Dual Sequence Research Articles

Novel export control of a Legionella Dot/Icm substrate is mediated by dual, independent signal sequences.

The Legionella pneumophila Dot/Icm T4SS injects ∼ 300 protein effector proteins into host cells. Dot/Icm substrates have been proposed to contain a carboxy-terminal signal sequence that is necessary and sufficient for export, although both traits have been demonstrated for only a small fraction of these proteins. In this study, we discovered that export of the substrate SidJ is mediated by dual signal sequences that include a conventional C-terminal domain and a novel internal motif. The C-terminal signal sequence facilitates secretion of SidJ into host cells at early points of infection, whereas the internal signal sequence mediates secretion at later time points. Interestingly, only the internal signal sequence is necessary for complementation of the intracellular growth defect of a ΔsidJ mutant. Although this is the first report of a Dot/Icm substrate being secreted by an internal signal sequence, many other substrates may be exported in a similar manner. In addition, efficient translocation of SidJ is dependent on the chaperone-like type IV adaptors IcmS/IcmW. Five IcmS/IcmW binding domains that are distinct from both signal sequences were elucidated and, interestingly, only secretion mediated by the internal signal sequence requires IcmS/IcmW. Thus, Legionella employs multiple sophisticated molecular mechanisms to regulate the export of SidJ.

Hypercube and tetrahedron algebra

Let D be an integer at least 3 and let H(D, 2) denote the hypercube. It is known that H(D, 2) is a Q-polynomial distance-regular graph with diameter D, and its eigenvalue sequence and its dual eigenvalue sequence are all {D − 2i}i=0D, Suppose that ⊠ denotes the tetrahedron algebra. In this paper, the authors display an action of ⊠ on the standard module V of H(D, 2). To describe this action, the authors define six matrices in MatX(ℂ), called $$A,A^* ,B,B^* ,K,K^* .$$ Moreover, for each matrix above, the authors compute the transpose and then compute the transpose of each generator of ⊠ on V.

Zonal T2* and T1Gd assessment of knee joint cartilage in various histological grades of cartilage degeneration: an observational in vitro study

ObjectivesAccurate assessment of cartilage status is increasingly becoming important to clinicians for offering joint preservation surgeries versus joint replacements. The goal of this study was to evaluate the validity of...

Two-Orthogonal Polynomial Sequences as Eigenfunctions of a Third-Order Differential Operator

This paper presents functional identities fulfilled by the forms of the dual sequence of polynomial eigenfunctions of certain differential operators, belonging to the class of the two-orthogonal polynomial sequences. For a specific third-order lowering operator, the correspondent matrix differential identity is deduced, proving that the resultant polynomial sequence is a classical polynomial sequence in the Hahn’s sense. As an example, the vectorial relation fulfilled by the tuple of functionals (u 0, u 1) of a two-orthogonal polynomial sequences analogous to the classical Laguerre polynomials is given, treated in a work of Ben Cheikh and Douak.

Preparation of click thiol-ene/thiol-epoxy thermosets by controlled photo/thermal dual curing sequence

A new dual curing procedure based in the combination of UV-induced thiol-ene and thermal thiol-epoxy reactions has been established by the use of a latent amine precursor that can catalyze the thermal process.

Circulating Current Suppressing Strategy for MMC-HVDC Based on Nonideal Proportional Resonant Controllers Under Unbalanced Grid Conditions

Modular multilevel converter (MMC) is considered as a promising topology for voltage-source converter (VSC) high-voltage, direct current (HVDC) applications. This paper presents a new control strategy for MMC-HVDC under unbalanced grid conditions. First, a new inner loop current control strategy based on nonideal proportional resonant (PR) controllers in stationary αβ frame is designed, which is more concise compared to the existing dual sequence current control scheme. Second, an analytical expression for circulating current is obtained which shows that the circulating currents will be asymmetric under unbalanced grid conditions and can be decomposed into positive-, negative-, and zero-sequence component. In order to suppress all these components, a new circulating current suppressing strategy is analyzed and designed also based on nonideal PR controllers. Application of nonideal PR controllers makes the control system well adapt to the fluctuation of grid frequency. The effectiveness of the proposed control strategy is verified through a simulation case of a 251-level MMC-HVDC transmission system using real-time digital simulator.

