Sciatica

This issue of eMedRef provides information to clinicians on the pathophysiology, diagnosis, and therapeutics of sciatica

Self-synchronized Encryption for Physical Layer in 10Gbps Optical Links

In this work a new self-synchronized encryption method for 10 Gigabit optical links is proposed and developed. Necessary modifications to introduce this kind of encryption in physical layers based on 64b/66b encoding, such as 10GBase-R, have been considered. The proposed scheme encrypts directly the 64b/66b blocks by using a symmetric stream cipher based on an FPE (Format Preserving Encryption) block cipher operating in PSCFB (Pipelined Statistical Cipher Feedback) mode. One of the main novelties in this paper is the security analysis done for this mode. For the first time, an expression for the IND-CPA (Indistinguishability under Chosen-Plaintext Attack) advantage of any adversary over this scheme has been derived. Moreover, it has been concluded that this mode can be considered secure in the same way of traditional modes are. In addition, the overall system has been simulated and implemented in an FPGA (Field Programmable Gate Array). An encrypted optical link has been tested with Ethernet data frames, concluding that it is possible to cipher traffic at this level, getting maximum throughput and hiding traffic pattern from passive eavesdroppers

A new method for format preserving encryption in high-data rate communications

In some encryption systems it is necessary to preserve the format and length of the encrypted data. This kind of encryption is called FPE (Format Preserving Encryption). Currently, only two AES (Advanced Encryption Standard) modes of operation recommended by the NIST (National Institute of Standards and Technology) are able to implement FPE algorithms, FF1 and FF3. These modes work in an electronic codebook fashion and can be configured to encrypt databases with an arbitrary format and length. However, there are no stream cipher proposals able to implement FPE encryption for high data rate information flows. The main novelty of this work is a new block cipher operation mode proposal to implement an FPE algorithm in a stream cipher fashion. It has been called CTR-MOD and it is based on a standard block cipher working in CTR (Counter) mode and a modulo operation. The confidentiality of this mode is analyzed in terms of its IND- CPA (Indistinguishability under Chosen Plaintext Attack) advantage of any adversary attacking it. Moreover, the encryption scheme has been implemented on an FPGA (Field Programmable Gate Array) and has been integrated in a Gigabit Ethernet interface to test an encrypted optical link with a real high data rate traffic flow

Self-Synchronized Encryption for Physical Layer in Gigabit Ethernet Optical Links

In this work a new self-synchronized symmetric encryption solution for high speed communication systems necessary to preserve the format of the plaintext is proposed, developed and tested. This new encryption mechanism is based on the block cipher operation mode called PSCFB (Pipelined Statistical Cipher Feedback) and the modulo operation. The confidentiality of this mode is analyzed in terms of its IND-CPA (Indistinguishability under Chosen-Plaintext Attack) advantage, concluding that it can be considered secure in the same way as traditional modes are. The encryption system has been integrated in the physical layer of a 1000Base-X Gigabit Ethernet Interface, where the 8b/10b symbol flow is encrypted at line rate. Moreover, an implementation of the proposed system has been carried out in an FPGA (Field Programmable Gate Array) device. Finally, an encrypted optical link has been tested with real Ethernet frames, getting maximum throughput and protecting the data traffic from passive eavesdroppers

Chaotic Encryption for 10-Gb Ethernet Optical Links

In this paper, a new physical layer encryption method for optical 10-Gb Ethernet links is proposed. Necessary modifications to introduce encryption in Ethernet 10GBase-R standard have been considered. This security enhancement has consisted of a symmetric streaming encryption of the 64b/66b data flow at physical coding sublayer level thanks to two keystream generators based on a chaotic algorithm. The overall system has been implemented and tested in a field programmable gate array. Ethernet traffic has been encrypted, transmitted, and decrypted over a multimode optical link. Experimental results are analyzed concluding that it is possible to cipher traffic at this level and hide the complete Ethernet traffic pattern from any passive eavesdropper. In addition, no overhead is introduced during encryption, getting no losses in the total throughput

Chaos-Based Bitwise Dynamical Pseudorandom Number Generator on FPGA

In this paper, a new pseudorandom number generator (PRNG) based on the logistic map has been proposed. To prevent the system to fall into short period orbits as well as increasing the randomness of the generated sequences, the proposed algorithm dynamically changes the parameters of the chaotic system. This PRNG has been implemented in a Virtex 7 field-programmable gate array (FPGA) with a 32-bit fixed point precision, using a total of 510 lookup tables (LUTs) and 120 registers. The sequences generated by the proposed algorithm have been subjected to the National Institute of Standards and Technology (NIST) randomness tests, passing all of them. By comparing the randomness with the sequences generated by a raw 32-bit logistic map, it is shown that, by using only an additional 16% of LUTs, the proposed PRNG obtains a much better performance in terms of randomness, increasing the NIST passing rate from 0.252 to 0.989. Finally, the proposed bitwise dynamical PRNG is compared with other chaos-based realizations previously proposed, showing great improvement in terms of resources and randomness

An Integrative Model of Graduate Education in Biodiversity Conservation and Sustainable Production in Fragmented Landscapes

To achieve biodiversity conservation and sustainable production in anthropogenically fragmented landscapes, scientists need to be trained in a holistic fashion that emphasizes integration and interdisciplinary collaboration. Traditional graduate programs in natural resources, conservation biology and agricultural sciences usually fall short of this goal as they train scientists with research knowledge and skills in narrowly defined disciplines. Rarely, if ever, is integration across disciplines facilitated, valued, or emphasized in either coursework or research activities

