bluuebunny/crossref_metadata_2025 huggingface dataset:
On a construction of the twistor spaces of Joyce metrics
Authors: Honda Nobuhiro
Published: August 2011

We explicitly construct the twistor spaces of some self-dual metrics with torus action given by D. Joyce. Starting from a fiber space over a projective line whose fibers are compact singular toric surfaces, we apply a number of birational transformations to obtain the desired twistor spaces. These constructions are based on a detailed analysis of the anticanonical system of the twistor spaces.
Chern classes of Schubert cells and varieties
Authors: Aluffi Paolo , Mihalcea Leonardo
Published: August 2011

We give explicit formulas for the Chern-Schwartz-MacPherson classes of all Schubert varieties in the Grassmannian of

d
d

-planes in a vector space, and conjecture that these classes are effective. We prove this is the case for

d
≤
2

d\le 2

.
Equisingularity of sections, (𝑡^{𝑟}) condition, and the integral closure of modules
Authors: Gaffney Terence , Trotman David , Wilson Leslie
Published: August 2011

This paper uses the theory of integral closure of modules to study the sections of both real and complex analytic spaces. The stratification conditions, which play a key role, are the

(

t

r

)

(t^{r})

conditions introduced by Thom and Trotman. Our results include an algebraic formulation of the

(

t

r

)

(t^{r})

in terms of the integral closure of modules, and a new simple proof showing how the

(

t

r

)

(t^{r})

conditions improve under Grassmann modification. In the complex analytic case, we characterise

(

t

r

)

(t^{r})

in terms of the genericity of the multiplicity of a certain submodule of the Jacobian module, then use the principle of specialisation of integral dependence for modules to give an equimultiplicity criterion for

(

t

r

)

(t^{r})

. As a consequence we obtain numerical criteria for Verdier equisingularity of families of plane sections in various situations.
Differentiability of volumes of divisors and a problem of Teissier
Authors: Boucksom Sébastien , Favre Charles , Jonsson Mattias
Published: August 2011

We give an algebraic construction of the positive intersection products of pseudo-effective classes and use them to prove that the volume function on the Néron–Severi space of a projective variety is

C

1

\mathcal {C}^1

-differentiable, expressing its differential as a positive intersection product. We also relate the differential to the restricted volumes. We then apply our differentiability result to prove an algebro-geometric version of the Diskant inequality in convex geometry, allowing us to characterize the equality case of the Khovanskii–Teissier inequalities for nef and big classes.
On the Casson Invariant Conjecture of Neumann–Wahl
Authors: Némethi András , Okuma Tomohiro
Published: August 2011

In this article we prove the Casson Invariant Conjecture of Neumann–Wahl for splice type surface singularities. Namely, for such an isolated complete intersection we show that the Casson invariant of the link is one-eighth the signature of the Milnor fiber, provided that the link is an integral homology sphere.
Laudal’s lemma in positive characteristic
Authors: Bonacini Paola
Published: August 2011

Laudal’s lemma states that if

C
C

is a curve of degree

d
>

s
2

+
1

d>s^2+1

in

P

3

\mathbb {P}^3

over an algebraically closed field of characteristic

0
0

such that its plane section is contained in an irreducible curve of degree

s
s

, then

C
C

lies on a surface of degree

s
s

. We show that the same result does not hold in positive characteristic and we find different bounds

d
>
f
(
s
)

d>f(s)

which ensure that

C
C

is contained in a surface of degree

s
s

.
The moduli space of cubic fourfolds
Authors: Laza Radu
Published: August 2011

We describe the GIT compactification of the moduli space of cubic fourfolds (cubic hypersurfaces in the five dimensional projective space), with a special emphasis on the role played by singularities. Our main result is that a cubic fourfold with only isolated simple (A-D-E) singularities is GIT stable. Conversely, with some minor exceptions, the stability for cubic fourfolds is characterized by this condition.
Holomorphic maps from rational homogeneous spaces onto projective manifolds
Authors: Lau Chi-Hin
Published: August 2011

In [Math. Ann. 142, 453-468], Remmert and Van de Ven conjectured that if

X
X

is the image of a surjective holomorphic map from

P

n

\mathbb {P}^n

, then

X
X

is biholomorphic to

P

n

\mathbb {P}^n

. This conjecture was proved by Lazarsfeld [Lect. Notes Math. 1092 (1984), 29-61] using Mori’s proof of Hartshorne’s conjecture [Ann. Math. 110 (1979), 593-606]. Then Lazarsfeld raised a more general problem, which was completely answered in the positive by Hwang and Mok.

Theorem 1 ([Invent. math. 136 (1999), 209-231] and [Asian J. Math. 8 (2004), 51-63]). Let

S
=
G

/

P

S=G/P

be a rational homogeneous manifold of Picard number

1
1

. For any surjective holomorphic map

f
:
S
→
X

f:S\to X

to a projective manifold

X
X

, either

X
X

is a projective space, or

f
f

is a biholomorphism.

