Network Modification Research Articles

ALGORITHM OF NEURON NETWORKS MODIFICATION

It is considered a problem of neuron network modification whose topology has been chosen previously as a result of optimization problem solution for given task. The proposed modification algorithm is based on two-stages procedure which consists of genetic algorithm and local algorithm of optimization. The problem of modification is represented as two tasks: the search of optimal neuron network structure and weight coefficients adjustment. For the solution of these two problems it is used two-stages algorithm, in which at the first stage it is applied hybrid multicriteria evolutionary algorithm and at the second stage it is determined values of weight coefficients with help of back propagation error method and method of steepest descent. The determination of optimal values of hidden layers quantity is executed with help of adaptive algorithm of merging and growing.

Differential Representation of Landmark and Self-Motion Information along the CA1 Radial Axis: Self-Motion Generated Place Fields Shift toward Landmarks during Septal Inactivation.

Spatial location in the environment can be defined in relation to specific landmarks or in relation to the global context, and is estimated from both the sensing of landmarks and the inner sense of cumulated locomotion referred to as path-integration. The respective contribution of landmark and path-integration to place-cell activity in the hippocampus is still unclear and complicated by the fact that the two mechanisms usually overlap. To bias spatial mechanisms toward landmark or path-integration, we use a treadmill equipped with a long belt on which male mice run sequentially through a zone enriched and a zone impoverished in visual-tactile cues. We show that inactivation of the medial septum (MS), which is known to disrupt the periodic activity of grid cells, impairs mice ability to anticipate the delivery of a reward in the cue-impoverished zone and transiently alter the spatial configuration of place fields in the cue-impoverished zone selectively: following MS inactivation, place fields in the cue-impoverished zone progressively shift backward and stabilize near the cues, resulting in the contraction of the spatial representation around cues; following MS recovery, the initial spatial representation is progressively restored. Furthermore, we found that place fields in the cue-rich and cue-impoverished zones are preferentially generated by cells from the deep and superficial sublayers of CA1, respectively. These findings demonstrate with mechanistic insights the contribution of MS to the spread of spatial representations in cue-impoverished zones, and indicate a segregation of landmark-based and path-integration-assisted spatial mechanisms into deep and superficial CA1, respectively.SIGNIFICANCE STATEMENT Cells encoding a cue-impoverished zone and the vicinity of landmarks responded differentially to septal inactivation and resided in distinct sublayers of CA1. These findings provide new insights on place field mechanisms: septal activity is critical for maintaining the spread of place fields in cue-impoverished areas, but not for the generation of place fields; Following MS inactivation, trial-by-trial network modifications by activity-dependent mechanisms are responsible for the gradual collapse of spatial representations. Furthermore, the findings suggest parallel coding streams for landmark and self-motion information. Superficial CA1 cells are better suited for encoding global position via the assist of path-integration, whereas deep CA1 cells can support spatial memory processes on an object-specific basis.

Network Structure and Connectivity in SnO-P2O5 Glasses: Results from 2D 31P and 119Sn NMR Spectroscopy.

The compositional evolution of the network structure and connectivity in binary SnO-P2O5 glasses with 35 ≤ mol % SnO ≤ 55 is studied using two-dimensional 119Sn and 31P NMR spectroscopy. The phosphate Q n species concentrations, as obtained from the analyses of the 31P NMR spectral line shapes suggest that the network modification can be described in terms of a binary Q-speciation model. On the other hand, the 119Sn NMR spectra suggest that the Sn-O coordination environment in these glasses is composition dependent. Sn is present in both 3-fold (trigonal pyramid) and 4-fold (trigonal bipyramid) coordinations with oxygen in these glasses. The relative fraction of the trigonal pyramidal environment increases with increasing SnO content. The unusually low glass transition temperature Tg of these glasses (241-266 °C) is argued to be related to the low coordination number of Sn, leading to a relatively sparsely connected structural network.

Abnormal Regional Homogeneity and Functional Connectivity of Baseline Brain Activity in Hepatitis B Virus-Related Cirrhosis With and Without Minimal Hepatic Encephalopathy.

