Computation of a 30750-Bit Binary Field Discrete Logarithm

This paper reports on the computation of a discrete logarithm in the finite field $\mathbb F_{2^{30750}}$, breaking by a large margin the previous record, which was set in January 2014 by a computation in $\mathbb F_{2^{9234}}$. The present computation made essential use of the elimination step of the quasi-polynomial algorithm due to Granger, Kleinjung and Zumbr\"agel, and is the first large-scale experiment to truly test and successfully demonstrate its potential when applied recursively, which is when it leads to the stated complexity. It required the equivalent of about 2900 core years on a single core of an Intel Xeon Ivy Bridge processor running at 2.6 GHz, which is comparable to the approximately 3100 core years expended for the discrete logarithm record for prime fields, set in a field of bit-length 795, and demonstrates just how much easier the problem is for this level of computational effort. In order to make the computation feasible we introduced several innovative techniques for the elimination of small degree irreducible elements, which meant that we avoided performing any costly Gr\"obner basis computations, in contrast to all previous records since early 2013. While such computations are crucial to the $L(\frac 1 4 + o(1))$ complexity algorithms, they were simply too slow for our purposes. Finally, this computation should serve as a serious deterrent to cryptographers who are still proposing to rely on the discrete logarithm security of such finite fields in applications, despite the existence of two quasi-polynomial algorithms and the prospect of even faster algorithms being developed.Comment: 22 page

The Design of a Low Noise, Multi-Channel Recording System for Use in Implanted Peripheral Nerve Interfaces

In the development of implantable neural interfaces, the recording of signals from the peripheral nerves is a major challenge. Since the interference from outside the body, other biopotentials, and even random noise can be orders of magnitude larger than the neural signals, a filter network to attenuate the noise and interference is necessary. However, these networks may drastically affect the system performance, especially in recording systems with multiple electrode cuffs (MECs), where a higher number of electrodes leads to complicated circuits. This paper introduces formal analyses of the performance of two commonly used filter networks. To achieve a manageable set of design equations, the state equations of the complete system are simplified. The derived equations help the designer in the task of creating an interface network for specific applications. The noise, crosstalk and common-mode rejection ratio (CMRR) of the recording system are computed as a function of electrode impedance, filter component values and amplifier specifications. The effect of electrode mismatches as an inherent part of any multi-electrode system is also discussed, using measured data taken from a MEC implanted in a sheep. The accuracy of these analyses is then verified by simulations of the complete system. The results indicate good agreement between analytic equations and simulations. This work highlights the critical importance of understanding the effect of interface circuits on the performance of neural recording systems

Performance of matrices developed to identify patients with early rheumatoid arthritis with rapid radiographic progression despite methotrexate therapy: an external validation study based on the ESPOIR cohort data

International audienceIntroduction Use of prediction matrices of risk or rapid radiographic progression (RRP) for early rheumatoid arthritis (RA) in clinical practice could help to better rationalise the first line of treatment. Before use, they must be validated in populations that have not participated in their construction. The main objective is to use the ESPOIR cohort to validate the performance of 3 matrices (ASPIRE, BEST and SONORA) to predict patients at high risk of RRP at 1 year of disease despite initial treatment with methotrexate (MTX).Methods We selected from the ESPOIR cohort 370 patients receiving MTX or leflunomide (LEF) for ≥3 months within the first year of follow-up. Patients were assessed clinically every 6 months, and structural damage progression seen on radiography was measured by the van der Heijde-modified Sharp score (vSHS) at 1 year. RRP was defined as an increase in the vSHS≥5 points during the first year.Results At 1 year, the mean vSHS score was 1.7±5.0 and 46 patients had RRP. The ASPIRE matrix had only moderate validity in the ESPOIR population, with area under the receiver operating characteristic curve (AUC) <0.7. The AUC for the BEST and SONORA matrices were 0.73 and 0.76. Presence of rheumatoid factor (RF)—or anti-citrullinated protein antibodies (ACPAs) and initial structural damage were always predictive of RRP at 1 year. Disease Activity Score in 28 joints (DAS28) and C reactive protein (ASPIRE threshold) were not associated with RRP.Conclusions Matrices to identify patients at risk of RRP tested in the ESPOIR cohort seem to perform moderately. There is no matrix that shows clearly superior performance

C-Reactive Protein in Arrhythmogenic Right Ventricular Dysplasia/Cardiomyopathy and Relationship with Ventricular Tachycardia

Background. The relationship between C-reactive protein (CRP) elevation and ventricular tachycardia (VT) in arrhythmogenic right ventricular dysplasia/cardiomyopathy (ARVD/C) is unclear. Methods and Results. In 91 consecutive patients with either ARVD/C with or without VT (cases) or idiopathic right ventricular outflow tract (RVOT) tachycardia (controls), blood sampling were taken to determine CRP levels. In ARVD/C patients with VT, we analyzed the association between VT occurrences and CRP level. Sixty patients had ARVD/C, and 31 had idiopathic RVOT VT. Patients with ARVD/C had a significant higher level of CRP compared to those with RVOT VT (3.5 ± 4.9 versus 1.1 ± 1.2 mg/l, P = .0004). In ARVD/C group, 77%, (n = 46) patients experienced VT. Of these, 37% (n = 17) underwent blood testing for CRP within 24 h after the onset of VT and the remaining 63% (n = 29) after 24 h of VT reduction. CRP level was similar in ARVD/C patients with or without documented VT (3.6 ± 5.1 mg/l versus 3.1 ± 4.1 mg/l, P = .372). However, in patients with ARVD/C and documented VT, CRP was significantly higher when measured within 24 hours following VT in comparison to that level when measured after 24 h (4.9 ± 6.2 mg/l versus 3.0 ± 4.4 mg/l, P = .049). Conclusion. Inflammatory state is an active process in patients with ARVD/C. Moreover, there is a higher level of CRP in patients soon after ventricular tachycardia, and this probably tends to decrease after the event

