bluuebunny/crossref_metadata_2025 huggingface dataset:
Understanding S-shaped current-voltage characteristics of organic solar cells: Direct measurement of potential distributions by scanning Kelvin probe
Authors: Saive Rebecca , Mueller Christian , Schinke Janusz , Lovrincic Robert , Kowalsky Wolfgang
Published: December 2013

We present a comparison of the potential distribution along the cross section of bilayer poly(3-hexylthiophene)/1-(3-methoxycarbonyl)propyl-1-phenyl[6,6]C61 (P3HT/PCBM) solar cells, which show normal and anomalous, S-shaped current-voltage (IV) characteristics. We expose the cross sections of the devices with a focussed ion beam and measure them with scanning Kelvin probe microscopy. We find that in the case of S-shaped IV-characteristics, there is a huge potential drop at the PCBM/Al top contact, which does not occur in solar cells with normal IV-characteristics. This behavior confirms the assumption that S-shaped curves are caused by hindered charge transport at interfaces.
Effect of carbon nanotubes on the field-induced nematic switching
Authors: Basu Rajratan
Published: December 2013

A small quantity of carbon nanotubes (CNT) was doped in a nematic liquid crystal (LC), and the LC + CNT hybrid was found to exhibit a faster field-induced nematic switching compared to that of the pure LC. The field-induced switching time was probed by means of the electro-optic response of the samples. The hybrid system also revealed a reduced rotational viscosity and an enhanced dielectric anisotropy. The results suggest that the hybrid system undergoes a faster field-induced switching, as the CNTs favorably alter the rotational viscosity and the dielectric anisotropy of the nematic matrix.
A study of random resistor-capacitor-diode networks to assess the electromagnetic properties of carbon nanotube filled polymers
Authors: Bychanok D. S. , Paddubskaya A. G. , Kuzhir P. P. , Maksimenko S. A. , Brosseau C. , Macutkevic J. , Bellucci S.
Published: December 2013

We determined the frequency dependent effective permittivity of a large ternary network of randomly positioned resistors, capacitors, and diodes. A linear circuit analysis of such systems is shown to match the experimental dielectric response of single-walled carbon nanotube (SWCNT) filled polymers. This modeling method is able to reproduce the two most important features of SWCNT filled composites, i.e., the low frequency dispersion and dipolar relaxation. As a result of the modeling important physical conclusion proved by the experimental data was done: the low frequency behavior of SWCNT-filled polymer composites is mostly caused by the fraction of semiconducting SWCNTs.
Robust room temperature ferromagnetism in epitaxial CoO thin film
Authors: Negi D. S. , Loukya B. , Dileep K. , Sahu R. , Nagaraja K. K. , Kumar N. , Datta R.
Published: December 2013

Co vacancy (VCo) induced robust room temperature ferromagnetism (Ms ∼ 60 emu/cm3 and coercivity ∼ 603 Oe) is experimentally realized in rock-salt CoO epitaxial thin film (∼110 nm) grown by pulsed laser deposition. Co charge state is found to be higher ∼+3.2 (from Co L3/L2 white line ratio) and this is due to the VCo induced charge transfer from the neighboring Co-3d to O-2p states in order to compensate for the hole formation. O-K and cathodoluminescence spectra corroborate the existence of VCo and higher charge state. Temperature dependent magnetization and exchange bias experiments confirm the coexistence of ferromagnetic and antiferromagnetic phases.
Mechanism of vacancy formation induced by hydrogen in tungsten
Authors: Liu Yi-Nan , Ahlgren T. , Bukonte L. , Nordlund K. , Shu Xiaolin , Yu Yi , Li Xiao-Chun , Lu Guang-Hong
Published: December 2013

We report a hydrogen induced vacancy formation mechanism in tungsten based on classical molecular dynamics simulations. We demonstrate the vacancy formation in tungsten due to the presence of hydrogen associated directly with a stable hexagonal self-interstitial cluster as well as a linear crowdion. The stability of different self-interstitial structures has been further studied and it is particularly shown that hydrogen plays a crucial role in determining the configuration of SIAs, in which the hexagonal cluster structure is preferred. Energetic analysis has been carried out to prove that the formation of SIA clusters facilitates the formation of vacancies. Such a mechanism contributes to the understanding of the early stage of the hydrogen blistering in tungsten under a fusion reactor environment.
Bauxite residue neutralisation precipitate stability in acidic environments
Authors: Couperthwaite Sara J. , Han Sujung , Santini Talitha , Kaur Gurkiran , Johnstone Dean W. , Millar Graeme J. , Frost Ray L.
Published: December 2013

Environmental context
Although land remediation programs for bauxite residues aim at vegetation coverage, the stability of compounds in the residues with acids produced by the vegetation has not been investigated. We show that, despite the instability of caustic components in the residues (negative effects on plant development), this instability actually assists in neutralising acidic soils. These results further affirm the suitability and sustainability of current land remediation programs for bauxite residues in terms of minimising acidic soil formation.