Background and Aims: Abnormalities in neural activity have been reported in cirrhosis with minimal hepatic encephalopathy (MHE). However, little is known about the neurophysiological mechanisms in this disorder. We aimed to investigate the altered patterns of regional synchronization and functional connections in hepatitis B virus-related cirrhosis (HBV-RC) patients with and without MHE using both regional homogeneity (ReHo) and region of interest (ROI)-based functional connectivity (FC) computational methods.Methods: Data of magnetic resonance imaging scans were collected from 30 HBV-RC patients with MHE, 32 HBV-RC patients without MHE (NMHE) and 64 well-matched controls. Several regions showing differences in ReHo after one-way analysis of variance (ANOVA) were defined as ROIs for FC analysis. Next, post hoc t-tests were applied to calculate the group differences in ReHo and FC (false discovery rate (FDR) correction, p < 0.05). Correlations between clinical variables and the altered ReHo and FC were then assessed in patient groups.Results: Across three groups, significant ReHo differences were found in nine ROI regions mainly within the visual network (VN), dorsal attention network (DAN), somatomotor network (SMN), fronto parietal control (FPC) network and thalamus. Compared with healthy controls (HC), the MHE group exhibited abnormal FC mainly between the right calcarine (CAL.R) and middle frontal gyrus (MFG.L)/right thalamus. The MHE patients showed increased FC between the MFG.L and CAL.R compared to NMHE patients. Disease duration of MHE patients was positively correlated with increased mean ReHo values in the right fusiform gyrus (FFG); psychometric hepatic encephalopathy score (PHES) test scores were negatively correlated with increased FC between MFG.L and CAL.R and positively correlated with reduced FC between the CAL.R and THA.R. For NMHE patients, the mean ReHo values in the right frontal pole were positively correlated with disease duration and positively correlated with the PHES scores.Conclusion: Our results exhibited that the functional brain modifications in patients with and without MHE are characterized by compound alterations in local coherence and functional connections in the VN, SMN, DAN, FPC networks and thalamus by using a combination of ReHo and ROI-based FC analysis. These functional imaging changes are correlated with disease duration/PHES. This study helped us gain a better understanding of the features of brain network modifications in cirrhosis.

The impact of silicon on cell wall composition and enzymatic saccharification of Brachypodium distachyon

BackgroundPlants and in particular grasses benefit from a high uptake of silicon (Si) which improves their growth and productivity by alleviating adverse effects of biotic and abiotic stress. However, the silicon present in plant tissues may have a negative impact on the processing and degradation of lignocellulosic biomass. Solutions to reduce the silicon content either by biomass engineering or development of downstream separation methods are therefore targeted. Different cell wall components have been proposed to interact with the silica pool in plant shoots, but the understanding of the underlying processes is still limited.ResultsIn the present study, we have characterized silicon deposition and cell wall composition in Brachypodium distachyon wild-type and low-silicon 1 (Bdlsi1-1) mutant plants. Our analyses included different organs and plant developmental stages. In the mutant defective in silicon uptake, low silicon availability favoured deposition of this element in the amorphous form or bound to cell wall polymers rather than as silicified structures. Several alterations in non-cellulosic polysaccharides and lignin were recorded in the mutant plants, indicating differences in the types of linkages and in the three-dimensional organization of the cell wall network. Enzymatic saccharification assays showed that straw from mutant plants was marginally more degradable following a 190 °C hydrothermal pretreatment, while there were no differences without or after a 120 °C hydrothermal pretreatment.ConclusionsWe conclude that silicon affects the composition of plant cell walls, mostly by altering linkages of non-cellulosic polymers and lignin. The modifications of the cell wall network and the reduced silicon concentration appear to have little or no implications on biomass recalcitrance to enzymatic saccharification.