The aim of this article is to give a generalization of Theorem 1. We will show that modulo canonical projections, Theorem 1 is true when

G
G

is simple without the assumption on Picard number. We need to find a dominating and generically unsplit family of rational curves which are of positive degree with respect to a given nef line bundle on

X
X

. Such a family may not exist in general, but we will prove its existence under a certain assumption which is applicable in our situation.
A simple proof for the existence of Zariski decompositions on surfaces
Authors: Bauer Thomas
Published: August 2011

In this note we give a quick and simple proof of the existence (and uniqueness) of Zariski decompositions on surfaces. While Zariski’s original proof employs a rather sophisticated procedure to construct the negative part of the decomposition, the present approach is based on the idea that the positive part can be constructed from a maximality condition. It may also be useful that this approach yields a practical algorithm for the computation of the positive part.
Maximal slope of tensor product of Hermitian vector bundles
Authors: Chen Huayi
Published: August 2011

We give an upper bound for the maximal slope of the tensor product of several non-zero Hermitian vector bundles on the spectrum of an algebraic integer ring. By Minkowski’s First Theorem, we need to estimate the Arakelov degree of an arbitrary Hermitian line subbundle

M
¯

\overline M

of the tensor product. In the case where the generic fiber of

M
M

is semistable in the sense of geometric invariant theory, the estimation is established by constructing, through the classical invariant theory, a special polynomial which does not vanish on the generic fibre of

M
M

. Otherwise we use an explicit version of a result of Ramanan and Ramanathan to reduce the general case to the former one.
The Multiplicity Polar Theorem and isolated singularities
Authors: Gaffney Terence
Published: August 2011

We show how the Multiplicity Polar Theorem can be used to calculate invariants which describe an “isolated singularity”. Examples include the defect of a function, which is related to the Euler obstruction, the index of a differential form, the dimension of the space of vanishing cycles of a sheaf of D-modules

M
M

relative to a function

f
f

at

0
0

, and a formula for the relative cohomology of the Milnor fiber of

f
f

where

f
f

has an isolated singularity on a complex analytic set with possibly non-isolated singularities. We apply the result on the defect to refine previous work on the

A

f

\mathrm {A}_f

condition.
Root numbers, Selmer groups, and non-commutative Iwasawa theory
Authors: Coates John , Fukaya Takako , Kato Kazuya , Sujatha Ramdorai
Published: August 2011

Let

E
E

be an elliptic curve over a number field

F
F

, and let

F
∞

F_\infty

be a Galois extension of

F
F

whose Galois group

G
G

is a

p
p

-adic Lie group. The aim of the present paper is to provide some evidence that, in accordance with the main conjectures of Iwasawa theory, there is a close connection between the action of the Selmer group of

E
E

over

F
∞

F_\infty

, and the global root numbers attached to the twists of the complex

L
L

-function of

E
E

by Artin representations of

G
G

.
On the geometry of the moduli space of spin curves
Authors: Ludwig Katharina
Published: August 2011

We determine the smooth locus and the locus of canonical singularities in the Cornalba compactification

S
¯

g

\overline {S}_g

of the moduli space

S
g

S_g

of spin curves, i.e., smooth curves of genus

g
g

with a theta characteristic. Moreover, the following lifting result for pluricanonical forms is proved: Every pluricanonical form on the smooth locus of

S
¯

g

\overline {S}_g

extends holomorphically to a desingularisation of

S
¯

g

\overline {S}_g

.
Some intersection numbers of divisors on toroidal compactifications of 𝒜_{ℊ}
Authors: Erdenberger C. , Grushevsky S. , Hulek K.
Published: August 2011

We study the top intersection numbers of the boundary and Hodge class divisors on toroidal compactifications of the moduli space

A

g

\mathcal {A}_g

of principally polarized abelian varieties and compute those numbers that live away from the stratum which lies over the closure of

A

g
−
3

\mathcal {A}_{g-3}

in the Satake compactification.
Eigencone, saturation and Horn problems for symplectic and odd orthogonal groups
Authors: Belkale Prakash , Kumar Shrawan
Published: August 2011

In this paper we consider the eigenvalue problem, intersection theory of homogeneous spaces (in particular, the Horn problem) and the saturation problem for the symplectic and odd orthogonal groups. The classical embeddings of these groups in the special linear groups play an important role. We deduce properties for these classical groups from the known properties for the special linear groups.
Arrangements of curves and algebraic surfaces
Authors: Urzúa Giancarlo
Published: August 2011

We prove a strong relation between Chern and log Chern invariants of algebraic surfaces. For a given arrangement of curves, we find nonsingular projective surfaces with Chern ratio arbitrarily close to the log Chern ratio of the log surface defined by the arrangement. Our method is based on sequences of random

p
p

-th root covers, which exploit a certain large scale behavior of Dedekind sums and lengths of continued fractions. We show that randomness is necessary for our asymptotic result, providing another instance of “randomness implies optimal”. As an application over

C

\mathbb {C}

, we construct nonsingular simply connected projective surfaces of general type with large Chern ratio. In particular, we improve the Persson-Peters-Xiao record for Chern ratios of such surfaces.
An Artin-Rees theorem in 𝐾-theory and applications to zero cycles
Authors: Krishna Amalendu
Published: August 2011

For the smooth normalization

f
:

X
¯

→
X

f : {\overline X} \to X

of a singular variety

X
X

over a field

k
k

of characteristic zero, we show that for any conducting subscheme

Y
Y

for the normalization, and for any

i
∈

Z

i \in \mathbb {Z}

, the natural map

K
i

(
X
,

X
¯

,
n
Y
)
→

K
i

(
X
,

X
¯

,
Y
)

K_i(X, {\overline X}, nY) \to K_i(X, {\overline X}, Y)

is zero for all sufficiently large

n
n

.

As an application, we prove a formula for the Chow group of zero cycles on a quasi-projective variety

X
X

over

k
k

with Cohen-Macaulay isolated singularities, in terms of an inverse limit of the relative Chow groups of a desingularization

X
~

\widetilde X

relative to the multiples of the exceptional divisor.

