Linear Prediction Approaches to Compensation of Missing Measurements in Kalman Filtering

Kalman filter relies heavily on perfect knowledge of sensor readings, used to compute the minimum mean square error estimate of the system state. However in reality, unavailability of output data might occur due to factors including sensor faults and failures, confined memory spaces of buffer registers and congestion of communication channels. Therefore investigations on the effectiveness of Kalman filtering in the case of imperfect data have, since the last decade, been an interesting yet challenging research topic. The prevailed methodology employed in the state estimation for imperfect data is the open loop estimation wherein the measurement update step is skipped during data loss time. This method has several shortcomings such as high divergence rate, not regaining its steady states after the data is resumed, etc. This thesis proposes a novel approach, which is found efficient for both stationary and nonstationary processes, for the above scenario, based on linear prediction schemes. Utilising the concept of linear prediction, the missing data (output signal) is reconstructed through modified linear prediction schemes. This signal is then employed in Kalman filtering at the measurement update step. To reduce the computational cost in the large matrix inversions, a modified Levinson-Durbin algorithm is employed. It is shown that the proposed scheme offers promising results in the event of loss of observations and exhibits the general properties of conventional Kalman filters. To demonstrate the effectiveness of the proposed scheme, a rigid body spacecraft case study subject to measurement loss has been considered

A bioactive cycloartane triterpene from <i>Garcinia hombroniana</i>

<p>The dichloromethane bark extract of <i>Garcinia hombroniana</i> yielded one new cycloartane triterpene; (22<i>Z</i>,24<i>E</i>)-3<i>β</i>-hydroxycycloart-14,22,24-trien-26-oic acid (<b>1</b>) together with five known compounds: garcihombronane G (<b>2</b>), garcihombronane J (<b>3</b>), 3<i>β</i> acetoxy-9<i>α</i>-hydroxy-17,14-friedolanostan-14,24-dien-26-oic acid (<b>4</b>), (22<i>Z</i>, 24<i>E</i>)-3<i>β</i>, 9<i>α</i>-dihydroxy-17,14-friedolanostan-14,22,24-trien-26-oic acid (<b>5</b>) and 3<i>β</i>, 23<i>α</i>-dihydroxy-17,14-friedolanostan-8,14,24-trien-26-oic acid (<b>6</b>). Their structures were established by the spectral techniques of NMR and ESI-MS. These compounds together with some previously isolated compounds; garcihombronane B (<b>7</b>), garcihombronane D (<b>8</b>) 2,3’,4,5’-tetrahydroxy-6-methoxybenzophenone (<b>9</b>), volkensiflavone (<b>10</b>), 4’’-<i>O</i>-methyll-volkensiflavone (<b>11</b>), volkensiflavone-7-<i>O</i>-glucopyranoside (<b>12</b>), volkensiflavone-7-<i>O</i>-rhamnopyranoside (<b>13</b>), Morelloflavone (<b>14</b>), 3’’-<i>O</i>-methyl-morelloflavone (<b>15</b>) and morelloflavone-7-<i>O</i>-glucopyranoside (<b>16</b>) were evaluated for cholinesterase enzymes inhibitory activities using acetylcholinesterase and butyrylcholinesterase. In these activities, compounds <b>1–9</b> showed good dual inhibition on both the enzymes while compounds <b>10–16</b> did not reasonably contribute to both the cholinesterases inhibitory effects.</p

Route of calcium entry differentially regulates PspA induced PD-L1 expression.

<p>Mouse bone marrow derived DCs were incubated with bio-pharmacological inhibitors to indicated molecules for 1h followed by stimulation with 15 μg/ml PspA for 24h. PD-L1 levels were monitored by flow cytometry. Dotted lines represent unstimulated cells. Thin lines represent cells stimulated with PspA. Bold lines represent cells treated with inhibitors to indicated molecules followed by stimulation with PspA. One of three independent experiments is shown. PD-L1 expression is represented as bar graph indicating fold increase in Relative Mean Fluorescence Intensity (MFI) for various groups. Bars represent mean ± SD of three independent experiments. For Panel B, mouse bone marrow derived DCs were incubated in the presence or absence of TMB-8 or EGTA for 1h followed by stimulations with 15 μg/ml PspA for 24h. Cells were incubated with phycoerythrin conjugated anti-mouse PD-L1 antibody. Merged images with DAPI (blue) and PD-L1 (red) staining are depicted. For Panel C total RNA was isolated from cells stimulated as indicated and PD-L1 transcript levels were measured by semi-quantitative RT-PCR. One of three independent experiments is shown.</p

Anti-SP0845^23–350 antibodies are functional as assessed by blood bactericidal assay.

<p>Pneumococcal cells (100–150 cfu) from strains TIGR4 (A), ATCC 6303 (B), ATCC 6314 (C) and D39 (D) were pretreated with either preimmune (PI, dark bar) or mouse anti-SP0845^23–350 hyperimmune (HI, grey bar) sera and incubated with peripheral blood from CBA/N mice at 37°C for 3 h with rotation. The surviving bacteria were enumerated by plating serial dilutions on TSA plates in duplicate. The data represents the mean ± SD values. The data was analyzed using Student's unpaired t test.</p

Purification and immunoblotting of SP0845.

