Showing papers by "Bar-Ilan University published in 2011"

Challenges in the development of advanced Li-ion batteries: a review

Abstract: Li-ion battery technology has become very important in recent years as these batteries show great promise as power sources that can lead us to the electric vehicle (EV) revolution. The development of new materials for Li-ion batteries is the focus of research in prominent groups in the field of materials science throughout the world. Li-ion batteries can be considered to be the most impressive success story of modern electrochemistry in the last two decades. They power most of today's portable devices, and seem to overcome the psychological barriers against the use of such high energy density devices on a larger scale for more demanding applications, such as EV. Since this field is advancing rapidly and attracting an increasing number of researchers, it is important to provide current and timely updates of this constantly changing technology. In this review, we describe the key aspects of Li-ion batteries: the basic science behind their operation, the most relevant components, anodes, cathodes, electrolyte solutions, as well as important future directions for R&D of advanced Li-ion batteries for demanding use, such as EV and load-leveling applications.

Organizational Learning: From Experience to Knowledge

Abstract: Organizational learning has been an important topic for the journal Organization Science and for the field. We provide a theoretical framework for analyzing organizational learning. According to the framework, organizational experience interacts with the context to create knowledge. The context is conceived as having both a latent component and an active component through which learning occurs. We also discuss current and emerging research themes related to components of our framework. Promising future research directions are identified. We hope that our perspective will stimulate future work on organizational learning and knowledge.

A review of advanced and practical lithium battery materials

Abstract: Presented herein is a discussion of the forefront in research and development of advanced electrode materials and electrolyte solutions for the next generation of lithium ion batteries. The main challenge of the field today is in meeting the demands necessary to make the electric vehicle fully commercially viable. This requires high energy and power densities with no compromise in safety. Three families of advanced cathode materials (the limiting factor for energy density in the Li battery systems) are discussed in detail: LiMn1.5Ni0.5O4 high voltage spinel compounds, Li2MnO3–LiMO2 high capacity composite layered compounds, and LiMPO4, where M = Fe, Mn. Graphite, Si, LixTOy, and MO (conversion reactions) are discussed as anode materials. The electrolyte is a key component that determines the ability to use high voltage cathodes and low voltage anodes in the same system. Electrode–solution interactions and passivation phenomena on both electrodes in Li-ion batteries also play significant roles in determining stability, cycle life and safety features. This presentation is aimed at providing an overall picture of the road map necessary for the future development of advanced high energy density Li-ion batteries for EV applications.

Sulfur‐Impregnated Activated Carbon Fiber Cloth as a Binder‐Free Cathode for Rechargeable Li‐S Batteries

Abstract: A route for the preparation of binder-free sulfur-carbon cathodes is developed for lithium sulfur batteries. The method is based on the impregnation of elemental sulfur into the micropores of activated carbon fibers. These electrodes demonstrate good electrochemical performance at high current density attributed to the uniform dispersion of sulfur inside the carbon fiber.

Robustness of a network of networks.

Abstract: Network research has been focused on studying the properties of a single isolated network, which rarely exists. We develop a general analytical framework for studying percolation of $n$ interdependent networks. We illustrate our analytical solutions for three examples: (i) For any tree of $n$ fully dependent Erd\ifmmode \mbox{\H{o}}\else \H{o}\fi{}s-R\'enyi (ER) networks, each of average degree $\overline{k}$, we find that the giant component is ${P}_{\ensuremath{\infty}}=p[1\ensuremath{-}\mathrm{exp} (\ensuremath{-}\overline{k}{P}_{\ensuremath{\infty}}){]}^{n}$ where $1\ensuremath{-}p$ is the initial fraction of removed nodes. This general result coincides for $n=1$ with the known second-order phase transition for a single network. For any $ng1$ cascading failures occur and the percolation becomes an abrupt first-order transition. (ii) For a starlike network of $n$ partially interdependent ER networks, ${P}_{\ensuremath{\infty}}$ depends also on the topology---in contrast to case (i). (iii) For a looplike network formed by $n$ partially dependent ER networks, ${P}_{\ensuremath{\infty}}$ is independent of $n$.

In Vivo Anomalous Diffusion and Weak Ergodicity Breaking of Lipid Granules

Abstract: Combining extensive single particle tracking microscopy data of endogenous lipid granules in living fission yeast cells with analytical results we show evidence for anomalous diffusion and weak ergodicity breaking. Namely we demonstrate that at short times the granules perform subdiffusion according to the laws of continuous time random walk theory. The associated violation of ergodicity leads to a characteristic turnover between two scaling regimes of the time averaged mean squared displacement. At longer times the granule motion is consistent with fractional Brownian motion.

