@article{8246, abstract = {The Staphylococcus aureus cell wall stress stimulon (CWSS) is activated by cell envelope-targeting antibiotics or depletion of essential cell wall biosynthesis enzymes. The functionally uncharacterized S. aureus LytR-CpsA-Psr (LCP) proteins, MsrR, SA0908 and SA2103, all belong to the CWSS. Although not essential, deletion of all three LCP proteins severely impairs cell division. We show here that VraSR-dependent CWSS expression was up to 250-fold higher in single, double and triple LCP mutants than in wild type S. aureus in the absence of external stress. The LCP triple mutant was virtually depleted of wall teichoic acids (WTA), which could be restored to different degrees by any of the single LCP proteins. Subinhibitory concentrations of tunicamycin, which inhibits the first WTA synthesis enzyme TarO (TagO), could partially complement the severe growth defect of the LCP triple mutant. Both of the latter findings support a role for S. aureus LCP proteins in late WTA synthesis, as in Bacillus subtilis where LCP proteins were recently proposed to transfer WTA from lipid carriers to the cell wall peptidoglycan. Intrinsic activation of the CWSS upon LCP deletion and the fact that LCP proteins were essential for WTA-loading of the cell wall, highlight their important role(s) in S. aureus cell envelope biogenesis.}, author = {Dengler, Vanina and Meier, Patricia Stutzmann and Heusser, Ronald and Kupferschmied, Peter and Fazekas, Judit and Friebe, Sarah and Staufer, Sibylle Burger and Majcherczyk, Paul A. and Moreillon, Philippe and Berger-Bächi, Brigitte and McCallum, Nadine}, issn = {0378-1097}, journal = {FEMS Microbiology Letters}, number = {2}, pages = {109--120}, publisher = {Oxford University Press}, title = {{Deletion of hypothetical wall teichoic acid ligases in Staphylococcus aureus activates the cell wall stress response}}, doi = {10.1111/j.1574-6968.2012.02603.x}, volume = {333}, year = {2012}, } @article{826, abstract = {Plants exhibit a unique developmental flexibility to ever-changing environmental conditions. To achieve their profound adaptability, plants are able to maintain permanent stem cell populations and form new organs during the entire plant life cycle. Signaling substances, called plant hormones, such as auxin, cytokinin, abscisic acid, brassinosteroid, ethylene, gibberellin, jasmonic acid, and strigolactone, govern and coordinate these developmental processes. Physiological and genetic studies have dissected the molecular components of signal perception and transduction of the individual hormonal pathways. However, over recent years it has become evident that hormones do not act only in a linear pathway. Hormonal pathways are interconnected by a complex network of interactions and feedback circuits that determines the final outcome of the individual hormone actions. This raises questions about the molecular mechanisms underlying hormonal cross talk and about how these hormonal networks are established, maintained, and modulated throughout plant development.}, author = {Vanstraelen, Marleen and Eva Benková}, journal = {Annual Review of Cell and Developmental Biology}, pages = {463 -- 487}, publisher = {Annual Reviews}, title = {{Hormonal interactions in the regulation of plant development}}, doi = {10.1146/annurev-cellbio-101011-155741}, volume = {28}, year = {2012}, } @article{829, abstract = {The architecture of a plant's root system, established postembryonically, results from both coordinated root growth and lateral root branching. The plant hormones auxin and cytokinin are central endogenous signaling molecules that regulate lateral root organogenesis positively and negatively, respectively. Tight control and mutual balance of their antagonistic activities are particularly important during the early phases of lateral root organogenesis to ensure continuous lateral root initiation (LRI) and proper development of lateral root primordia (LRP). Here, we show that the early phases of lateral root organogenesis, including priming and initiation, take place in root zones with a repressed cytokinin response. Accordingly, ectopic overproduction of cytokinin in the root basal meristem most efficiently inhibits LRI. Enhanced cytokinin responses in pericycle cells between existing LRP might restrict LRI near existing LRP and, when compromised, ectopic LRI occurs. Furthermore, our results demonstrate that young LRP are more sensitive to perturbations in the cytokinin activity than are developmentally more advanced primordia. We hypothesize that the effect of cytokinin on the development of primordia possibly depends on the robustness and stability of the auxin gradient.