Segmental Mode Research Articles

Radial sample load distribution under overload conditions: Analytical scale columns

ABSTRACTThe homogeneity of the sample load across the radial cross section of analytical scale columns was determined when operating under overload conditions. The study was performed using active flow technology columns operating in parallel segmentation mode. The outlet segmentation ratio was varied to enable different volume fractions of mobile phase, and thus sample, to elute from the peripheral and central flow regions of the column. The amount of solute exiting the peripheral and radial central exit ports was determined as a function of the flow segmentation ratio. The experimental data using an analytical scale column with dimensions, 100 × 4.6 mm, indicated that the sample load distribution was essentially uniform as a function of the column radial cross section.

Simple-liquid dynamics emerging in the mechanical shear spectra of poly(propylene glycol)

The present dielectric investigations of methyl-terminated poly(propylene glycol) (PPG) oligomers reveal that near the glass transition the normal modes and segmental relaxation merge in a single-process susceptibility spectrum, similar to previous observations on OH-terminated species. Moreover, the present shear-mechanical measurements demonstrate that the vanishing of chain modes can be monitored without recourse to dielectric investigations, which are able to access chain dynamics only for the relatively small fraction of type A polymers. As the normal and segmental modes merge, the viscosity displays a crossover from a polymer-like regime governed by the chain dynamics, to a simple-liquid regime governed by the structural relaxation.

Contribution of cell proliferation to axial elongation in the red flour beetle Tribolium castaneum.

Most arthropods generate their posterior bodies by adding segments periodically, as the embryo grows, from a posteriorly located region called the segment addition zone. This mode of segmentation is shared with vertebrates and relies on oscillatory mechanisms, where the temporal periodicity of a clock is translated into repetitive spatial patterns. This ordered anterior-to-posterior pattern is achieved at the same time as the tissue elongates, opening the question of the functional coordination between the mechanisms of segmental patterning and posterior growth. The study of these processes in different arthropods has played an important role in unravelling some of the molecular mechanisms of segment formation. However, the behavior of cells during elongation and how cellular processes affect this segmental patterning has been poorly studied. Cell proliferation together with cell rearrangements are presumed to be the major forces driving axis elongation in the red flour beetle Tribolium castaneum. However, there still no strong evidence about the role and distribution of cell proliferation within the embryo. In this study, we propose to address these questions by using whole embryo cultures and pharmacological manipulation. We show that considerable cell proliferation occurs during germband elongation, measured by incorporation of the nucleoside analog of thymidine 5-Ethynyl-2’-deoxyuridine, EdU. Moreover, proliferating cells appeared to be spread along the elongating embryo with a posterior bias at early segmentation. In addition, when we blocked cell division, treated germbands were always shorter than controls and in some cases not able to fully elongate, even when control embryos already started to retract and leg buds are evident. Finally, we found that the absence of cell proliferation has no apparent effect on segmental patterning, as evidenced by Tc-engrailed (Tc-en) gene expression.

Misattributed tsunami 5: the Namie, Japan (Mw 6.9) 2016.11.21 earthquake

The Namie (Japan) 2016.11.21 Mw 6.9 earthquake (d=9.0km) initiated a tsunami which, contrary to forecasts of up to 3m based on preliminary earthquake magnitude, nowhere exceeded 1.4m. The hypocentre of the main shock was bordered in the succeeding 24h by a tight cluster of 24M ≤4.5 shallow (d≤20km) earthquakes. Two of them nucleated close to a M4.6 tremor that had preceded the main earthquake by 2.34h, raising the possibility that a single structure hosted all three. Granted the ultimate cause was subduction at the Japan Trench, these events reaffirm the need for focused seafloor monitoring and fault history to supplement teleseismic data for realistic tsunami forecasting. Earthquake clustering in the 24h after the main earthquake may also reflect a mode of megathrust segmentation which discourages the generation of great (Mw∼9) earthquakes.

Time and Temperature as Key Parameters Controlling Dynamics and Properties of Spatially Restricted Polymers

The annealing behavior of poly(propylene glycol) (PPG, Mw = 4000 g/mol) incorporated into the nanoporous aluminum oxide (AAO) membranes of different pore diameter was investigated by broadband dielectric spectroscopy (BDS) and differential scanning calorimetry (DSC). The presence of two subsets of molecules of different dynamics (interfacial and core) allows to produce conditions, where only one fraction (interfacial) is vitrified. Upon these conditions, annealed samples undergo continuous changes reflected in a shift of dielectric processes (segmental and normal mode). This unusual behavior was observed to be a reversible effect strictly governed by chain diffusion, indicated by the coupling between the equilibration constant (τanneal) and the relaxation times of normal mode (τNM). Despite the similarity in macroscopic changes observed upon the annealing of 2D and 1D materials [Napolitano, S.; Nat. Commun. 2011, 2, 260], the examined behavior occurs accordingly to a totally different mechanism than the o...

