Acquisition Trajectories Research Articles

Internationalization process, impact of slack resources, and role of the CEO: The duality of structure and agency in evolution of cross-border acquisition decisions

This paper examines how the internationalization process evolves. We do so by examining the cross-border acquisition (CBA) decisions of multinationals under the contingent impact of slack resources and CEO power and influence. Grounding our arguments in Giddens’ (1984) structuration theory, we identify how and why path-dependencies associated with CBA decisions give way to strategic change, demonstrating the duality of structure and agency in this evolutionary process. Further, we show that organizational slack and CEO overconfidence affect this relationship, albeit in dramatically different ways. Our hypotheses are tested on a large sample of 4812 CBAs of U.S. firms during 2000–2010, across 41 industries and in 44 target countries. The results hold for acquisition trajectories of multinationals in both categories of CBA decisions: majority as well as minority-owned.

Iterative image reconstruction for limited-angle inverse helical cone-beam computed tomography.

Helical trajectory satisfying the condition of exact reconstruction, has been widely utilized in the commercial computed tomography (CT). While limited by the scanning environment in some practical applications, the conventional helical cone-beam CT imaging is hard to complete, thus, developing an imaging system suited for long-object may be valuable. Three-dimensional C-arm CT is an innovative imaging technique which has been greatly concerned. Since there is a high degree of freedom of C-arm, more flexible image acquisition trajectories for 3D imaging can be achieved. In this work, a fast iterative reconstruction algorithm based on total variation minimization is developed for a trajectory of limited-angle inverse helical cone-beam CT, which can be applied to detect long-object without slip-ring technology. The experimental results show that the developed algorithm can yield reconstructed images of low noise level and high image quality.

Epipolar Consistency in Transmission Imaging.

This paper presents the derivation of the Epipolar Consistency Conditions (ECC) between two X-ray images from the Beer-Lambert law of X-ray attenuation and the Epipolar Geometry of two pinhole cameras, using Grangeat's theorem. We motivate the use of Oriented Projective Geometry to express redundant line integrals in projection images and define a consistency metric, which can be used, for instance, to estimate patient motion directly from a set of X-ray images. We describe in detail the mathematical tools to implement an algorithm to compute the Epipolar Consistency Metric and investigate its properties with detailed random studies on both artificial and real FD-CT data. A set of six reference projections of the CT scan of a fish were used to evaluate accuracy and precision of compensating for random disturbances of the ground truth projection matrix using an optimization of the consistency metric. In addition, we use three X-ray images of a pumpkin to prove applicability to real data. We conclude, that the metric might have potential in applications related to the estimation of projection geometry. By expression of redundancy between two arbitrary projection views, we in fact support any device or acquisition trajectory which uses a cone-beam geometry. We discuss certain geometric situations, where the ECC provide the ability to correct 3D motion, without the need for 3D reconstruction.

Spectral CT of the Extremities with a Silicon Strip Photon Counting Detector.

Photon counting x-ray detectors (PCXDs) are an important emerging technology for spectral imaging and material differentiation with numerous potential applications in diagnostic imaging. We report development of a Si-strip PCXD system originally developed for mammography with potential application to spectral CT of musculoskeletal extremities, including challenges associated with sparse sampling, spectral calibration, and optimization for higher energy x-ray beams. A bench-top CT system was developed incorporating a Si-strip PCXD, fixed anode x-ray source, and rotational and translational motions to execute complex acquisition trajectories. Trajectories involving rotation and translation combined with iterative reconstruction were investigated, including single and multiple axial scans and longitudinal helical scans. The system was calibrated to provide accurate spectral separation in dual-energy three-material decomposition of soft-tissue, bone, and iodine. Image quality and decomposition accuracy were assessed in experiments using a phantom with pairs of bone and iodine inserts (3, 5, 15 and 20 mm) and an anthropomorphic wrist. The designed trajectories improved the sampling distribution from 56% minimum sampling of voxels to 75%. Use of iterative reconstruction (viz., penalized likelihood with edge preserving regularization) in combination with such trajectories resulted in a very low level of artifacts in images of the wrist. For large bone or iodine inserts (>5 mm diameter), the error in the estimated material concentration was <16% for (50 mg/mL) bone and <8% for (5 mg/mL) iodine with strong regularization. For smaller inserts, errors of 20-40% were observed and motivate improved methods for spectral calibration and optimization of the edge-preserving regularizer. Use of PCXDs for three-material decomposition in joint imaging proved feasible through a combination of rotation-translation acquisition trajectories and iterative reconstruction with optimized regularization.