Abstract
This investigation used a combination of techniques, such as X-ray diffraction, inductively coupled plasma optical emission spectroscopy and infrared spectroscopy, to determine the dissolution mechanisms of the Bayer precipitate and the associated rate of dissolution in acetic, citric and oxalic acid environments. The Bayer precipitate is a mixture of hydrotalcite, calcium carbonate and sodium chloride that forms during the seawater neutralisation of Bayer liquors (waste residue of the alumina industry). The dissolution rate of a Bayer precipitate is found to be dependent on (1) the strength of the organic acid and (2) the number of donating H+ ions. The dissolution mechanism for a Bayer precipitate consists of several steps involving: (1) the dissolution of CaCO3, (2) formation of whewellite (calcium oxalate) when oxalic acid is used and (3) multiple dissolution steps for hydrotalcite that are highly dependent on the pH of solution. The decomposition of the Al–OH hydrotalcite layers resulted in the immediate formation of Al(OH)3, which is stable until the pH decreases below 5.5. This investigation has found that the Bayer precipitate is stable across a wide pH range in the presence of common organic acids found in the rhizosphere, and that initial decomposition steps are likely to be beneficial in supporting plant growth through the release of nutrients such as Ca2+ and Mg2+.
Using humour as an extrinsic source of emotion regulation in young and older adults
Authors: Harm Jonathan , Vieillard Sandrine , Didierjean André
Published: December 2013

It has been suggested that intrinsic abilities for regulating emotions remain stable or improve with ageing, but, to date, no studies have examined age-related differences in extrinsic emotion regulation. Since humour has been found to be an effective form of emotion regulation, we used a paradigm similar to that of Strick and colleagues (2009) with two objectives: to compare extrinsic humorous emotion regulation in young and older adults and to test whether the potential beneficial effect of humour on negative emotion is better explained by the cognitive distraction hypothesis or by the positive affect elicitation hypothesis. To this end, neutral, moderately, and strongly negative pictures followed by humorous, simply positive, or weird cartoons, controlled for both their funniness and cognitive demands, were presented to 26 young and 25 older adults with the instruction to report their negative feelings. When induced to feel moderately negative emotions, both young and older adults reported a lower negative feeling after viewing the humorous cartoons than after the other ones. This indicates that the extrinsic humorous emotion regulation skill remains stable with ageing and suggests that the beneficial effect of humour on emotional feeling cannot be seen as a purely cognitive distraction.
Climate change, social policy, and global governance
Authors: Gough Ian
Published: December 2013

This paper considers the challenge to global social policy posed by global climate change. It sets side by side global social policies and global climate change policies, and surveys the governance of each. The first part summarises global social policy in recent years, distinguishing (1) the policies and practices pursued in the global arena, and (2) the structures of global governance and the role of significant global actors. The second part repeats this at a greater length for global climate change. The third part then considers the relationship between these two sets of policies/practices and governance structures, in particular the potential conflicts between the pursuit of social justice and environmental sustainability. It identifies two possible responses – compensation and co-benefits – and maps these onto current global actors, before concluding with a radical vision of eco-social policy.
Minimal 𝑁-point diameters and 𝑓-best-packing constants in ℝ^{𝕕}
Authors: Bondarenko A. , Hardin D. , Saff E.
Published: December 2013

In terms of the minimal

N
N

-point diameter

D
d

(
N
)

D_d(N)

for

R

d

,

\mathbb {R}^d,

we determine, for a class of continuous real-valued functions

f
f

on

[
0
,
+
∞
]
,

[0,+\infty ],

the

N
N

-point

f
f

-best-packing constant

min
{
f
(
‖
x
−
y
‖
)

:

x
,
y
∈

R

d

}

\min \{f(\|x-y\|)\, :\, x,y\in \mathbb {R}^d\}

, where the minimum is taken over point sets of cardinality

N
.

N.

We also show that
\[
<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" alttext="upper N Superscript 1 slash d Baseline normal upper Delta Subscript d Superscript negative 1 slash d Baseline minus 2 less-than-or-equal-to upper D Subscript d Baseline left-parenthesis upper N right-parenthesis less-than-or-equal-to upper N Superscript 1 slash d Baseline normal upper Delta Subscript d Superscript negative 1 slash d Baseline comma upper N greater-than-or-equal-to 2 comma">

N

1

/

d

Δ
d

−
1

/

d

−
2
≤

D
d

(
N
)
≤

N

1

/

d

Δ
d

−
1

/

d

,

N
≥
2
,

N^{1/d}\Delta _d^{-1/d}-2\le D_d(N)\le N^{1/d}\Delta _d^{-1/d}, \quad N\ge 2,

\]
where

Δ
d

\Delta _d

is the maximal sphere packing density in

R

d

\mathbb {R}^d

. Further, we provide asymptotic estimates for the

f
f

-best-packing constants as

N
→
∞

N\to \infty

.
Quantum double Schubert polynomials represent Schubert classes
Authors: Lam Thomas , Shimozono Mark
Published: December 2013

The quantum double Schubert polynomials studied by Kirillov and Maeno, and by Ciocan-Fontanine and Fulton, are shown to represent Schubert classes in Kim’s presentation of the equivariant quantum cohomology of the flag variety. Parabolic analogues of quantum double Schubert polynomials are introduced and shown to represent Schubert classes in the equivariant quantum cohomology of partial flag varieties. This establishes a new method for computing equivariant Gromov-Witten invariants for partial flag varieties. For complete flags Anderson and Chen have announced a proof with different methods.
Baseline Sensitivity of Guignardia citricarpa Isolates from Florida to Azoxystrobin and Pyraclostrobin
Authors: Hincapie Martha , Wang Nan-Yi , Peres Natalia A. , Dewdney Megan M.
Published: December 2013