Hybrid PET/MR imaging: an algorithm to reduce metal artifacts from dental implants in Dixon-based attenuation map generation using a multiacquisition variable-resonance image combination sequence.

It was the aim of this study to implement an algorithm modifying Dixon-based MR imaging datasets for attenuation correction in hybrid PET/MR imaging with a multiacquisition variable resonance image combination (MAVRIC) sequence to reduce metal artifacts. After ethics approval, in 8 oncologic patients with dental implants data were acquired in a trimodality setup with PET/CT and MR imaging. The protocol included a whole-body 3-dimensional dual gradient-echo sequence (Dixon) used for MR imaging-based PET attenuation correction and a high-resolution MAVRIC sequence, applied in the oral area compromised by dental implants. An algorithm was implemented correcting the Dixon-based μ maps using the MAVRIC in areas of Dixon signal voids. The artifact size of the corrected μ maps was compared with the uncorrected MR imaging μ maps. The algorithm was robust in all patients. There was a significant reduction in mean artifact size of 70.5% between uncorrected and corrected μ maps from 697 ± 589 mm(2) to 202 ± 119 mm(2) (P = 0.016). The proposed algorithm could improve MR imaging-based attenuation correction in critical areas, when standard attenuation correction is hampered by metal artifacts, using a MAVRIC.

Potential of Gd-EOB-DTPA-enhanced MR imaging for evaluation of bile duct ligation-induced liver injury in rabbits.

The aim of this study was to evaluate the potential of gadoxetic acid (Gd-EOB-DTPA)-enhanced MRI for assessment of bile duct ligation (BDL)-induced chelostatic liver injury in an animal model by T1 relaxation time measurements and first-pass perfusion analyses. Twenty-four rabbits were classified into three groups as follows: control group (N group), n = 8; BDL group studied on the 5th postoperative day (BDL-5d group), n = 8; BDL group studied on the 14th postoperative day (BDL-14d group), n = 8. A dual flip angle three-dimensional gradient echo sequence with volumetric interpolated breath-hold examination was performed before and at 20 min [hepatobiliary phase (HBP)] after Gd-EOB-DTPA administration. Besides, early dynamic contrast-enhanced MRI was performed for 4.32 min with a temporal resolution of 2.2 s. T1 relaxation times of liver parenchyma were measured and perfusion parameters were calculated. Dilatation of intra-hepatic bile duct was found only in the BDL-14d group. HBP T1 relaxation times of the BDL-5d and BDL-14d groups were significantly prolonged (p < 0.001) and the enhancement slope percentage of BDL-5d and BDL-14d groups were significantly lowered in comparison with that of the N group (p < 0.001). There were no differences between the BDL-5d group and the BDL-14d group for HBP T1 relaxation times and the enhancement slope percentage (p > 0.05). Area under the receiver operating characteristic curve of HBP T1 relaxation time and the enhancement slope percentage for the selection of chelostatic liver were 0.98 and 0.92 for the BDL-5d group, and 0.96 and 0.98 for the BDL-14d group, respectively. HBP T1 relaxation time measurement in combination with first-pass enhancement slope percentage withhold promise to assess extrahepatic chelostatic liver injury.

A note on Fejér-monotone sequences in product spaces and its applications to the dual convergence of augmented Lagrangian methods

In a recent Math. Program. paper, Eckstein and Silva proposed a new error criterion for the approximate solutions of augmented Lagrangian subproblems. Based on a saddle-point formulation of the primal and dual problems, they proved that dual sequences generated by augmented Lagrangians under this error criterion are bounded and that their limit points are dual solutions. In this note, we prove a new result about the convergence of Fejer-monotone sequences in product spaces (which seems to be interesting by itself) and, as a consequence, we obtain the full convergence of the dual sequence generated by augmented Lagrangians under Eckstein and Silva's criterion.

Angle $$R$$ R

We generalize the characterizations of the direct sum decomposition of a Hilbert space in terms of the angle $$R$$ and, using this result, present another proof of the equality concerning the norms of the projections $$P$$ and $$I-P$$ . As an application to abstract frame theory, we show that the ranges of the analysis operators of oblique dual frame sequences satisfy the the angle condition.