Vibration model of a multi-supported guide bar and analysis on the effect of supports location

Two methods (equivalent force method and segmental mode assuming method) of calculating the natural frequencies and mode shapes of a free-free-multi-supported beam subjected to an axial load is found, considering the structure characteristic of the guide bar, which has long length but small section, and supported by many bearings. The calculation shows that these two methods are convenient for computer programing and have the same results in obtaining the natural frequencies and mode shapes of a free-free-multi-supported beam subjected to an axial load, solving the problem that the vibration function of this kind of beam is hard to deal with because it cannot be simplified with the boundary condition of two ends. Then the segmental mode assuming method is used to analyze the impact of the support location on the natural frequencies and mode shapes of the guide bar. The relation graphs of the natural frequencies with support location, as well as the support locations where the natural frequencies reached the maximum and the minimum are found, providing a reference for the support location selection for the guide bar. The changing curves of the mode shapes with support location are plotted, which show that the bending deformation is homogeneous when the length of each segment is approximately equal, avoiding the phenomenon that bending stresses concentrates at the large-amplitude segments and cause breakage while less stress exists in small-amplitude segments and hinder the exploiting of their performance, providing a reference for the structure design of the guide bar.

Joint Provisioning of Lightpaths and Storage in Store-and-Transfer Wavelength-Division Multiplexing Networks

So-called store-and-transfer wavelengthdivision multiplexing networks (STWNs) can store data and provision lightpaths at an optimal time when the wavelengths are clear of conflicts. If the wavelength utilization of the wavelength-division multiplexing network is not uniform, the embedded storage nodes can store data and the lightpath is segmented so conflicts along separate segments of the lightpath can be resolved independently. Consequently, blocked requests can be reduced, and the resource utilization of the network can be improved. In this work, we investigate three extensions of the sliding scheduled traffic model, which is a variant of advance reservations. First, we segment a lightpath with embedded storage nodes, split the transfer window into smaller ones, and sequentially assign a smaller window to each segment of the lightpath. Each segment of the lightpath has fewer hops, and thus, overall blocking can be decreased. Second, we allocate fixed time slots in continuous frames over multiple wavelengths for a time-division multiplexing (TDM) mode large data transfer. The resource allocations are more flexible in resolving conflicts, and thus, blocking can be decreased. Third, we use segmented lightpaths and TDM mode transfer along each segment of the lightpath. Since the first two extensions are orthogonal, the combination can decrease the blocking further. We propose four heuristic algorithms to evaluate the extensions. We also propose two parallel implementations of the four heuristic algorithms. The simulations show the following: the provisioning algorithms for the first two extensions have similar performances, and both decrease blocking by 20%. If the service time is long, the second one performs better. The provisioning algorithm for the last extension decreases blocking by 40%. The first extension requires 10% more storage, and the second extension requires 20% less storage. Under a large load and with 8 CPUs, the parallel implementations improve the speed by three times. It also shows that the number of time slots per frame influences the performance; the influence is not monotonic; and, if the value increases too much, the blocking rate increases by 20% and the storage size increases by 30%.

An adaptive and selective segmentation model based on local and global image information

This study investigates the application of partial differential equations in image segmentation field. A novel selective segmentation mode is proposed for the existing selective segmentation model which cannot segment the intensity inhomogeneity and fuzzy edge image. In this novel model, a weighting function based on local information is constructed. This weighting function can introduce the global and local information of the image into the novel model which can realise the adaptive segmentation of the image. Compared with the existing selective segmentation model, the novel selective segmentation model proposed in this paper can realise the adaptive segmentation of intensity inhomogeneity and fuzzy edge images. Experimental results show that the novel model is more effective and adaptive to segment images with intensity inhomogeneity or fuzzy edge, and less sensitive to the location of initial contour, without choosing the weighting parameter between global and local information by manual method.