Citrus black spot (CBS), caused by Guignardia citricarpa, is an emerging disease in Florida. Fungicide applications are the main control measure worldwide. The in vitro activity and baseline sensitivity of G. citricarpa isolates to quinone outside inhibitor (QoI) fungicides (azoxystrobin and pyraclostrobin) were evaluated. The effective concentration needed to reduce mycelial growth or spore germination by 50% (EC50) was determined for 86 isolates obtained from Florida counties where CBS is found. The effect of salicylhydroxamic acid (SHAM) plus azoxystrobin and pyraclostrobin was also assessed for mycelial growth and conidial germination. The mean EC50 for mycelial growth for azoxystrobin was 0.027 μg/ml and that for pyraclostrobin was significantly lower at 0.007 μg/ml (P < 0.0001). Similarly, the mean EC50 for conidial germination for azoxystrobin was 0.016 μg/ml and that for pyraclostrobin was significantly lower at 0.008 μg/ml (P < 0.0001). There was no effect of SHAM on inhibition of mycelial growth or conidial germination by the QoI fungicides but SHAM slightly affected mycelium inhibition by pyraclostrobin. Cytochrome b was partially sequenced and three group 1 introns were found. One intron was immediately post G143, likely inhibiting resistance-conferring mutations at that site. It is surmised that the QoI resistance risk is low in the Florida G. citricarpa population.
A Phytoplasma Belonging to a 16SrIII-A Subgroup and dsRNA Virus Associated with Cassava Frogskin Disease in Brazil
Authors: de Souza Adriana N. , da Silva Fábio N. , Bedendo Ivan P. , Carvalho Claudine M.
Published: December 2013

Cassava frogskin disease (CFSD) is a particular threat in cassava because symptoms remain hidden until harvest and losses can be total. The information related to the etiological agent of this disease is contradictory, because some authors believe it is caused by phytoplasmas while others believe that it is caused by a virus. In order to refine detection protocols and to characterize organisms associated with CFSD in Brazil, 32 symptomatic and 20 asymptomatic cassava plants were collected in Minas Gerais state. Total DNA was extracted and used for nested polymerase chain reaction (PCR) to detect phytoplasmas. Because endophytic Bacillus spp. led to false positives, primers were designed to facilitate the detection of phytoplasma in the presence of bacteria. In addition, double-stranded (ds)RNA was extracted from tubers and used in reverse-transcription PCR for the detection of the RNA-dependent RNA polymerase gene from Cassava frogskin virus segment 4. The detected phytoplasma was identified as belonging to the group 16SrIII-A by restriction fragment length polymorphism (RFLP), sequencing, and RFLP in silico. This is the first report of a phytoplasma belonging to the 16SrIII-A group associated with cassava plants, the first molecular characterization of a phytoplasma associated with CFSD in Brazil, and a first report of phytoplasma and a dsRNA virus (possible reovirus) co-infecting cassava plants with CFSD symptoms.
Distribution and Survival of Pseudomonas sp. on Italian Ryegrass and Curly Dock in Georgia
Authors: Dutta Bhabesh , Gitaitis Ronald D. , Webster Theodore M. , Sanders Hunt , Smith Samuel , Langston David B.
Published: December 2013

Yellow bud, caused by Pseudomonas sp., is an emerging bacterial disease of onion. A polymerase chain reaction assay based on the coronafacate ligase (cfl) and HrpZ genes was used to detect initial suspected bacteria on weeds. Growth on an agar medium, ability to cause a hypersensitive response in tobacco, pathogenicity on onion, and sequence analysis of 16S ribosomal RNA and cfl genes were used to confirm the identity of Pseudomonas sp. recovered from 10 asymptomatic weed species in the Vidalia onion-growing zone (VOZ) of Georgia. Among the weeds identified as epiphytic hosts for Pseudomonas sp., Italian ryegrass (Lolium multiflorum) and curly dock (Rumex crispus) were prominent because ≥73% of the samples from five sample sites were positive for the bacterium. These weeds are commonly found throughout Georgia and, thus, were selected to assess their role in yellow bud epidemiology. Samples of the two weed species were collected from sites along the perimeter of and within the VOZ (n = 5 sites) during late June, August, and September 2012 and 2013, which represented the time interval between onion growing seasons. Samples (n = 10/weed species/site) were collected and processed for bacterial detection as described above. In June (2012 and 2013), Pseudomonas sp. was detected from Italian ryegrass and curly dock in 100 and 40% of the sample sites, respectively. During the months of August and September (2012), the bacterium was recovered from Italian ryegrass in 60 and 10% of the sample sites, respectively; whereas, in August (2013), Pseudomonas sp. was recovered from 40% of the sample sites. However, the bacterium was not recovered from any of the sites in September (2013). In contrast, during August and September (2012), Pseudomonas sp. was recovered from curly dock in 20 and 80% of the sample sites, respectively. Similarly, in August and September (2013), the bacterium was detected from 40 and 100% of the sample sites, respectively. These data demonstrated that the Pseudomonas sp. responsible for yellow bud can survive as an epiphyte on Italian ryegrass and curly dock between onion crops. Furthermore, using artificially infested onion seed, we demonstrated that Pseudomonas sp. can be transmitted through contaminated seed.
Complex Molecular Relationship Between Vegetative Compatibility Groups (VCGs) in Verticillium dahliae: VCGs Do Not Always Align with Clonal Lineages
Authors: Jiménez-Gasco María del Mar , Malcolm Glenna M. , Berbegal Mónica , Armengol Josep , Jiménez-Díaz Rafael M.
Published: December 2013

