bluuebunny/crossref_metadata_2025 huggingface dataset:
Polymer Primary Structures Studied by ESCA and EHCO Methods
Authors: J J Pireaux  , J Riga  , R Caudano  , J J Verbist  , J Delhalle  , S Delhalle  , J M André  , Y Gobillon
Published: January 2007

The electronic structure (core and valence levels) of various simple polymers has been investigated by ESCA (Electron Spectroscopy for Chemical Analysis), with the aid of original EHCO (Extended Hückel Crystalline Orbitals) calculations giving corresponding density of states and band structure schemes. Simple monosubstituted homopolymers derived from polyethylene ([CH2-CHX]n) have been chosen in order to study the influence of X substituents (X = -F, -Cl, -OH, -CH3, -CH2CH3, -C6H5, -C6H11corresponding respectively to poly(vinyl fluoride), poly(vinyl chloride), poly(vinyl alcohol), poly(propylene), poly(1-butene), poly(styrene), and poly(vinyl cyclohexane)) through the chemical shifts measured for the core levels, and the alteration of the valence band structures. Assignment of the valence molecular orbitals is made with the aid of the theoretical calculations and with comparison of spectra recorded for molecules similar to the monomeric units. Emphasis is put on the very significant information provided by the valence band spectra for polymers containing only carbon and hydrogen atoms. Valence band data are used to calculate physical parameters (first ionization potential, energy gap, work function) of importance to deduce electrical properties for the polymers.
The Analysis of Polymer Degradation Products by UV-Photoelectron Spectroscopy
Authors: D Betteridge  , D J Joyner  , F Greening  , N R Shoko  , M E A Cudby  , H A Willis  , T E Attwood  , L Henriksen
Published: January 2007

Uv-photoelectron spectroscopy has been used for the qualitative and quantitative analysis of polymer degradation products. The degradation can be carried out under flowing or static conditions and with different atmospheres. Typically, a few μg of decomposition products gives rise to an acceptable spectrum, and decomposition rates of 5 μg min-1 (0.05% per hour) are easily monitored. The method has been applied to PVC, polycarbonates and PTFE. It is well suited to the detection and determination of small molecules such as HCl, CO2 and tetrafluoroethylene, which are major decomposition products and N2 and O2 whose role in degradation is of interest.
A Comparative E.S.C.A. Study of the Electronic Structure of Solid Acenes: benzene, naphthalene, anthracene, and tetracene
Authors: J Riga  , J J Pireaux  , R Caudano  , J J Verbist
Published: January 2007

By comparison of the E.S.C.A. valence band spectra recorded in the solid phase for polyacenes (benzene, naphthalene, anthracene, and tetracene) with gas phase results, important energy parameters (energy gap, work function) of these compounds have been obtained. The trends observed in the evolution of the main C1sshake-up positions and intensities serve to assign the π satellites to transitions of the type nb1→b1*.
Electronic Structure of Rutile Oxides TiO2, RuO2 and IrO2 Studied by X-ray Photoelectron Spectroscopy
Authors: J Riga  , C Tenret-Noël  , J J Pireaux  , R Caudano  , J J Verbist  , Y Gobillon
Published: January 2007

Valence band X-ray photoelectron spectra of the rutile oxides TiO2, RuO2, and IrO2 show a distinct evolution as a function of the increasing number of metal d-electrons. The observations are found to be in excellent agreement with recent theoretical models. Intensity analysis and photo-ionization cross sections are used to confirm the nature of the band responsible for conducting properties. The result is in accordance with a crystal field model proposed earlier. The deduced number of "free electrons" in the valence band is used to correlate the asymmetry recorded for the core level lines.
ESCA Study of Gold Organometallics. Correlation of the binding energy with calculated charges
Authors: D F van de Vondel  , G P van der Kelen  , H Schmidbaur  , A Wolleben  , F E Wagner
Published: January 2007

The core electron binding energies have been measured for a series of 16 gold compounds. They allow the identification of the rare Au II formal oxidation state in a number of these compounds. The binding energies of the Au 4f electrons are correlated with the partial atomic charges calculated by means of the electronegativity equalization procedure.
Application of a Potential Model to the Interpretation of XPS Spectra of Group V Organometallics
Authors: S C F Hoste  , D F van de Vondel  , G P van der Kelen
Published: January 2007

The XPS spectra of 19 triphenylphosphorus derivatives are measured in the solid state. Net atomic charges, derived from electronegativity equalization considerations in simple structures provide a better correlation with experimental binding energies when the potential model is used neglecting the calculated molecular potential. Overall correlation is not improved upon introduction of more sophisticated π-bonding characteristics except in a few cases where very pronounced back donation to phosphorus occurs.
ESCA and UPS Spectra of Nitronaphthylamines. Shake-up structures, relaxation effects and through-space interaction between the two substituents
Authors: Giuseppe Distefano  , Derek Jones  , Alberto Modelli  , Salvatore Pignataro
Published: January 2007

The X-ray and UV photoelectron spectra of several nitronaphthylamine isomers are reported. In some cases, the nitro N1ssignal is accompanied by an intense satellite band 1.5-2.0 eV from the main photoline having 60-150% of its intensity; also in the corresponding O1senergy region a satellite band is present having a larger energy separation from the main peak (2.0-2.35eV) and smaller relative intensity (Ish= 10-30%). The difference between the ionization energy values of the nitro and amino N1ssignal (ΔN1s) is found to follow the same trend found for the intensity of the satellite and log ϵ, the optical absorption coefficient of the HOMO-LUMO charge-transfer (CT) transition.