Proofs of ownership in remote storage systems

Abstract: Cloud storage systems are becoming increasingly popular. A promising technology that keeps their cost down is deduplication, which stores only a single copy of repeating data. Client-side deduplication attempts to identify deduplication opportunities already at the client and save the bandwidth of uploading copies of existing files to the server. In this work we identify attacks that exploit client-side deduplication, allowing an attacker to gain access to arbitrary-size files of other users based on a very small hash signatures of these files. More specifically, an attacker who knows the hash signature of a file can convince the storage service that it owns that file, hence the server lets the attacker download the entire file. (In parallel to our work, a subset of these attacks were recently introduced in the wild with respect to the Dropbox file synchronization service.) To overcome such attacks, we introduce the notion of proofs-of-ownership (PoWs), which lets a client efficiently prove to a server that that the client holds a file, rather than just some short information about it. We formalize the concept of proof-of-ownership, under rigorous security definitions, and rigorous efficiency requirements of Petabyte scale storage systems. We then present solutions based on Merkle trees and specific encodings, and analyze their security. We implemented one variant of the scheme. Our performance measurements indicate that the scheme incurs only a small overhead compared to naive client-side deduplication.

Robustness of interdependent networks under targeted attack.

Abstract: When an initial failure of nodes occurs in interdependent networks, a cascade of failure between the networks occurs. Earlier studies focused on random initial failures. Here we study the robustness of interdependent networks under targeted attack on high or low degree nodes. We introduce a general technique which maps the targeted-attack problem in interdependent networks to the random-attack problem in a transformed pair of interdependent networks. We find that when the highly connected nodes are protected and have lower probability to fail, in contrast to single scale-free (SF) networks where the percolation threshold pc = 0, coupled SF networks are significantly more vulnerable with pc significantly larger than zero. The result implies that interdependent networks are difficult to defend by strategies such as protecting the high degree nodes that have been found useful to significantly improve robustness of single networks.

Coral and mollusc resistance to ocean acidification adversely affected by warming

Abstract: Increasing atmospheric carbon dioxide (CO2) concentrations are expected to decrease surface ocean pH by 0.3‐0.5 units by 2100 (refs 1,2), lowering the carbonate ion concentration of surface waters. This rapid acidification is predicted to dramatically decrease calcification in many marine organisms 3,4 . Reduced skeletal growth under increased CO2 levels has already been shown for corals, molluscs and many other marine organisms 4‐9 . The impact of acidification on the ability of individual species to calcify has remained elusive, however, as measuring net calcification fails to disentangle the relative contributions of gross calcification and dissolution rates on growth. Here, we show that corals and molluscs transplanted along gradients of carbonate saturation state at Mediterranean CO2 vents are able to calcify and grow at even faster than normal rates when exposed to the high CO2 levels projected for the next 300 years. Calcifiers remain at risk, however, owing to the dissolution of exposed shells and skeletons that occurs as pH levels fall. Our results show that tissues and external organic layers play a major role in protecting shells and skeletons from corrosive sea water, limiting dissolution and allowing organisms to calcify 10,11 . Our combined field and

Maternal and paternal plasma, salivary, and urinary oxytocin and parent-infant synchrony: considering stress and affiliation components of human bonding.

Abstract: Studies in mammals have implicated the neuropeptide oxytocin (OT) in processes of bond formation and stress modulation, yet the involvement of OT in human bonding throughout life remains poorly understood. We assessed OT in the plasma, saliva, and urine of 112 mothers and fathers interacting with their 4-6-month-old infants. Parent-infant interactions were micro-coded for parent and child's social behaviors and for the temporal coordination of their socio-affective cues. Parents were interviewed regarding their attachment to the infant and reported on bonding to own parents, romantic attachment, and parenting stress. Results indicated that OT in plasma (pOT) and saliva (sOT) were inter-related and were unrelated to OT in urine (uOT). pOT and sOT in mothers and fathers were associated with parent and child's social engagement, affect synchrony, and positive communicative sequences between parent and child. uOT was related to moments of interactive stress among mothers only, indexed by the co-occurrence of infant negative engagement and mother re-engagement attempts. pOT and sOT were associated with mothers' and fathers' attachment relationships throughout life: to own parents, partner, and infant, whereas uOT correlated with relationship anxiety and parenting stress among mothers only. Similar to other mammals, OT is involved in human attachment and contingent parenting. The dual role of OT in stress and affiliation underscores its complex involvement in processes of social bonding throughout life.

