Low-complexity iterative frequency domain decision feedback equalization

Single-carrier transmission with frequency domain equalization (SC-FDE) offers a viable design alternative to the classic orthogonal frequency division multiplexing technique. However, SC-FDE using a linear equalizer may suffer from serious performance deterioration for transmission over severely frequency-selective fading channels. An effective method of solving this problem is to introduce non-linear decision feedback equalization (DFE) to SC-FDE. In this contribution, a low complexity iterative decision feedback equalizer operating in the frequency domain of single-carrier systems is proposed. Based on the minimum mean square error criterion, a simplified parameter estimation method is introduced to calculate the coefficients of the feed-forward and feedback filters, which significantly reduces the implementation complexity of the equalizer. Simulation results show that the performance of the proposed simplified design is similar to the traditional iterative block DFE under various multipath fading channels but it imposes a much lower complexity than the latter

Statistics and decision making as applied to printing conformity assessment

Conformity assessment, a relatively new activity in the printing industry, is an attestation that specified requirements relating to a product or process have been fulfilled. Printing certification bodies assess printing conformity according to sampling, aim points, tolerances, and decision-making rules that are stipulated by printing standards. However, do we know if: sampling is too large or too small; normative requirements are too many or too few; tolerances are set too tightly or too loosely; and the pass/fail criterion is too stringent or too relaxed? Moreover, how do these factors impact the passing probability of a sample, a job, and the database as a whole? To study inter-dependencies of these factors in production variation conformity, this research assumes that the number of jobs to be assessed for printing conformity is very large and that samples selected from a job are random. Statistical theory is used to study the relation between the passing probabilities of a printing job, a single sheet within each job, and each normative requirement. In our theoretical frame, given the tolerance levels of certain normative requirements, we can determine the passing probabilities of the criteria, the passing probability of a single sheet, and the overall passing probability of a printing job. Given the passing probability of a printing job, we can also determine the tolerance level of each normative requirement by reversing the procedure. This research uses a real-life printing dataset and simulation techniques to determine the passing probabilities of a job as a function of sampling, tolerances, and the pass/fail criterion of a job. This research offers two meaningful inferences: (1) the printing standards development community, i.e., ISO/TC 130, needs to be aware that sampling requirements, the number of normative requirements and their associated tolerances, and the pass/fail criteria impact the passing probability of a job; and (2) printers who are seeking printing certification need to know that, although sampling is random, the passing probability of a job ultimately depends on the process calibration and the effectiveness of local process control

Single-scatter channel impulse response model of non-line-of-sight ultraviolet communications

Previous studies on the temporal characteristics of single-scatter transmission in non-line-of-sight (NLOS) ultraviolet communications (UVC) were based on the prolate-spheroidal coordinate system. In this work, a novel single-scatter channel impulse response (CIR) model is proposed in the spherical coordinate system, which is more natural and comprehensible than the prolate-spheroidal coordinate system in practical applications. Additionally, the results of the widely accepted Monte-Carlo (MC)-based channel model of NLOS UVC are provided to verify the proposed single-scatter CIR model. Results indicate that the computational time costed by the proposed single-scatter CIR model is decreased to less than 0.7% of the MC-based one with comparable accuracy in assessing the temporal characteristics of NLOS UVC channels.Comment: 10 pages, 4 figure

Molecular characterization of a mosaic locus in the genome of 'Candidatus Liberibacter asiaticus'

<p>Abstract</p> <p>Background</p> <p>Huanglongbing (HLB) is a highly destructive disease of citrus production worldwide. '<it>Candidatus </it>Liberibacter asiaticus', an unculturable alpha proteobacterium, is a putative pathogen of HLB. Information about the biology and strain diversity of '<it>Ca</it>. L. asiaticus' is currently limited, inhibiting the scope of HLB research and control.</p> <p>Results</p> <p>A genomic region (CLIBASIA_05640 to CLIBASIA_05650) of '<it>Ca</it>. L. asiaticus' showing hyper-sequence variation or locus mosaicism was identified and investigated using 262 bacterial strains (188 from China and 74 from Florida). Based on the characteristic electrophoretic profiles of PCR amplicons generated by a specific primer set, eight electrophoretic types (E-types) were identified, six E-types (A, B, C, D, E, and F) in China and four E-types (A, C, G, and H) in Florida. The '<it>Ca</it>. L. asiaticus' strains from China consisted predominately of E-type A (71.3%) and E-type B (19.7%). In contrast, the '<it>Ca</it>. L. asiaticus' strains from Florida was predominated by E-type G (82.4%). Diversity of '<it>Ca</it>. L. asiaticus' in China was also evidenced. Strains from the high altitude Yunnan Province consisted of five E-types with E-type B being the majority (62.8%), whereas strains from the low altitude coastal Guangdong Province consisted of only two E-types with E-type A as the majority (97.0%). Sequence analyses revealed that variation of DNA amplicons was due to insertion/deletion events at CLIBASIA_05650 and the downstream intergenic region.</p> <p>Conclusions</p> <p>This study demonstrated the genomic mosaicism of '<it>Ca</it>. L. asiaticus' resulted from active DNA insertion/deletion activities. Analyses of strain variation depicted the significant inter- and intra-continent diversity of '<it>Ca</it>. L. asiaticus'.</p