„Poetyckie Dyptyki” w poezji ks. Janusza St. Pasierba

‘Poetic diptychs’ in Fr. Janusz St. Pasierb’s poetry ‘Poetic diptychs’ distinguish themselves from a group o Fr. Janusz St. Pasierb’s poems inspired by the art of painting. These dual poems refer to the same branches of art (painting, sculpture, architecture) as a general rule. The dual sequences are put in the volumes next to each other. Apart from the subject matter they are linked by similar characteristics and nearly identical formulation of their titles. References to art are a pretext to ponder upon in a theological, existential and metapoetic manner. Dual nature of the voice points to multiple ways in which the visible can be interpreted. It also shows the necessity of precise defining of any meanings and presents the scope of difficulties related to inexpressibility.

Underground localization using dual magnetic field sequence measurement and pose graph SLAM for directional drilling

With the development of unconventional gas, the technology of directional drilling has become more advanced. Underground localization is the key technique of directional drilling for real-time path following and system control. However, there are problems such as vibration, disconnection with external infrastructure, and magnetic field distortion. Conventional methods cannot solve these problems in real time or in various environments. In this paper, a novel underground localization algorithm using a re-measurement of the sequence of the magnetic field and pose graph SLAM (simultaneous localization and mapping) is introduced. The proposed algorithm exploits the property of the drilling system that the body passes through the previous pass. By comparing the recorded measurement from one magnetic sensor and the current re-measurement from another magnetic sensor, the proposed algorithm predicts the pose of the drilling system. The performance of the algorithm is validated through simulations and experiments.

Identification of some Piper crude drugs based on Fourier transform infrared spectrometry

The common peak ratio and variant peak ratio were calculated by FTIR spectroscopy of seven medicinal plants of Piper. The dual index sequence of common peak ratio and variant peak ratio was established, which showed the sibship of the medicinal plants. The common peak ratio of Piper kadsura (Choisy) Ohwi, Piper wallichii (Miq.) Hand.-Mazz. Piper laetispicum (C. DC.) was greater than 77%, and the variant peak ratio was less than 30%. The results showed the near sibship between the three drugs. The common peak ratio of Piper kadsura (Choisy) Ohwi, Piper nigrum L. and Piper boehmeriae folium Wall (Miq.) C. DC. Var. tonkinense (C. DC.) was about 61% which showed the farther sibship. The common peak ratio of Piper kadsura (Choisy) Ohwi and Piper betle (Linn.) was only 44%, which showed the farthest sibship. Piper kadsura (choisy) Ohwi and its adulterants, such as Piper wallichii (Miq.) Hand. -Mazz., Piper boehmeriaefolium Wall (Miq.) C. DC. Var. tonkinense C. DC. , Piper laetispicum C. DC., Piper nigrum L., could be identified by comparing their second order derivative IR spectrum of the samples. FTIR technique is a non-destructive analysis method which provides information of functional group, type and hydrogen bond without complex pretreatment procedures such as extraction and separatioin. FTIR method has some characteristics such as rapid and simple analysis procedure, good reproducibility, non-destructive testing, few amount of required sample and low cost and is environment-friendly. The method solved the problems of limit in resource of Piper kadsura (Choisy) Ohwi, many fakes and difficulties in identification, and brought the security for the clinical medication. FTIR provides a new method for identification of Piper kadsura (choisy) Ohwi and its fakes and meets the requirement for comprehensive analy sis and global analysis of traditional Chinese medicine.

G-Riesz dual sequences for g-Bessel sequences

Duality principles in Gabor theory play a fundamental role for analyzing Gabor systems. In this paper, we obtain some results of duality principles for g-frames. Let {γj ∈ B(H, Hj) : j ∈ ℕ} and {ηi ∈ B(H, Hi) : i ∈ ℕ} be g-orthonormal bases for H with respect to {Hi}i∈ℕ. For a g-Bessel sequence Λ = {Λi ∈ B(H, Hi) : i ∈ ℕ}, we define [Formula: see text]. Then we describe some properties of the sequence [Formula: see text]. We also characterize the sequence [Formula: see text] when Ψ = {Ψi ∈ B(H, Hi) : i ∈ ℕ} is a dual g-frame of {Λi}i∈ℕ.