Verticillium wilts caused by the soilborne fungus Verticillium dahliae are among the most challenging diseases to control. Populations of this pathogen have been traditionally studied by means of vegetative compatibility groups (VCGs) under the assumption that VCGs comprise genetically related isolates that correlate with clonal lineages. We aimed to resolve the phylogenetic relationships among VCGs and their subgroups based on sequences of the intergenic spacer region (IGS) of the ribosomal DNA and six anonymous polymorphic sequences containing single-nucleotide polymorphisms (VdSNPs). A collection of 68 V. dahliae isolates representing the main VCGs and subgroups (VCGs 1A, 1B, 2A, 2B, 3, 4A, 4B, and 6) from different geographic origins and hosts was analyzed using the seven DNA regions. Maximum parsimony (MP) phylogenies inferred from IGS and VdSNP sequences showed five and six distinct clades, respectively. Phylogenetic analyses of individual and combined data sets indicated that certain VCG subgroups (e.g., VCGs 1A and 1B) are closely related and share a common ancestor; however, other subgroups (e.g., VCG 4B) are more closely related to members of a different VCG (e.g., VCG 2A) than to subgroups of the same VCG (VCG 4B). Furthermore, MP analyses indicated that VCG 2B is polyphyletic, with isolates placed in at least three distinct phylogenetic lineages based on IGS sequences and two lineages based on VdSNP sequences. Results from our study suggest the existence of main VCG lineages that contain VCGs 1A and 1B; VCGs 2A and 4B; and VCG 4A, for which both phylogenies agree; and the existence of other VCGs or VCG subgroups that seem to be genetically heterogeneous or show discrepancies in their phylogenetic placement: VCG 2B, VCG 3, and VCG 6. These results raise important caveats regarding the interpretation of VCG analyses: genetic homogeneity and close evolutionary relationship between members of a VCG should not be assumed.
Assessment of Vertebral Curves Using the Manual Post-It Technique
Authors: Gladnick Brian P. , Schreiber Joseph J. , Ishmael Chad R. , Bjerke-Kroll Benjamin T. , Cunningham Matthew E.
Published: December 2013

Study Design:

A prospective study of a new technique.

Objective:

The aims of this study were to report a manual technique for measuring vertebral curves on digital spine radiographs, and to assess the agreement of this technique with that of digital software for measuring vertebral curves.

Summary of Background Data:

Modern picture archiving and communication systems (PACS) typically include software for evaluating radiographic measurements. However, in the outpatient spine setting, patients may present with radiographs stored on a physical disc, which may not include software for measuring vertebral curves. Certain smartphone applications may be used to determine curve magnitude; however, the need exists for an accurate manual technique to measure vertebral curves on digital radiographs in the absence of available analytic software or smartphone technology.

Methods:

We prospectively reviewed anteroposterior and lateral spine radiographs of 24 spinal deformity patients. Two independent observers measured Cobb angles for: (1) the major coronal curve; (2) the thoracic kyphosis (T2–T12); and (3) the lumbar lordosis (T12–S1). Measurements were made: (1) digitally using our institution’s PACS; and (2) by a manual technique, which involves placement of an adhesive Post-It note directly on the computer screen, transcribing the angle onto the Post-It note with a pencil, and measuring the angle with a handheld goniometer. Intraclass correlation coefficients (ICCs) were calculated to determine the agreement between the 2 methods.

Results:

For both observers, the agreement between the digital PACS and manual Post-It techniques was graded as excellent for both coronal and sagittal plane curves (all ICCs>0.9). Interobserver reliability between the 2 observers was also graded as excellent for both the PACS and Post-It techniques (all ICCs>0.9).

Conclusions:

The Post-It technique for measuring Cobb angles demonstrated excellent agreement with the PACS system in our series of spinal deformity patients. Curves on digital radiographs can be accurately measured using a convenient manual technique.
Latitudinal gradients in intraspecific ecological diversity
Authors: Araújo Márcio S. , Costa-Pereira Raul
Published: December 2013

The increase in the number of species with decreasing latitude is a striking pattern of global biodiversity. An important feature of studies of this pattern up to now has been the focus on species as the fundamental unit of interest, neglecting potential within-species ecological diversity. Here, we took a new perspective on this topic by measuring the degree to which individuals within populations differ in niche attributes across a latitudinal gradient (range: 54.01° S to 69.12° N). We show that 156 populations of 76 species across a wide range of vertebrate and invertebrate animal taxa contain more ecologically diverse assemblages of individuals towards lower latitudes. Our results add a new level of complexity to our understanding of global patterns of biodiversity and suggest the possibility that niche variation is partly responsible for the latitudinal gradients of species diversity.
Chameleons communicate with complex colour changes during contests: different body regions convey different information
Authors: Ligon Russell A. , McGraw Kevin J.
Published: December 2013