Modeling the conductance and DNA blockade of solid-state nanopores.

Abstract: We present measurements and theoretical modeling of the ionic conductance G of solid-state nanopores with 5-100 nm diameters, with and without DNA inserted into the pore. First, we show that it is essential to include access resistance to describe the conductance, in particular for larger pore diameters. We then present an exact solution for G of an hourglass-shaped pore, which agrees very well with our measurements without any adjustable parameters, and which is an improvement over the cylindrical approximation. Subsequently we discuss the conductance blockade ΔG due to the insertion of a DNA molecule into the pore, which we study experimentally as a function of pore diameter. We find that ΔG decreases with pore diameter, contrary to the predictions of earlier models that forecasted a constant ΔG. We compare three models for ΔG, all of which provide good agreement with our experimental data.

Antifungal activity of ZnO nanoparticles--the role of ROS mediated cell injury.

Abstract: Metal oxide nanoparticles have marked antibacterial activity. The toxic effect of these nanoparticles, such as those comprised of ZnO, has been found to occur due to an interaction of the nanoparticle surface with water, and to increase with a decrease in particle size. In the present study, we tested the ability of ZnO nanoparticles to affect the viability of the pathogenic yeast, Candida albicans (C. albicans). A concentration-dependent effect of ZnO on the viability of C. albicans was observed. The minimal fungicidal concentration of ZnO was found to be 0.1 mg ml(-1) ZnO; this concentration caused an inhibition of over 95% in the growth of C. albicans. ZnO nanoparticles also inhibited the growth of C. albicans when it was added at the logarithmic phase of growth. Addition of histidine (a quencher of hydroxyl radicals and singlet oxygen) caused reduction in the effect of ZnO on C. albicans depending on its concentration. An almost complete elimination of the antimycotic effect was achieved following addition of 5 mM of histidine. Exciting the ZnO by visible light increased the yeast cell death. The effects of histidine suggest the involvement of reactive oxygen species, including hydroxyl radicals and singlet oxygen, in cell death. In light of the above results it appears that metal oxide nanoparticles may provide a novel family of fungicidal compounds.

Advancing paternal age and risk of autism: new evidence from a population-based study and a meta-analysis of epidemiological studies.

Abstract: Advanced paternal age has been suggested as a risk factor for autism, but empirical evidence is mixed. This study examines whether the association between paternal age and autism in the offspring (1) persists controlling for documented autism risk factors, including family psychiatric history, perinatal conditions, infant characteristics and demographic variables; (2) may be explained by familial traits associated with the autism phenotype, or confounding by parity; and (3) is consistent across epidemiological studies. Multiple study methods were adopted. First, a Swedish 10-year birth cohort (N=1 075 588) was established. Linkage to the National Patient Register ascertained all autism cases (N=883). Second, 660 families identified within the birth cohort had siblings discordant for autism. Finally, meta-analysis included population-based epidemiological studies. In the birth cohort, autism risk increased monotonically with increasing paternal age. Offspring of men aged ⩾50 years were 2.2 times (95% confidence interval: 1.26–3.88: P=0.006) more likely to have autism than offspring of men aged ⩽29 years, after controlling for maternal age and documented risk factors for autism. Within-family analysis of discordant siblings showed that affected siblings had older paternal age, adjusting for maternal age and parity (P<0.0001). Meta-analysis demonstrated advancing paternal age association with increased risk of autism across studies. These findings provide the strongest evidence to date that advanced paternal age is a risk factor for autism in the offspring. Possible biological mechanisms include de novo aberration and mutations or epigenetic alterations associated with aging.

Cascade of failures in coupled network systems with multiple support-dependence relations.

Abstract: We study, both analytically and numerically, the cascade of failures in two coupled network systems A and B, where multiple support-dependence relations are randomly built between nodes of networks A and B. In our model we assume that each node in one network can function only if it has at least a single support link connecting it to a functional node in the other network. We assume that networks A and B have (i) sizes N{A} and N{B}, (ii) degree distributions of connectivity links P{A}(k) and P{B}(k), (iii) degree distributions of support links P{A}(k) and P{B}(k), and (iv) random attack removes (1-R{A})N{A} and (1-R{B})N{B} nodes form the networks A and B, respectively. We find the fractions of nodes μ{∞}{A} and μ{∞}{B} which remain functional (giant component) at the end of the cascade process in networks A and B in terms of the generating functions of the degree distributions of their connectivity and support links. In a special case of Erdős-Renyi networks with average degrees a and b in networks A and B, respectively, and Poisson distributions of support links with average degrees a and b in networks A and B, respectively, μ{∞}{A}=R{A}[1-exp(-aμ{∞}{B})][1-exp(-aμ{∞}{A})] and μ{∞}{B}=R{B}[1-exp(-bμ{∞}{A})][1-exp(-bμ{∞}{B})]. In the limit of a→∞ and b→∞, both networks become independent, and our model becomes equivalent to a random attack on a single Erdős-Renyi network. We also test our theory on two coupled scale-free networks, and find good agreement with the simulations.