Throwing good money after SPAD? Exploring the cost of signal passed at danger (SPAD) incidents to Australasian rail organisations

This study sought direct estimates of incidence, preventative costs, and reactive costs associated with the occurrence of low risk (‘typical’) Signal Passed at Danger (SPAD) events in Australasian rail. In a cross-sectional multiple-case design, a descriptive questionnaire was sent to eight operators, and completed by managerial personnel with responsibility for SPAD-risk mitigation. Items addressed SPAD frequency, operator delays, and a range of preventative and reactive costs associated with low-severity (‘low-risk’) SPADs. Delay costs varied between cases, with each having different organisational size and network density. Preventative costs were mostly comprised of internal SPAD prevention team maintenance, participation in a collaborative SPAD Group, and resultant network modifications. Reactive costs were largely comprised of driver-related factors and in two cases, of higher low-risk investigation and regulatory costs. The ratio of preventative to reactive costs (P:R) varied widely, approaching equilibrium for two cases only—both participated in internal and external SPAD preventative team consultation. One freight organisation noted a large P:R imbalance due to very low preventative costs. Low-risk SPADs represent a host of substantial annual costs for each Australasian passenger- and freight-rail organisation. As this study gives preliminary estimates, these likely underestimate the full costs, as multiple other factors are yet to be accounted for. This study justifies the need for detailed analysis of SPAD-associated costs to contrast data from multiple rail organisations, and a clearer picture of how organisational expenses are allocated within SPAD prevention and reaction.

Indoor Channel Capacity Measurement of 2 x 2 MIMO Polarization Diversity Antenna

&lt;span&gt;This paper presents the channel capacity investigation and the polarization reconfigurable antenna analysis for MIMO system in an indoor scenario. A single and dual-port polarization reconfigurable antenna is used at the receiver end to study the effect of polarization diversity configurations towards the achievable performance of the channel capacity. The polarization reconfigurable antennas are developed through two techniques, which are slits perturbation for single-port and feeding network modification for dual-port. The benefits offered by the designed antennas are investigated when being used as a receiver in both line-of-sight (LOS) and non-line-of-sight (NLOS) scenarios. The results show the proposed antennas are suitable to be adopted and highly potential to improve the channel capacity of the MIMO systems.&lt;/span&gt;

The relationship between river types and land cover in riparian zones

Fluvial systems are dynamic and the characteristics of every assessed reach are variable and difficult to quantify based on river type threshold values. The authors of this study considered whether taking into account detailed land cover data from the riparian zone could be of any help in more accurately defining river types and establishing hydromorphological reference conditions. Detailed land cover data from riparian zones (50 m and 200 m buffers along main rivers) were included among the hydromorphological characteristics of the main rivers on the territory of the Czech Republic, and the relationship between established river types and land cover in riparian zones was evaluated.Land cover data from main river reaches categorized by river type indicate fundamental land cover differences between types that closely correspond with the hydromorphological characteristics of channels. If we examine riparian zones with no or minimal anthropogenic impact, significant land cover classes emerge for distinct river types that at the same time facilitate more accurate descriptions of river types. For rivers in agricultural lowlands, land cover contributes to revealing modifications of the river network. This study demonstrates that detailed land cover data can be used to explain differences between river types and can be included among river characteristics for establishing hydromorphological reference conditions or for assessing the level of anthropogenic impact in the riparian zone, which generally has an effect on the channel as well. At the same time, detailed land cover data may significantly help locate new reference sites, or exclude unsuitable sites.

Mid‐IR transparent TeO2‐TiO2‐La2O3 glass and its crystallization behavior for photonic applications