Many animals display static coloration (e.g. of feathers or fur) that can serve as a reliable sexual or social signal, but the communication function of rapidly changing colours (as in chameleons and cephalopods) is poorly understood. We used recently developed photographic and mathematical modelling tools to examine how rapid colour changes of veiled chameleons
Chamaeleo calyptratus
predict aggressive behaviour during male–male competitions. Males that achieved brighter stripe coloration were more likely to approach their opponent, and those that attained brighter head coloration were more likely to win fights; speed of head colour change was also an important predictor of contest outcome. This correlative study represents the first quantification of rapid colour change using organism-specific visual models and provides evidence that the rate of colour change, in addition to maximum display coloration, can be an important component of communication. Interestingly, the body and head locations of the relevant colour signals map onto the behavioural displays given during specific contest stages, with lateral displays from a distance followed by directed, head-on approaches prior to combat, suggesting that different colour change signals may evolve to communicate different information (motivation and fighting ability, respectively).
Preference patterns for skewed gambles in rhesus monkeys
Authors: Strait Caleb E. , Hayden Benjamin Y.
Published: December 2013

While standard models of risky choice account for the first and second statistical moments of reward outcome distributions (mean and variance, respectively), they often ignore the third moment, skewness. Determining a decision-maker's attitude about skewness is useful because it can help constrain process models of the mental steps involved in risky choice. We measured three rhesus monkeys’ preferences for gambles whose outcome distributions had almost identical means and variances but differed in skewness. We tested five distributions of skewness: strong negative, weak negative, normal, weak positive and strong positive. Monkeys preferred positively skewed gambles to negatively skewed ones and preferred strongly skewed and normal (i.e. unskewed) gambles to weakly skewed ones. This pattern of preferences cannot be explained solely by monotonic deformations of the utility curve or any other popular single account, but can be accounted for by multiple interacting factors.
Global warming alters sound transmission: differential impact on the prey detection ability of echolocating bats
Authors: Luo Jinhong , Koselj Klemen , Zsebők Sándor , Siemers Björn M. , Goerlitz Holger R.
Published: December 2013

Climate change impacts the biogeography and phenology of plants and animals, yet the underlying mechanisms are little known. Here, we present a functional link between rising temperature and the prey detection ability of echolocating bats. The maximum distance for echo-based prey detection is physically determined by sound attenuation. Attenuation is more pronounced for high-frequency sound, such as echolocation, and is a nonlinear function of both call frequency and ambient temperature. Hence, the prey detection ability, and thus possibly the foraging efficiency, of echolocating bats and susceptible to rising temperatures through climate change. Using present-day climate data and projected temperature rises, we modelled this effect for the entire range of bat call frequencies and climate zones around the globe. We show that depending on call frequency, the prey detection volume of bats will either decrease or increase: species calling above a crossover frequency will lose and species emitting lower frequencies will gain prey detection volume, with crossover frequency and magnitude depending on the local climatic conditions. Within local species assemblages, this may cause a change in community composition. Global warming can thus directly affect the prey detection ability of individual bats and indirectly their interspecific interactions with competitors and prey.
The teacher taught? What Charles Darwin owed to John Lubbock
Authors: Pearn Alison
Published: December 2013

The period around the publication of John Lubbock's
Origin of civilisation
in 1870 and Charles Darwin's
Descent of man and selection in relation to sex
the following year is key to a re-evaluation of the relationship between the two men, usually characterized as that of pupil and master. It is in the making of
Descent
that Lubbock's role as a scientific collaborator is most easily discerned, a role best understood within the social and political context of the time. Lubbock made Darwin—both the man and his science—acceptable and respectable. Less obvious is Darwin's conscious cultivation of Lubbock's patronage in both his private and public life, and Lubbock's equally conscious bestowal, culminating in his role in Darwin's burial in Westminster Abbey.
Faunal record identifies Bering isthmus conditions as constraint to end-Pleistocene migration to the New World
Authors: Meiri Meirav , Lister Adrian M. , Collins Matthew J. , Tuross Noreen , Goebel Ted , Blockley Simon , Zazula Grant D. , van Doorn Nienke , Dale Guthrie R. , Boeskorov Gennady G. , Baryshnikov Gennady F. , Sher Andrei , Barnes Ian
Published: December 2013

Human colonization of the New World is generally believed to have entailed migrations from Siberia across the Bering isthmus. However, the limited archaeological record of these migrations means that details of the timing, cause and rate remain cryptic. Here, we have used a combination of ancient DNA, 14C dating, hydrogen and oxygen isotopes, and collagen sequencing to explore the colonization history of one of the few other large mammals to have successfully migrated into the Americas at this time: the North American elk (
Cervus elaphus canadensis
), also known as wapiti. We identify a long-term occupation of northeast Siberia, far beyond the species’s current Old World distribution. Migration into North America occurred at the end of the last glaciation, while the northeast Siberian source population became extinct only within the last 500 years. This finding is congruent with a similar proposed delay in human colonization, inferred from modern human mitochondrial DNA, and suggestions that the Bering isthmus was not traversable during parts of the Late Pleistocene. Our data imply a fundamental constraint in crossing Beringia, placing limits on the age and mode of human settlement in the Americas, and further establish the utility of ancient DNA in palaeontological investigations of species histories.
High strength-of-ties and low mobility enable the evolution of third-party punishment
Authors: Roos Patrick , Gelfand Michele , Nau Dana , Carr Ryan
Published: December 2013