Mother and infant coordinate heart rhythms through episodes of interaction synchrony.

Abstract: a b s t r a c t Animal studies demonstrated the powerful impact of maternal-infant social contact on the infant's physiological systems, yet the online effects of social interactions on the human infant's physiology remain poorly understood. Mothers and their 3-month old infants were observed during face-to-face interactions while cardiac output was collected from mother and child. Micro-analysis of the partners' behavior marked episodes of gaze, affect, and vocal synchrony. Time-series analysis showed that mother and infant coordinate heart rhythms within lags of less than 1 s. Bootstrapping analysis indicated that the concordance between maternal and infant biological rhythms increased significantly during episodes of affect and vocal synchrony compared to non-synchronous moments. Humans, like other mammals, can impact the physiological processes of the attachment partner through the coordination of visuo-affective social signals.

Aggression, Impulsivity, and Suicide Behavior: A Review of the Literature

Abstract: This article reviews the literature on the association between impulsivity aggression and suicide. The key words impulsivity, aggression, and suicide were entered into the pubmed, psychlit, and proqest databases. Significant articles were scrutinized for relevant information. Impulsivity and aggression are highly correlated with suicidal behavior across psychiatric samples, nosological borders, and non-psychiatric populations. Impulsivity and aggression are related but the nature of this relationship remains unclear. The literature is confusing and contradictory. This is probably due to the difficulty in defining and separating out these concepts and the fact that there is much overlap between them. Future research should aim at clarifying and refining these concepts as well as their link to all the different forms of suicidal behavior.

A transgenic mouse for in vivo detection of endogenous labeled mRNA

Abstract: Live-cell single mRNA imaging is a powerful tool but has been restricted in higher eukaryotes to artificial cell lines and reporter genes. We describe an approach that enables live-cell imaging of single endogenous labeled mRNA molecules transcribed in primary mammalian cells and tissue. We generated a knock-in mouse line with an MS2 binding site (MBS) cassette targeted to the 3' untranslated region of the essential β-actin gene. As β-actin-MBS was ubiquitously expressed, we could uniquely address endogenous mRNA regulation in any tissue or cell type. We simultaneously followed transcription from the β-actin alleles in real time and observed transcriptional bursting in response to serum stimulation with precise temporal resolution. We tracked single endogenous labeled mRNA particles being transported in primary hippocampal neurons. The MBS cassette also enabled high-sensitivity fluorescence in situ hybridization (FISH), allowing detection and localization of single β-actin mRNA molecules in various mouse tissues.

Breastfeeding, brain activation to own infant cry, and maternal sensitivity

Abstract: Background: Research points to the importance of breastfeeding for promoting close mother–infant contact and social-emotional development. Recent functional magnetic resonance imaging (fMRI) studies have identified brain regions related to maternal behaviors. However, little research has addressed the neurobiological mechanisms underlying the relationship between breastfeeding and maternal behavior in human mothers. We investigated the associations between breastfeeding, maternal brain response to own infant stimuli, and maternal sensitivity in the early postpartum. Methods: Seventeen biological mothers of healthy infants participated in two matched groups according to feeding method – exclusive breastfeeding and exclusive formula-feeding at 2–4 weeks postpartum. fMRI scanning was conducted in the first postpartum month to examine maternal brain activation in response to her own baby’s cry versus control baby-cry. Dyadic interactions between mothers and infants at 3–4 months postpartum were videotaped in the home and blindly coded for maternal sensitivity. Results: In the first postpartum month, breastfeeding mothers showed greater activations in the superior frontal gyrus, insula, precuneus, striatum, and amygdala while listening to their own baby-cry as compared to formula-feeding mothers. For both breastfeeding and formulafeeding mothers, greater activations in the right superior frontal gyrus and amygdala were associated with higher maternal sensitivity at 3–4 months postpartum. Conclusions: Results suggest links between breastfeeding and greater response to infant cues in brain regions implicated in maternal– infant bonding and empathy during the early postpartum. Such brain activations may facilitate greater maternal sensitivity as infants enter their social world. Keywords: Breastfeeding, infancy, maternal sensitivity, mother–infant interaction, neuroimaging. Abbreviations: ANOVA: analysis of variance; BOLD: blood-oxygen-level-dependent; CIB: Coding Interactive Behavior; fMRI: functional magnetic resonance imaging; GLM: general linear model; MPOA: medial preoptic area; OLS: ordinary least squares.