Impact of hydrogen bonds dynamics on mechanical behavior of supramolecular elastomer

Here our special consideration is devoted to the relationship between dynamics and mechanical behaviours of supramolecular elastomer (SE) based on 2-ureido-4[1H]-pyrimidinone (UPy) groups. We find that SE exhibits a new relaxation mode (α′ relaxation) which differs from segmental relaxation mode (α relaxation) and normal relaxation mode (NM). Calculated by Arrhenius model, supramolecular interactions are much lower than the bonds energy of covalent bonds; this enables high energy dissipation as the elastomer is subjected to deformation. Moreover, unlike covalent bonds, the hydrogen bonds of UPy groups are dynamic and longer waiting time leads to better re-association efficiency, as evidenced by recovery of hysteresis loop during cyclic tensile tests. This work on the relationship between dynamics and mechanical properties will not only improve the understanding of reversible bonds relaxation, but also provide an idea on preparing mechanically robust SE for us.

Blastoderm segmentation in Oncopeltus fasciatus and the evolution of insect segmentation mechanisms.

Segments are formed simultaneously in the blastoderm of the fly Drosophila melanogaster through a hierarchical cascade of interacting transcription factors. Conversely, in many insects and in all non-insect arthropods most segments are formed sequentially from the posterior. We have looked at segmentation in the milkweed bug Oncopeltus fasciatus. Posterior segments are formed sequentially, through what is probably the ancestral arthropod mechanism. Formation of anterior segments bears many similarities to the Drosophila segmentation mode. These segments appear nearly simultaneously in the blastoderm, via a segmentation cascade that involves orthologues of Drosophila gap genes working through a functionally similar mechanism. We suggest that simultaneous blastoderm segmentation evolved at or close to the origin of holometabolous insects, and formed the basis for the evolution of the segmentation mode seen in Drosophila. We discuss the changes in segmentation mechanisms throughout insect evolution, and suggest that the appearance of simultaneous segmentation as a novel feature of holometabolous insects may have contributed to the phenomenal success of this group.

Studies on the Temperature and Time Induced Variation in the Segmental and Chain Dynamics in Poly(propylene glycol) Confined at the Nanoscale

The effect of 2D confinement on the dynamics of the normal mode (chain mobility) and segmental relaxation in poly(propylene glycol) (PPG) has been studied with the use of broadband dielectric spectroscopy (BDS) and differential scanning calorimetry (DSC). It is shown that both processes become faster with increasing degree of confinement. Interestingly, the crossover from VFT to the Arrhenius-like behavior of chain and segmental dynamics, observed in the examined system, is strictly related to the vitrification of the adsorbed polymers. We also report that the mean relaxation times of the normal, τNM, and segmental modes, τα, depend on the thermal history of confined PPG and can be significantly modified using different thermal treatments. It is demonstrated that annealing of the samples below the crossover temperature, Tc, leads to a systematic shift of the segmental relaxation and normal mode toward lower frequencies, resulting in an increase in the glass transition temperature of the spatially restrict...

Curvature of iris profile in spectral domain optical coherence tomography and dependency to refraction, age and pupil size - the MIPH Eye&Health Study.

Optical coherence tomography (OCT) of the anterior segment allows quantitative analysis of the geometry of the iris. We performed spectral domain OCT examinations in healthy emmetropic, hyperopic and myopic subjects to investigate iris curvature and its associations. In a cross-sectional study, out of 4617 eyes (2309 subjects) those with refractive errors of <-4 or >+3 dioptres were identified by objective refraction. The iris was examined using the anterior segment mode of a spectral domain 3D OCT-2000 (Topcon Inc., Japan) in the temporal meridian, and OCT scans were investigated with respect to presence and amount of convex and concave iris configuration. Ninety-three eyes of 50 subjects served as emmetropic group (-0.5≤x≤+0.5 dioptres). Previous ocular surgery was exclusion criterion. Six hundred and sixty-eight eyes of 398 persons [292 male (76%); age range; 18-66years] were included in the study. In the myopic group, 105 eyes had a concave iris configuration (26%), while in the hyperopic group, no eye had this configuration (0%) and in the emmetropic group five eyes (5%). Convex iris configuration was found in 96% of hyperopic, in 85% of the emmetropic and in 67% of the myopic eyes. There was an association between concave iris configuration and myopia, younger age and male gender, and with anterior chamber angle width. Spectral domain OCT images can be used for analysis of the iris structure and geometry. Our results are limited to the properties of the study population having an age range from 18 to 66years and consisting mainly of men.

Semiautomated segmentation of head and neck cancers in 18F-FDG PET scans: A just-enough-interaction approach.

