Generalised Mersenne Numbers Revisited

Generalised Mersenne Numbers (GMNs) were defined by Solinas in 1999 and feature in the NIST (FIPS 186-2) and SECG standards for use in elliptic curve cryptography. Their form is such that modular reduction is extremely efficient, thus making them an attractive choice for modular multiplication implementation. However, the issue of residue multiplication efficiency seems to have been overlooked. Asymptotically, using a cyclic rather than a linear convolution, residue multiplication modulo a Mersenne number is twice as fast as integer multiplication; this property does not hold for prime GMNs, unless they are of Mersenne's form. In this work we exploit an alternative generalisation of Mersenne numbers for which an analogue of the above property --- and hence the same efficiency ratio --- holds, even at bitlengths for which schoolbook multiplication is optimal, while also maintaining very efficient reduction. Moreover, our proposed primes are abundant at any bitlength, whereas GMNs are extremely rare. Our multiplication and reduction algorithms can also be easily parallelised, making our arithmetic particularly suitable for hardware implementation. Furthermore, the field representation we propose also naturally protects against side-channel attacks, including timing attacks, simple power analysis and differential power analysis, which is essential in many cryptographic scenarios, in constrast to GMNs.Comment: 32 pages. Accepted to Mathematics of Computatio

Cisco networking: using Skype and Netlab+ for distance practical learning

Delivering a 'hands on' ICT practical lesson online offers vocationally based courses an increased presence in a learning sphere otherwise dominated by remote learning, exercise and material based courses. This paper explores work within the UK Open University to deliver collaborative learning with Cisco Systems, the technological pitfalls and how these are being overcome by the use of Skype', Messenger and Netlab+�

VERTICAL INTEGRATION AND TRADE POLICY: THE CASE OF SUGAR

The degree of vertical integration in the U.S. sugar industry between raw sugar processing and sugar refining cannot be explained using theories of vertical integration based on transaction costs (e.g. Williamson). We graphically decompose the economic rents accruing to each level in the marketing channel. Different strategies of several major sugar producing, processing and refining entities with regard to sugar quota policy are explored.Agribusiness, Industrial Organization,

The role of VPAC₂ receptors and PKA in neuropathic pain

In animal models of neuropathic pain, changes in afferent and spinal cord neurones after pe1ipheral nerve injury lead to hyperexcitability within the spinal dorsal horn, termed "central sensitisation". This causes a persistent pain state with enhanced responses to noxious stimuli (hyperalgesia) and pain-like responses to previously innocuous stimuli (allodynia).The role of the VPAC₂ receptor in CCI was investigated. In VPAC₂R(⁻/⁻) mice, the enhanced reflex responses to noxious heat and innocuous mechanical stimulation seen in wild type (WT) mke were attenuated. No morihological differences were seen between peripheral nerves of WT and VPAC2R c--) mice. Furthermore, intrathecal administration of a VPAC₂R inhibitor attenuated the enhanced reflex withdrawal responses to noxious heat and innocuous mechanical stimuli in WT mice following CCI, with no effect in VPAC₂R (⁻/⁻) mice.In normal rats, intrathecal administration of PKA inhibitors attenuated the enhanced reflex withdrawal responses due to CCI. In situ hybridisation for isofo1ms of PKA regulatory (R) and catalytic (C) subunits showed a spinal increase in C-subunit , but not R-subunit mRNA ipsilaterally at the peak of CCI sensitisation. Immunoblots confiimed an ipsilateral increase in C-subunits and showed a bilateral decrease in the RI~ subunit.The role of the proteasome in neuropathic sensitisation was studied. Electrophysiological recordings made from dorsal horn neurones in anaesthetised rats showed that proteasome inhibitors applied by ionophoresis inhibi ted activity evoked by innocuous brush and cold in CCI rats, while nociceptive responses were inhibited in CCI and normal animals. Intrathecal administration of proteasome inhibitors attenuated the enhanced paw withdrawal behaviours ipsilateral to CCI. The mRNA and protein levels for UCH-Ll, (a key enzyme in proteasomal function) were increased ipsilaterally. PKA enzymatic activity was increased in spinal cord ipsilateral to nerve injury and this increment was prevented by topical application of proteasome inhibitors.This investigation demonstrates the involvement of the VPAC₂ receptor, the corresponding cAMP/PKA signal transduction cascade and the proteasome (a regulator of PKA activity) in the spinal sensitisation caused by CCI