}, author = {Bielach, Agnieszka and Podlesakova, Katerina and Peter Marhavy and Duclercq, Jérôme and Candela Cuesta and Muller, Bruno and Grunewald, Wim and Tarkowski, Petr and Eva Benková}, journal = {The Plant Cell}, number = {10}, pages = {3967 -- 3981}, publisher = {American Society of Plant Biologists}, title = {{Spatiotemporal regulation of lateral root organogenesis in Arabidopsis by cytokinin}}, doi = {10.1105/tpc.112.103044}, volume = {24}, year = {2012}, } @article{846, abstract = {Whether or not evolutionary change is inherently irreversible remains a controversial topic. Some examples of evolutionary irreversibility are known; however, this question has not been comprehensively addressed at the molecular level. Here, we use data from 221 human genes with known pathogenic mutations to estimate the rate of irreversibility in protein evolution. For these genes, we reconstruct ancestral amino acid sequences along the mammalian phylogeny and identify ancestral amino acid states that match known pathogenic mutations. Such cases represent inherent evolutionary irreversibility because, at the present moment, reversals to these ancestral amino acid states are impossible for the human lineage. We estimate that approximately 10% of all amino acid substitutions along the mammalian phylogeny are irreversible, such that a return to the ancestral amino acid state would lead to a pathogenic phenotype. For a subset of 51 genes with high rates of irreversibility, as much as 40% of all amino acid evolution was estimated to be irreversible. Because pathogenic phenotypes do not resemble ancestral phenotypes, the molecular nature of the high rate of irreversibility in proteins is best explained by evolution with a high prevalence of compensatory, epistatic interactions between amino acid sites. Under such mode of protein evolution, once an amino acid substitution is fixed, the probability of its reversal declines as the protein sequence accumulates changes that affect the phenotypic manifestation of the ancestral state. The prevalence of epistasis in evolution indicates that the observed high rate of irreversibility in protein evolution is an inherent property of protein structure and function.}, author = {Soylemez, Onuralp and Fyodor Kondrashov}, journal = {Genome Biology and Evolution}, number = {12}, pages = {1213 -- 1222}, publisher = {Oxford University Press}, title = {{Estimating the rate of irreversibility in protein evolution}}, doi = {10.1093/gbe/evs096}, volume = {4}, year = {2012}, } @article{8463, abstract = {The 1H dipolar network, which is the major obstacle for applying proton detection in the solid-state, can be reduced by deuteration, employing the RAP (Reduced Adjoining Protonation) labeling scheme, which yields random protonation at non-exchangeable sites. We present here a systematic study on the optimal degree of random sidechain protonation in RAP samples as a function of the MAS (magic angle spinning) frequency. In particular, we compare 1H sensitivity and linewidth of a microcrystalline protein, the SH3 domain of chicken α-spectrin, for samples, prepared with 5–25 % H2O in the E. coli growth medium, in the MAS frequency range of 20–60 kHz. At an external field of 19.96 T (850 MHz), we find that using a proton concentration between 15 and 25 % in the M9 medium yields the best compromise in terms of sensitivity and resolution, with an achievable average 1H linewidth on the order of 40–50 Hz. Comparing sensitivities at a MAS frequency of 60 versus 20 kHz, a gain in sensitivity by a factor of 4–4.5 is observed in INEPT-based 1H detected 1D 1H,13C correlation experiments. In total, we find that spectra recorded with a 1.3 mm rotor at 60 kHz have almost the same sensitivity as spectra recorded with a fully packed 3.2 mm rotor at 20 kHz, even though ~20× less material is employed. The improved sensitivity is attributed to 1H line narrowing due to fast MAS and to the increased efficiency of the 1.3 mm coil.