As punishment can be essential to cooperation and norm maintenance but costly to the punisher, many evolutionary game-theoretic studies have explored how direct punishment can evolve in populations. Compared to direct punishment, in which an agent acts to punish another for an interaction in which both parties were involved, the evolution of third-party punishment (3PP) is even more puzzling, because the punishing agent itself was not involved in the original interaction. Despite significant empirical studies of 3PP, little is known about the conditions under which it can evolve. We find that punishment reputation is not, by itself, sufficient for the evolution of 3PP. Drawing on research streams in sociology and psychology, we implement a structured population model and show that high strength-of-ties and low mobility are critical for the evolution of responsible 3PP. Only in such settings of high social-structural constraint are punishers able to induce self-interested agents toward cooperation, making responsible 3PP ultimately beneficial to individuals as well as the collective. Our results illuminate the conditions under which 3PP is evolutionarily adaptive in populations. Responsible 3PP can evolve and induce cooperation in cases where other mechanisms alone fail to do so.
The importance of invertebrates when considering the impacts of anthropogenic noise
Authors: Morley Erica L. , Jones Gareth , Radford Andrew N.
Published: December 2013

Anthropogenic noise is now recognized as a major global pollutant. Rapidly burgeoning research has identified impacts on individual behaviour and physiology through to community disruption. To date, however, there has been an almost exclusive focus on vertebrates. Not only does their central role in food webs and in fulfilling ecosystem services make imperative our understanding of how invertebrates are impacted by all aspects of environmental change, but also many of their inherent characteristics provide opportunities to overcome common issues with the current anthropogenic noise literature. Here, we begin by explaining why invertebrates are likely to be affected by anthropogenic noise, briefly reviewing their capacity for hearing and providing evidence that they are capable of evolutionary adaptation and behavioural plasticity in response to natural noise sources. We then discuss the importance of quantifying accurately and fully both auditory ability and noise content, emphasizing considerations of direct relevance to how invertebrates detect sounds. We showcase how studying invertebrates can help with the behavioural bias in the literature, the difficulties in drawing strong, ecologically valid conclusions and the need for studies on fitness impacts. Finally, we suggest avenues of future research using invertebrates that would advance our understanding of the impact of anthropogenic noise.
Ordered, Random, Monotonic, and Non-monotonic Digital Nanodot Gradients
Authors: Ongo Grant , Ricoult Sébastien G. , Kennedy Timothy E. , Juncker David
Published: December 2013

Cell navigation is directed by inhomogeneous distributions of extracellular cues. It is well known that noise plays a key role in biology and is present in naturally occurring gradients at the micro- and nanoscale, yet it has not been studied with gradientsin vitro. Here, we introduce novel algorithms to produce ordered and random gradients of discrete nanodots – called digital nanodot gradients (DNGs) – according to monotonic and non-monotonic density functions. The algorithms generate continuous DNGs, with dot spacing changing in two dimensions along the gradient direction according to arbitrary mathematical functions, with densities ranging from 0.02% to 44.44%. The random gradient algorithm compensates for random nanodot overlap, and the randomness and spatial homogeneity of the DNGs were confirmed with Ripley’s K function. An array of 100 DNGs, each 400 × 400 µm2, comprising a total of 57 million 200 × 200 nm2dots was designed and patterned into silicon using electron-beam lithography, then patterned as fluorescently labeled IgGs on glass using lift-off nanocontact printing. DNGs will facilitate the study of the effects of noise and randomness at the micro- and nanoscales on cell migration and growth.
A Wheat Allene Oxide Cyclase Gene Enhances Salinity Tolerance via Jasmonate Signaling
Authors: Zhao Yang , Dong Wei , Zhang Naibo , Ai Xinghui , Wang Mengcheng , Huang Zhigang , Xiao Langtao , Xia Guangmin
Published: December 2013

One of the two branches of the α-linolenic acid metabolism pathway is catalyzed by 12-oxo-phytodienoic acid reductase I, and the other is involved in jasmonic acid (JA) synthesis. The former is known to be active in the response to salinity tolerance in wheat (Triticum aestivum), but the participation of the latter in this response has not been established as yet. Here, the salinity-responsive bread wheat gene TaAOC1, which encodes an allene oxide cyclase involved in the α-linolenic acid metabolism pathway, was constitutively expressed in both bread wheat and Arabidopsis (Arabidopsis thaliana). In both species, transgenic lines exhibited an enhanced level of tolerance to salinity. The transgenic plants accumulated a higher content of JA and developed shorter roots. Both the shortened roots and the salinity tolerance were abolished in a background lacking a functional AtMYC2, a key component of the JA and abscisic acid signaling pathway, but were still expressed in a background deficient with respect to abscisic acid synthesis. We provide the first evidence, to our knowledge, suggesting that JA is also involved in the plant salinity response and that the α-linolenic acid metabolism pathway has a regulatory role over this response.
ArabidopsisERG28 Tethers the Sterol C4-Demethylation Complex to Prevent Accumulation of a Biosynthetic Intermediate That Interferes with Polar Auxin Transport
Authors: Mialoundama Alexis Samba , Jadid Nurul , Brunel Julien , Di Pascoli Thomas , Heintz Dimitri , Erhardt Mathieu , Mutterer Jérôme , Bergdoll Marc , Ayoub Daniel , Van Dorsselaer Alain , Rahier Alain , Nkeng Paul , Geoffroy Philippe , Miesch Michel , Camara Bilal , Bouvier Florence
Published: December 2013