These satellites are ascribed to a shake-up process involving a CT transition from the naphthylamine part of the molecule towards a π* MO localized on the nitro group on the basis of a simple model we have previously proposed for nitroanilines and other aromatic derivatives.

The trend of ΔN1sis thought to derive mainly from a greater "interatomic" valence band relaxation accompanying nitro N1sionization than amino N1sionization, rather than from variation of the ground state charges at the two nitrogen atoms.

The UPS spectra indicate that there is no sizeable variation of the ground state mesomeric interaction between the two substituents on changing the position of the nitro group, and suggest mutual interaction of the two substituents when they are adjacent.
Intense Shake-up satellites in ESCA Spectra of Transition Metal, Lanthanide and Actinide Compounds
Authors: Sven Larsson
Published: January 2007

Satellite structure which occurs in ESCA spectra of transition metal, lanthanide and actinide compounds is rationalized in terms of a simple model. The relationship between high intensity and "covalency" is pointed out and it is shown that the word "covalency" has to be used with caution in this context.
Intermediate X-ray Sources for ESCA
Authors: R Nyholm  , A Berndtsson  , R Nilsson  , J Hedman  , C Nordling
Published: January 2007

The applicability of the YMζ (hv= 132 eV) and the FKα (hv= 676 eV) X-ray lines for generating photoelectron spectra is demonstrated. The N2valence electron spectra excited by YMζ and A1Kα are studied in regard to relative intensities and shake-up structure. Relative intensities of electron levels in Au excited by FKα and A1Kα are measured. Cross-section ratios for FKα and A1Kα excited spin-orbit components in Ar and Au are determined. Experimental and theoretical cross-section ratios of the Hg 5dspin-orbit components are reviewed for excitation energies between 21 eV and 2 700 eV.
Studies of Surface Electronic Structure and Surface Chemistry Using Synchrotron Radiation
Authors: W E Spicer  , I Lindau  , J N Miller  , D T Ling  , P Pianetta  , P W Chye  , C M Garner
Published: January 2007

Photoemission studies for hv < 400 eV are used to illustrate some of the advantages of synchrotron radiation for studying the surface electronic structure and chemistry of solids. Studies of GaAs and Pt are used to illustrate the following advantages (all of which depend on a source of radiation with a continuously tunable photon energy): (1) both valence and core states can be examined, (2) photon energies can be chosen so that the electron escape length can be minimized, restricting the studies to the first several atomic or molecular layers of the solids, (3) since the escape depth minimum is rather shallow the matrix element for excitation from a given set of levels may be maximized consistent with probing the last few layers, (4) when two sets of levels are degenerate or near degenerate in energy, e.g. the solid valence levels and the orbits of an adsorbed gas, the photon energy dependence of the matrix element can be used to separate the photoemission from the two states, and (5) good energy resolution (often 0.2 eV or better) can be obtained. For GaAs, studies of the surface valence electronic structure (hv ≈ 21 eV) in conjunction with LEED results indicated that rearrangement of the atoms within the last unit cell of the surface plays an important role in determining the electronic structure associated with this last layer of the crystal. In fact, it appears that measurement of this electronic structure may prove to be one of the most sensitive ways of determining the details of the atomic rearrangement. Studies of the Ga and As 3d core shifts on chemisorption of oxygen indicate that electrons are transferred from the As to the oxygen. The next step in oxidation, the formation of true As and Ga oxides, has also been followed using the core shifts. CO adsorbed on metals has been studied extensively previously using photoemission methods; however, neither the CO 3σ levels nor the "shake up" structure has been clearly seen in the past due to background produced by the strong Pt 5d valence photoemission. Making use of the Cooper minimum in the 5d excitation cross section at hv = 150 eV, the CO 3σ and "shake up" structures have been clearly seen for the first time.
Oxidation of Aluminum Surfaces Studied by Synchrotron Radiation Photoelectron Spectroscopy
Authors: S B M Hagström  , R Z Bachrach  , R S Bauer  , S A Flodström
Published: January 2007

A review is presented of a series of electron spectroscopic measurements investigating the surface properties of aluminum by its interaction with molecular oxygen. The studies performed at the Stanford Synchrotron Radiation Laboratory have used the unique properties of synchrotron radiation. The tunability of the excitation source in the spectral range 30-700 eV has made it possible to obtain maximum surface sensitivity and measure core-level photoabsorption.
Electron Spectroscopic Study of Nitric Oxide Adsorbed on Copper
Authors: M H Matloob  , M W Roberts
Published: January 2007

The interaction of NO with copper has been investigated by electron spectroscopy. Nitric oxide is shown to be molecularly adsorbed in a linearly bonded configuration at 85 K; this adlayer is unstable above 120 K, resulting in an exclusively oxygen adlayer at 295 K, the nitrogen being desorbed. At 85 K N(1s) peaks observed at 401 and 406 eV are associated with two different surface species. We suggest that the former dissociates while the latter desorbs at a binding energy of 406 eV on thermal activation of the adlayer.