}, author = {Asami, Sam and Szekely, Kathrin and Schanda, Paul and Meier, Beat H. and Reif, Bernd}, issn = {0925-2738}, journal = {Journal of Biomolecular NMR}, number = {2}, pages = {155--168}, publisher = {Springer Nature}, title = {{Optimal degree of protonation for 1H detection of aliphatic sites in randomly deuterated proteins as a function of the MAS frequency}}, doi = {10.1007/s10858-012-9659-9}, volume = {54}, year = {2012}, } @article{8465, abstract = {We demonstrate that conformational exchange processes in proteins on microsecond-to-millisecond time scales can be detected and quantified by solid-state NMR spectroscopy. We show two independent approaches that measure the effect of conformational exchange on transverse relaxation parameters, namely Carr–Purcell–Meiboom–Gill relaxation-dispersion experiments and measurement of differential multiple-quantum coherence decay. Long coherence lifetimes, as required for these experiments, are achieved by the use of highly deuterated samples and fast magic-angle spinning. The usefulness of the approaches is demonstrated by application to microcrystalline ubiquitin. We detect a conformational exchange process in a region of the protein for which dynamics have also been observed in solution. Interestingly, quantitative analysis of the data reveals that the exchange process is more than 1 order of magnitude slower than in solution, and this points to the impact of the crystalline environment on free energy barriers.}, author = {Tollinger, Martin and Sivertsen, Astrid C. and Meier, Beat H. and Ernst, Matthias and Schanda, Paul}, issn = {0002-7863}, journal = {Journal of the American Chemical Society}, number = {36}, pages = {14800--14807}, publisher = {American Chemical Society}, title = {{Site-resolved measurement of microsecond-to-millisecond conformational-exchange processes in proteins by solid-state NMR spectroscopy}}, doi = {10.1021/ja303591y}, volume = {134}, year = {2012}, } @article{8466, abstract = {Recent advances in NMR spectroscopy and the availability of high magnetic field strengths now offer the possibility to record real-time 3D NMR spectra of short-lived protein states, e.g., states that become transiently populated during protein folding. Here we present a strategy for obtaining sequential NMR assignments as well as atom-resolved information on structural and dynamic features within a folding intermediate of the amyloidogenic protein β2-microglobulin that has a half-lifetime of only 20 min.}, author = {Rennella, Enrico and Cutuil, Thomas and Schanda, Paul and Ayala, Isabel and Forge, Vincent and Brutscher, Bernhard}, issn = {0002-7863}, journal = {Journal of the American Chemical Society}, number = {19}, pages = {8066--8069}, publisher = {American Chemical Society}, title = {{Real-time NMR characterization of structure and dynamics in a transiently populated protein folding intermediate}}, doi = {10.1021/ja302598j}, volume = {134}, year = {2012}, } @article{8467, abstract = {Partial deuteration is a powerful tool to increase coherence life times and spectral resolution in proton solid-state NMR. The J coupling to deuterium needs, however, to be decoupled to maintain the good resolution in the (usually indirect) 13C dimension(s). We present a simple and reversible way to expand a commercial 1.3 mm HCN MAS probe with a 2H channel with sufficient field strength for J-decoupling of deuterium, namely 2–3 kHz. The coil is placed at the outside of the stator and requires no significant modifications to the probe. The performance and the realizable gains in sensitivity and resolution are demonstrated using perdeuterated ubiquitin, with selectively CHD2-labeled methyl groups.}, author = {Huber, Matthias and With, Oliver and Schanda, Paul and Verel, René and Ernst, Matthias and Meier, Beat H.