We use this formula to verify a conjecture of Srinivas about the Chow group of zero cycles on the affine cone over a smooth projective variety which is arithmetically Cohen-Macaulay.
Blow-analytic equivalence of two variable real analytic function germs
Authors: Koike Satoshi , Parusiński Adam
Published: August 2011

Blow-analytic equivalence is a notion for real analytic function germs, introduced by Tzee-Char Kuo in order to develop real analytic equisingularity theory. In this paper we give complete characterisations of blow-analytic equivalence in the two dimensional case, in terms of the real tree model for the arrangement of real parts of Newton-Puiseux roots and their Puiseux pairs, and in terms of minimal resolutions. These characterisations show that in the two dimensional case the blow-analytic equivalence is a natural analogue of topological equivalence of complex analytic function germs. Moreover, we show that in the two-dimensional case the blow-analytic equivalence can be made cascade, and hence satisfies several geometric properties. It preserves, for instance, the contact order of real analytic arcs.

In the general

n
n

-dimensional case, we show that a singular real modification satisfies the arc-lifting property.
The maximum number of singular points on rational homology projective planes
Authors: Hwang Dongseon , Keum Jonghae
Published: August 2011

A normal projective complex surface is called a rational homology projective plane if it has the same Betti numbers with the complex projective plane

C

P

2

\mathbb {C}\mathbb {P}^2

. It is known that a rational homology projective plane with quotient singularities has at most

5
5

singular points. So far all known examples have at most

4
4

singular points. In this paper, we prove that a rational homology projective plane

S
S

with quotient singularities such that

K
S

K_S

is nef has at most

4
4

singular points except one case. The exceptional case comes from Enriques surfaces with a configuration of 9 smooth rational curves whose Dynkin diagram is of type

3

A
1

⊕
2

A
3

3A_1 \oplus 2A_3

.

We also obtain a similar result in the differentiable case and in the symplectic case under certain assumptions which all hold in the algebraic case.
Secant varieties of ℙ¹×⋯×ℙ¹ (𝕟-times) are NOT defective for 𝕟≥5
Authors: Catalisano Maria , Geramita Anthony , Gimigliano Alessandro
Published: August 2011

Let

V
n

V_n

be the Segre embedding of

P

1

×
⋯
×

P

1

{\mathbb {P}^1}\times \cdots \times {\mathbb {P}^1}

(

n
n

times). We prove that the higher secant varieties

σ
s

(

V
n

)

\sigma _s(V_n)

always have the expected dimension, except for

σ
3

(

V
4

)

\sigma _3(V_4)

, which is of dimension 1 less than expected.
On quasismooth weighted complete intersections
Authors: Chen Jheng-Jie , Chen Jungkai , Chen Meng
Published: August 2011

We prove two conjectures on weighted complete intersections (cf. London Mathematical Society, Lecture Note Series, 281, Cambridge University Press, 2000, 101–173) and give the complete classification of threefold weighted complete intersections in weighted projective space that are canonically or anticanonically embedded.
Smooth affine surfaces with non-unique ℂ*-actions
Authors: Flenner Hubert , Kaliman Shulim , Zaidenberg Mikhail
Published: August 2011

In this paper we complete the classification of effective

C

∗

\mathbb {C}^*

-actions on smooth affine surfaces up to conjugation in the full automorphism group and up to inversion

λ
↦

λ

−
1

\lambda \mapsto \lambda ^{-1}

of

C

∗

\mathbb {C}^*

. If a smooth affine surface

V
V

admits more than one

C

∗

\mathbb {C}^*

-action, then it is known to be Gizatullin i.e., it can be completed by a linear chain of smooth rational curves. In [Transformation Groups 13:2, 2008, pp. 305–354] we gave a sufficient condition, in terms of the Dolgachev-Pinkham-Demazure (or DPD) presentation, for the uniqueness of a

C

∗

\mathbb {C}^*

-action on a Gizatullin surface. In the present paper we show that this condition is also necessary, at least in the smooth case. In fact, if the uniqueness fails for a smooth Gizatullin surface

V
V

which is neither toric nor Danilov-Gizatullin, then

V
V

admits a continuous family of pairwise non-conjugated

C

∗

\mathbb {C}^*

-actions depending on one or two parameters. We give an explicit description of all such surfaces and their

C

∗

\mathbb {C}^*

-actions in terms of DPD presentations. We also show that for every

k
>
0

k>0

one can find a Danilov-Gizatullin surface

V
(
n
)

V(n)

of index

n
=
n
(
k
)

n=n(k)

with a family of pairwise non-conjugate

C

+

\mathbb {C}_+

-actions depending on

k
k

parameters.
Mirror symmetry via logarithmic degeneration data, II
Authors: Gross Mark , Siebert Bernd
Published: August 2011

This paper continues the authors’ program of studying mirror symmetry via log geometry and toric degenerations, relating affine manifolds with singularities, log Calabi-Yau spaces, and toric degenerations of Calabi-Yau spaces. The main focus of this paper is the calculation of the cohomology of a Calabi-Yau variety associated to a given affine manifold with singularities

B
B

. We show that the Dolbeault cohomology groups of the Calabi-Yau associated to

B
B

are described in terms of certain cohomology groups of sheaves on

B
B

, as expected. This is proved first by calculating the log de Rham and log Dolbeault cohomology groups on the log Calabi-Yau space associated to