Mathematical model to predict the dry matter intake of dairy cows on pasture

In pasture-based dairy systems, there is a close relationship between milk production and dry matter intake (DMI), hence the importance of measuring these variables, although obtaining this information implies high labour and costs. The objective of this study was to design a mathematical model to predict DMI for grazing dairy cows. This model was based on the basic principle of the fill-unit system. In this scheme, cows and feedstuffs were described in terms of feed intake capacity (FIC) and fill (unit/amount of feed), respectively. The FIC was determined by the animal’s ability to regulate feed intake which depends on factors such as body size, age and lactation status. The “fill” was determined by the nutritional properties of the feedstuff such as its dry matter (DM) digestibility and crude protein (CP) content, among others. In the design of the model, ad lib. feed consumption was assumed. Parity, state of lactation and gestation were considered to estimate the cow ingestion capacity. Satiety values (SV) were determined for Festuca arundinacea and Lolium multiflorum and these values were incorporated into the model, including DM, CP, neutral detergent fibre (NDF) and in vitro digestible organic matter (dOM). The fixed parameters of the model were determined by adjusting a polynomial regression to the data from three experiments with lactating Holstein cows from Baja California, Mexico (n=30).The model allows predicting DMI, using as inputs, easily measured data and does not require knowing daily milk yield (MY) or body weight (BW), so the model is practical and consistent. The results obtained from the model were satisfactory because they were similar to those attained experimentally. Average DMI was 21.68 kg/d in one group and 23.44 kg/d in the other; when applying the model, we obtained an estimate of 22.82 kg/d for a cow with characteristics similar to those of the cows under stud

Anti-prion drug mPPIg5 inhibits PrP(C) conversion to PrP(Sc).

Prion diseases, also known as transmissible spongiform encephalopathies, are a group of fatal neurodegenerative diseases that include scrapie in sheep, bovine spongiform encephalopathy (BSE) in cattle and Creutzfeldt-Jakob disease (CJD) in humans. The 'protein only hypothesis' advocates that PrP(Sc), an abnormal isoform of the cellular protein PrP(C), is the main and possibly sole component of prion infectious agents. Currently, no effective therapy exists for these diseases at the symptomatic phase for either humans or animals, though a number of compounds have demonstrated the ability to eliminate PrPSc in cell culture models. Of particular interest are synthetic polymers known as dendrimers which possess the unique ability to eliminate PrP(Sc) in both an intracellular and in vitro setting. The efficacy and mode of action of the novel anti-prion dendrimer mPPIg5 was investigated through the creation of a number of innovative bio-assays based upon the scrapie cell assay. These assays were used to demonstrate that mPPIg5 is a highly effective anti-prion drug which acts, at least in part, through the inhibition of PrP(C) to PrP(Sc) conversion. Understanding how a drug works is a vital component in maximising its performance. By establishing the efficacy and method of action of mPPIg5, this study will help determine which drugs are most likely to enhance this effect and also aid the design of dendrimers with anti-prion capabilities for the future

IL-7 Induces SAMHD1 Phosphorylation in CD4+ T Lymphocytes, Improving Early Steps of HIV-1 Life Cycle

HIV-1 post-integration latency in CD4+ lymphocytes is responsible for viral persistence despite treatment, but mechanisms involved in the establishment of latent viral reservoirs are not fully understood. We determined that both interleukin 2 (IL-2) and IL-7 induced SAMHD1 phosphorylation in T592, abrogating its antiviral activity. However, IL-7 caused a much more profound stimulatory effect on HIV-1 reverse transcription and integration than IL-2 that required chemokine co-stimulation. Both cytokines barely induced transcription due to low NF-κB induction, favoring the establishment of latent reservoirs. Effect of IL-7 on SAMHD1 phosphorylation was confirmed in IL-7-treated patients (ACTG 5214 study). Dasatinib--a tyrosine-kinase inhibitor--blocked SAMHD1 phosphorylation induced by IL-2 and IL-7 and restored HIV-1 restriction. We propose that γc-cytokines play a major role in the reservoir establishment not only by driving homeostatic proliferation but also by increasing susceptibility of CD4+ lymphocytes to HIV-1 infection through SAMHD1 inactivation.The authors thank the patients for their participation in the study. We are indebted to Dr. Irini Sereti (NIAID, NIH), Amanda Zadzilka (Frontier Science and Technology Research Foundation), and Eugenia Aga (Harvard School of Public Health) for assistance with A5214 data and samples. We greatly appreciate the secretarial assistance of Mrs. Olga Palao. We thank the Centro Regional de Transfusión for supplying the buffy coats. We also thank Drs. Javier Martínez-Picado and Maria del Carmen Puertas (IrsiCaixa Institute) for their help with the standardization of qPCR in our laboratory. From Bristol-Myers Squibb, we especially acknowledge Drs. Stephen Mason and Carey Hwang for helpful discussion about this manuscript and Drs. Fred Asare and Frank Lee for kindly providing us with dasatinib. This research was supported by the Spanish Ministry of Economy and Competitiveness (SAF2010-18388, SAF2013-44677-R, and FIS PI12/00506), the SPANISH AIDS Research Network RD12/0017/0015 that is included in the Spanish I+D+I Plan and is co-financed by ISCIII-Subdirección General de Evaluación and European Funding for Regional Development (FEDER), Bristol-Myers Squibb (BMS AI471-041), joined program of the Agence nationale de recherches sur le sida et les hépatites virales (ANRS 2014-2), and the European FP7-HEALTH project HIT HIDDEN HIV. The work of E.M. is supported by Instituto de Salud Carlos III (MPY 1371/12). The work of B.D. is supported by the European FP7-HEALTH project HIT HIDDEN HIV. The ACTG study A5214 was supported by the NIH (AI 069501).S