AbstractIn this report, effect of enhanced rare earth (La2O3) concentration on substitution of TeO2 within ternary TeO2‐TiO2‐La2O3 (TTL) glass system has been studied with respect to its thermal, structural, mechanical, optical, and crystallization properties with an aim to achieve glass and glass‐ceramics having rare‐earth‐rich crystalline phase for nonlinear optical and infrared photonic applications. DSC analysis (10°C/min) demonstrates a progressive increase in glass‐transition temperature (Tg) from 359 to 452°C with the increase in La2O3 content. Continuous glass network modification with transformation of [TeO4] to [TeO3/TeO3+1] units is evidenced from Raman spectra which is corroborated with XPS studies. While mechanical properties demonstrate enhancement of cross‐linking density in the network. These glasses exhibit optical transmission window extended from 0.4 to 6 μm with calculated zero dispersion wavelength (λZDW) varying from 2.41 to 2.28 μm depending upon La2O3 content. Crystallization kinetics of TTL10 (80TeO2‐10TiO2‐10La2O3 in mol%) glass has been studied via established models. Activation energy (Ea) has been evaluated and dimensionality of crystal growth (m) suggests formation of surface crystals. Glass‐ceramic with crystalline phase of La2Te6O15 has been realized in heat‐treated TTL10 glass samples (at 450°C). As predicted from DSC analysis, FESEM study unveils the formation of surface crystallized glass‐ceramics.

Different property studies with network improvement of CdO doped alkali borate glass

Quaternary alkali borate glass matrix doped with CdO (0, 2, 4, 6, 8, 10 mol%) have been prepared by using conventional melting and quenching technique. For these glass systems structural properties were investigated by using X-ray diffraction, FE-SEM, EDS, FTIR and Raman spectroscopy characterization techniques. X-ray diffraction pattern and FE-SEM studies confirms the amorphous nature of prepared oxide glass. The optical absorption studies were done by using UV–Vis spectroscopy technique at room temperature. The physical parameters of all the glass samples were evaluated with respect to the composition, such as bulk density (ρ), average molar mass (M), molar volume (Vm), ionic concentration (N), interionic distance (ri). They exhibit the non-linearity supporting evidence for the borate glass network modification. Investigations of FTIR and Raman spectroscopy of prepared glass samples have been employed to confirm the role of oxides in the formation of glass network. These glasses are made up from converting [BO3] to [BO4] units without increasing the concentration of non-bridging oxygen. Experimental fraction of 4-coordinated boron atoms expressed by the parameter N4 was calculated and represented with the addition of concentration of CdO (mol%). The optical absorption studies revealed that the average refractive index (nav), optical band gap energy (Eg) nonlinearly increases. The electronic polarizability and optical basicity of the oxide ion (αO2−), as function of refractive index and optical band gap energy were also examined.

Mapping spatial accessibility of public transportation network in an urban area – A case study of Shanghai Hongqiao Transportation Hub

Accessibility is a key metric when assessing the efficiency of an urban public transportation network. This research develops a methodology for evaluating spatial accessibility of a system with multiple transportation modes in an urban area, Shanghai Hongqiao Transportation Hub (SHTH) and its surrounding area. The method measured total traveling time as an accessibility indicator, which summed the time people spent on walking, waiting, transfer and transportation in a journey from the SHTH to destinations. Spatial accessibility was classified into five levels from very high to very low. The evaluation was conducted at a cell-by-cell basis under an overall scenario and three specific scenarios. Evaluation results were presented in a series of maps. The overall accessibility scenario shows a concentric-ring trend decreasing from the SHTH to the fringe of the study area. Areas along the metro lines generally have a much higher accessibility than those along the bus lines with some exceptions where bus routes play a more important role. Metro stations identified as either time-saving or time-consuming points are mainly distributed around the urban center. Some suggestions are proposed for improving accessibility of public transportation network in the study area. The results from this study provide a scientific basis and useful information for supporting decision-making on urban planning, and assisting dwellers to travel in a time-efficient manner. The methodology offers a simple, flexible way to the spatial evaluation, metro station identification and network modification of accessibility of public transportation systems with multiple transportation modes.