Delayed gadolinium-enhanced MRI of the fibrocartilage disc of the temporomandibular joint – a feasibility study

ObjectiveTo 1) test the feasibility of delayed Gadolinium-Enhanced Magnetic Resonance Imaging of Cartilage (dGEMRIC) at 3 T in the temporomandibular joint (TMJ) and 2) to determine the optimal delay for measurements of the TMJ disc after i.v. contrast agent (CA) administration. DesignMRI of the right and left TMJ of six asymptomatic volunteers was performed at 3 T using a dedicated coil. 2D inversion recovery (2D-IR) sequences were performed at 4 time points covering 120minutes and 3D gradient-echo (3D GRE) dual flip-angle sequences were performed at 14 time points covering 130minutes after the administration of 0.2mmol/kg of Gd-diethylenetriamine pentaacetic acid ion (Gd-DTPA)2-, i.e., 0.4mL of Magnevist™ per kg body weight. Pair-wise tests were used to assess differences between pre-and post-contrast T1 values. Results2D-IR sequences showed a statistically significant drop (p<0.001) in T1 values after i.v. CA administration. The T1 drop of 50% was reached 60minutes after bolus injection in the TMJ disc. The 3D GRE dual flip-angle sequences confirmed these results and show plateau of T1 after 60minutes. ConclusionsT1(Gd) maps calculated from dGEMRIC data allow in vivo assessment of the fibrocartilage disc of the TMJ. The recommended measurement time for dGEMRIC in the TMJ after i.v. CA administration is from 60 to 120minutes.

Exploitation of stem-loop DNA as a dual-input gene sensing platform: extension to subtyping of influenza A viruses

We herein report a strategy coupling DNA structural switches with an enzymatic cascade reaction for the specific and sensitive identification of dual-target nucleic acids toward the subtyping of influenza viruses. During the recognition process, a hairpin DNA was hybridized with dual target sequences at its stem and a partial section of the loop region to form duplexes. The concurrent presence of dual targets was reported as an explicit output interpreted by the enzymatic cascade reaction. The conformational changes of the hairpin–targets duplex and the reaction kinetics upon dual hybridization were explored using a molecular beacon in conjunction with a FRET approach. The unzipping event was found to be predominated by a strand displacement which occurred in the stem of hairpins, and its rate constants were calculated as 3.1 × 103 M−1 s−1 (gHA alone) and 5.8 × 103 M−1 s−1 (gHA & gNA). This strategy was further demonstrated on a multi-well electrochemical chip for the subtyping of influenza viruses (e.g., A/duck/Taiwan/DV30-2/2005 (H5N2)) through the simultaneous identification of genes encoding hemagglutinin (HA) and neuraminidase (NA). Moreover, this genosensor featured an effective capability to analyze unpurified amplicons generated from the genuine viral genome, as it could unambiguously discriminate between H5N2 and non-H5N2 viruses. To the best of our knowledge, this study is the first to demonstrate the leveraging of an individual hairpin DNA across concurrent analysis of dual target genes. Pursuant to the elegant characterizations with high applicability, extensible flexibility, and powerful utility, this platform holds great promise for use as a sophisticated molecular diagnostics tool against variable influenza viruses.

Weighted subtraction in 3D ultrashort echo time (UTE) imaging for visualization of short T2 tissues of the knee

Ultrashort echo time (UTE) image to directly visualize short T2 tissues requires postprocessing for the suppression of the surrounding long T2 tissues in a clinical magnetic resonance imaging (MRI) scanner. Weighted subtraction of UTE images with an optimal weighting factor could provide high positive contrast with adequate suppression. To demonstrate in-vivo UTE MRI with weighted subtractions of dual echo UTE imaging using a 3 T clinical MRI and to determine the optimal weighting factors through the analyses of signal-to-noise ratios (SNRs) and contrast-to-noise ratios (CNRs). Forty-seven consecutive knee MR including dual echo 3D UTE sequence (TE of 70 µs and 3.82 ms) were reviewed. Seven patients with normal findings in the knee MR were included in the current study. For variably weighted subtraction images, the initial UTE image was rescaled relative to that of the second echo image with weighting factors from 0.1 to 4.0. Thirty-five pairs of the ROI measurements of the UTE image and second long echo images were repeated after 2 weeks. For quantitative assessment, SNR and CNR were measured from the ROIs on the patellar tendon, cartilage, cortical bone, meniscus, and infrapatellar fat pad. Intra-observer agreement was assessed by using both Cohen's Kappa and Bland-Altman approach. The short T2 tissue could be visualized with adequate suppression on the subtraction images. Considering the CNRs and SNRs, the optimal ranges of the weighting factors could be suggested: 0.3 for the tendon, 0.4 for the cortical bone, and 1.0 for the meniscus. The 35 paired measurements showed excellent agreement with statistical significance (P < 0.05). The 3D UTE MRI provides imaging of short T2 tissues which cannot be visualized by conventional MRI. Using weighted subtractions with optimal weighting values, each tissue can be optimally depicted by overcoming the reduced T2 contrast.