Interaction of nitric oxide with Cu at 295 K results in dissociative chemisorption with both oxygen and nitrogen retained at the surface. The surface concentration suggests that each nitrogen and oxygen adatom is bridge-bonded to two surface copper atoms. Estimates of absolute surface coverages are made by comparing the intensities of the N(1s) and O(1s) peaks with the Cu(2p) substrate intensity, while valence level spectroscopy (He I and II radiation) supplements core-level spectroscopy for discriminating between molecular and dissociated surface species.
Clean and Oxygen Exposed Potassium Studied by Photoelectron Spectroscopy
Authors: L-G Petersson  , S-E Karlsson
Published: January 2007

Clean evaporated potassium films have been studied in a combined UV-X-ray photoelectron instrument. The valence band and the K 3plevel were studied using 21.2 and 40.8 eV radiation. In the 40.8 eV excited spectrum a structure attributed to surface and volume plasma losses was resolved. Using AlKα excitation the binding energies of the core levels in potassium were determined. Potassium films at a temperature of 77 K were exposed to oxygen at a pressure of about 10-5Pa for increasing time periods. The intensity and shape of the core levels as well as of the valence band were studied after each exposure. The shapes of the O 1sline and the valence band excited by 40.8 eV radiation were followed as a function of increasing temperature after an initial exposure of 45 L O2. For comparison spectra from a sample exposed to about 45 L H2O were recorded.
Preparation of Alloys for ESCA Investigation
Authors: B O Elfström  , I Olefjord
Published: January 2007

The surface compositions of stainless steels–Fe, Cr, Ni, Mo-alloys–after scraping in vacuum, mechanical polishing in air, electropolishing and ion etching have been studied by ESCA. The most representative surface composition is obtained after scraping the sample with a diamond tool in UHV. All other methods produce enrichment of some species on the surface. Mechanical polishing in air leads to a preferential oxidation of Fe and Cr and a concurrent accumulation of Mo and Ni atoms underneath the oxide. During electropolishing in perchloric acid Fe is selectively dissolved into the solution, while Cr and Mo are enriched in their metallic states in the surface region. (It is suggested that it is the enrichment of these alloy components which gives electropolished stainless steels their excellent corrosion properties.) Ion etching lowers the Cr and Ni content in the outermost layer of the metal by selective sputtering mechanism.
ESCA Investigations of Ion Beam Effects on Surfaces
Authors: R Holm  , S Storp
Published: January 2007

The sampling depth of ESCA is about two to three times the mean escape depth of the photoelectrons; thus, in general, a surface layer with a thickness of about 100 Å contributes to the signal. Within this range, information concerning the depth distribution of elements and compounds can be obtained non-destructively. ESCA can therefore be used to reveal the nature of the artefacts that are inevitably formed during the removal of surface layers by ion bombardment. Examples are given of the following effects: selective sputtering (accumulation of Cu on brass, depletion of Cr in the removal of oxide layers on steels), implantation of primary ions and surface atoms, and ion-induced reactions (destruction and formation of compounds). Particular attention is paid to the processes occurring in the bombardment of the oxide-metal interface.
Investigation of the Electronic Structure of V2VI3 Compounds by Means of X-ray Emission and Photoelectron Spectroscopy
Authors: G Leonhardt  , H Neumann  , A Kosakov  , T Götze  , M Petke
Published: January 2007

Ultraviolet and x-ray excited photoelectron spectra and soft X-ray emission spectra have been measured for the compounds As2S3, Sb2S3, As2O3, Sb2O3 and Bi2O3. All compounds exhibit quite similar photoelectron spectra of the density of valence states which can be interpreted with the same model based on the atomic electronic properties of the compound constituents accounting for the chemical order and the chemical composition of the compounds. This model is confirmed by the X-ray emission spectra. Cluster calculations using the CNDO approximation have been performed for As2O3 and Sb2O3. The influence of the cluster symmetry, the cluster size and the CNDO parameters on the calculated spectra was investigated. Reasonable agreement between theory and experiment could be obtained using suitable chosen parameter sets.
The moduli space of quadratic rational maps
Authors: DeMarco Laura
Published: January 2007

Let

M
2

M_2

be the space of quadratic rational maps

f
:

P

1

→

P

1

f:\textbf {P}^1\to \textbf {P}^1

, modulo the action by conjugation of the group of Möbius transformations. In this paper a compactification

X
X

of

M
2

M_2

is defined, as a modification of Milnor’s

M
¯

2

≃

CP

2

\overline {M}_2\simeq \textbf {CP}^2

, by choosing representatives of a conjugacy class

[
f
]
∈

M
2

[f]\in M_2

such that the measure of maximal entropy of

f
f

has conformal barycenter at the origin in

R

3

\textbf {R}^3

and taking the closure in the space of probability measures. It is shown that

X
X

is the smallest compactification of

M
2

M_2

such that all iterate maps

[
f
]
↦
[

f
n

]
∈

M

2
n

[f]\mapsto [f^n]\in M_{2^n}

extend continuously to

X
→

M
¯

2
n

X \to \overline {M}_{2^n}

, where

M
¯

d

\overline {M}_d

is the natural compactification of

M
d

M_d

coming from geometric invariant theory.
Noncommutative maximal ergodic theorems
Authors: Junge Marius , Xu Quanhua
Published: January 2007

This paper is devoted to the study of various maximal ergodic theorems in noncommutative

L
p

L_p

-spaces. In particular, we prove the noncommutative analogue of the classical Dunford-Schwartz maximal ergodic inequality for positive contractions on

L
p

L_p

and the analogue of Stein’s maximal inequality for symmetric positive contractions. We also obtain the corresponding individual ergodic theorems. We apply these results to a family of natural examples which frequently appear in von Neumann algebra theory and in quantum probability.
Minimal surfaces with the area growth of two planes: The case of infinite symmetry
Authors: Meeks William , Wolf Michael
Published: January 2007