Sterols are vital for cellular functions and eukaryotic development because of their essential role as membrane constituents. Sterol biosynthetic intermediates (SBIs) represent a potential reservoir of signaling molecules in mammals and fungi, but little is known about their functions in plants. SBIs are derived from the sterol C4-demethylation enzyme complex that is tethered to the membrane by Ergosterol biosynthetic protein28 (ERG28). Here, using nonlethal loss-of-function strategies focused on Arabidopsis thaliana ERG28, we found that the previously undetected SBI 4-carboxy-4-methyl-24-methylenecycloartanol (CMMC) inhibits polar auxin transport (PAT), a key mechanism by which the phytohormone auxin regulates several aspects of plant growth, including development and responses to environmental factors. The induced accumulation of CMMC in Arabidopsis erg28 plants was associated with diagnostic hallmarks of altered PAT, including the differentiation of pin-like inflorescence, loss of apical dominance, leaf fusion, and reduced root growth. PAT inhibition by CMMC occurs in a brassinosteroid-independent manner. The data presented show that ERG28 is required for PAT in plants. Furthermore, it is accumulation of an atypical SBI that may act to negatively regulate PAT in plants. Hence, the sterol pathway offers further prospects for mining new target molecules that could regulate plant development.
Phosphatidylinositol 4,5-Bisphosphate Influences PIN Polarization by Controlling Clathrin-Mediated Membrane Trafficking inArabidopsis
Authors: Ischebeck Till , Werner Stephanie , Krishnamoorthy Praveen , Lerche Jennifer , Meijón Mónica , Stenzel Irene , Löfke Christian , Wiessner Theresa , Im Yang Ju , Perera Imara Y. , Iven Tim , Feussner Ivo , Busch Wolfgang , Boss Wendy F. , Teichmann Thomas , Hause Bettina , Persson Staffan , Heilmann Ingo
Published: December 2013

The functions of the minor phospholipid phosphatidylinositol-4,5-bisphosphate [PtdIns(4,5)P2] during vegetative plant growth remain obscure. Here, we targeted two related phosphatidylinositol 4-phosphate 5-kinases (PI4P 5-kinases) PIP5K1 and PIP5K2, which are expressed ubiquitously in Arabidopsis thaliana. A pip5k1 pip5k2 double mutant with reduced PtdIns(4,5)P2 levels showed dwarf stature and phenotypes suggesting defects in auxin distribution. The roots of the pip5k1 pip5k2 double mutant had normal auxin levels but reduced auxin transport and altered distribution. Fluorescence-tagged auxin efflux carriers PIN-FORMED (PIN1)–green fluorescent protein (GFP) and PIN2-GFP displayed abnormal, partially apolar distribution. Furthermore, fewer brefeldin A–induced endosomal bodies decorated by PIN1-GFP or PIN2-GFP formed in pip5k1 pip5k2 mutants. Inducible overexpressor lines for PIP5K1 or PIP5K2 also exhibited phenotypes indicating misregulation of auxin-dependent processes, and immunolocalization showed reduced membrane association of PIN1 and PIN2. PIN cycling and polarization require clathrin-mediated endocytosis and labeled clathrin light chain also displayed altered localization patterns in the pip5k1 pip5k2 double mutant, consistent with a role for PtdIns(4,5)P2 in the regulation of clathrin-mediated endocytosis. Further biochemical tests on subcellular fractions enriched for clathrin-coated vesicles (CCVs) indicated that pip5k1 and pip5k2 mutants have reduced CCV-associated PI4P 5-kinase activity. Together, the data indicate an important role for PtdIns(4,5)P2 in the control of clathrin dynamics and in auxin distribution in Arabidopsis.
Alignment of low-dose X-ray fluorescence tomography images using differential phase contrast
Authors: Hong Young Pyo , Gleber Sophie-Charlotte , O'Halloran Thomas V. , Que Emily L. , Bleher Reiner , Vogt Stefan , Woodruff Teresa K. , Jacobsen Chris
Published: December 2013