Application of Entropy and Fractal Dimension Analyses to the Pattern Recognition of Contaminated Fish Responses in Aquaculture

The objective of the work was to develop a non-invasive methodology for image acquisition, processing and nonlinear trajectory analysis of the collective fish response to a stochastic event. Object detection and motion estimation were performed by an optical flow algorithm in order to detect moving fish and simultaneously eliminate background, noise and artifacts. The Entropy and the Fractal Dimension (FD) of the trajectory followed by the centroids of the groups of fish were calculated using Shannon and permutation Entropy and the Katz, Higuchi and Katz-Castiglioni’s FD algorithms respectively. The methodology was tested on three case groups of European sea bass (Dicentrarchus labrax), two of which were similar (C1 control and C2 tagged fish) and very different from the third (C3, tagged fish submerged in methylmercury contaminated water). The results indicate that Shannon entropy and Katz-Castiglioni were the most sensitive algorithms and proved to be promising tools for the non-invasive identification and quantification of differences in fish responses. In conclusion, we believe that this methodology has the potential to be embedded in online/real time architecture for contaminant monitoring programs in the aquaculture industry.

Recent Advances in Acquisition/Reconstruction Algorithms for Undersampled Magnetic Resonance Imaging

Several applications of Magnetic Resonance Imaging (MRI), in particular dynamic MRI and functional MRI (fMRI), require rapid acquisition to measure dynamic processes changes. Experimental data are collected in the k-space by following different trajectories to cover the whole space. Complete data acquisition necessitates waiting for a fixed time interval: a reduced number of collected trajectories allows acquisition time reduction but undersampling occurs, often producing artifacts. In what follows, a review of methods for sparse sampling acquisition and reconstruction is presented.In particular, a differentiation is done between sparse acquisition methods which do not use any restoration algorithm (artifacts are tolerated) and those methods for which a restoration algorithm is essential. The first class contains also methods where spatial information is shared between temporal images to reduce the collected data. In the second class of methods, a differentiation is done between those reconstruction/restoration methods that reduce artifacts independently of the sample shape, and those restoration methods that adapt their action by modifying the acquisition trajectories during the acquisition, i.e. the chosen trajectories (both in number and directions) are dependent on the sample shape. A third emerging class of methods, those including hybrid forms of the second class, are also reported.

Leadership Capital: Measuring the Dynamics of Leadership

This article argues that the extent to which political office-holders can effectively attain and wield authority is a function of the stock of 'leadership capital.' Drawing on the concept of political capital, we define leadership capital as aggregate authority composed of three dimensions: skills; relations; and reputation of a leader. Leadership capital ebbs and flows over time within a trajectory of acquisition, expenditure and inevitable depreciation. We present a Leadership Capital Index (LCI) that systematically maps out the three broad areas combining concrete measures with interpretive aspects. This can be used as a tool for systematically tracking and comparing the political fortunes of leaders in a way that is both more nuanced and robust than exclusive reliance on the latest approval ratings. We offer an illustrative case study of Tony Blair demonstrating the LCI. We conclude by discerning several promising paths for future development of the LCI.

Assessing the Authority of Political Office-Holders: The Leadership Capital Index

This article argues that the extent to which political office-holders can effectively attain and wield authority is a function of the stock of ‘leadership capital’. Drawing on the concept of political capital, the article defines leadership capital as aggregate authority composed of three dimensions: skills, relations and reputation of a leader. Leadership capital ebbs and flows over time within a trajectory of acquisition, expenditure and inevitable depreciation. The article presents a Leadership Capital Index (LCI) that systematically maps out the three broad areas combining concrete measures with interpretive aspects. This can be used as a tool for systematically tracking and comparing the political fortunes of leaders in a way that is both more nuanced and robust than exclusive reliance on the latest approval ratings. An illustrative case study of Tony Blair is used to demonstrate the LCI. The article concludes by discerning several promising paths for future development of the LCI.