Treatment of Large Knee Osteochondral Lesions With a Biomimetic Scaffold

Background: Osteochondral knee lesions represent a challenging condition encountered by orthopaedic surgeons. A variety of methods have been developed to repair articular cartilage defects. However, these techniques are limited by donor site morbidity or by the requirement for a staged procedure. Purpose: To assess the effectiveness of a biomimetic osteochondral scaffold for the treatment of large osteochondral knee lesions. Study Design: Case series; Level of evidence, 4. Methods: From 2009 to 2011, a total of 49 patients affected by isolated large osteochondral knee lesions (mean [± SD] size, 4.35 ± 1.26 cm2) were treated with the biomimetic scaffold. Patients were evaluated using the International Knee Documentation Committee (IKDC), Tegner, and visual analog scale (VAS) pain scores, as well as magnetic resonance imaging (MRI) up to 3-year follow-up. The MOCART (magnetic resonance observation of cartilage repair tissue) score was performed to analyze different variables. Biopsies were carried out in 5 patients. Four of the 5 second-look arthroscopies and biopsies were performed on patients with failed results because of ethical issues. Results: The mean IKDC subjective score increased significantly from 45.45 ± 19.29 preoperatively to 70.86 ± 18.08 at 1-year follow-up and to 75.42 ± 19.31 at 2-year follow-up (P < .001). The IKDC objective score changed from 50% normal and nearly normal knees before treatment to 89.79% at the 2-year follow-up. There was a statistically significant improvement (P < .005) in VAS score from the preoperative level (6.69 ± 1.88) to the 2-year follow-up (1.96 ± 2.47). Tegner scores increased (P < .001) from the preoperative value (2.20 ± 0.67) to the 2-year follow-up (4.9 ± 1.73) without achieving preinjury level. A correlation was found between the IKDC subjective score and age (P < .001, r = −0.497, ρ = −0.502). Patients affected by osteochondritis dissecans (OCD) achieved a statistically significantly better outcome (P < .05). A subgroup of 19 competitive athletes showed a statistically significantly improvement (P < .001) in the subjective IKDC (86.5 ± 13.2) compared with the nonathletic subpopulation (69.03 ± 19.41) at the 2-year follow-up. The MRI findings of 30 patients were available at 2-year follow-up: 70% showed complete filling of the lesion, 63.3% had an intact articular surface, and 86% had mild or no effusion. In all cases, in dual T2-weighted fast spin echo sequence, the repair tissue showed a hyperintensive signal with respect to the surrounding subchondral bone; however, no edema was observed. Conclusion: The study findings indicate that the biomimetic scaffold that was investigated is an off-the-shelf, cell-free, and cost-effective implant that can regenerate either cartilage or subchondral bone. The scaffold allows a 1-step surgical procedure that can be used for osteochondral lesions, OCD, and in some cases osteonecrosis.

T2 Mapping: how many echoes does it require?