Purpose:The purpose of this work was to develop, validate, and compare a highly computer-aided method for the segmentation of hot lesions in head and neck 18F-FDG PET scans.Methods:A semiautomated segmentation method was developed, which transforms the segmentation problem into a graph-based optimization problem. For this purpose, a graph structure around a user-provided approximate lesion centerpoint is constructed and a suitable cost function is derived based on local image statistics. To handle frequently occurring situations that are ambiguous (e.g., lesions adjacent to each other versus lesion with inhomogeneous uptake), several segmentation modes are introduced that adapt the behavior of the base algorithm accordingly. In addition, the authors present approaches for the efficient interactive local and global refinement of initial segmentations that are based on the “just-enough-interaction” principle. For method validation, 60 PET/CT scans from 59 different subjects with 230 head and neck lesions were utilized. All patients had squamous cell carcinoma of the head and neck. A detailed comparison with the current clinically relevant standard manual segmentation approach was performed based on 2760 segmentations produced by three experts.Results:Segmentation accuracy measured by the Dice coefficient of the proposed semiautomated and standard manual segmentation approach was 0.766 and 0.764, respectively. This difference was not statistically significant (p = 0.2145). However, the intra- and interoperator standard deviations were significantly lower for the semiautomated method. In addition, the proposed method was found to be significantly faster and resulted in significantly higher intra- and interoperator segmentation agreement when compared to the manual segmentation approach.Conclusions:Lack of consistency in tumor definition is a critical barrier for radiation treatment targeting as well as for response assessment in clinical trials and in clinical oncology decision-making. The properties of the authors approach make it well suited for applications in image-guided radiation oncology, response assessment, or treatment outcome prediction.

Local and Global Dynamics in Polypropylene Glycol/Silica Composites

The local segmental and global dynamics of a series of polypropylene glycol / silica nanocomposites were studied using rheometry and mechanical and dielectric spectroscopies. The particles cause substantial changes in the rheology, including higher viscosities that become non-Newtonian and the appearance of stress overshoots in the transient shear viscosity. However, no change was observed in the mean relaxation times for either the segmental or normal mode dynamics measured dielectrically. This absence of an effect of the particles is due to masking of the interfacial response by polymer chains remote from the particles. When the unattached polymer was extracted to isolate the interfacial material, very large reductions in the relaxation times were measured. This speeding up of the dynamics is due in part to the reduced density at the interface, presumably a consequence of poorer packing of tethered chains. In addition, binding of the ether oxygens of the polypropylene glycol chains truncates the normal mode, which shifts the corresponding relaxation peak to higher frequencies.

A Local Search-Based GeneSIS algorithm for the Segmentation and Classification of Remote-Sensing Images

A local search-based version of the so-called genetic sequential image segmentation (GeneSIS) algorithm is presented in this paper, for the classification of remotely sensed images. The new method combines the properties of the GeneSIS framework with the principles of the region growing segmentation algorithms. Localized GeneSIS operates on a fine-segmented image obtained after preliminary watershed transformation. Segmentation proceeds by iterative expansions emanating from object cores, i.e., connected components of marked watersheds. At each expansion trial, the process involves three successively performed operations: 1) generation of the object’s neighborhood to a specified order; 2) local exploration of the neighborhood through an evolutionary algorithm to identify the best expansion to be merged; and 3) rearrangement of the object neighborhoods. We propose two priority strategies for the selection of the objects to be expanded and two different modes of operation performing either supervised or semisupervised segmentation of the image. The combination of the priority strategies and segmentation modes lead to four different implementations of localized GeneSIS. Due to the local search approach adopted here, the resulting algorithms have considerably lower execution times, while at the same time, they provide comparable classification accuracies compared to those produced by previous GeneSIS variants. Experimental analysis is conducted using a hyperspectral forest image, a multispectral agricultural image, and the Pavia Centre image over an urban area. Comparative results are also provided with existing segmentation algorithms.

Influence of block sequence and molecular weight on morphological, rheological and dielectric properties of weakly and strongly segregated styrene-isoprene triblock copolymers