Synthesis, thermal, structural and linear optical properties of new glasses within the TeO2-TiO2-WO3 system

The glass-forming domain and physical properties, namely, the density, thermal, structural and linear optical properties of new glasses within the TeO2-TiO2-WO3 system have been investigated. By means of micro-Raman spectroscopy, the structure of these glasses was examined based on a full-scale spectral decomposition. The optical transmission and refractive index dispersion were measured by UV–Vis-NIR spectroscopy and spectroscopic ellipsometry respectively. Consistent correlations were established between the structural and linear optical properties. Only minor structural modifications of the original TeO2-rich network are taking place upon adding TiO2 or WO3, suggesting the absence of Te–O–Te bond network depolymerization. Our results also suggest that, upon increasing TiO2 content, a phase separation occurs between amorphous TeO2-rich and amorphous TiO2-rich regions. We also argue that the structural trends upon adding WO3 evolve from uniformly dispersed WO6 octahedra (at low WO3 content) to amorphous WO3-like regions (at higher WO3 content) before the crystallization of γ-WO3 at 30 mol% of WO3. The compositional dependence of the refractive index and several optical constants (Urbach EU and dispersion Ed energies, oxide ion polarizabilities) is highlighted. These glasses collectively exhibit high refractive indices in the order of ~2.2.

On service-chaining strategies using Virtual Network Functions in operator networks

Network functions (e.g., firewalls, load balancers, etc.) have been traditionally provided through proprietary hardware appliances. Often, hardware appliances need to be hardwired back-to-back to form a service chain providing chained network functions. These hardware appliances cannot be provisioned on-demand since they are statically embedded in the network topology, making creation, insertion, modification, upgrade, and removal of service chains complex, and also slowing down service innovation. Hence, network operators are starting to deploy Virtual Network Functions (VNFs), which are virtualized over commodity hardware. VNFs can be deployed in Data Centers (DCs) or in Network Function Virtualization (NFV)-capable network elements (nodes) such as routers and switches. NFV-capable nodes and DCs together form a Network-enabled Cloud (NeC) that helps to facilitate the dynamic service chaining required to support today’s evolving network traffic and its service demands. In this study, we focus on the VNF service-chain placement and traffic routing problem, and build a model for placing a VNF service chain while minimizing network-resource consumption. Further, we study the network-resource consumption of various service-chaining strategies, which can be a NeC having a varying number of NFV-capable nodes or a proprietary hardware solution. Our results indicate that a NeC having a DC and NFV-capable nodes can significantly reduce network-resource consumption.

Default mode network modifications in Fabry disease: A resting-state fMRI study with structural correlations.

Aim of the study was to evaluate the presence of Default Mode Network (DMN) modifications in Fabry Disease (FD), and their possible correlations with structural alterations and neuropsychological scores. Thirty-two FD patients with a genetically confirmed diagnosis of classical FD (12 males, mean age 43.3 ± 12.2) were enrolled, along with 35 healthy controls (HC) of comparable age and sex (14 males, mean age 42.1 ± 14.5). Resting-State fMRI data were analyzed using a seed-based approach, with six different seeds sampling the main hubs of the DMN. Structural modifications were assessed by means of Voxel-Based Morphometry (VBM) and Tract-Based Spatial Statistics analyses. Between-group differences and correlations with neuropsychological variables were probed voxelwise over the whole brain. Possible correlations between FC modifications and global measures of microstructural alteration were also tested in FD patients with a partial correlation analysis. In the FD group, clusters of increased functional connectivity involving both supratentorial and infratentorial regions emerged, partially correlated to the widespread white matter (WM) damage found in these patients. No gray matter volume differences were found at VBM between the two groups. The connectivity between right inferior frontal gyrus and precuneus was significantly correlated with the Corsi block-tapping test results (p = .0001). Widespread DMN changes are present in FD patients that correlate with WM alterations and cognitive performance. Our results confirm the current view of a cerebral involvement in FD patients not simply associated to major cerebrovascular events, but also related to significant and diffuse microstructural and functional changes.

Magnetic resonance markers of tissue damage related to connectivity disruption in multiple sclerosis.