B
B

, and then proving a base-change theorem for cohomology in our logarithmic setting. As applications, this shows that our mirror symmetry construction via Legendre duality of affine manifolds results in the usual interchange of Hodge numbers expected in mirror symmetry and gives an explicit description of the monodromy of a smoothing.
Non-vanishing theorem for log canonical pairs
Authors: Fujino Osamu
Published: August 2011

We obtain a correct generalization of Shokurov’s non-vanishing theorem for log canonical pairs. It implies the base point free theorem for log canonical pairs. We also prove the rationality theorem for log canonical pairs. As a corollary, we obtain the cone theorem for log canonical pairs. We do not need Ambro’s theory of quasi-log varieties.
Twisted stable maps to tame Artin stacks
Authors: Abramovich Dan , Olsson Martin , Vistoli Angelo
Published: August 2011

We develop the theory of twisted stable maps into a tame Artin stack

M

\mathcal {M}

. We show that the stacks

K

g
,
n

(

M

)

\mathcal {K}_{g,n}(\mathcal {M})

of twisted stable maps are algebraic, and proper and quasi-finite over the corresponding stacks

K

g
,
n

(
M
)

\mathcal {K}_{g,n}(M)

of stable maps of the coarse moduli space

M
M

of

M

\mathcal {M}

. In the special case where

M

=

B

G

\mathcal {M}=\mathcal {B}G

, the classifying stack of a linearly reductive group scheme

G
G

, we show that

K

g
,
n

(

B

G
)
→

M

¯

g
,
n

\mathcal {K}_{g,n}(\mathcal {B}G)\to \overline {\mathcal {M}}_{g,n}

is a flat morphism with local complete intersection fibers.
Automorphisms mapping a point into a subvariety
Authors: Poonen Bjorn
Published: August 2011

The problem of deciding, given a complex variety

X
X

, a point

x
∈
X

x \in X

, and a subvariety

Z
⊆
X

Z \subseteq X

, whether there is an automorphism of

X
X

mapping

x
x

into

Z
Z

is proved undecidable. Along the way, we prove the undecidability of a version of Hilbert’s tenth problem for systems of polynomials over

Z

\mathbb {Z}

defining an affine

Q

\mathbb {Q}

-variety whose projective closure is smooth.
Ample divisors on moduli spaces of pointed rational curves
Authors: Fedorchuk Maksym , Smyth David
Published: August 2011

We introduce a new technique for proving positivity of certain divisor classes on

M
¯

0
,
n

\overline {M}_{0,n}

and its weighted variants

M
¯

0
,

A

\overline {M}_{0,\mathcal {A}}

. Our methods give a complete description of the models arising in the Hassett’s log minimal model program for

M
¯

0
,
n

\overline {M}_{0,n}

.
Reconstructing the architecture of the ancestral amniote genome
Authors: Ouangraoua Aïda , Tannier Eric , Chauve Cedric
Published: August 2011

Motivation: The ancestor of birds and mammals lived approximately 300 million years ago. Inferring its genome organization is key to understanding the differentiated evolution of these two lineages. However, detecting traces of its chromosomal organization in its extant descendants is difficult due to the accumulation of molecular evolution since birds and mammals lineages diverged.

Results: We address several methodological issues for the detection and assembly of ancestral genomic features of ancient vertebrate genomes, which encompass adjacencies, contiguous segments, syntenies and double syntenies in the context of a whole genome duplication. Using generic, but stringent, methods for all these problems, some of them new, we analyze 15 vertebrate genomes, including 12 amniotes and 3 teleost fishes, and infer a high-resolution genome organization of the amniote ancestral genome, composed of 39 ancestral linkage groups at a resolution of 100 kb. We extensively discuss the validity and robustness of the method to variations of data and parameters. We introduce a support value for each of the groups, and show that 36 out of 39 have maximum support.

Conclusions: Single methodological principle cannot currently be used to infer the organization of the amniote ancestral genome, and we demonstrate that it is possible to gather several principles into a computational paleogenomics pipeline. This strategy offers a solid methodological base for the reconstruction of ancient vertebrate genomes.

Availability: Source code, in C++ and Python, is available at http://www.cecm.sfu.ca/~cchauve/SUPP/AMNIOTE2010/

Contact:  cedric.chauve@sfu.ca

Supplementary information:  Supplementary data are available at Bioinformatics online.
Comment on “Benford's Law and the Detection of Election Fraud”
Authors: Mebane Walter R.
Published: August 2011

“Benford's Law and the Detection of Election Fraud” raises doubts about whether a test based on the mean of the second significant digit of vote counts equals 4.187 is useful as a test for the occurrence of election fraud. The paper mistakenly associates such a test with Benford's Law, considers a simulation exercise that has no apparent relevance for any actual election, applies the test to inappropriate levels of aggregation, and ignores existing analysis of recent elections in Russia. If tests based on the second significant digit of precinct-level vote counts are diagnostic of election fraud, the tests need to use expectations that take into account the features of ordinary elections, such as strategic actions. Whether the tests are useful for detecting fraud remains an open question, but approaching this question requires an approach more nuanced and tied to careful analysis of real election data than one sees in the discussed paper.
Exploring the Function of Alcohol Dehydrogenases During the Endophytic Life of Azoarcus Sp. Strain BH72
Authors: Krause Andrea , Bischoff Birte , Miché Lucie , Battistoni Federico , Reinhold-Hurek Barbara
Published: August 2011