We prove that a connected properly immersed minimal surface in

E

3

{\mathbb E}^3

with infinite symmetry group and area growth constant less than

3
π

3\pi

is a plane, a catenoid, or a Scherk singly-periodic minimal surface. As a consequence, the Scherk minimal surfaces are the only connected periodic minimal desingularizations of the intersections of two planes.
On the restriction of Deligne-Lusztig characters
Authors: Reeder Mark
Published: January 2007

We study the multiplicities of Deligne-Lusztig characters upon restriction from a finite reductive group to a finite reductive subgroup. The result is a qualitative formula for the growth of multiplicities in terms of complexity. For restrictions from

S

O

2
n
+
1

SO_{2n+1}

to

S

O

2
n

SO_{2n}

we get exact multiplicities.
Compatibility of local and global Langlands correspondences
Authors: Taylor Richard , Yoshida Teruyoshi
Published: January 2007

We prove the compatibility of local and global Langlands correspondences for

G

L
n

GL_n

, which was proved up to semisimplification in M. Harris and R. Taylor, The Geometry and Cohomology of Some Simple Shimura Varieties, Ann. of Math. Studies 151, Princeton Univ. Press, Princeton-Oxford, 2001. More precisely, for the

n
n

-dimensional

l
l

-adic representation

R
l

(
Π
)

R_l(\Pi )

of the Galois group of an imaginary CM-field

L
L

attached to a conjugate self-dual regular algebraic cuspidal automorphic representation

Π
\Pi

of

G

L
n

(

A

L

)

GL_n(\mathbb A_L)

, which is square integrable at some finite place, we show that Frobenius semisimplification of the restriction of

R
l

(
Π
)

R_l(\Pi )

to the decomposition group of a place

v
v

of

L
L

not dividing

l
l

corresponds to

Π
v

\Pi _v

by the local Langlands correspondence. If

Π
v

\Pi _v

is square integrable for some finite place

v

⧸

|

l

v \not | l

we deduce that

R
l

(
Π
)

R_l(\Pi )

is irreducible. We also obtain conditional results in the case

v

|

l

v|l

.
Spongiform Neurodegeneration-associated E3 Ligase Mahogunin Ubiquitylates TSG101 and Regulates Endosomal Trafficking
Authors: Kim Bong Yoon , Olzmann James A. , Barsh Gregory S. , Chin Lih-Shen , Li Lian
Published: January 2007

A null mutation in the gene encoding the putative E3 ubiquitin–protein ligase Mahogunin causes spongiform neurodegeneration, a recessively transmitted prion-like disease in mice. However, no substrates of Mahogunin have been identified, and the cellular role of Mahogunin is unknown. Here, we report the identification of TSG101, a key component of the endosomal sorting complex required for transport (ESCRT)-I, as a specific Mahogunin substrate. We find that Mahogunin interacts with the ubiquitin E2 variant (UEV) domain of TSG101 via its PSAP motif and that it catalyzes monoubiquitylation of TSG101 both in vivo and in vitro. Depletion of Mahogunin by small interfering RNAs in mammalian cells disrupts endosome-to-lysosome trafficking of epidermal growth factor receptor, resulting in prolonged activation of a downstream signaling cascade. Our findings support a role for Mahogunin in a proteasome-independent ubiquitylation pathway and suggest a link between dysregulation of endosomal trafficking and spongiform neurodegeneration.
Functional Interaction of Aurora-A and PP2A during Mitosis
Authors: Horn Virginie , Thélu Jacques , Garcia Alphonse , Albigès-Rizo Corinne , Block Marc R. , Viallet Jean
Published: January 2007

Entry into mitosis is a highly regulated process, promoted by the activated Cyclin B1/Cdk1 complex. Activation of this complex is controlled, in part, by the protein kinase Aurora-A, which is a member of a multigenic serine/threonine kinase family. In normal cells, Aurora-A activity is regulated, at least in part, by degradation through the APC-ubiquitin-proteasome pathway. It has recently been proposed that, in Xenopus, Aurora-A degradation can be inhibited by phosphorylation. It would thus be expected that a phosphatase activity would release this blockade at the end of mitosis. Here, we have shown that the protein phosphatase PP2A and Aurora-A are colocalized at the cell poles during mitosis in human cells and interact within the same complex. Using the PP2A inhibitor okadaic acid and an RNAi approach, we have shown that this interaction is functional within the cell. PP2A/Aurora-A interaction is promoted by an S51D mutation in Aurora-A and inhibited by a phosphomimetic peptide centered around Aurora-A S51, thereby strongly suggesting that PP2A controls Aurora-A degradation by dephosphorylating serine 51 in the A box of the human enzyme.
The APC/C inhibitor, Emi1, is essential for prevention of rereplication
Authors: Machida Yuichi J. , Dutta Anindya
Published: January 2007

Emi1 (early mitotic inhibitor) inhibits APC/C (anaphase-promoting complex/cyclosome) activity during S and G2 phases, and is believed to be required for proper mitotic entry. We report that Emi1 plays an essential function in cell proliferation by preventing rereplication. Rereplication seen after Emi1 depletion is due to premature activation of APC/C that results in destabilization of geminin and cyclin A, two proteins shown here to play redundant roles in preventing rereplication in mammalian cells. Geminin is known to inhibit the replication initiation factor Cdt1. The rereplication block by cyclin A is mediated through its association with S and G2/M cyclin-dependent kinases (Cdks), Cdk2 and Cdk1, suggesting that phosphorylation of proteins by cyclin A–Cdk is responsible for the block. Rereplication upon Emi1 depletion activates the DNA damage checkpoint pathways. These data suggest that Emi1 plays a critical role in preserving genome integrity by blocking rereplication, revealing a previously unrecognized function of this inhibitor of APC/C.
The Spt6 SH2 domain binds Ser2-P RNAPII to direct Iws1-dependent mRNA splicing and export
Authors: Yoh Sunnie M. , Cho Helen , Pickle Loni , Evans Ronald M. , Jones Katherine A.
Published: January 2007