Patients with multiple sclerosis (MS) display reduced structural connectivity among brain regions, but the pathogenic mechanisms underlying network disruption are still unknown. We aimed to investigate the association between the loss of diffusion-based structural connectivity, measured with graph theory metrics, and magnetic resonance (MR) markers of microstructural damage. Moreover, we evaluated the cognitive consequences of connectivity changes. We analysed the frontoparietal network in 102 MS participants and 25 healthy volunteers (HV). MR measures included radial diffusivity (RD), as marker of demyelination, and ratios of myo-inositol, N-acetylaspartate and glutamate+glutamine with creatine in white (WM) and grey matter as markers of astrogliosis, neuroaxonal integrity and glutamatergic neurotoxicity. Patients showed decreased global and local efficiency, and increased assortativity (p < 0.01) of the network, as well as increased RD and myo-inositol, and decreased N-acetylaspartate in WM compared with HV (p < 0.05). In patients, the age-adjusted OR of presenting abnormal global and local efficiency was increased for each increment of 0.01 points in RD and myo-inositol, while it was decreased for each increment of 0.01 points in N-acetylaspartate (the increase of N-acetylaspartate reduced the risk of having abnormal connectivity), all in WM. In a multiple logistic regression analysis, the OR of presenting abnormal global efficiency was 0.95 (95% confidence interval, CI: 0.91–0.99, p = 0.011) for each 0.01 increase in N-acetylaspartate, and the OR of presenting abnormal local efficiency was 1.39 (95% CI: 1.14–1.71, p = 0.001) for each 0.01 increase in RD. Patients with abnormal efficiency had worse performance in attention, working memory and processing speed (p < 0.05). In conclusion, patients with MS exhibit decreased structural network efficiency driven by diffuse microstructural impairment of the WM, probably related to demyelination, astroglial and neuroaxonal damage. The accumulation of neuroaxonal pathological burden seems to magnify the risk of global network collapse, while demyelination may contribute to the regional disorganization. These network modifications have negative consequences on cognition.

Baseline biomarkers of connectome disruption and atrophy predict future processing speed in early multiple sclerosis

The development of accurate prognoses in multiple sclerosis is difficult, as the disease is characterized by heterogeneous patterns of brain abnormalities that relate in an unclear way to future impairments. Here, we use a statistical modeling approach to determine if the baseline pattern of connectome disruption due to T2-FLAIR lesions could predict a patient's future processing speed, as measured using the Symbol Digits Modality Test scores. Imaging data, demographics and Symbol Digits Modality Test scores were collected from 61 early relapsing remitting multiple sclerosis patients. The Network Modification Tool was used to estimate damage to the connectome by quantifying white matter abnormalities' effects on 1) global network properties, 2) regional connectivity and 3) connectivity between pairs of regions. MS subjects showed significant improvement of processing speed between baseline and follow-up (t = −2.6, p = 0.0096); however, both baseline (t = −4.01, p = 0.00012) and follow-up (t = −2.10, p = 0.038) processing speed were significantly lower than age-matched healthy controls. Partial Least Squares Regression was used to create models that predict future processing speed from between baseline imaging metrics and demographics. The model based on region-pair disconnection and gray matter atrophy had the lowest AIC and highest prediction accuracy (R2 = 0.79) compared to models based on global (R2 = 0.41) or regional (R2 = 0.66) disconnection and gray matter atrophy, overlap with an ROI-based atlas and gray matter atrophy (R2 = 0.73) or gray matter atrophy alone (R2 = 0.71). We found that baseline measures of connectivity disruption in various parietal, temporal, occipital and subcortical regions and atrophy in the putamen were important predictors of future processing speed. We conclude that information about disruptions to pairwise brain connections is more informative of future processing speed than regional or global metrics or gray matter atrophy alone. The combination of quantitative disconnectome metrics, gray matter atrophy and statistical modeling approaches could enable clinicians in developing more accurate, individualized prognoses of future cognitive status in multiple sclerosis patients.

Predicting language outcomes after stroke: Is structural disconnection a useful predictor?

