Error correction for deep space network teletype circuits

Error detection codes and correction devices for Deep Space Network /DSN/ teletypewriter system

Efficient indexing of necklaces and irreducible polynomials over finite fields

We study the problem of indexing irreducible polynomials over finite fields, and give the first efficient algorithm for this problem. Specifically, we show the existence of poly(n, log q)-size circuits that compute a bijection between {1, ... , |S|} and the set S of all irreducible, monic, univariate polynomials of degree n over a finite field F_q. This has applications in pseudorandomness, and answers an open question of Alon, Goldreich, H{\aa}stad and Peralta[AGHP]. Our approach uses a connection between irreducible polynomials and necklaces ( equivalence classes of strings under cyclic rotation). Along the way, we give the first efficient algorithm for indexing necklaces of a given length over a given alphabet, which may be of independent interest

Minimal Niven numbers

Define a(k,q) to be the smallest positive multiple of k such that the sum of its digits in base q is equal to k. The asymptotic behavior, lower and upper bound estimates of a(k,q) are investigated. A characterization of the minimality condition is also considered.Comment: 28 pages, 2 figure

Some Results on Sprout

Abstract. Sprout is a lightweight stream cipher proposed by Armknecht and Mikhalev at FSE 2015. It has a Grain-like structure with two State Registers of size 40 bits each, which is exactly half the state size of Grain v1. In spite of this, the cipher does not appear to lose in security against generic Time-Memory-Data Tradeoff attacks due to the novelty of its design. In this paper, we first present improved results on Key Recovery with partial knowledge of the internal state. We show that if 50 of the 80 bits of the internal state are guessed then the remaining bits along with the Secret Key can be found in a reasonable time using a SAT solver. Thereafter we show that it is possible to perform a distinguishing attack on the full Sprout stream cipher in the multiple IV setting using around 240 randomly chosen IVs on an average. The attack requires around 248 bits of memory. Thereafter we will show that for every Secret Key, there exist around 230 IVs for which the LFSR used in Sprout enters the all zero state during the Keystream generating phase. Using this observation, we will first show that it is possible to enumerate Key-IV pairs that produce keystream bits with period as small as 80. We will then outline a simple Key recovery attack that takes time equivalent to 266.7 encryptions with negligible memory requirement. This although is not the best attack reported against this cipher in terms of the Time complexity, it is the best in terms of the memory required to perform the attack

Antipersistent binary time series

Completely antipersistent binary time series are sequences in which every time that an $N$-bit string $\mu$ appears, the sequence is continued with a different bit than at the last occurrence of $\mu$. This dynamics is phrased in terms of a walk on a DeBruijn graph, and properties of transients and cycles are studied. The predictability of the generated time series for an observer who sees a longer or shorter time window is investigated also for sequences that are not completely antipersistent.Comment: 6 pages, 6 figure

Injection-seeded internal-reflection-mode p-Ge laser exceeds 10 W peak terahertz power

Injection seeding of a large active p-Ge laser crystal operating on total internal reflection modes is demonstrated with peak output power at the level of 40 W in the 1.5-4.2 THz spectral range. The improvement over traditional 1 W axial mode p-Ge lasers is due both to spatially and temporally more efficient use of the available population inversion

Pulse separation control for mode-locked far-infrared p-Ge lasers

Active mode locking of the far-infrared p-Ge laser giving a train of 200 ps pulses is achieved via gain modulation by applying an rf electric field together with an additional bias at one end of the crystal parallel to the Voigt-configured magnetic field. Harmonic mode locking yields a train of pulse pairs with variable time separation from zero to half the roundtrip period, where pulse separation is electrically controlled by the external bias to the rf field

Neutron transmutation doped far-infrared p-Ge laser

A far-infrared p-type germanium laser with active crystal prepared from ultra pure single-crystal Ge by neutron transmutation doping (NTD) is demonstrated. Calculations show that the high uniformity of Ga acceptor distribution achieved by NTD significantly improves average gain. The stronger ionized impurity scattering due to high compensation in NTD Ge is shown to have insignificant negative impact on the gain at the moderate doping concentrations sufficient for laser operation. Experimentally, this first NTD laser is found to have lower current-density lasing threshold than the best of a number of melt-doped laser crystals studied for comparison

A finite characterization of K -matrices in dimensions less than four

The class of real n × n matrices M , known as K -matrices, for which the linear complementarity problem w − Mz = q, w ≥ 0, z ≥ 0, w T z =0 has a solution whenever w − Mz =q, w ≥ 0, z ≥ 0 has a solution is characterized for dimensions n <4. The characterization is finite and ‘practical’. Several necessary conditions, sufficient conditions, and counterexamples pertaining to K -matrices are also given. A finite characterization of completely K -matrices ( K -matrices all of whose principal submatrices are also K -matrices) is proved for dimensions <4.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/47913/1/10107_2005_Article_BF01589438.pd

Fourier transform ion cyclotron resonance mass spectrometric detection of small Ca2+-induced conformational changes in the regulatory domain of human cardiac troponin C

AbstractTroponin C (TnC), a calcium-binding protein of the thin filament of muscle, plays a regulatory role in skeletal and cardiac muscle contraction. NMR reveals a small conformational change in the cardiac regulatory N-terminal domain of TnC (cNTnC) on binding of Ca2+ such that the total exposed hydrophobic surface area increases very slightly from 3090 ± 86 Å2 for apo-cNTnC to 3108 ± 71 Å2 for Ca2+-cNTnC. Here, we show that measurement of solvent accessibility for backbone amide protons by means of solution-phase hydrogen/deuterium (H/D) exchange followed by pepsin digestion, high-performance liquid chromatography, and electrospray ionization high-field (9.4 T) Fourier transform Ion cyclotron resonance mass spectrometry is sufficiently sensitive to detect such small ligand binding-induced conformational changes of that protein. The extent of deuterium incorporation increases significantly on binding of Ca2+ for each of four proteolytic segments derived from pepsin digestion of the apo- and Ca2+-saturated forms of cNTnC. The present results demonstrate that H/D exchange monitored by mass spectrometry can be sufficiently sensitive to detect and identify even very small conformational changes in proteins, and should therefore be especially informative for proteins too large (or too insoluble or otherwise intractable) for NMR analysis