Spt6 promotes transcription elongation at many genes and functions as a histone H3 chaperone to alter chromatin structure during transcription. We show here that mammalian Spt6 binds Ser2-phosphorylated (Ser2P) RNA polymerase II (RNAPII) through a primitive SH2 domain, which recognizes phosphoserine rather than phosphotyrosine residues. Surprisingly, a point mutation in the Spt6 SH2 domain (R1358K) blocked binding to RNAPIIo without affecting transcription elongation rates in vitro. However, HIV-1 and c-myc RNAs formed in cells expressing the mutant Spt6 protein were longer than normal and contained splicing defects. Ectopic expression of the wild-type, but not mutant, Spt6 SH2 domain, caused bulk poly(A)+ RNAs to be retained in the nucleus, further suggesting a widespread role for Spt6 in mRNA processing or assembly of export-competent mRNP particles. We cloned the human Spt6-interacting protein, hIws1 (interacts with Spt6), and found that it associates with the nuclear RNA export factor, REF1/Aly. Depletion of endogenous hIws1 resulted in mRNA processing defects, lower levels of REF1/Aly at the c-myc gene, and nuclear retention of bulk HeLa poly(A)+ RNAs in vivo. Thus binding of Spt6 to Ser2-P RNAPII provides a cotranscriptional mechanism to recruit Iws1, REF1/Aly, and associated mRNA processing, surveillance, and export factors to responsive genes.
IRES-mediated functional coupling of transcription and translation amplifies insulin receptor feedback
Authors: Marr Michael T. , D’Alessio Joseph A. , Puig Oscar , Tjian Robert
Published: January 2007

It is generally accepted that the growth rate of an organism is modulated by the availability of nutrients. One common mechanism to control cellular growth is through the global down-regulation of cap-dependent translation by eIF4E-binding proteins (4E-BPs). Here, we report evidence for a novel mechanism that allows eukaryotes to coordinate and selectively couple transcription and translation of target genes in response to a nutrient and growth signaling cascade. The Drosophila insulin-like receptor (dINR) pathway incorporates 4E-BP resistant cellular internal ribosome entry site (IRES) containing mRNAs, to functionally couple transcriptional activation with differential translational control in a cell that is otherwise translationally repressed by 4E-BP. Although examples of cellular IRESs have been previously reported, their critical role mediating a key physiological response has not been well documented. Our studies reveal an integrated transcriptional and translational response mechanism specifically dependent on a cellular IRES that coordinates an essential physiological signal responsible for monitoring nutrient and cell growth conditions.
Telomerase abrogation dramatically accelerates TRF2-induced epithelial carcinogenesis
Authors: Blanco Raquel , Muñoz Purificación , Flores Juana M. , Klatt Peter , Blasco María A.
Published: January 2007

TRF2 is a telomere-binding protein with roles in telomere protection and telomere-length regulation. The fact that TRF2 is up-regulated in some human tumors suggests a role of TRF2 in cancer. Mice that overexpress TRF2 in the skin, K5TRF2 mice, show critically short telomeres and are susceptible to UV-induced carcinogenesis as a result of deregulated XPF/ERCC1 activity, a nuclease involved in UV damage repair. Here we demonstrate that, when in combination with telomerase deficiency, TRF2 acts as a very potent oncogene in vivo. In particular, we show that telomerase deficiency dramatically accelerates TRF2-induced epithelial carcinogenesis in K5TRF2/Terc−/− mice, coinciding with increased chromosomal instability and DNA damage. Telomere recombination is also increased in these mice, suggesting that TRF2 favors the activation of alternative telomere maintenance mechanisms. Together, these results demonstrate that TRF2 increased expression is a potent oncogenic event that along with telomerase deficiency accelerates carcinogenesis, coincidental with a derepression of telomere recombination. These results are of particular relevance given that TRF2 is up-regulated in some human cancers. Furthermore, these data suggest that telomerase inhibition might not be effective to cease the growth of TRF2-overexpressing tumors.
Structure of an aluminophosphate EMM-8: a multi-technique approach
Authors: Cao Guang , Afeworki Mobae , Kennedy Gordon J. , Strohmaier Karl G. , Dorset Douglas L.
Published: January 2007