For many years, researchers have sought to understand whether and when stroke survivors with acquired language impairment (aphasia) will recover. There is broad agreement that lesion location information should play some role in these predictions, but still no consensus on the best or right way to encode that information. Here, we address the emerging emphasis on the structural connectome in this work – specifically the claim that disrupted white matter connectivity conveys important, unique prognostic information for stroke survivors with aphasia.Our sample included 818 stroke patients extracted from the PLORAS database, which associates structural MRI from stroke patients with language assessment scores from the Comprehensive Aphasia Test (CAT) and basic demographic. Patients were excluded when their lesions were too diffuse or small (<1 cm3) to be detected by the Automatic Lesion Identification toolbox, which we used to encode patients' lesions as binary lesion images in standard space. Lesions were encoded using the 116 regions defined by the Automatic Anatomical Labelling atlas. We examined prognostic models driven by both “lesion load” in these regions (i.e. the proportion of each region destroyed by each patient's lesion), and by the disconnection of the white matter connections between them which was calculated via the Network Modification toolbox. Using these data, we build a series of prognostic models to predict first one (“naming”), and then all of the language scores defined by the CAT.We found no consistent evidence that connectivity disruption data in these models improved our ability to predict any language score. This may be because the connectivity disruption variables are strongly correlated with the lesion load variables: correlations which we measure both between pairs of variables in their original form, and between principal components of both datasets. Our conclusion is that, while both types of structural brain data do convey useful, prognostic information in this domain, they also appear to convey largely the same variance. We conclude that connectivity disruption variables do not help us to predict patients' language skills more accurately than lesion location (load) data alone.

Community detection in dynamic networks via adaptive label propagation.

An adaptive label propagation algorithm (ALPA) is proposed to detect and monitor communities in dynamic networks. Unlike the traditional methods by re-computing the whole community decomposition after each modification of the network, ALPA takes into account the information of historical communities and updates its solution according to the network modifications via a local label propagation process, which generally affects only a small portion of the network. This makes it respond to network changes at low computational cost. The effectiveness of ALPA has been tested on both synthetic and real-world networks, which shows that it can successfully identify and track dynamic communities. Moreover, ALPA could detect communities with high quality and accuracy compared to other methods. Therefore, being low-complexity and parameter-free, ALPA is a scalable and promising solution for some real-world applications of community detection in dynamic networks.

Computing Minimum Reaction Modifications in a Boolean Metabolic Network.

In metabolic network modification, we newly add enzymes or/and knock-out genes to maximize the biomass production with minimum side-effect. Although this problem has been studied for various problem settings via mathematical models including flux balance analysis, elementary mode, and Boolean models, some important problem settings still remain to be studied. In this paper, we consider the Boolean Reaction Modification (BRM) problem, where a host metabolic network and a reference metabolic network are given in the Boolean model. The host network initially produces some toxic compounds and cannot produce some necessary compounds, but the reference network can produce the necessary compounds, and we should minimize the total number of removed reactions from the host network and added reactions from the reference network so that the toxic compounds are not producible, but the necessary compounds are producible in the resulting host network. We developed integer linear programming (ILP)-based methods for BRM, and compared them with OptStrain and SimOptStrain. The results show that our method performed better for reducing the total number of added and removed reactions, while OptStrain and SimOptStrain performed better for optimizing the production of the target compound. Our developed software is freely available at "http://sunflower.kuicr.kyoto-u.ac.jp/~rogi/solBRM/solBRM.html ".

Experimental Evidence for the Formation of Solvation Shells by Soluble Species at a Nonuniform Air–Ice Interface

Soluble species induce surface premelting at the air–ice interface in the thermodynamic ice stability domain below the liquidus. This quasi-liquid layer is thought to increase in thickness with concentration of impurities and to represent a reservoir into which larger amounts of soluble species dissolve compared to a more rigid ice surface. To directly investigate the response of the quasi-liquid layer to increasing amounts of solutes and to clarify the distribution of these at the ice surface with depth, we use a combination of Auger electron yield X-ray absorption and photoelectron spectroscopies. We studied the adsorption of formic acid to ice at 251 K. These two complementary methods allow concluding that solutes enter the air–ice interface but do not necessarily induce a thicker quasi-liquid layer. Rather, modifications of the hydrogen-bonding network seem to be linked to the formation of solvation shells. We suggest that the flexibility of water molecules in the quasi-liquid layer is essential to fo...