The endophytic bacterium Azoarcus sp. strain BH72 is capable of colonizing the interior of rice roots, where it finds suitable physicochemical properties for multiplying and fixing nitrogen. Because these properties are poorly understood, a microtiter-plate-based screening of a transcriptional gfp (green fluorescent protein) fusion library of Azoarcus sp. grown under different conditions was performed. Monitoring of the GFP activity allowed the identification of a gene highly expressed in medium supplemented with ethanol. Sequence analysis revealed that this gene encodes a pyrrolo-quinoline quinone-dependent alcohol dehydrogenase (ADH). Inspection of the complete genome sequence of the Azoarcus sp. strain BH72 identified seven additional genes encoding putative ADH, indicating that BH72 is well equipped to survive in different environmental conditions offering various alcohols as carbon source. Analyses of these eight putative ADH showed that expression of three was induced by ethanol, of which two were also expressed inside rice roots. The fact that waterlogged plants such as rice accumulate ethanol suggests that ethanol occurs in sufficiently high concentration within the root to induce expression of bacterial ADH. Disruption of these two ADH evoked a reduced competitiveness to the wild type in colonizing rice roots internally. Thus, it is likely that ethanol is an important carbon source for the endophytic life of Azoarcus sp.
The Biology of Frankia sp. Strains in the Post-Genome Era
Authors: Benson David R. , Brooks James M. , Huang Ying , Bickhart Derek M. , Mastronunzio Juliana E.
Published: August 2011

Progress in understanding symbiotic determinants involved in the N2-fixing actinorhizal plant symbioses has been slow but steady. Problems persist with studying the bacterial contributions to the symbiosis using traditional microbiological techniques. However, recent years have seen the emergence of several genomes from Frankia sp. strains and the development of techniques for manipulating plant gene expression. Approaches to understanding the bacterial side of the symbiosis have employed a range of techniques that reveal the proteomes and transcriptomes from both cultured and symbiotic frankiae. The picture beginning to emerge provides some perspective on the heterogeneity of frankial populations in both conditions. In general, frankial populations in root nodules seem to maintain a rather robust metabolism that includes nitrogen fixation and substantial biosynthesis and energy-generating pathways, along with a modified ammonium assimilation program. To date, particular bacterial genes have not been implicated in root nodule formation but some hypotheses are emerging with regard to how the plant and microorganism manage to coexist. In particular, frankiae seem to present a nonpathogenic presence to the plant that may have the effect of minimizing some plant defense responses. Future studies using high-throughput approaches will likely clarify the range of bacterial responses to symbiosis that will need to be understood in light of the more rapidly advancing work on the plant host.
Habitat tracking, stasis and survival in Neogene large mammals
Authors: Raia P. , Passaro F. , Fulgione D. , Carotenuto F.
Published: August 2011

Species response to environmental change may vary from adaptation to the new conditions, to dispersal towards territories with better ecological settings (known as habitat tracking), and to extinction. A phylogenetically explicit analysis of habitat tracking in Caenozoic large mammals shows that species moving over longer distances during their existence survived longer. By partitioning the fossil record into equal time intervals, we showed that the longest distance was preferentially covered just before extinction. This supports the idea that habitat tracking is a key reaction to environmental change, and confirms that tracking causally prolongs species survival. Species covering longer distances also have morphologically less variable cheek teeth. Given the tight relationship between cheek teeth form and habitat selection in large mammals, this supports the well-known, yet little tested, idea that habitat tracking bolsters morphological stasis.
Nicholas Kemmer. 7 December 1911 — 21 October 1998
Authors: Dyson Freeman
Published: August 2011

Nicholas Kemmer was a theoretical physicist whose most famous contribution to science was the prediction in 1938 of the existence of three kinds of particle—one positive, one negative and one neutral—coupled to protons and neutrons in a symmetrical way so as to produce nuclear forces independent of charge. Three particle species were discovered experimentally 10 years later and found to have the nuclear couplings specified by Kemmer. They are the particles now known as π mesons or pions. Other sets of three species with the same symmetry were discovered later. The long interval between prediction and verification was caused by World War I, which interrupted the progress of particle physics in general and Kemmer’s career in particular. After the war he devoted his life to teaching rather than research, and became a beloved mentor and friend to several generations of younger physicists. Among the scientists that he launched into successful research careers are Abdus Salam FRS (Nobel laureate), Paul Matthews FRS, Richard Dalitz FRS and the present writer. In the American Mathematical Society Mathematical Genealogy Project, which includes physicists as well as mathematicians, Kemmer is academic ancestor to 217 descendants.
Stephen Finney Mason. 6 July 1923 — 11 December 2007
Authors: Grinter Roger
Published: August 2011

Stephen Mason’s professional career comprised three distinct periods. After completing his DPhil on the physicochemical properties of antimalarial drugs in 1947 he first worked in the history of science and wrote a notable book on that subject,
A history of the sciences: main currents of scientific thought
. In 1953 his interest turned again to ‘modern’ chemical research, and until his retirement in 1988 he was active at the forefront of the application of the spectroscopic and theoretical techniques developed during the middle third of the twentieth century to the elucidation of the structures of organic and inorganic molecules. In the last, post-retirement, phase he returned to the history of science. This pattern reflected his extremely wide interest in and comprehensive knowledge of science, especially chemistry, which was manifest in his approach to university teaching and to all the research problems with which he engaged.
William Platt Jencks. 15 August 1927 — 3 January 2007
Authors: Kirsch Jack F. , Richard John P.
Published: August 2011