X-ray fluorescence nanotomography provides unprecedented sensitivity for studies of trace metal distributions in whole biological cells. Dose fractionation, in which one acquires very low dose individual projections and then obtains high statistics reconstructions as signal from a voxel is brought together (Hegerl & Hoppe, 1976), requires accurate alignment of these individual projections so as to correct for rotation stage runout. It is shown here that differential phase contrast at 10.2 keV beam energy offers the potential for accurate cross-correlation alignment of successive projections, by demonstrating that successive low dose, 3 ms per pixel, images acquired at the same specimen position and rotation angle have a narrower and smoother cross-correlation function (1.5 pixels FWHM at 300 nm pixel size) than that obtained from zinc fluorescence images (25 pixels FWHM). The differential phase contrast alignment resolution is thus well below the 700 nm × 500 nm beam spot size used in this demonstration, so that dose fractionation should be possible for reduced-dose, more rapidly acquired, fluorescence nanotomography experiments.
The Bionanoprobe: hard X-ray fluorescence nanoprobe with cryogenic capabilities
Authors: Chen S. , Deng J. , Yuan Y. , Flachenecker C. , Mak R. , Hornberger B. , Jin Q. , Shu D. , Lai B. , Maser J. , Roehrig C. , Paunesku T. , Gleber S. C. , Vine D. J. , Finney L. , VonOsinski J. , Bolbat M. , Spink I. , Chen Z. , Steele J. , Trapp D. , Irwin J. , Feser M. , Snyder E. , Brister K. , Jacobsen C. , Woloschak G. , Vogt S.
Published: December 2013

Hard X-ray fluorescence microscopy is one of the most sensitive techniques for performing trace elemental analysis of biological samples such as whole cells and tissues. Conventional sample preparation methods usually involve dehydration, which removes cellular water and may consequently cause structural collapse, or invasive processes such as embedding. Radiation-induced artifacts may also become an issue, particularly as the spatial resolution increases beyond the sub-micrometer scale. To allow imaging under hydrated conditions, close to the `natural state', as well as to reduce structural radiation damage, the Bionanoprobe (BNP) has been developed, a hard X-ray fluorescence nanoprobe with cryogenic sample environment and cryo transfer capabilities, dedicated to studying trace elements in frozen-hydrated biological systems. The BNP is installed at an undulator beamline at sector 21 of the Advanced Photon Source. It provides a spatial resolution of 30 nm for two-dimensional fluorescence imaging. In this first demonstration the instrument design and motion control principles are described, the instrument performance is quantified, and the first results obtained with the BNP on frozen-hydrated whole cells are reported.
Combining µXANES and µXRD mapping to analyse the heterogeneity in calcium carbonate granules excreted by the earthwormLumbricus terrestris
Authors: Brinza Loredana , Schofield Paul F. , Hodson Mark E. , Weller Sophie , Ignatyev Konstantin , Geraki Kalotina , Quinn Paul D. , Mosselmans J. Frederick W.
Published: December 2013

The use of fluorescence full spectral micro-X-ray absorption near-edge structure (µXANES) mapping is becoming more widespread in the hard energy regime. This experimental method using the CaK-edge combined with micro-X-ray diffraction (µXRD) mapping of the same sample has been enabled on beamline I18 at Diamond Light Source. This combined approach has been used to probe both long- and short-range order in calcium carbonate granules produced by the earthwormLumbricus terrestris. In granules produced by earthworms cultured in a control artificial soil, calcite and vaterite are observed in the granules. However, granules produced by earthworms cultivated in the same artificial soil amended with 500 p.p.m. Mg also contain an aragonite. The two techniques, µXRD and µXANES, probe different sample volumes but there is good agreement in the phase maps produced.
Axin expression delays herpes simplex virus‐induced autophagy and enhances viral replication in L929 cells
Authors: Choi Eun‐Jin , Kee Sun‐Ho
Published: December 2013

Axin, a negative regulator of the Wnt signaling pathway, plays a critical role in various cellular events including cell proliferation and cell death. Axin‐regulated cell death affects multiple processes, including viral replication. For example, axin expression suppresses herpes simplex virus (HSV)‐induced necrotic cell death and enhances viral replication. Based on these observations, this study investigated the involvement of autophagy in regulation of HSV replication and found axin expression inhibits autophagy‐mediated suppression of viral replication in L929 cells. HSV infection induced autophagy in a time‐ and viral dose‐dependent manner in control L929 cells (L‐EV), whereas virus‐induced autophagy was delayed in axin‐expressing L929 cells (L‐axin). Subsequent analysis showed that induction of autophagy by rapamycin reduced HSV replication, and that inhibiting autophagy by 3‐methyladenine (3MA) and beclin‐1 knockdown facilitated viral replication in L‐EV cells. In addition, preventing autophagy with 3MA suppressed virus‐induced cytotoxicity in L‐EV cells. In contrast, HSV replication in L‐axin cells was resistant to changes in autophagy. These results suggest that axin expression may render L929 cells resistant to HSV‐infection induced autophagy, leading to enhanced viral replication.
Subsurface offset behaviour in velocity analysis with extended reflectivity images
Authors: Mulder W.A.
Published: December 2013

Migration velocity analysis with the constant‐density acoustic wave equation can be accomplished by the focusing of extended migration images, obtained by introducing a subsurface shift in the imaging condition. A reflector in a wrong velocity model will show up as a curve in the extended image. In the correct model, it should collapse to a point. The usual approach to obtain a focused image involves a cost functional that penalizes energy in the extended image at non‐zero shift. Its minimization by a gradient‐based method should then produce the correct velocity model. Here, asymptotic analysis and numerical examples show that this method may be too sensitive to amplitude peaks at large shifts at the wrong depth and to artefacts. A more robust alternative is proposed that can be interpreted as a generalization of stack power and maximizes the energy at zero‐subsurface shift. A real‐data example is included.