Computation of a 30 750-Bit Binary Field Discrete Logarithm

This paper reports on the computation of a discrete logarithm in the finite field $\mathbb F_{2^30750}$, breaking by a large margin the previous record, which was set in January 2014 by a computation in $\mathbb F_{2^30750}$. The present computation made essential use of the elimination step of the quasi-polynomial algorithm due to Granger, Kleinjung and Zumbrägel, and is the first large-scale experiment to truly test and successfully demonstrate its potential when applied recursively, which is when it leads to the stated complexity. It required the equivalent of about 2900 core years on a single core of an Intel Xeon Ivy Bridge processor running at 2.6 GHz, which is comparable to the approximately 3100 core years expended for the discrete logarithm record for prime fields, set in a field of bit-length 795, and demonstrates just how much easier the problem is for this level of computational effort. In order to make the computation feasible we introduced several innovative techniques for the elimination of small degree irreducible elements, which meant that we avoided performing any costly Gröbner basis computations, in contrast to all previous records since early 2013. While such computations are crucial to the $L(1/4 + o(1))$ complexity algorithms, they were simply too slow for our purposes. Finally, this computation should serve as a serious deterrent to cryptographers who are still proposing to rely on the discrete logarithm security of such finite fields in applications, despite the existence of two quasi-polynomial algorithms and the prospect of even faster algorithms being developed

Jupyter Notebooks – a publishing format for reproducible computational workflows

It is increasingly necessary for researchers in all fields to write computer code, and in order to reproduce research results, it is important that this code is published. We present Jupyter notebooks, a document format for publishing code, results and explanations in a form that is both readable and executable. We discuss various tools and use cases for notebook documents

A rapid ammonium fluoride method to determine the oxygen isotope ratio of available phosphorus in tropical soils

Rationale The isotopic composition of oxygen bound to phosphorus (δ18OP value) offers an opportunity to gain insight into P cycling mechanisms. However, there is little information for tropical forest soils, which presents a challenge for δ18OP measurements due to low available P concentrations. Here we report the use of a rapid ammonium fluoride extraction method (Bray‐1) as an alternative to the widely used anion‐exchange membrane (AEM) method for quantification of δ18OP values of available P in tropical forest soils. Methods We compared P concentrations and δ18OP values of available and microbial P determined by AEM and Bray‐1 extraction for a series of tropical forest soils from Panama spanning a steep P gradient. This involved an assessment of the influence of extraction conditions, including temperature, extraction time, fumigation time and solution‐to‐soil ratio, on P concentrations and isotope ratios. Results Depending on the extraction conditions, Bray‐1 P concentrations ranged from 0.2 to 66.3 mg P kg−1 across the soils. Extraction time and temperature had only minor effects on Bray‐1 P, but concentrations increased markedly as the solution‐to‐soil ratio increased. In contrast, extraction conditions did not affect Bray‐1 δ18OP values, indicating that Bray‐1 provides a robust measure of the isotopic composition of available soil P. For a relatively high P soil, available and fumigation‐released (microbial) δ18OP values determined by Bray‐1 extraction (20‰ and 16‰, respectively) were higher than those determined by the AEM method (18‰ and 12‰, respectively), which we attribute to slightly different P pools extracted by the two methods and/or differences resulting from the longer extraction time needed for the AEM method. Conclusions The short extraction time, insensitivity to extraction conditions and smaller mass of soil required to extract sufficient P for isotopic analysis make Bray‐1extraction a suitable alternative to the AEM method for the determination of δ18OP values of available P in tropical soils

Plasma Plasmodium falciparum Histidine-Rich Protein-2 Concentrations Are Associated with Malaria Severity and Mortality in Tanzanian Children

Plasma Plasmodium falciparum histidine-rich protein-2 (PfHRP-2) concentrations, a measure of parasite biomass, have been correlated with malaria severity in adults, but not yet in children. We measured plasma PfHRP-2 in Tanzanian children with uncomplicated (n = 61) and cerebral malaria (n = 45; 7 deaths). Median plasma PfHRP-2 concentrations were higher in cerebral malaria (1008 [IQR 342–2572] ng/mL) than in uncomplicated malaria (465 [IQR 36–1426] ng/mL; p = 0.017). In cerebral malaria, natural log plasma PfHRP-2 was associated with coma depth (r = −0.42; p = 0.006) and mortality (OR: 3.0 [95% CI 1.03–8.76]; p = 0.04). In this relatively small cohort study in a mesoendemic transmission area of Africa, plasma PfHRP-2 was associated with pediatric malaria severity and mortality. Further studies among children in areas of Africa with higher malaria transmission and among children with different clinical manifestations of severe malaria will help determine the wider utility of quantitative PfHRP-2 as a measure of parasite biomass and prognosis in sub-Saharan Africa