The crystal structure of an aluminophosphate, EMM-8 (ExxonMobil Material #8), was determined in its calcined, anhydrous form from synchrotron powder diffraction data using the computer program FOCUS. A linkage of double four-ring (D4R) building units forms a two-dimensional framework with 12-MR and 8-MR channels, and differs from a similar SAPO-40 (AFR) framework only by the relationship between paired D4R units. Rietveld refinement reveals a fit of the model to the observed synchrotron data by R
wp = 0.1118, R(F
2) = 0.1769. Local environments of the tetrahedral phosphorus and aluminium sites were established by solid-state NMR, which detects distinct differences between as-synthesized and calcined materials. Distinct, reversible changes in the local symmetry of the P and Al atoms were observed by NMR upon calcination and subsequent hydration. These NMR data provided important constraints on the number of tetrahedral (T) atoms per unit cell and the connectivities of the T atoms. Detailed local structural information obtained by solid-state NMR thereby guided the ultimate determination of the structure of AlPO EMM-8 from the powder data. Comparisons are made to the recently published crystal structure of the fluoride-containing, as-synthesized SSZ-51, indicating that the unit-cell symmetry, axial dimensions and framework structure are preserved after calcination.
Three isomeric 1-(2-chloronicotinoyl)-2-(nitrophenyl)hydrazines, including three polymorphs of 1-(2-chloronicotinoyl)-2-(2-nitrophenyl)hydrazine: hydrogen-bonded supramolecular structures in two and three dimensions
Authors: Wardell Solange M. S. V. , Souza Marcus V. N. de , Wardell James L. , Low John N. , Glidewell Christopher
Published: January 2007

1-(2-Chloronicotinoyl)-2-(2-nitrophenyl)hydrazine, C12H9ClN4O3, crystallizes in three polymorphic forms, two monoclinic forms in space groups Cc (Ia) and P21 (Ib), and an orthorhombic form in space group Pbcn (Ic). In the Cc polymorph (Ia) the molecules are linked into sheets by combinations of one N—H...O and two C—H...O hydrogen bonds, while in the P21 polymorph (Ib) the molecules are linked into sheets by combinations of three hydrogen bonds, one each of N—H...O, C—H...N and C—H...O types. In the orthorhombic polymorph (Ic) the molecules are linked into a complex three-dimensional framework structure by a combination of one N—H...O, one N—H...N and three C—H...O hydrogen bonds, and an aromatic π...π stacking interaction. In the isomeric compound 1-(2-chloronicotinoyl)-2-(3-nitrophenyl)hydrazine (II) the molecules are again linked into a three-dimensional framework, this time by a combination of three hydrogen bonds, one each of N—H...O, N—H...N and C—H...O types, weakly augmented by a π...π stacking interaction. The molecules of 1-(2-chloronicotinoyl)-2-(4-nitrophenyl)hydrazine (III) are linked into sheets by a combination of three hydrogen bonds, one each of N—H...O, N—H...N and C—H...O types.
Structural filiations in the new complex titanates SrLiMTi4O11 (M = Cr, Fe)
Authors: Imaz I. , Péchev S. , Koseva I. , Bourée F. , Gravereau P. , Peshev P. , Chaminade J.-P.
Published: January 2007

Two new titanates of strontium, lithium and a 3d metal, with the composition SrLiMTi4O11 (M = Cr, Fe), have been discovered. Single crystals were obtained by spontaneous crystallization from a high-temperature solution with LiBO2 as the solvent. The structure of SrLiCrTi4O11 was refined in the orthorhombic space group Pnma (Z = 4), while SrLiFeTi4O11 appeared to adopt a four-times larger orthorhombic unit cell with Pbcn (Z = 16). The structures can be described by a close-packed arrangement of Sr and O atoms. The unit cell contains six `compact planes' perpendicular to [100] in the layer sequence ABACBC [(chc)2]. Ti and Cr or Fe atoms occupy some of the interstitial octahedral sites created, whereas Li atoms are in tetrahedral sites. Depending on the synthesis conditions of SrLiCrTi4O11, the distribution of Cr and Ti atoms on the four possible crystallographic sites is not the same. Having a similar compact-planes sequence, SrLiCrTi4O11 and SrLiFeTi4O11 structures differ in the arrangement of Sr and O atoms per layer of close packing, which also induces a correlated variation in the Li-tetrahedra distribution.
Structure determination of di-μ-hydroxo-bis[(2-(2-pyridyl)phenyl-κ2
N,C
1)palladium(II)] by X-ray powder diffractometry
Authors: Pérez J. , Serrano J. L. , Galiana J. M. , Cumbrera F. L. , Ortiz A. L. , Sánchez G. , García J.
Published: January 2007

The title compound was synthesized in the form of a powder, and was studied by elemental analysis, IR spectroscopy, thermogravimetry and mass spectroscopy. Its crystal structure was then determined by X-ray powder diffractometry, using X-ray diffraction data collected in the reflection Bragg–Brentano geometry. The methodology followed in the present study to resolve the crystal structure consisted of peak indexing, then the use of the Monte-Carlo/parallel tempering search algorithm, and finally Rietveld refinement coupled with difference-Fourier synthesis. We found that the crystals are composed of monoclinic unit cells, with 1.5 molecules in the asymmetric unit and therefore six molecules per unit cell. In addition, we concluded that the complexes adopt a planar conformation, forming trimers created by groups of parallel molecules.
Pitfalls of data mining: triclinic polymorph of 2,2-aziridinedicarboxamide revisited
Authors: Podsiadło Marcin , Dziubek Kamil , Katrusiak Andrzej
Published: January 2007

Several procedures have been employed for validating structural models refined on poor quality single-crystal diffraction data. Analysis of intra- and intermolecular distances in the structures of 2,2-aziridinedicarboxamide polymorphs proved to be a robust means, and a means independent of the chosen unit cell and symmetry, of detecting several incorrect atom-type assignments in the reported structure of the triclinic polymorph of 2,2-aziridinedicarboxamide [Brückner (1982). Acta Cryst. B38, 2405–2408]. The corrected model, refined in the space group P\overline 1, rules out the existence of any conformational polymorphism in this compound. Small differences in the powder-diffraction patterns calculated for the original and corrected structures of the triclinic polymorph illustrate the sensitivity of the above method for polymorph validation.
Sensitive detection of mirror symmetry by CBED applied to LaAlO3 and GdAlO3
Authors: Jones Daniel M.
Published: January 2007

