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Masha M Rosenberg, Alfred G Redfield, Mary Roberts, Lizbeth Hedstrom
The ability of enzymes to modulate the dynamics of bound substrates and cofactors is a critical feature of catalysis, but the role of dynamics has largely been approached from the perspective of the protein. Here we use an underappreciated NMR technique, subtesla high resolution field cycling31 P NMR relaxometry, to interrogate the dynamics of enzyme bound substrates and cofactors in guanosine-5'-monophosphate reductase (GMPR). These experiments reveal distinct binding modes and dynamic profiles associated with the31 P nuclei in the Michaelis complexes for the deamination and hydride transfer steps of the catalytic cycle...
March 16, 2018: Biochemistry
E Lázaro-Lázaro, J A Moreno-Razo, M Medina-Noyola
Upon compression, the equilibrium hard-sphere liquid [pair potential uHS (r)] freezes at a packing fraction ϕf = 0.494 or, if crystallization is prevented, becomes metastable up to its glass transition at ϕg ≈ 0.58. Throughout the fluid regime (ϕ < ϕg ), we are, thus, certain that this model liquid does not exhibit any form of kinetic arrest. If, however, a small portion of these spheres (packing fraction ϕ2 ≪ ϕ) happen to ignore each other [u22 (r) = 0] but do not ignore the remaining "normal" hard spheres [u12 (r) = u21 (r) = u11 (r) = uHS (r)], whose packing fraction is thus ϕ1 = ϕ - ϕ2 , they run the risk of becoming dynamically arrested before they demix from the "normal" particles...
March 14, 2018: Journal of Chemical Physics
Christopher Ebsch, Robert Rosenbaum
Understanding the relationship between external stimuli and the spiking activity of cortical populations is a central problem in neuroscience. Dense recurrent connectivity in local cortical circuits can lead to counterintuitive response properties, raising the question of whether there are simple arithmetical rules for relating circuits' connectivity structure to their response properties. One such arithmetic is provided by the mean field theory of balanced networks, which is derived in a limit where excitatory and inhibitory synaptic currents precisely balance on average...
March 15, 2018: PLoS Computational Biology
Doris E Braun, Ulrich J Griesser
The observed moisture- and temperature dependent transformations of the dapsone (4,4'-diaminodiphenyl sulfone, DDS) 0. 33-hydrate were correlated to its structure and the number and strength of the water-DDS intermolecular interactions. A combination of characterization techniques was used, including thermal analysis (hot-stage microscopy, differential scanning calorimetry and thermogravimetric analysis), gravimetric moisture sorption/desorption studies and variable humidity powder X-ray diffraction, along with computational modeling (crystal structure prediction and pair-wise intermolecular energy calculations)...
2018: Frontiers in Chemistry
Robert N Collins, Tamara M Rosner, Bruce Milliken
Rosner, Lopez-Benitez, D'Angelo, Thomson, and Milliken (2017) reported a novel recognition memory effect using an immediate repetition method during the study phase. During each trial of an incidental study phase, participants named a target word that followed a prime word that had the same identity (repeated trials) or a different identity (not-repeated trials). Recognition in the following test phase was better for the not-repeated trials. In the present study, we examined the influence of prime encoding demands on this counterintuitive effect...
March 2018: Canadian Journal of Experimental Psychology, Revue Canadienne de Psychologie Expérimentale
Shakir Bilal, Edwin Michael
We study implications of complexity and seasonality in vector-host epidemiological models exhibiting backward bifurcation. Vector-host diseases represent complex infection systems that can vary in the transmission processes and population stages involved in disease progression. Seasonal fluctuations in external forcing factors can also interact in a complex way with internal host factors to govern the transmission dynamics. In backward bifurcation, the insufficiency of R 0  < 1 for predicting the stability of the disease-free equilibrium (DFE) state arises due to existence of bistability (coexisting DFE and endemic equilibria) for a range of R 0 values below one...