<p>SP0845^23–350 was expressed in <i>E</i>. <i>coli</i> and purified using Ni-NTA affinity and DEAE sepharose anion-exchange chromatography. The purified recombinant protein was resolved on 12% SDS-PAG and stained with Coomassie brilliant blue R250 (A) or transferred to nitrocellulose membrane and visualized using anti-histidine affinity tag antibody followed by horseradish peroxidase conjugated goat anti-mouse Ig as secondary antibody and 3, 3' diaminobenzidine/ H₂O₂ as substrate (B). The molecular mass marker (in kDa) is shown on the left of the panels.</p

<i>S</i>. <i>pneumoniae</i> upregulates PD-L1 on DCs.

<p>For Panel A, mouse bone marrow derived DCs were infected with wild typ<i>e S</i>. <i>pneumoniae</i> strain D39, R6 or JY2008 (<i>see</i><a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0133601#sec002" target="_blank">Materials and Methods</a>) and PD-L1 levels were monitored by flow cytometry. Thin lines represent uninfected cells while bold lines represent cells incubated with indicated strain of <i>S</i>. <i>pneumoniae</i>. For Panel B, DCs were incubated with either TMB-8 or EGTA for 1h followed by incubation with D39 and PD-L1 levels were monitored by flow cytometry. Dotted line represents uninfected cells. Thin lines represent cells incubated with D39 while thick lines represent cells treated with indicated inhibitors followed by incubation with D39. Data from one of two independent experiments are shown. Bars in Panel C and D represent fold increase in Relative Mean Fluorescence Intensity (MFI; mean ± SD) for various groups. ns represents non-significant differences between compared groups.</p

SP0845 is accessible to antibodies.

<p>(A) Mid-logarithmic phase TIGR4 cells were incubated with mouse anti-SP0845^23–350 or mouse preimmune sera (negative control) followed by incubation with F(ab')₂ fragment phycoerythrin-conjugated goat anti-mouse IgG + IgM (H + L) antibody. The processed samples were observed under a fluorescence microscope. The fluorescent images obtained with anti-SP0845^23–350 and preimmune sera are in the upper left and right panels, respectively. The lower panels show the corresponding phase contrast images (magnification = 1000X). Surface expression of SP0845 was studied for pneumococcal strains TIGR4 (B), ATCC 6303 (C), ATCC 6314 (D), D39 (E) and R36A (F). Pneumococcal cells were incubated with either preimmune or anti-SP0845^23–350 sera for 1 hr followed by a FITC-conjugated F(ab')₂ fragment goat anti-mouse IgG + IgM (H + L) antibody as secondary antibody. The surface staining was detected by flow cytometry.</p

SP0845-specific serum antibody endpoint titers.

<p>^<i>a</i> The SP0845-specific antibody endpoint titer was determined by ELISA after pooling serum from 12 mice immunized subcutaneously with recombinant SP0845. The endpoint titer was determined using two times the optical density obtained for the preimmune sera (diluted 1 in 100) as the cut off value.</p><p>SP0845-specific serum antibody endpoint titers.</p

Immunoreactive pneumococcal proteins identified in this study by mass spectrometry.

<p>^<i>a</i> For spot numbers 1 through 8 refer to <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0118154#pone.0118154.g001" target="_blank">Fig. 1</a>. Spot number 9 and 10 were identified from an independent experiment performed under similar experimental conditions.</p><p>^<i>b</i> Gene and protein annotations are according to the genome sequence of <i>S</i>. <i>pneumoniae</i> TIGR4 (GenBank accession no. AE005672). ORF, open reading frame.</p><p>^<i>c</i> Percentage of total protein sequence covered by the experimentally detected peptides.</p><p>^<i>d</i> Identification probability of the fragment match.</p><p>^<i>e</i> MASCOT scores greater than the cut-off value were considered statistically significant (<i>p</i> ≤ 0.05).</p><p>Immunoreactive pneumococcal proteins identified in this study by mass spectrometry.</p

PspA induces PD-L1 expression in a MyD88 dependent pathway.

<p>Mouse bone marrow derived DCs were transfected with siRNAs against indicated molecules for 36h followed by stimulations with 1 μg/ml Pam₃Csk₄ and 15 μg/ml PspA for 24h. PD-L1 levels were monitored by flow cytometry. Dotted line represents unstimulated cells transfected with control siRNAs. Thin lines represent cells transfected with control siRNAs followed by stimulations with 1 μg/ml Pam₃Csk₄ and 15 μg/ml PspA. Bold lines represent cells transfected with specific siRNAs to indicated molecules followed by stimulations with 1 μg/ml Pam₃Csk₄ and 15 μg/ml PspA. Data from one of three independent experiments are shown. In Panel B, PD-L1 expression is represented as bars indicating fold increase in Relative Mean Fluorescence Intensity (MFI) for various groups. Bars represent mean ± S.D. of three independent experiments.</p