L2 vs. L1 Use of Synonymy: An Empirical Study of Synonym Use/Acquisition

AbstractSynonymy is important but difficult for language learners to grasp. Using a forced-choice question instrument, along with corpus data as reference, this study examines the use of four sets of synonyms by intermediate/advanced Chinese EFL/ESL learners and native English speakers. The data analyses reveal several key findings, including a general synonym acquisition trajectory. First, synonyms are often differentiated by their typical collocates; hence, the acquisition of synonyms is largely the learning of their salient collocates. Secondly, construal of the communicative purpose/context at hand also plays an important role in synonym selection. Thirdly, EFL/ESL learners begin to show some grasp of the salient usages/meanings of synonyms, and their grasp of synonyms advances significantly as their English proficiency increases to advanced level, but advanced learners still exhibit difficulties in synonym use, including an inadequate ability in forming context-called-for unique construals. Fourthly, frequency plays a crucial role in synonym acquisition, as low-frequency synonyms and salient synonym collocation usages with a low raw frequency are especially difficult for L2 learners. Implications for pedagogy and future research are also discussed.

A cross-cultural comparison of the network capability development of entrepreneurial firms

The business-to-business network literature has made interesting and insightful contributions in relation to networks as a core trajectory for external resource acquisition for the small, entrepreneurial firm. Using the micro-brewing industry in Ireland and Belgium as an empirical base, the purpose of this paper is to extend this research through examining the relationship between national culture and the development of network capability in an entrepreneurial context. Findings from in-depth interviews with fourteen firms, and analysed in light of Hofstede's five dimensions illustrate that culture matters. Low power distance facilitated network capability development through wider network engagement. High masculinity and individualism negatively impacted network capability development as evidenced by a lack of experience in interaction, a desire for control and independence and minimal information sharing. Strong uncertainty avoidance scores allowed for joint problem-solving and industry cooperation whereas a short-term orientation led to more transaction-based exchange within the value chain. The core contribution of this paper stems from it being the first rigorous investigation regarding how national culture impacts network capability development in a business-to-business network context.

Accelerated whole‐heart coronary MRA using motion‐corrected sensitivity encoding with three‐dimensional projection reconstruction

To achieve whole-heart coronary magnetic resonance angiography (MRA) with (1.0 mm)(3) spatial resolution and 5 min of free-breathing scan time. We used an electrocardiograph-gated, T2-prepared and fat-saturated balanced steady state free precession sequence with 3DPR trajectory for free-breathing data acquisition with 100% gating efficiency. For image reconstruction, we used a self-calibrating iterative SENSE scheme with integrated retrospective motion correction. We performed healthy volunteer study to compare the proposed method with motion-corrected gridding at different retrospective undersampling levels on apparent signal-to-noise ratio (aSNR) and subjective coronary artery (CA) visualization scores. Compared with gridding, the proposed method significantly improved both image quality metrics for undersampled datasets with 6000, 8000, and 10,000 projections. With as few as 10,000 projections, the proposed method yielded good CA visualization scores (3.02 of 4) and aSNR values comparable to those with 20,000 projections. Using the proposed method, good image quality was observed for free breathing whole-heart coronary MRA at (1.0 mm)(3) resolution with an achievable scan time of 5 min.

An Algorithm for Variable Density Sampling with Block-Constrained Acquisition

Reducing acquisition time is of fundamental importance in various imaging modalities. The concept of variable density sampling provides a nice framework to achieve this. It was justified recently from a theoretical point of view in the compressed sensing (CS) literature. Unfortunately, the sampling schemes suggested by current CS theories may not be relevant since they do not take the acquisition constraints into account (for example, continuity of the acquisition trajectory in Magnetic Resonance Imaging - MRI). In this paper, we propose a numerical method to perform variable density sampling with block constraints. Our main contribution is to propose a new way to draw the blocks in order to mimic CS strategies based on isolated measurements. The basic idea is to minimize a tailored dissimilarity measure between a probability distribution defined on the set of isolated measurements and a probability distribution defined on a set of blocks of measurements. This problem turns out to be convex and solvable in high dimension. Our second contribution is to define an efficient minimization algorithm based on Nesterov's accelerated gradient descent in metric spaces. We study carefully the choice of the metrics and of the prox function. We show that the optimal choice may depend on the type of blocks under consideration. Finally, we show that we can obtain better MRI reconstruction results using our sampling schemes than standard strategies such as equiangularly distributed radial lines.