Internalin profiling and multilocus sequence typing suggest four Listeria innocua subgroups with different evolutionary distances from Listeria monocytogenes

<p>Abstract</p> <p>Background</p> <p>Ecological, biochemical and genetic resemblance as well as clear differences of virulence between <it>L. monocytogenes </it>and <it>L. innocua </it>make this bacterial clade attractive as a model to examine evolution of pathogenicity. This study was attempted to examine the population structure of <it>L. innocua </it>and the microevolution in the <it>L. innocua</it>-<it>L. monocytogenes </it>clade via profiling of 37 internalin genes and multilocus sequence typing based on the sequences of 9 unlinked genes <it>gyrB</it>, <it>sigB</it>, <it>dapE</it>, <it>hisJ</it>, <it>ribC</it>, <it>purM</it>, <it>gap</it>, <it>tuf </it>and <it>betL</it>.</p> <p>Results</p> <p><it>L. innocua </it>was genetically monophyletic compared to <it>L. monocytogenes</it>, and comprised four subgroups. Subgroups A and B correlated with internalin types 1 and 3 (except the strain 0063 belonging to subgroup C) and internalin types 2 and 4 respectively. The majority of <it>L. innocua </it>strains belonged to these two subgroups. Subgroup A harbored a whole set of <it>L. monocytogenes</it>-<it>L. innocua </it>common and <it>L. innocua</it>-specific internalin genes, and displayed higher recombination rates than those of subgroup B, including the relative frequency of occurrence of recombination versus mutation (ρ/θ) and the relative effect of recombination versus point mutation (r/m). Subgroup A also exhibited a significantly smaller exterior/interior branch length ratio than expected under the coalescent model, suggesting a recent expansion of its population size. The phylogram based on the analysis with correction for recombination revealed that the time to the most recent common ancestor (TMRCA) of <it>L. innocua </it>subgroups A and B were similar. Additionally, subgroup D, which correlated with internalin type 5, branched off from the other three subgroups. All <it>L. innocua </it>strains lacked seventeen virulence genes found in <it>L. monocytogenes </it>(except for the subgroup D strain L43 harboring <it>inlJ </it>and two subgroup B strains bearing <it>bsh</it>) and were nonpathogenic to mice.</p> <p>Conclusions</p> <p><it>L. innocua </it>represents a young species descending from <it>L. monocytogenes </it>and comprises four subgroups: two major subgroups A and B, and one atypical subgroup D serving as a link between <it>L. monocytogenes </it>and <it>L. innocua </it>in the evolutionary chain. Although subgroups A and B appeared at approximately the same time, subgroup A seems to have experienced a recent expansion of the population size with higher recombination frequency and effect than those of subgroup B, and might represent the possible evolutionary direction towards adaptation to enviroments. The evolutionary history in the <it>L. monocytogenes</it>-<it>L. innocua </it>clade represents a rare example of evolution towards reduced virulence of pathogens.</p

Prolonged mixed phase induced by high pressure in MnRuP

Hexagonally structured MnRuP was studied under high pressure up to 35 GPa from 5 to 300 K using synchrotron X-ray diffraction. We observed that a partial phase transition from hexagonal to orthorhombic symmetry started at 11 GPa. The new and denser orthorhombic phase coexisted with its parent phase for an unusually long pressure range, {\Delta}P ~ 50 GPa. We attribute this structural transformation to a magnetic origin, where a decisive criterion for the boundary of the mixed phase lays in the different distances between the Mn-Mn atoms. In addition, our theoretical study shows that the orthorhombic phase of MnRuP remains steady even at very high pressures up to ~ 250 GPa, when it should transform to a new tetragonal phase.Comment: 15 pages, 5 figures, supplementary materia

Transient hypercapnia reveals an underlying cerebrovascular pathology in a murine model for HIV-1 associated neuroinflammation: role of NO-cGMP signaling and normalization by inhibition of cyclic nucleotide phosphodiesterase-5

Cerebral blood flow (CBF) is known to be dysregulated in persons with human immunodeficiency virus 1 (HIV-1), for uncertain reasons. This is an important issue because impaired vasoreactivity has been associated with increased risk of ischemic stroke, elevated overall cardiovascular risk and cognitive impairment