Purpose: The purpose of this study is to determine the difference between T2 relaxation times obtained from varying numbers of echoes. The results from phantoms and cartilage are compared between the varying number of echoes. Methods: Phantoms comprised of varying concentrations of copper sulfate were placed on the anterior of the knee, just distal to the patella and offset laterally. The knee and phantom were then imagedd using a dual echo sequence, as well as multiple-echoe sequences. All imaging was performed on a GE Signa HDx 1.5T. Cartilage on one slice of the series was then identified, as well as the phantoms. T2 maps were calculated from the dual-echo using a least-squares linear fit to the natural log of the signal values. For the multiple-echo sequence, two methods were used - one where all the echoes were used in the estimate of T2, and one where the first echo was dropped. For very short T2 relaxation times (less than 2× the first echo time), all echoes were used for both cases. The mean and standard deviation of the T2 relaxation times in each of the regions was then calculated. Results: Results are shown in the table below. The image shows an example of the T2 relaxation time for the cartilage calculated using the multiple-echo sequence.Tabled 1Calculated T2 Relaxation TimesDual-EchoDropped First EchoAll EchoesMeanStdDevMeanStdDevMeanStdDevPhantom 131.213.017.06.116.93.8Phantom 241.94.844.29.339.14.0Phantom 391.47.991.121.577.38.1Phantom 4240.375.7159.950.2131.020.4Cartilage50.319.437.517.436.213.9 Open table in a new tab Conclusions: Stimulated echoes play a large part in the variability of T2 measurements obtained from multiple-echo sequences. The effect of stimulated echoes can be mitigated in the pulse sequence by applying crusher gradients (GE’s Cartigram sequence), or by ignoring the first echo in sequences that do not attempt to reduce the stimulated echoes. The disadvantage of ignoring the first echo is that it contains the most signal, and tissue with relatively short T2 relaxation times will not be estimated accurately. Using a dual-echo sequence, with a second echo that is not a multiple of the first echo, also eliminates the effect of stimulated echoes, but provides an estimate of T2 which is much more susceptible to noise. The values estimated for T2 are over-estimated for lower values of T2 because the second echo will hit the noise floor. The values are also over-estimated for areas of lower signal intensity for the same reason. This explains why the phantom values are very close between the multiple-echo sequence and the dual-echo sequence in the range of 40–90 ms, but the cartilage values in the same range are over-estimated by the dual-echo sequence.

Bone area demonstrates change in 3 months in a very small OA cohort

Purpose: In order to stimulate the production of novel drugs and treatments of osteoarthritis (OA), responsive measures of structural progression are required. Ideally, proof of concept studies would take no longer than 6 months and require small cohorts. Changes in bone shape and size show promise as a potential progression biomarker, which can be accurately measured using modern magnetic resonance imaging (MRI) analysis. This post-hoc study analysed the changes in bone area of knee OA, using a convenience cohort selected for high risk of OA progression, with MR images acquired at 3 months and 6 months. A previous study using this cohort demonstrated no significant change in cartilage thickness in the medial femur or tibia at either time point Methods: 27 females with knee pain, a body mass index (BMI) ≥ 25 kg/m2, radiographic evidence of medial compartment OA and varus mal-alignment, were recruited in a multi-centre, non-randomized, observational cohort study at four sites in the US. MR images were acquired using 3T Siemens systems, using the Dual Echo Steady State water excitation acquisition sequence. Images were automatically segmented using active appearance models (AAMs) of the femur. The primary endpoint for this study was change of the area of subchondral bone in the medial femorotibial region (MF), with a secondary endpoint of change in the lateral femur (LF) area. Repeatability of the AAM method was assessed using double baseline images, using root-mean-square coefficients of variation (CoV), and smallest detectable difference (SDD), defined as the 95% limits of agreement; the mean of the differences ± 1.96 standard deviations. Change was assessed using a paired t-test of the change at each time point, compared with the average of the 2 baseline images. Results: Repeatability for the MF region was 0.39% (CoV) and 1.1% (SDD), and for the LF region was 0.66% (CoV) and 1.9% (SDD). Change in bone area of the MF region (the primary endpoint) was statistically significant at both 3 months and 6 months, with the 6 month change being almost twice that seen at 3 months. At 3 months, mean change was 0.29% [95% confidence interval (CI) (0.57%, 0.02%)], and at 6 months 0.58% [0.30%, 0.85]. In the LF region, the changes were not significant at 3 months 0.24% [−0.81%, 0.66], but became significant at 6 months 0.51% [0.21%, 0.81] (see Fig. 1 for comparison with previous cartilage study). Conclusions: In this small cohort selected for high risk of OA progression, bone area changed in an approximately linear manner at 3 and 6 months from baseline. Bone area shows promise as a highly sensitive biomarker of OA progression, detecting change when current imaging outcomes are unable to do so, and provides a potential tool for small short-duration proof of concept studies.