Whole-Heart Cine MRI in a Single Breath-Hold – A Compressed Sensing Accelerated 3D Acquisition Technique for Assessment of Cardiac Function

The aim of this study was to perform functional MR imaging of the whole heart in a single breath-hold using an undersampled 3 D trajectory for data acquisition in combination with compressed sensing for image reconstruction. Measurements were performed using an SSFP sequence on a 3 T whole-body system equipped with a 32-channel body array coil. A 3 D radial stack-of-stars sampling scheme was utilized enabling efficient undersampling of the k-space and thereby accelerating data acquisition. Compressed sensing was applied for the reconstruction of the missing data. A validation study was performed based on a fully sampled dataset acquired by standard Cartesian cine imaging of 2 D slices on a healthy volunteer. The results were investigated with regard to systematic errors and resolution losses possibly introduced by the developed reconstruction. Subsequently, the proposed technique was applied for in-vivo functional cardiac imaging of the whole heart in a single breath-hold of 27 s. The developed technique was tested on three healthy volunteers to examine its reproducibility. By means of the results of the simulation (temporal resolution: 47 ms, spatial resolution: 1.4 × 1.4 × 8 mm, 3 D image matrix: 208 × 208 × 10), an overall acceleration factor of 10 has been found where the compressed sensing reconstructed image series shows only very low systematic errors and a slight in-plane resolution loss of 15 %. The results of the in-vivo study (temporal resolution: 40.5 ms, spatial resolution: 2.1 × 2.1 × 8 mm, 3 D image matrix: 224 × 224 × 12) performed with an acceleration factor of 10.7 confirm the overall good image quality of the presented technique for undersampled acquisitions. The combination of 3 D radial data acquisition and model-based compressed sensing reconstruction allows high acceleration factors enabling cardiac functional imaging of the whole heart within only one breath-hold. The image quality in the simulated dataset and the in-vivo measurement highlights the great potential of the presented technique for an efficient assessment of cardiac functional parameters.

Airborne SAR-Efficient Signal Processing for Very High Resolution

Frequency-domain synthetic aperture radar (SAR) image formation algorithms are of lower computation cost (both in number of elementary operations and in required memory storage) than direct time-domain integration, and do not make the narrowband (monochromatic) assumption. Both advantages are critical to very-high-resolution imaging because a lower complexity yields a drastic computation time decrease as cross-range resolution increases, and the narrowband assumption is more and more a concern as range resolution (hence bandwidth) increases. Though an exact formulation exists (ω- k algorithm) for a perfect linear uniform acquisition trajectory, in a real-life airborne case, the unavoidable trajectory deviation from a straight line needs to be compensated. This motion compensation (MoComp) operation is much more complicated in the case of frequency-domain processing. An efficient technique for this purpose is presented. This method keeps the parallel processing aspect, and has been programmed both for multithread on multicore/symmetrical multiprocessor central processing units (CPUs) and for graphic processor units (GPUs).