Revisiting the Gender Gap in Time-Use Patterns: Multitasking and Well-Being among Mothers and Fathers in Dual-Earner Families

Abstract: This study suggests that multitasking constitutes an important source of gender inequality, which can help explain previous findings that mothers feel more burdened and stressed than do fathers eve...

Single particle tracking in systems showing anomalous diffusion: the role of weak ergodicity breaking

Abstract: Anomalous diffusion has been widely observed by single particle tracking microscopy in complex systems such as biological cells. The resulting time series are usually evaluated in terms of time averages. Often anomalous diffusion is connected with non-ergodic behaviour. In such cases the time averages remain random variables and hence irreproducible. Here we present a detailed analysis of the time averaged mean squared displacement for systems governed by anomalous diffusion, considering both unconfined and restricted (corralled) motion. We discuss the behaviour of the time averaged mean squared displacement for two prominent stochastic processes, namely, continuous time random walks and fractional Brownian motion. We also study the distribution of the time averaged mean squared displacement around its ensemble mean, and show that this distribution preserves typical process characteristics even for short time series. Recently, velocity correlation functions were suggested to distinguish between these processes. We here present analytical expressions for the velocity correlation functions. The knowledge of the results presented here is expected to be relevant for the correct interpretation of single particle trajectory data in complex systems.

The Effect of Conformist and Attentive-To-Detail Members on Team Innovation: Reconciling the Innovation Paradox

Abstract: To resolve “the innovation paradox,” we examined whether cognitive styles associated with idea implementation (i.e., conformity and attention to detail) have an influence on team radical innovation...

Past purchase and intention to purchase in e‐commerce: The mediation of social presence and trust

Abstract: Purpose – Purchasing on the internet has unique features that make it different from the traditional shopping process, particularly with regard to its social context. This study seeks to investigate the relationship between past online purchases and purchasing intentions, representing the social context by the notions of social presence and trust.Design/methodology/approach – A sample of 115 working MBA students purchased an item online (but were stopped at the stage of paying), and then completed a questionnaire on social presence and trust.Findings – The results show that past purchasing predicts intentions to purchase and that trust and social presence act as partial mediators.Practical implications – Social context is important for understanding how past behavior affects future purchasing. Designs should therefore enhance social presence and trust. Moreover, it may be beneficial to monitor these mediators to detect potential problems.Originality/value – The study demonstrates the important role of soc...

Anatomical properties of the arcuate fasciculus predict phonological and reading skills in children

Abstract: For more than a century, neurologists have hypothesized that the arcuate fasciculus carries signals that are essential for language function; however, the relevance of the pathway for particular behaviors is highly controversial. The primary objective of this study was to use diffusion tensor imaging to examine the relationship between individual variation in the microstructural properties of arcuate fibers and behavioral measures of language and reading skills. A second objective was to use novel fiber-tracking methods to reassess estimates of arcuate lateralization. In a sample of 55 children, we found that measurements of diffusivity in the left arcuate correlate with phonological awareness skills and arcuate volume lateralization correlates with phonological memory and reading skills. Contrary to previous investigations that report the absence of the right arcuate in some subjects, we demonstrate that new techniques can identify the pathway in every individual. Our results provide empirical support for the role of the arcuate fasciculus in the development of reading skills.

PbS as a Highly Catalytic Counter Electrode for Polysulfide-Based Quantum Dot Solar Cells

Abstract: We show that a significant improvement of the light to electric power conversion efficiency of quantum dot sensitized solar cells with a polysulfide electrolyte can be achieved when a PbS counter electrode is used. An acid pretreatment of a Pb metal foil followed by dipping into polysulfide solution provides a counter electrode which improves the short circuit current, open circuit voltage, and fill factor compared to commonly used Pt electrodes. Electrochemical impedance spectroscopy reveals a low charge transfer resistance between polysulfide and PbS, indicating the high catalytic activity of PbS. Moreover, a comparison with reported charge transfer resistance values at open circuit potential for alternative counter electrodes for polysulfide shows that PbS is the most catalytic of all. For a CdSe quantum dot sensitized mesoporous TiO2 electrode, we achieved a conversion efficiency of 3% using PbS as a counter electrode.