The field of enzymology was profoundly affected by the death of Bill Jencks on 3 January 2007, after a 17-year struggle against Alzheimer’s disease. Jencks was a major innovator, a superb teacher, a devoted husband and father, and a helpful friend and colleague. Those of us who had the privilege of working with Bill, or of knowing him professionally, are poorer for his passing.
The Portuguese
cholera morbus
epidemic of 1853–56 as seen by the press
Authors: de Almeida Maria Antónia Pires
Published: August 2011

This is a study of how scientific knowledge reached common citizens in nineteenth-century Portugal, using newspapers as the main source. Despite the population's limited access to written material, each leading newspaper might be read by 30 000 people a day in Lisbon. This made newspapers the most widely available vehicle for the diffusion of the latest scientific information to the general public. With a
cholera morbus
epidemic affecting the second largest Portuguese town and all the northern regions, as well as the Algarve, reports on the course of the epidemic were considered essential. The author bases her study on a database of news about the disease in 1855 and 1856, especially with regard to prevention and treatment.
Impact of aragonite saturation state changes on migratory pteropods
Authors: Comeau Steeve , Gattuso Jean-Pierre , Nisumaa Anne-Marin , Orr James
Published: August 2011

Thecosome pteropods play a key role in the food web of various marine ecosystems and they calcify, secreting the unstable CaCO3mineral aragonite to form their shell material. Here, we have estimated the effect of ocean acidification on pteropod calcification by exploiting empirical relationships between their gross calcification rates (CaCO3precipitation) and aragonite saturation stateΩa, combined with model projections of futureΩa. These were corrected for modern model-data bias and taken over the depth range where pteropods are observed to migrate vertically. Results indicate large reductions in gross calcification at temperate and high latitudes. Over much of the Arctic, the pteropodLimacina helicinawill become unable to precipitate CaCO3by the end of the century under the IPCC SRES A2 scenario. These results emphasize concerns over the future of shelled pteropods, particularlyL. helicinain high latitudes. Shell-lessL. helicinaare not known to have ever existed nor would we expect them to survive. Declines of pteropod populations could drive dramatic ecological changes in the various pelagic ecosystems in which they play a critical role.
For better or worse: reduced adult lifespan following early-life stress is transmitted to breeding partners
Authors: Monaghan Pat , Heidinger Britt J. , D'Alba Liliana , Evans Neil P. , Spencer Karen A.
Published: August 2011

Stressful conditions early in life can give rise to exaggerated stress responses, which, while beneficial in the short term, chronically increase lifetime exposure to stress hormones and elevate disease risk later in life. Using zebra finchesTaeniopygia guttata, we show here that individuals whose glucocorticoid stress hormones were experimentally increased for only a brief period in early post-natal life, inducing increased stress sensitivity, had reduced adult lifespans. Remarkably, the breeding partners of such exposed individuals also died at a younger age. This negative effect on partner longevity was the same for both sexes; it occurred irrespective of the partner's own early stress exposure and was in addition to any longevity reduction arising from this. Furthermore, this partner effect continued even after the breeding partnership was terminated. Only 5 per cent of control birds with control partners had died after 3 years, compared with over 40 per cent in early stress–early stress pairs. In contrast, reproductive capability appeared unaffected by the early stress treatment, even when breeding in stressful environmental circumstances. Our results clearly show that increased exposure to glucocorticoids early in life can markedly reduce adult life expectancy, and that pairing with such exposed partners carries an additional and substantial lifespan penalty.
Current Status of Human Adipose–Derived Stem Cells: Differentiation into Hepatocyte-Like Cells
Authors: Al Battah Feras , De Kock Joery , Vanhaecke Tamara , Rogiers Vera
Published: August 2011

The shortage of human organ donors and the low cell quality of available liver tissues represent major obstacles for the clinical application of orthotropic liver transplantation and hepatocyte transplantation, respectively. Therefore, worldwide research groups are investigating alternative extrahepatic cell sources. Recentin vitrostudies have demonstrated that mesenchymal stem cells (MSCs) from various sources, including human bone marrow, adipose tissue, and umbilical cord, can be differentiated into hepatocyte-like cells when appropriate conditions are used. In particular, interest exists for human adipose–derived stems cells (hASCs) as an attractive cell source for generating hepatocyte-like cells. The hASCs are multipotent MSCs that reside in adipose tissue, with the ability to self-renew and differentiate into multiple cell lineages. Moreover, these cells can secrete multiple growth factors and cytokines that exert beneficial effects on organ or tissue injury. In this review, we will not only present recent data regarding hASC biology, their isolation, and differentiation capability towards hepatocytes, but also the potential application of hASC-derived hepatocytes to study drug toxicity. Additionally, this review will discuss the therapeutic potential of hASCs as undifferentiated cells in liver regeneration.
Hydroxylapatite lattice preferred orientation in bone: a study of macaque, human and bovine samples
Authors: Voltolini Marco , Wenk Hans-Rudolf , Gomez Barreiro Juan , Agarwal Sabrina C.
Published: August 2011