}, issn = {1090-7807}, journal = {Journal of Magnetic Resonance}, pages = {76--80}, publisher = {Elsevier}, title = {{A supplementary coil for 2H decoupling with commercial HCN MAS probes}}, doi = {10.1016/j.jmr.2011.10.010}, volume = {214}, year = {2012}, } @article{8502, abstract = {The famous ergodic hypothesis suggests that for a typical Hamiltonian on a typical energy surface nearly all trajectories are dense. KAM theory disproves it. Ehrenfest (The Conceptual Foundations of the Statistical Approach in Mechanics. Ithaca, NY: Cornell University Press, 1959) and Birkhoff (Collected Math Papers. Vol 2, New York: Dover, pp 462–465, 1968) stated the quasi-ergodic hypothesis claiming that a typical Hamiltonian on a typical energy surface has a dense orbit. This question is wide open. Herman (Proceedings of the International Congress of Mathematicians, Vol II (Berlin, 1998). Doc Math 1998, Extra Vol II, Berlin: Int Math Union, pp 797–808, 1998) proposed to look for an example of a Hamiltonian near H0(I)=⟨I,I⟩2 with a dense orbit on the unit energy surface. In this paper we construct a Hamiltonian H0(I)+εH1(θ,I,ε) which has an orbit dense in a set of maximal Hausdorff dimension equal to 5 on the unit energy surface.}, author = {Kaloshin, Vadim and Saprykina, Maria}, issn = {0010-3616}, journal = {Communications in Mathematical Physics}, keywords = {Mathematical Physics, Statistical and Nonlinear Physics}, number = {3}, pages = {643--697}, publisher = {Springer Nature}, title = {{An example of a nearly integrable Hamiltonian system with a trajectory dense in a set of maximal Hausdorff dimension}}, doi = {10.1007/s00220-012-1532-x}, volume = {315}, year = {2012}, } @article{8503, abstract = {We prove there are finitely many isometry classes of planar central configurations (also called relative equilibria) in the Newtonian 5-body problem, except perhaps if the 5-tuple of positive masses belongs to a given codimension 2 subvariety of the mass space.}, author = {Albouy, Alain and Kaloshin, Vadim}, issn = {0003-486X}, journal = {Annals of Mathematics}, number = {1}, pages = {535--588}, publisher = {Princeton University Press}, title = {{Finiteness of central configurations of five bodies in the plane}}, doi = {10.4007/annals.2012.176.1.10}, volume = {176}, year = {2012}, } @article{8504, abstract = {In this paper we present a surprising example of a Cr unimodal map of an interval f:I→I whose number of periodic points Pn(f)=∣{x∈I:fnx=x}∣ grows faster than any ahead given sequence along a subsequence nk=3k. This example also shows that ‘non-flatness’ of critical points is necessary for the Martens–de Melo–van Strien theorem [M. Martens, W. de Melo and S. van Strien. Julia–Fatou–Sullivan theory for real one-dimensional dynamics. Acta Math.168(3–4) (1992), 273–318] to hold.}, author = {Kaloshin, Vadim and KOZLOVSKI, O. S.}, issn = {0143-3857}, journal = {Ergodic Theory and Dynamical Systems}, keywords = {Applied Mathematics, General Mathematics}, number = {1}, pages = {159--165}, publisher = {Cambridge University Press}, title = {{A Cr unimodal map with an arbitrary fast growth of the number of periodic points}}, doi = {10.1017/s0143385710000817}, volume = {32}, year = {2012}, } @article{858, abstract = {ackground: The evolution and genomic stop codon frequencies have not been rigorously studied with the exception of coding of non-canonical amino acids. Here we study the rate of evolution and frequency distribution of stop codons in bacterial genomes.Results: We show that in bacteria stop codons evolve slower than synonymous sites, suggesting the action of weak negative selection. However, the frequency of stop codons relative to genomic nucleotide content indicated that this selection regime is not straightforward. The frequency of TAA and TGA stop codons is GC-content dependent, with TAA decreasing and TGA increasing with GC-content, while TAG frequency is independent of GC-content. Applying a formal, analytical model to these data we found that the relationship between stop codon frequencies and nucleotide content cannot be explained by mutational biases or selection on nucleotide content. However, with weak nucleotide content-dependent selection on TAG, -0.5 < Nes < 1.5, the model fits all of the data and recapitulates the relationship between TAG and nucleotide content. For biologically plausible rates of mutations we show that, in bacteria, TAG stop codon is universally associated with lower fitness, with TAA being the optimal for G-content < 16% while for G-content > 16% TGA has a higher fitness than TAG.Conclusions: Our data indicate that TAG codon is universally suboptimal in the bacterial lineage, such that TAA is likely to be the preferred stop codon for low GC content while the TGA is the preferred stop codon for high GC content. The optimization of stop codon usage may therefore be useful in genome engineering or gene expression optimization applications.Reviewers: This article was reviewed by Michail Gelfand, Arcady Mushegian and Shamil Sunyaev. For the full reviews, please go to the Reviewers' Comments section.