Natural Disasters and the Yield Curve of Florida Valencias

Crop Production/Industries,

WHERE IS THE WALRASIAN AUCTIONEER FOR AGRICULTURAL MARKETS? AN EXAMINATION OF THE MARKETING INSTITUTION

In the classical development of economic equilibrium and efficiency, transaction costs are seldom considered. This study develops a micro- market model of an agricultural market based on quality differences. The study then develops a model of market structure based on the New Theory of the Firm. Using the two models, we draw conclusions about economic potential for E-Commerce.Marketing,

The brave new world: imperfect information, segregation costs, and genetically modified organisms

The introduction of genetically modified (GM) crops in the mid 1990s appeared to be the latest in a string of technological innovations in agriculture. However, consumer resistance, particularly in Europe has limited the sector’s enthusiasm. One response to the limited enthusiasm has been the emergence of segregated markets for GM and non-GM products. These separated markets reduce economic welfare because they require additional costs in the marketing system. Offsetting these segregation costs, however, the introduction of GM technologies offers increased economic welfare through reduced commodity prices for consumers who are indifferent to the presence of GM traits and increased profits to producers who adopt GM technologies. This study develops the combinations of segregation costs and increased supplies that leave societal surplus unchanged. Any GM technology that yields a larger increase in supply for any segregation cost depicted in this relationship meets the compensation principle and, thus, improves societal welfare. In this case, market based adoption of these technologies improve economic surplus. On the other hand, technologies that yields less increase in supply for any segregation cost reduces societal welfare. Under this scenario, market based adoption will not be welfare improving and, hence, government regulation may be required.genetically modified (GM) crops, compensation principle, segregation costs, Pareto principle, immiserizing growth, Agricultural and Food Policy, Research and Development/Tech Change/Emerging Technologies,

The Effect of Increased Energy Prices on Agriculture: A Differential Supply Approach

The increase in energy prices between 2004 and 2007 has several potential consequences for aggregate agriculture in the U.S. We estimate the derived input demand elasticities for energy as well as capital, labor, and materials using the differential supply formulation. Given that the derived input demand for energy is inelastic, it is more price-responsive than the other inputs. The results also indicate that the U.S. aggregate agricultural supply function is responsive to energy prices.differential input demand, concavity constrained, energy, Agribusiness, Agricultural Finance, Demand and Price Analysis, Financial Economics, Industrial Organization, Labor and Human Capital, Land Economics/Use, Marketing, Production Economics, Productivity Analysis, Research Methods/ Statistical Methods, C30, Q11, Q42,

The pharmacology and function of receptors for short-chain fatty acids

Despite some blockbuster G protein–coupled receptor (GPCR) drugs, only a small fraction (∼15%) of the more than 390 nonodorant GPCRs have been successfully targeted by the pharmaceutical industry. One way that this issue might be addressed is via translation of recent deorphanization programs that have opened the prospect of extending the reach of new medicine design to novel receptor types with potential therapeutic value. Prominent among these receptors are those that respond to short-chain free fatty acids of carbon chain length 2–6. These receptors, FFA2 (GPR43) and FFA3 (GPR41), are each predominantly activated by the short-chain fatty acids acetate, propionate, and butyrate, ligands that originate largely as fermentation by-products of anaerobic bacteria in the gut. However, the presence of FFA2 and FFA3 on pancreatic β-cells, FFA3 on neurons, and FFA2 on leukocytes and adipocytes means that the biologic role of these receptors likely extends beyond the widely accepted role of regulating peptide hormone release from enteroendocrine cells in the gut. Here, we review the physiologic roles of FFA2 and FFA3, the recent development and use of receptor-selective pharmacological tool compounds and genetic models available to study these receptors, and present evidence of the potential therapeutic value of targeting this emerging receptor pair