Hydroxylpatite crystallites in lamellar bone show preferred orientation. In this study, the texture (lattice preferred orientation) of the crystallites in cortical bone samples has been studied by means of synchrotron hard X-ray diffraction, performing a combined analysis with the Rietveld method to quantify fully the preferred orientation features and to obtain lattice and microstructural parameters (such as crystallite size) simultaneously. The samples were ribs from four adult female macaques of different ages, and two femurs chosen for comparison, one from a human child and one from an adult cow. The effect of the preferred orientation of the mineral component on the elastic properties is also briefly discussed. All six samples, averaging volumes of ∼0.5 mm3, show strong preferred orientation, with the hydroxylapatitecaxis parallel to the bone axis. The symmetry of the texture is almost perfectly axial and clearly displays a uniform girdle of theaaxis perpendicular to the bone axis. The texture strength is very similar for the four macaque rib samples, while some variation is observed in the human (weaker) and bovine (stronger) femurs. The crystallite size (8 × 30 nm) and unit-cell lattice parameters are similar in all samples. The Rietveld analysis provides for the first time a quantitative texture analysis combined with structural and microstructural hydroxylapatite analysis of the same bone samples.
Modification of preferred martensitic variant distribution by high magnetic field annealing in an Ni–Mn–Ga alloy
Authors: Cong D. Y. , Zhang Y. D. , Esling C. , Wang Y. D. , Zhao X. , Zuo L.
Published: August 2011

The preferred martensitic variant distribution in Ni53Mn25Ga22ferromagnetic shape memory alloy (FSMA) samples annealed without and with a high magnetic field of 12 T applied during the annealing process was investigated by electron backscatter diffraction. It is revealed that the high magnetic field applied during annealing enhances the regular arrangement of martensitic variants from the morphological point of view and effectively modifies the preferred orientation distribution of martensitic variants without changing the misorientation between them from the crystallographic point of view. Only one texture component, \{ 1{\overline 1}0\} \langle 33{\overline 2}\rangle, exists in the sample annealed without a magnetic field, whereas two additional texture components, \{ 4{\overline 6} 3\} \langle 31{\overline 2}\rangle and \{ 1\overline 1 0\} \langle 110 \rangle, are developed in the sample annealed in a high magnetic field. The new finding that the preferred martensitic variant distribution can be efficiently modified by introducing a high magnetic field during the annealing process will shed light on the development of high-performance polycrystalline FSMAsvianovel processing techniques.
Electrical and structural characterization of (KxNa1−x)NbO3ceramics modified with Li and Ta
Authors: Mgbemere Henry E. , Hinterstein Manuel , Schneider Gerold A.
Published: August 2011

(KxNa1−x)NbO3ceramics modified with Li+and Ta5+have been produced using the mixed-oxide synthesis method. Synchrotron X-ray diffraction measurements were made on the samples from 12 K to temperatures above their ferroelectric–paraelectric transition points with 10 K measurement steps. Rietveld refinement was used to refine the patterns. Depending on the composition and temperature, rhombohedral phases, orthorhombic phases, tetragonal phases, cubic phases and two-phase mixtures were obtained. Space groupsR3c(161),Amm2 (38),P4mm(99) and Pm{\overline 3}m (221) and their combinations were used to refine the rhombohedral, orthorhombic, tetragonal, cubic and mixed phases, respectively. Li+addition suppressed the formation of the rhombohedral low-temperature phase and increased the Curie temperature. This is attributed to the size difference in ionic radii of theA-site elements, which leads to increased atomic polarizability and increased interaction with theB-site element. Li+and Ta5+co-doping led to a wide temperature range of coexistence between the orthorhombic and tetragonal phases. Electrical characterizations by dielectric and hysteresis measurements were used to compare with the results from the structural studies.
Quantitative X-ray diffraction phase analysis of poorly ordered nontronite clay in nickel laterites
Authors: Wang Xiaodong , Li Jian , Hart Robert D. , van Riessen Arie , McDonald Robbie
Published: August 2011

Studies of the extraction of nickel from low-grade laterite ores require a much better quantitative understanding of the poorly ordered mineral phases present, including turbostratically disordered nontronite. Whole pattern refinements with nontronite X-ray diffraction data from a Western Australian nickel deposit (Bulong) using a nontronite lattice model (Pawley phase) with two space groups (P3 andC2/m) and a peaks phase group model were performed to improve the accuracy of quantitative X-ray diffraction of nickel laterite ore samples. Modifications were applied when building the new models to accommodate asymmetric peak shape and anisotropic peak broadening due to the turbostratic disorder. Spherical harmonics were used as convolution factors to represent anisotropic crystal size and strain and asymmetric peak shape when using the lattice model. A peaks phase group model was also developed to fit the anisotropic peak broadening in the nontronite pattern. The quantitative results of the new Pawley phase and peaks phase group models were compared and verified with synthetic mixtures of nontronite, quartz and goethite simulating various West Australian laterite ore compositions. The models developed in this paper demonstrate adequate accuracy for quantification of nontronite in the synthesized reference materials and should be generally applicable to quantitative phase analysis of nontronite in nickel laterite ore samples.
In situobservation of morphological changes of γ′ precipitates in a pre-deformed single-crystal Ni-base superalloy
Authors: Strunz Pavel , Schumacher Gerhard , Klingelhöffer Hellmuth , Wiedenmann Albrecht , Šaroun Jan , Keiderling Uwe
Published: August 2011