Convergent-beam electron diffraction (CBED) patterns tilted away from major zone axes have been used to re-examine the space groups of LaAlO3 and GdAlO3 perovskites. The higher-order Laue zones (HOLZ) in CBED patterns at such tilted orientations have been found to have high sensitivity to the presence of mirror symmetry. This sensitivity has enabled the space group of LaAlO3, previously claimed to be cubic (Fm\bar 3c), to be confirmed as rhombohedral R\bar 3c by CBED. It is clear that patterns of sufficient tilt will be more sensitive for distinguishing between screw axes and glide planes than the observation of HOLZ deficit lines in zero-order Laue zone reflections. No symmetry degrading effects due to the influence of tilted crystal surfaces could be observed.
Halogen...halogen interactions in pressure-frozen ortho- and meta-dichlorobenzene isomers
Authors: Bujak Maciej , Dziubek Kamil , Katrusiak Andrzej
Published: January 2007

Isomers 1,2-dichlorobenzene (o-DCB) and 1,3-dichlorobenzene (m-DCB) were high-pressure frozen in-situ in a Merrill–Bassett diamond–anvil cell and their structures determined at room temperature and at 0.18 (5) GPa for o-DCB, and 0.17 (5) GPa for m-DCB by single-crystal X-ray diffraction. The patterns of halogen...halogen intermolecular interactions in these structures can be considered to be the main cohesive forces responsible for the molecular arrangements in these crystals. The molecular packing of dichlorobenzene isomers, including three polymorphs of 1,4-dichlorobenzene (p-DCB), have been compared and relations between their molecular symmetry, packing arrangements, intermolecular interactions and melting points discussed. The topology of the crystal packing in dichlorobenzene isomers results from the interplay of the molecular shape, steric hindrances and intermolecular interactions. The non-planar arrangement of the dichlorobenzene molecules in the crystal structures can be justified by the distributions of the electrostatic potential on molecular surfaces, which determines electrostatic intermolecular interactions.
Structural study of four complexes of the M-N2S2 type derived from diethylphenylazothioformamide and the metals palladium, platinum, copper and nickel
Authors: Nielsen Kim T. , Harris Pernille , Bechgaard Klaus , Krebs Frederik C.
Published: January 2007

The four electron-transfer complexes trans-(di(N,N-diethyl-(2-phenyldiazenyl)thioformamide-κS,κN
2))nickel, trans-(di(N,N-diethyl-(2-phenyldiazenyl)thioformamide-κS,κN
2))copper, trans-(di(N,N-diethyl-(2-phenyldiazenyl)thioformamide-κS,κN
2))palladium and trans-(di(N,N-diethyl-(2-phenyldiazenyl)thioformamide-κS,κN
2))platinum have been crystallized, and their structures have been determined at low temperature. All the complexes are of the M-N2S2 type. The crystals of both the nickel and the copper complex belong to the tetragonal P41212 system, in which the central metal ion lies on a twofold axis. The tetrahedral molecular symmetry around the central metal ion is unusual for the M-N2S2 electron-transfer complexes. The crystals of the palladium and platinum complexes on the other hand belong to the monoclinic C2/c system in which the metal ion lies on an inversion centre. The molecular symmetry around these metal ions is square planar. It is demonstrated that the π electron density in the ligand planes has a high degree of delocalization. Furthermore, unusually large line broadening of the 1H NMR spectra was observed and investigated as a function of temperature for the palladium complex.
Assessment of degradation and generation of humus in a coffee soil affected by weed cover by means of a stable carbon isotopic ratio
Authors: Watanabe A. , Takada H. , Sarno  , Afandi  , Adachi T. , Oki Y. , Senge M.
Published: January 2007

We evaluated the effect of soil conservation by weeds on the degradation and generation of humic acids, fulvic acids, and water‐soluble non‐humic substances (WS‐NHS) in a red‐acid soil (Vertic Dystrudept) (Indonesia) from the changes in humus composition and stable carbon isotopic ratio (δ13C). Three plots, a weeded plot (T‐1; the common practice), a plot covered with Paspalum conjugatum Berg., a C4 plant (T‐2), and a plot in which native weeds were allowed to grow (T‐3), were prepared. An incubation experiment determined the δ13C values of the humus fractions generated from Paspalum in soil. Based on the increase in δ13C value, the proportion of total C that originated from Paspalum C after 4 years under coffee was 16 ± 4% in the T‐2 topsoil (0–10 cm). Humic and fulvic acids in the T‐1 topsoil decreased to 46 and 84%, respectively, whilst both increased or remained constant in the T‐2 and T‐3 soils. The WS‐NHS content varied little and was independent of land management. The preferential loss of the humic acids with a smaller degree of humification as assessed by their darkness in colour was shown in T‐1. The decrease in the degree of humification suggested the accumulation of the weed‐derived humic acids in T‐2 and T‐3. In the T‐2 topsoil, 36 ± 2%, 13 ± 3% and 15 ± 2% of C in the humic acids, fulvic acids and WS‐NHS, respectively, were estimated to be Paspalum‐derived after 4 years. The estimated initial C loss during the same period was 17 ± 3%, 14 ± 2% and 7 ± 2%, respectively, for those fractions, which suggests the fastest turnover rate for the humic acids and significant retardation of their degradation in soil colonized by weeds.
Effects of transverse movement of water in xylem on patterns of water transport within current‐year shoots of kudzu vine, Pueraria lobata
Authors: TANEDA H. , TATENO M.
Published: January 2007

This study investigated the effects on water transport patterns of the transverse water movement in xylem, on a whole‐shoot scale, using current‐year shoots of kudzu vine (Pueraria lobata (Willd.) Ohwi).