Abstract In this work, morphological, thermal, viscoelastic and dielectric properties of triblock copolymers consisting of styrene (S) and isoprene (I) blocks are discussed. SIS and ISI triblock copolymers were synthesized by sequential anionic polymerization, three of them exhibiting molecular weights below the entanglement molecular weight Me, three of them exhibiting molecular weights in the order of Me and two of them exhibiting molecular weights above Me. The objective of this work is the investigation of the influence of molecular weight and block sequence on relaxation of the block copolymer chains. Morphological investigations using small angle X-ray scattering and transmission electron microscopy studies reveal that a larger molecular weight is associated with a more pronounced microphase separation. The presence of two glass transition temperatures reveals microphase separation of the PI and PS blocks. The Fox-Flory equation was applied in order to describe the molecular weight dependence of the glass transition temperature of the polyisoprene and the polystyrene blocks. The analysis of rheological data reveals a Maxwell fluid behavior for the weakly segregated block copolymers, whereas for the strongly segregated block copolymers a pronounced elastic behavior at low frequencies of small amplitude shear oscillations was observed. In the intermediate regime of molecular weight, a complex viscoelastic behavior appears. The plateau modulus G N o is influenced by the sequence of the PS and the PI blocks (SIS or ISI). Our analysis of segmental and normal mode relaxation in dielectric spectroscopy experiments show that the relaxation processes are strongly influenced by the block sequence (PI blocks tethered at one or both ends) and the molecular weight. As a result, the block sequence in triblock copolymers influences dynamical properties in the glassy state and in the melt.

Исследование влияния режимов сегментной электромеханической закалки на сдвигоустойчивость прессового соединения типа «втулка-корпус»

Исследование влияния режимов сегментной электромеханической закалки на сдвигоустойчивость прессового соединения типа «втулка-корпус»

Handheld, rapidly switchable, anterior/posterior segment swept source optical coherence tomography probe.

We describe the first handheld, swept source optical coherence tomography (SSOCT) system capable of imaging both the anterior and posterior segments of the eye in rapid succession. A single 2D microelectromechanical systems (MEMS) scanner was utilized for both imaging modes, and the optical paths for each imaging mode were optimized for their respective application using a combination of commercial and custom optics. The system has a working distance of 26.1 mm and a measured axial resolution of 8 μm (in air). In posterior segment mode, the design has a lateral resolution of 9 μm, 7.4 mm imaging depth range (in air), 4.9 mm 6dB fall-off range (in air), and peak sensitivity of 103 dB over a 22° field of view (FOV). In anterior segment mode, the design has a lateral resolution of 24 μm, imaging depth range of 7.4 mm (in air), 6dB fall-off range of 4.5 mm (in air), depth-of-focus of 3.6 mm, and a peak sensitivity of 99 dB over a 17.5 mm FOV. In addition, the probe includes a wide-field iris imaging system to simplify alignment. A fold mirror assembly actuated by a bi-stable rotary solenoid was used to switch between anterior and posterior segment imaging modes, and a miniature motorized translation stage was used to adjust the objective lens position to correct for patient refraction between -12.6 and + 9.9 D. The entire probe weighs less than 630 g with a form factor of 20.3 x 9.5 x 8.8 cm. Healthy volunteers were imaged to illustrate imaging performance.

Using active flow technology columns for high through-put and efficient analyses: The drive towards ultra-high through-put high-performance liquid chromatography with mass spectral detection

The performance of active flow technology chromatography columns in parallel segmented flow mode packed with 5μm Hypersil GOLD particles was compared to conventional UHPLC columns packed with 1.9μm Hypersil GOLD particles. While the conventional UHPLC columns produced more theoretical plates at the optimum flow rate, when separations were performed at maximum through-put the larger particle size AFT column out-performed the UHPLC column. When both the AFT column and the UHPLC column were operated such that they yielded the same number of theoretical plates per separation, the separation on the AFT column was twice as fast as that on the UHPLC column, with the same level of sensitivity and at just 70% of the back pressure. Furthermore, as the flow velocity further increased the performance gain on the AFT column compared to the UHPLC column improved. An additional advantage of the AFT column was that the flow stream at the exit of the column was split in the radial cross section of the peak profile. This enables the AFT column to be coupled to a flow limiting detector, such as a mass spectrometer. When operated under high through-put conditions separations as fast as six seconds, using mobile phase flow rates in the order of 5–6mL/min have been recorded.

The performance of second generation silica monoliths, operating in parallel segmented flow mode

This study investigates the chromatographic performance of second generation monoliths in its conventional design, as well as replacing the standard outlet with an Active Flow Technology (AFT) assembly to minimise inefficient flow contributions. The AFT coupled monolith resulted in up to 50% improvement on the conventional monolith's efficiency and a 16% improvement in sensitivity. Exploitation of the current second generation monolith's silica infrastructure and AFT coupling in the parallel segmented flow (PSF) mode of operation would benefit high through-put analyses that demand highly efficient, sensitive, low volume detection, front end separation solutions utilizing conventional HPLC systems.