Osvojovanie slovesnej lexiky v ranej ontogenéze reči / Werbs Acquisition in Early Childhood

AbstractThe main aim of the study is to introduce a new method which has not been applied in the Slovak study of child language so far, and to answer 4 main research questions: (1) What is the development of understanding and production of verbs in early lexical development of Slovak-speaking children? (2) Are there any differences in verbs understanding and production between Slovak-speaking girls and boys? (3) What is the linguistic picture of the world given by incipient verbal lexicon of Slovak-speaking children? (4) Is there any difference between the linguistic picture of the world of Slovak-speaking girls and boys? The method is based on the quantitative and qualitative analysis of the lexical part of the Slovak version of CDI 1 Test of communicative abilities TEKOS 1: Words and gestures with 44 verbs in the part “actions and states”. Parents were asked to fill in the checklist and choose from three options: i) child understands and speaks, ii) understands, iii) does not understand The research sample consists of 323 girls and 330 boys in their age from 8 to 16 months. The results show the unanimous developmental trajectory in verbs acquisition in both, girls and boys. The differences shown in production in favor of girls in last two months are not statistically significant. The linguistic picture of the world is cognitively and semantically gender-universal, concentrated on corporeal concepts connected with social concept. The prototypical verbs in first 16 months of the age of the children are jesť (to eat) and dať (to give)

High efficiency multishot interleaved spiral‐in/out: Acquisition for high‐resolution BOLD fMRI

Growing demand for high spatial resolution blood oxygenation level dependent (BOLD) functional magnetic resonance imaging faces a challenge of the spatial resolution versus coverage or temporal resolution tradeoff, which can be addressed by methods that afford increased acquisition efficiency. Spiral acquisition trajectories have been shown to be superior to currently prevalent echo-planar imaging in terms of acquisition efficiency, and high spatial resolution can be achieved by employing multiple-shot spiral acquisition. The interleaved spiral in/out trajectory is preferred over spiral-in due to increased BOLD signal contrast-to-noise ratio (CNR) and higher acquisition efficiency than that of spiral-out or noninterleaved spiral in/out trajectories (Law & Glover. Magn Reson Med 2009; 62:829-834.), but to date applicability of the multishot interleaved spiral in/out for high spatial resolution imaging has not been studied. Herein we propose multishot interleaved spiral in/out acquisition and investigate its applicability for high spatial resolution BOLD functional magnetic resonance imaging. Images reconstructed from interleaved spiral-in and -out trajectories possess artifacts caused by differences in T2 decay, off-resonance, and k-space errors associated with the two trajectories. We analyze the associated errors and demonstrate that application of conjugate phase reconstruction and spectral filtering can substantially mitigate these image artifacts. After applying these processing steps, the multishot interleaved spiral in/out pulse sequence yields high BOLD CNR images at in-plane resolution below 1 × 1 mm while preserving acceptable temporal resolution (4 s) and brain coverage (15 slices of 2 mm thickness). Moreover, this method yields sufficient BOLD CNR at 1.5 mm isotropic resolution for detection of activation in hippocampus associated with cognitive tasks (Stern memory task). The multishot interleaved spiral in/out acquisition is a promising technique for high spatial resolution BOLD functional magnetic resonance imaging applications.

SU-E-J-05: Validation of an Iterative Tomosynthesis Algorithm for Low Dose on Board Cone Beam CT Patient Localization.

Cone beam CT (CBCT) is a well established technique to localize patients using bone and soft tissue anatomy. Current protocols are limited to one weekly CBCT due to the considerable imaging dose delivered to the patient. The purpose of this project is to develop and validate a low dose CBCT algorithm to reduce dose and imaging time of current 3D imaging localization procedures using a novel iterative tomosynthesis algorithm to allow daily CBCT for patient positioning and target localization. The algorithm is based on the combination of a tomosynthesis filtered back propagation (TFBP) acquisition geometry algorithm and a maximum likelihood expectation maximization (MLEM) iterative reconstruction. Circular or arc acquisition trajectory, projection number, and angular projection position are optimized according to the anatomical treatment site and region of interest. The TFBP method provides the first 3D image estimate, and the MLEM improves its quality. In this study, we focused on head and neck treatment localization imaging. We studied the performance of our tomosynthesis algorithm imaging resolution on an anthropomorphic head and neck phantom to determine image quality as a function of dose reduction techniques. Reconstructed anatomy shows that a 1/8 dose reduction provides similar image quality and resolution as current CBCT protocols. Seven iterations show an optimal compromise between image quality and reconstruction time. Tomosynthesis images provide digitally reconstructed radiographs with similar resolution and contrast as full CBCT. We verified that the iterative process eliminates phantom images originated by the acquired sparse angular data projections. We developed and validated an iterative algorithm for low dose cone beam CT based on circular or arc tomosynthesis geometries and iterative reconstruction techniques. The algorithm combines the strengths of both techniques to provide a novel low dose method to image patient anatomy for patient positioning and target localization.