Exposure of a superalloy to an external load results in anisotropic coarsening of the γ′ precipitates, so-called rafting. It was reported in the past that γ′ rafting can also occur as a result of purely thermal treatment, without the simultaneous presence of an external load, if the specimen has been pre-deformed at relatively low temperature. The evolution of γ′ morphology in pre-deformed specimens of SCA425 Ni-base superalloy was examined in the present study. Unlike in the previous experiments, the compressive stress was used for pre-straining.In situsmall-angle neutron scattering (SANS) was employed, which enabled the determination of the morphology directly at high temperature. Both for strong and for weak pre-straining, rounding of the originally cuboidal precipitates towards an ellipsoidal shape on heating was observed. Weak pre-straining (0.1, 0.5%) does not cause rafting on subsequent heating. On the other hand, the detailed evaluation of SANS data provides some indication of rafting during the subsequent heating after severe compressive pre-straining (2%). The experiment indicates the role of dislocation rearrangement at the matrix/precipitate interface during pre-straining.
Automated microfluidic sample-preparation platform for high-throughput structural investigation of proteins by small-angle X-ray scattering
Authors: Lafleur Josiane P. , Snakenborg Detlef , Nielsen Søren S. , Møller Magda , Toft Katrine N. , Menzel Andreas , Jacobsen Jes K. , Vestergaard Bente , Arleth Lise , Kutter Jörg P.
Published: August 2011

A new microfluidic sample-preparation system is presented for the structural investigation of proteins using small-angle X-ray scattering (SAXS) at synchrotrons. The system includes hardware and software features for precise fluidic control, sample mixing by diffusion, automated X-ray exposure control, UV absorbance measurements and automated data analysis. As little as 15 µl of sample is required to perform a complete analysis cycle, including sample mixing, SAXS measurement, continuous UV absorbance measurements, and cleaning of the channels and X-ray cell with buffer. The complete analysis cycle can be performed in less than 3 min. Bovine serum albumin was used as a model protein to characterize the mixing efficiency and sample consumption of the system. The N2 fragment of an adaptor protein (p120-RasGAP) was used to demonstrate how the device can be used to survey the structural space of a protein by screening a wide set of conditions using high-throughput techniques.
Crk‐associated substrate lymphocyte type regulates myeloid cell motility and suppresses the progression of leukemia induced by p210Bcr/Abl
Authors: Seo Sachiko , Nakamoto Tetsuya , Takeshita Masataka , Lu Jun , Sato Tomohiko , Suzuki Takahiro , Kamikubo Yasuhiko , Ichikawa Motoshi , Noda Masaki , Ogawa Seishi , Honda Hiroaki , Oda Hideaki , Kurokawa Mineo
Published: August 2011

The p210Bcr/Abl and p190Bcr/Abl fusion oncoproteins are known to cause chronic myelogenous leukemia (CML) and acute lymphoblastic leukemia (ALL). Bcr/Abl phosphorylates several proteins that can lead to leukemogenesis. Crk‐associated substrate lymphocyte type (Cas‐L)/human enhancer of filamentation‐1 (HEF1)/neural precursor cell expressed, developmentally down‐regulated 9 (NEDD9) is an adapter protein at focal adhesions known to be associated with solid tumor metastasis. Crk‐associated substrate lymphocyte type has also been reported to be tyrosine phosphorylated by p190Bcr/Abl. We demonstrated that Cas‐L was expressed in murine granulocytes, as well as in lymphocytes, and that Cas‐L‐deficient (Cas‐L−/−) granulocytes had increased migratory activity and decreased adhesiveness. To examine whether Cas‐L was involved in leukemogenesis by p210Bcr/Abl, we generated Cas‐L−/− p210Bcr/Abl transgenic mice. The mice displayed early development of myeloproliferative neoplasm seen in the chronic phase of CML, which resulted in the early death of the mice. Pathologically, increased infiltration of myeloid cells into several tissues was detected in the absence of Cas‐L. In a hematopoietic reconstitution assay, Cas‐L−/− p210Bcr/Abl transgenic cells showed a low population in the spleen, although only their myeloid cell population was normal. Thus, Cas‐L seems to regulate the progression of CML in a negative way, presumably by attenuating extramedullary hyperplasia. (Cancer Sci 2011; 102: 2109–2117)
Baby – and toddler – steps toward immunotherapy for food allergy
Authors: Keet C. A. , Wood R. A.
Published: August 2011

Cite this as: C. A. Keet and R. A. Wood, Clinical & Experimental Allergy, 2011 (41) 1175–1176.
Modelling the effect of size on the aerial dispersal of microorganisms
Authors: Wilkinson David M. , Koumoutsaris Symeon , Mitchell Edward A. D. , Bey Isabelle
Published: August 2011

Aim  We investigate the long‐standing question of whether the small size of microbes allows most microbial species to colonize all suitable sites around the globe or whether their ranges are limited by opportunities for dispersal. In this study we use a modelling approach to investigate the effect of size on the probability of between‐continent dispersal using virtual microorganisms in a global model of the Earth’s atmosphere.

Location  Global.

Methods  We use a computer model of global atmospheric circulation to investigate the effect of microbe size (effective diameters of 9, 20, 40 and 60 μm) on the probability of aerial dispersal.

Results  We found that for smaller microbes, once airborne, dispersal is remarkably successful over a 1‐year period. The most striking results are the extensive within‐hemisphere distribution of virtual microbes of 9 and 20 μm diameter and the lack of dispersal between the Northern and Southern Hemispheres during the year‐long time‐scale of our simulations.

Main conclusions  Above a diameter of 20 μm wind dispersal of virtual microbes between continents becomes increasingly unlikely, and it does not occur at all (within our simulated 1‐year period) for those of 60 μm diameter. Within our simulation, the success of small microbes in long‐distance dispersal is due both to their greater abundance and to their longer time in the atmosphere – once airborne – compared with larger microbes.