}, author = {Povolotskaya, Inna and Fyodor Kondrashov and Ledda, Alice and Vlasov, Peter K}, journal = {Biology Direct}, publisher = {BioMed Central}, title = {{Stop codons in bacteria are not selectively equivalent}}, doi = {10.1186/1745-6150-7-30}, volume = {7}, year = {2012}, } @article{887, abstract = {A subject of extensive study in evolutionary theory has been the issue of how neutral, redundant copies can be maintained in the genome for long periods of time. Concurrently, examples of adaptive gene duplications to various environmental conditions in different species have been described. At this point, it is too early to tell whether or not a substantial fraction of gene copies have initially achieved fixation by positive selection for increased dosage. Nevertheless, enough examples have accumulated in the literature that such a possibility should be considered. Here, I review the recent examples of adaptive gene duplications and make an attempt to draw generalizations on what types of genes may be particularly prone to be selected for under certain environmental conditions. The identification of copy-number variation in ecological field studies of species adapting to stressful or novel environmental conditions may improve our understanding of gene duplications as a mechanism of adaptation and its relevance to the long-term persistence of gene duplications.}, author = {Fyodor Kondrashov}, journal = {Proceedings of the Royal Society of London Series B Biological Sciences}, number = {1749}, pages = {5048 -- 5057}, publisher = {Royal Society, The}, title = {{Gene duplication as a mechanism of genomic adaptation to a changing environment}}, doi = {10.1098/rspb.2012.1108}, volume = {279}, year = {2012}, } @article{900, abstract = {The main forces directing long-term molecular evolution remain obscure. A sizable fraction of amino-acid substitutions seem to be fixed by positive selection, but it is unclear to what degree long-term protein evolution is constrained by epistasis, that is, instances when substitutions that are accepted in one genotype are deleterious in another. Here we obtain a quantitative estimate of the prevalence of epistasis in long-term protein evolution by relating data on amino-acid usage in 14 organelle proteins and 2 nuclear-encoded proteins to their rates of short-term evolution. We studied multiple alignments of at least 1,000 orthologues for each of these 16 proteins from species from a diverse phylogenetic background and found that an average site contained approximately eight different amino acids. Thus, without epistasis an average site should accept two-fifths of all possible amino acids, and the average rate of amino-acid substitutions should therefore be about three-fifths lower than the rate of neutral evolution. However, we found that the measured rate of amino-acid substitution in recent evolution is 20 times lower than the rate of neutral evolution and an order of magnitude lower than that expected in the absence of epistasis. These data indicate that epistasis is pervasive throughout protein evolution: about 90 per cent of all amino-acid substitutions have a neutral or beneficial impact only in the genetic backgrounds in which they occur, and must therefore be deleterious in a different background of other species. Our findings show that most amino-acid substitutions have different fitness effects in different species and that epistasis provides the primary conceptual framework to describe the tempo and mode of long-term protein evolution.