The initial stages of first-language acquisition begun in adolescence: when late looks early

Children typically acquire their native language naturally and spontaneously at a very young age. The emergence of early grammar can be predicted from children's vocabulary size and composition (Bateset al., 1994; Bates, Bretherton &amp; Snyder, 1998; Bates &amp; Goodman, 1997). One central question in language research is understanding what causes the changes in early language acquisition. Some researchers argue that the qualitative and quantitative shifts in word learning simply reflect the changing character of the child's cognitive maturity (for example, Gentner, 1982), while others argue that the trajectory of early language acquisition is driven by the child's growing familiarity with the language (Gillette, Gleitman, Gleitman &amp; Lederer, 1999; Snedeker &amp; Gleitman, 2004). These hypotheses are difficult to adjudicate because language acquisition in virtually all hearing children begins from birth and occurs simultaneously with cognitive development and brain maturation. The acquisition of sign languages, in contrast, is frequently delayed until older ages. In the USA, over 90% of deaf children are born to hearing parents who do not use sign language (Schein, 1989). As a result, deaf children are often exposed to sign language as a first language at a range of ages well beyond infancy (Mayberry, 2007). In rare cases, some deaf individuals are isolated from all linguistic input until adolescence when they start receiving special services and begin to learn sign language through immersion (Morford, 2003). Case studies of language acquisition in such extreme late first-language (L1) learners provide a unique opportunity to investigate first-language learning. The current study investigates three cases of young teens who are in the early stages of acquiring American Sign Language (ASL) as a first language, to determine what first-language acquisition in adolescence looks like.

Trajectories of land acquisition and enclosure: development schemes, virtual land grabs, and green acquisitions in Indonesia's Outer Islands

While the size and speculative nature of land transactions in the wake of energy, food and climate crises have surprised observers, the reasons for partial implementation of many land developments remain largely unexamined. This contribution investigates trajectories of land acquisition and enclosure by analyzing four acquisition processes in Indonesia – those associated with rice, oil palm, Jatropha and carbon sequestration – considering their implications for comparative studies elsewhere. The paper finds that current patterns of land usechange represent a continuation of ongoing land transformation processes. Itdescribes the logic leading to partial realization of large-scale schemes. Highlighting the importance of interactions between formal and vernacular rural land development processes, the essay concludes that many large-scale schemes are better understood as virtual land acquisitions.

Towards Quantification of Functional Breast Images Using Dedicated SPECT With Non-Traditional Acquisition Trajectories

Quantification of radiotracer uptake in breast lesions can provide valuable information to physicians in deciding patient care or determining treatment efficacy. Physical processes (e.g., scatter, attenuation), detector/collimator characteristics, sampling and acquisition trajectories, and reconstruction artifacts contribute to an incorrect measurement of absolute tracer activity and distribution. For these experiments, a cylinder with three syringes of varying radioactivity concentration, and a fillable 800 mL breast with two lesion phantoms containing aqueous (99m)Tc pertechnetate were imaged using the SPECT sub-system of the dual-modality SPECT-CT dedicated breast scanner. SPECT images were collected using a compact CZT camera with various 3D acquisitions including vertical axis of rotation, 30° tilted, and complex sinusoidal trajectories. Different energy windows around the photopeak were quantitatively compared, along with appropriate scatter energy windows, to determine the best quantification accuracy after attenuation and dual-window scatter correction. Measured activity concentrations in the reconstructed images for syringes with greater than 10 µCi /mL corresponded to within 10% of the actual dose calibrator measured activity concentration for ±4% and ±8% photopeak energy windows. The same energy windows yielded lesion quantification results within 10% in the breast phantom as well. Results for the more complete complex sinsusoidal trajectory are similar to the simple vertical axis acquisition, and additionally allows both anterior chest wall sampling, no image distortion, and reasonably accurate quantification.