structure of the cage·cycloundecanone complex shows that the guest carbonyl oxygen is directed into a binding pocket defined by a convergent set of CH groups, which act as weak hydrogen-bond donors, and also shows close contacts between the exterior surface of the disc-shaped guest and the interior surface of the pseudospherical cage cavity despite the slight mismatch in shape
On the Regression and Assimilation for Air Quality Mapping Using Dense Low-Cost WSN
International audienceThe use of low-cost Wireless Sensor Networks (WSNs) for air quality monitoring has recently attracted a great deal of interest. Indeed, the cost-effectiveness of emerging sensors and their small size allow for dense deployments and hence improve the spatial granularity. However, these sensors offer a low accuracy and their measurement errors may be significant due to the underlying sensing technologies. The main aim of this work is to reconsider and compare some regression approaches to assimilation ones while taking into account the intrinsic characteristics of dense deployment of low cost WSN for air quality monitoring (high density, numerical model errors and sensing errors). For that, we propose a general framework that allows the comparison of different strategies based on numerical simulations and an adequate estimation of the simulation error covariances as well as the sensing errors covariances. While considering the case of Lyon city and a widely used numerical model, we characterize the simulation errors, conduct extensive simulations and compare several regression and assimilation approaches. The results show that from a given sensing error threshold, regression methods present an optimal sensor density from which the mapping quality decreases. Results also show that the Random Forest method is often the best regression approach but still less efficient than the BLUE assimilation approach when using adequate correction parameters
Controlling a superconducting nanowire single-photon detector using tailored bright illumination
We experimentally demonstrate that a superconducting nanowire single-photon
detector is deterministically controllable by bright illumination. We found
that bright light can temporarily make a large fraction of the nanowire length
normally-conductive, can extend deadtime after a normal photon detection, and
can cause a hotspot formation during the deadtime with a highly nonlinear
sensitivity. In result, although based on different physics, the
superconducting detector turns out to be controllable by virtually the same
techniques as avalanche photodiode detectors. As demonstrated earlier, when
such detectors are used in a quantum key distribution system, this allows an
eavesdropper to launch a detector control attack to capture the full secret key
without being revealed by to many errors in the key.Comment: Expanded discussions, updated references. 9 pages, 8 figure
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How do things become strategic? ‘Strategifying’ corporate social responsibility
How do things become ‘strategic’? Despite the development of strategy-as-practice studies and the recognized institutional importance of strategy as a social practice, little is known about how strategy boundaries change within organizations. This article focuses on this gap by conceptualizing ‘strategifying’ – or making something strategic – as a type of institutional work that builds on the institution of strategy to change the boundaries of what is regarded as strategy within organizations. We empirically investigate how corporate social responsibility has been turned into strategy at a UK electricity company, EnergyCorp. Our findings reveal the practices that constitute three types of strategifying work – cognitive coupling, relational coupling and material coupling – and show how, together and over time, these types of work changed the boundaries of strategy so that corporate social responsibility became included in EnergyCorp’s official strategy, became explicitly attended to by strategists and corporate executives and became inscribed within strategy devices. By disambiguating the notions of strategifying and strategizing, our study introduces new perspectives for analysing the institutional implications of the practice of strategy
Wheat-barley hybridization – the last forty years
Abstract Several useful alien gene transfers have
been reported from related species into wheat (Triticum
aestivum), but very few publications have dealt
with the development of wheat/barley (Hordeum
vulgare) introgression lines. An overview is given
here of wheat 9 barley hybridization over the last
forty years, including the development of
wheat 9 barley hybrids, and of addition and translocation
lines with various barley cultivars. A short
summary is also given of the wheat 9 barley hybrids
produced with other Hordeum species. The meiotic
pairing behaviour of wheat 9 barley hybrids is presented,
with special regard to the detection of wheat–
barley homoeologous pairing using the molecular
cytogenetic technique GISH. The effect of in vitro
multiplication on the genome composition of intergeneric
hybrids is discussed, and the production and
characterization of the latest wheat/barley translocation
lines are presented. An overview of the agronomical
traits (b-glucan content, earliness, salt tolerance,
sprouting resistance, etc.) of the newly developed
introgression lines is given. The exploitation and
possible use of wheat/barley introgression lines for
the most up-to-date molecular genetic studies
(transcriptome analysis, sequencing of flow-sorted
chromosomes) are also discussed
Metabolism during anaesthesia and recovery in colic and healthy horses: a microdialysis study
<p>Abstract</p> <p>Background</p> <p>Muscle metabolism in horses has been studied mainly by analysis of substances in blood or plasma and muscle biopsy specimens. By using microdialysis, real-time monitoring of the metabolic events in local tissue with a minimum of trauma is possible. There is limited information about muscle metabolism in the early recovery period after anaesthesia in horses and especially in the colic horse. The aims were to evaluate the microdialysis technique as a complement to plasma analysis and to study the concentration changes in lactate, pyruvate, glucose, glycerol, and urea during anaesthesia and in the recovery period in colic horses undergoing abdominal surgery and in healthy horses not subjected to surgery.</p> <p>Methods</p> <p>Ten healthy university-owned horses given anaesthesia alone and ten client-owned colic horses subjected to emergency abdominal surgery were anaesthetised for a mean (range) of 230 min (193–273) and 208 min (145–300) respectively. Venous blood samples were taken before anaesthesia. Venous blood sampling and microdialysis in the gluteal muscle were performed during anaesthesia and until 24 h after anaesthesia. Temporal changes and differences between groups were analysed with an ANOVA for repeated measures followed by Tukey Post Hoc test or Planned Comparisons.</p> <p>Results</p> <p>Lactate, glucose and urea, in both dialysate and plasma, were higher in the colic horses than in the healthy horses for several hours after recovery to standing. In the colic horses, lactate, glucose, and urea in dialysate, and lactate in plasma increased during the attempts to stand. The lactate-to-pyruvate ratio was initially high in sampled colic horses but decreased over time. In the colic horses, dialysate glycerol concentrations varied considerably whereas in the healthy horses, dialysate glycerol was elevated during anaesthesia but decreased after standing. In both groups, lactate concentration was higher in dialysate than in plasma. The correspondence between dialysate and plasma concentrations of glucose, urea and glycerol varied.</p> <p>Conclusion</p> <p>Microdialysis proved to be suitable in the clinical setting for monitoring of the metabolic events during anaesthesia and recovery. It was possible with this technique to show greater muscle metabolic alterations in the colic horses compared to the healthy horses in response to regaining the standing position.</p
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