February 2018: Royal Society Open Science
Tomer J Czaczkes, Birgit Brandstetter, Isabella di Stefano, Jürgen Heinze
Expending effort is generally considered to be undesirable. However, both humans and vertebrates will work for a reward they could also get for free. Moreover, cues associated with high-effort rewards are preferred to low-effort associated cues. Many explanations for these counterintuitive findings have been suggested, including cognitive dissonance (self-justification) or a greater contrast in state (e.g., energy or frustration level) before and after an effort-linked reward. Here, we test whether effort expenditure also increases perceived value in ants, using both classical cue-association methods and pheromone deposition, which correlates with perceived value...
March 5, 2018: Journal of Comparative Psychology
Kathryn Demanelis, Shama Virani, Justin A Colacino, Niladri Basu, Muneko Nishijo, Werawan Ruangyuttikarn, Witaya Swaddiwudhipong, Kowit Nambunmee, Laura S Rozek
DNA methylation changes with age, and may serve as a biomarker of aging. Cadmium (Cd) modifies cellular processes that promote aging and disrupts methylation globally. Whether Cd modifies aging processes by influencing establishment of age-associated methylation marks is currently unknown. In this pilot study, we characterized methylation profiles in > 450 000 CpG sites in 40 non-smoking women (age 40-80) differentially exposed to environmental Cd from Thailand. Based on specific gravity adjusted urinary Cd, we classified them as high (HE) and low (LE) exposed and age-matched within 5 years...
May 2017: Environmental Epigenetics
William C Foster, Connor M Armstrong, Gregory T Chism, Jonathan N Pruitt
Temporally consistent individual differences in behavior, also known as animal personality, can have large impacts on individual fitness. Here, we explore the degree to which individual differences in anti-predator response (or boldness) influence survival rates in groups of snails Chlorostoma funebralis when they encounter a predatory sea star Pisaster giganteus . The snail C. funebralis shows consistent individual variation in predator response where some fearful snails actively flee bodies of water occupied by predators whereas bolder snails consistently do not...
December 2017: Current Zoology
Maria Manousidaki, Vladimir Yu Fedorov, Dimitrios G Papazoglou, Maria Farsari, Stelios Tzortzakis
We demonstrate that paraxial ring-Airy beams can approach the wavelength limit, while observing a counterintuitive, strong enhancement of their focal peak intensity. Using numerical simulations, we show that this behavior is a result of the coherent constructive action of paraxial and nonparaxial energy flow. A simple theoretical model enables us to predict the parameter range over which this is possible.
March 1, 2018: Optics Letters
T Gao, G Li, E Estrecho, T C H Liew, D Comber-Todd, A Nalitov, M Steger, K West, L Pfeiffer, D W Snoke, A V Kavokin, A G Truscott, E A Ostrovskaya
We demonstrate the generation of chiral modes-vortex flows with fixed handedness in exciton-polariton quantum fluids. The chiral modes arise in the vicinity of exceptional points (non-Hermitian spectral degeneracies) in an optically induced resonator for exciton polaritons. In particular, a vortex is generated by driving two dipole modes of the non-Hermitian ring resonator into degeneracy. Transition through the exceptional point in the space of the system's parameters is enabled by precise manipulation of real and imaginary parts of the closed-wall potential forming the resonator...
February 9, 2018: Physical Review Letters
Samantha K Jones, Yannick Griep
Employees often draw meaning from personal experiences and contributions in their work, particularly when engaging in organizational activities that align with their personal identity or values. However, recent empirical findings have demonstrated how meaningful work can also have a negative effect on employee's well-being as employees feel so invested in their work, they push themselves beyond their limits resulting in strain and susceptibility to burnout. We develop a framework to understand this "double edged" role of meaningful work by drawing from ideological psychological contracts (iPCs), which are characterized by employees and their employer who are working to contribute to a shared ideology or set of values...
2018: Frontiers in Psychology
Xin Zhang, Chang Xu, Zhongzhou Ren
Demands for single-photon sources are ubiquitous in quantum information processing as well as in quantum metrology. In many protocols for producing single photons, a cavity-emitter configuration is used. In such cavity quantum electrodynamical systems, the cavity can enforce a well-defined output mode for the photon and enhance its collection efficiency, while the emitter is indispensable for single photon emission. Here we show the two cavity-one two-level emitter configuration can be used to produce exclusively photon pairs, with each photon in a separate mode...