}, author = {Breen, Michael S and Kemena, Carsten and Vlasov, Peter K and Notredame, Cédric and Fyodor Kondrashov}, journal = {Nature}, number = {7421}, pages = {535 -- 538}, publisher = {Nature Publishing Group}, title = {{Epistasis as the primary factor in molecular evolution}}, doi = {10.1038/nature11510}, volume = {490}, year = {2012}, } @article{9014, abstract = {In this Letter, we explore experimentally the phase behavior of a dense active suspension of self-propelled colloids. In addition to a solidlike and gaslike phase observed for high and low densities, a novel cluster phase is reported at intermediate densities. This takes the form of a stationary assembly of dense aggregates—resulting from a permanent dynamical merging and separation of active colloids—whose average size grows with activity as a linear function of the self-propelling velocity. While different possible scenarios can be considered to account for these observations—such as a generic velocity weakening instability recently put forward—we show that the experimental results are reproduced mathematically by a chemotactic aggregation mechanism, originally introduced to account for bacterial aggregation and accounting here for diffusiophoretic chemical interaction between colloidal swimmers.}, author = {Theurkauff, I. and Cottin-Bizonne, C. and Palacci, Jérémie A and Ybert, C. and Bocquet, L.}, issn = {10797114}, journal = {Physical Review Letters}, number = {26}, publisher = {American Physical Society }, title = {{Dynamic clustering in active colloidal suspensions with chemical signaling}}, doi = {10.1103/physrevlett.108.268303}, volume = {108}, year = {2012}, } @article{9049, abstract = {Diffusiophoretic motion of colloids and macromolecules under salt gradients exhibits a logarithmic-sensing, i.e. the particle velocity is proportional to the spatial gradient of the logarithm of the salt concentration, as VDP = DDP∇logc. Here we explore experimentally the implications of this log-sensing behavior, on the basis of a hydrogel microfluidic device allowing to build spatially and temporally controlled gradients. We first demonstrate that the non-linearity of the salt-taxis leads to a trapping of particles under concentration gradient oscillations via a rectification of the motion. As an alternative, we make use of the high sensitivity of diffusiophoretic migration to vanishing salt concentration due to the log-sensing: in a counter-intuitive way, a vanishing gradient can lead to measurable velocity provided that the solute concentration is low enough, thus keeping ∇c/c finite. We show that this leads to a strong segregation of particles in osmotic shock configuration, resulting from a step change of the salt concentration at the boundaries. These various phenomena are rationalized on the basis of a theoretical description for the time-dependent Smoluchowski equation for the colloidal density.}, author = {Palacci, Jérémie A and Cottin-Bizonne, Cécile and Ybert, Christophe and Bocquet, Lydéric}, issn = {1744-6848}, journal = {Soft Matter}, number = {4}, pages = {980--994}, publisher = {Royal Society of Chemistry}, title = {{Osmotic traps for colloids and macromolecules based on logarithmic sensing in salt taxis}}, doi = {10.1039/c1sm06395b}, volume = {8}, year = {2012}, } @article{91, abstract = {We demonstrate how to appropriately estimate the zero-frequency (static) hyperpolarizability of an organic molecule from its charge distribution, and we explore applications of these estimates for identifying and evaluating new organic nonlinear optical (NLO) materials. First, we calculate hyperpolarizabilities from Hartree-Fock-derived charge distributions and find order-of-magnitude agreement with experimental values. We show that these simple arithmetic calculations will enable systematic searches for new organic NLO molecules. Second, we derive hyperpolarizabilities from crystallographic data using a multipolar charge-density analysis and find good agreement with empirical calculations. This demonstrates an experimental determination of the full static hyperpolarizability tensor in a solid-state sample. }, author = {Higginbotham, Andrew P and Cole, Jacqueline and Blood Forsythe, Martin and Hickstein, Daniel}, journal = {Journal of Applied Physics}, number = {3}, publisher = {American Institute of Physics}, title = {{Identifying and evaluating organic nonlinear optical materials via molecular moments}}, doi = {10.1063/1.3678593}, volume = {111}, year = {2012}, } @article{9142, abstract = {In models of radiative–convective equilibrium it is known that convection can spontaneously aggregate into one single localized moist region if the domain is large enough. The large changes in the mean climate state and radiative fluxes accompanying this self-aggregation raise questions as to what simulations at lower resolutions with parameterized convection, in similar homogeneous geometries, should be expected to produce to be considered successful in mimicking a cloud-resolving model. The authors investigate this self-aggregation in a nonrotating, three-dimensional cloud-resolving model on a square domain without large-scale forcing. It is found that self-aggregation is sensitive not only to the domain size, but also to the horizontal resolution. With horizontally homogeneous initial conditions, convective aggregation only occurs on domains larger than about 200km and with resolutions coarser than about 2km in the model examined. The system exhibits hysteresis, so that with aggregated initial conditions, convection remains aggregated even at our finest resolution, 500m, as long as the domain is greater than 200–300km. The sensitivity of self-aggregation to resolution and domain size in this model is due to the sensitivity of the distribution of low clouds to these two parameters. Indeed, the mechanism responsible for the aggregation of convection is the dynamical response to the longwave radiative cooling from low clouds. Strong longwave cooling near cloud top in dry regions forces downward motion, which by continuity generates inflow near cloud top and near-surface outflow from dry regions. This circulation results in the net export of moist static energy from regions with low moist static energy, yielding a positive feedback.}, author = {Muller, Caroline J and Held, Isaac M.}, issn = {0022-4928}, journal = {Journal of the Atmospheric Sciences}, keywords = {Atmospheric Science}, number = {8}, pages = {2551--2565}, publisher = {American Meteorological Society}, title = {{Detailed investigation of the self-aggregation of convection in cloud-resolving simulations}}, doi = {10.1175/jas-d-11-0257.1}, volume = {69}, year = {2012}, } @article{922, abstract = {We study theoretically the morphologies of biological tubes affected by various pathologies. When epithelial cells grow, the negative tension produced by their division provokes a buckling instability. Several shapes are investigated: varicose, dilated, sinuous, or sausagelike. They are all found in pathologies of tracheal, renal tubes, or arteries. The final shape depends crucially on the mechanical parameters of the tissues: Young's modulus, wall-to-lumen ratio, homeostatic pressure. We argue that since tissues must be in quasistatic mechanical equilibrium, abnormal shapes convey information as to what causes the pathology. We calculate a phase diagram of tubular instabilities which could be a helpful guide for investigating the underlying genetic regulation.}, author = {Hannezo, Edouard B and Prost, Jacques and Joanny, Jean}, journal = {Physical Review Letters}, number = {1}, publisher = {American Physical Society}, title = {{Mechanical instabilities of biological tubes}}, doi = {10.1103/PhysRevLett.109.018101}, volume = {109}, year = {2012}, } @article{7074, abstract = {The Seebeck coefficients, electrical resistivities, total thermal conductivities, and magnetization are reported for temperatures between 5 and 350 K for n-type Bi0.88Sb0.12 nano-composite alloys made by Ho-doping at the 0, 1, and 3 % atomic levels. The alloys were prepared using a dc hot-pressing method, and are shown to be single phase for both Ho contents with grain sizes on the average of 900 nm. We find the parent compound has a maximum of ZT = 0.28 at 231 K, while doping 1 % Ho increases the maximum ZT to 0.31 at 221 K and the 3 % doped sample suppresses the maximum ZT = 0.24 at a temperature of 260 K.}, author = {Lukas, K. C. and Joshi, G. and Modic, Kimberly A and Ren, Z. F. and Opeil, C. P.}, issn = {1573-4803}, journal = {Journal of Materials Science}, number = {15}, pages = {5729--5734}, publisher = {Springer Nature}, title = {{Thermoelectric properties of Ho-doped Bi0.88Sb0.12}}, doi = {10.1007/s10853-012-6463-6}, volume = {47}, year = {2012}, }