February 16, 2018: Scientific Reports
Tuomas Nurmi, Kalle Parvinen, Vesa Selonen
We propose a novel mathematical model for a metapopulation in which dispersal occurs on two levels: juvenile dispersal from the natal site is mandatory but it may take place either locally within the natal patch or globally between patches. Within each patch, individuals live in sites. Each site can be inhabited by at most one individual at a time and it may be of high or low quality. A disperser immigrates into a high-quality site whenever it obtains one, but it immigrates into a low-quality site only with a certain probability that depends on the time within the dispersal season...
February 13, 2018: Journal of Theoretical Biology
Wolfgang Tremel, Karsten Korschelt, Muhammad Nawaz Tahir
We describe elementary concepts, up-to-date developments, and per-spectives of the emerging field of nanoparticle enzyme mimics (so-called "nanozymes") at the interface of chemistry, biology, materials, and nanotechnology. The design and synthesis of functional enzyme mimics is a long-standing goal of biomimetic chemistry. Metal com-plexes, polymers and engineered biomolecules capturing the structure of natural enzymes or their active centers have been made to achieve high rates and enhanced selectivities...
February 15, 2018: Chemistry: a European Journal
Naomi J Fox, George L Caldow, Hilary Liebeschuetz, Karen Stevenson, Michael R Hutchings
Paratuberculosis (Johne's disease) is caused by the bacterium Mycobacterium avium subspecies paratuberculosis ( Map ). Achieving herd-level control of mycobacterial infection is notoriously difficult, despite widespread adoption of test-and-cull-based control strategies. The presence of infection in wildlife populations could be contributing to this difficulty. Rabbits are naturally infected with the same Map strain as cattle, and can excrete high levels in their faeces. The aim of this study is to determine if implementation of paratuberculosis control in cattle leads to a decline in Map infection levels in rabbits...
February 14, 2018: Veterinary Record
Hui Chen, Richard A Carlson, Brad Wyble
We often remember information without its source (e.g., word or picture format). This phenomenon has been studied extensively in long-term memory but rarely in the context of short-term working memory (WM), which leaves open the question of whether source amnesia can result from a lack of memory encoding rather than forgetting. This study provided a series of striking and novel demonstrations showing participants' inability to report the source of a color representation immediately after that color was used in a task and stored in memory...
February 1, 2018: Psychological Science
Kabir A Khan, Robert S Kerbel
Immunotherapies have revolutionized medical oncology following the remarkable and, in some cases, unprecedented outcomes observed in certain groups of patients with cancer. Combination with other therapeutic modalities, including anti-angiogenic agents, is one of the many strategies currently under investigation to improve the response rates and duration of immunotherapies. Such a strategy might seem counterintuitive given that anti-angiogenic agents can increase tumour hypoxia and reduce the number of blood vessels within tumours...
February 13, 2018: Nature Reviews. Clinical Oncology
Emmanuelle Weber, Giuseppe Sicoli, Hervé Vezin, Ghislaine Frébourg, Daniel Abergel, Geoffrey Bodenhausen, Dennis Kurzbach
Mixtures of water and glycerol provide popular matrices for low-temperature spectroscopy of vitrified samples. However, they involve counterintuitive physicochemical properties, such as spontaneous nanoscopic phase separations (NPS) in solutions that appear macroscopically homogeneous. We demonstrate that such phenomena can substantially impact the efficiency of dynamic nuclear polarization (DNP) by factors up to 20% by causing fluctuations in local concentrations of polarization agents (radicals). Thus, a spontaneous NPS of water/glycerol mixtures that takes place on time scales on the order of 30-60 min results in a confinement of polarization agents in nanoscopic water-rich vesicles, which in return affects the DNP...
February 12, 2018: Angewandte Chemie
William R Smith
Several prominent writers including Norman Daniels, James Sabin, Amy Gutmann, Dennis Thompson and Leonard Fleck advance a view of legitimacy according to which, roughly, policies are legitimate if and only if they result from democratic deliberation, which employs only public reasons that are publicised to stakeholders. Yet, the process described by this view contrasts with the actual processes involved in creating the Affordable Care Act (ACA) and in attempting to pass the Health Securities Act (HSA). Since the ACA seems to be legitimate, as the HSA would have been had it passed, they seem to be counterexamples to this view...
February 5, 2018: Journal of Medical Ethics
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