The connections between xylem vessels were detected by dye injection and were found to be distributed throughout the internode. This means that short internodes limit the connections between vessels. The hydraulic conductance of the internode‐to‐petiole path decreased with successive cutting of the internodes.

To estimate hydraulic patterns at the whole‐shoot scale, the hydraulic conductance of the shoot base‐to‐petiole path (KBP) were measured. These were compared with two mathematical models representing extreme examples of connections between vessels – the interconnected model and the independent model. The former model assumes a high capacity for the transverse movement of water in xylem tissues. The KBP values measured were explained more accurately by the interconnected model than by the independent model.

These results suggest that kudzu vine has a large capacity for the transverse movement of water in xylem, which contributes to the effective transport of water from internodes to leaves that offsets sectored transport at the whole‐shoot scale.
DNA study of bladder papillary tumours chemically induced by N‐butyl‐N‐(4‐hydroxybutyl) nitrosamine in Fisher rats
Authors: Oliveira Paula A. , Adega Filomena , Palmeira Carlos A. , Chaves Raquel M. , Colaço Aura A. , Guedes‐Pinto Henrique , De la Cruz P Luis F. , Lopes Carlos A.
Published: January 2007

To examine DNA abnormalities in bladder papillary tumours induced by N‐butyl‐N‐(4‐hydroxybutyl) nitrosamine (BBN) in female rats, using image cytometric DNA analysis and cytogenetics.

Thirty female rats were exposed to BBN in their drinking water for 20 weeks. One group of 10 animals served as controls. The animals exposed to BBN were killed at a rate of two per week, with the bladder being collected under aseptic conditions and those tumours with exophytic growth removed. The nuclear DNA content of the tumours was evaluated using image cytometric analysis. In two rats part of the tumour pieces was stipulated for culturing. Cytogenetic analysis was performed on at least 30 cells from each cell population and on both tumours.

Papillary carcinomas were classified as low grade and high grade. DNA ploidy studies were carried out on 28 low‐grade and 21 high‐grade papillary carcinomas. Histograms obtained by image analysis showed that a normal urothelium was diploid; 28.6% and 100% of low‐and high‐grade papillary carcinomas were aneuploid respectively. Both tumours used for cell culture showed multiple numerical and structural chromosome alterations and several marker chromosomes.

Image cytometric DNA analysis proved to be a good and reliable method for examining DNA alterations in papillary bladder carcinomas. The present findings establish that the DNA content is statistically different between low‐grade and high‐grade papillary carcinomas and that deviation from the diploid number is markedly higher in the high‐grade ones. In addition, the occurrence of marker chromosomes seems to be related to the aggressiveness of the tumour.
HAART and the heart: changes in coronary risk factors and implications for coronary risk in men starting antiretroviral therapy
Authors: Sterne J. A. C. , May M. , Bucher H. C. , Ledergerber B. , Furrer H. , Cavassini M. , Bernasconi E. , Hirschel B. , Egger M. ,   the Swiss HIV Cohort Study
Published: January 2007

Objectives.  To estimate changes in coronary risk factors and their implications for coronary heart disease (CHD) rates in men starting highly active antiretroviral therapy (HAART).

Methods.  Men participating in the Swiss HIV Cohort Study with measurements of coronary risk factors both before and up to 3 years after starting HAART were identified. Fractional polynomial regression was used to graph associations between risk factors and time on HAART. Mean risk factor changes associated with starting HAART were estimated using multilevel models. A prognostic model was used to predict corresponding CHD rate ratios.

Results.  Of 556 eligible men, 259 (47%) started a nonnucleoside reverse transcriptase inhibitor (NNRTI) and 297 a protease inhibitor (PI) based regimen. Levels of most risk factors increased sharply during the first 3 months on HAART, then more slowly. Increases were greater with PI‐ than NNRTI‐based HAART for total cholesterol (1.18 vs. 0.98 mmol L−1), systolic blood pressure (3.6 vs. 0 mmHg) and BMI (1.04 vs. 0.55 kg m2) but not HDL cholesterol (0.24 vs. 0.32 mmol L−1) or glucose (1.02 vs. 1.03 mmol L−1). Predicted CHD rate ratios were 1.40 (95% CI 1.13–1.75) and 1.17 (0.95–1.47) for PI‐ and NNRTI‐based HAART respectively.

Conclusions.  Coronary heart disease rates will increase in a majority of patients starting HAART: however the increases corresponding to typical changes in risk factors are relatively modest and could be offset by lifestyle changes.
Naming of depression: nursing, social and personal descriptors
Authors: FEELY M. , SINES D. , LONG A.
Published: January 2007

This paper explores descriptors of depression and begins by exploring nursing descriptors including the nature of assessment and nursing diagnosis and progresses to underpin these major processes by considering social descriptors such as cultural and spiritual constructs. The role and influence of stigma is discussed and an examination of gender influences and experiences is undertaken. The paper concludes by examining personal descriptors in the literature. The overall aim of the paper is (1) to add to nursing knowledge by depicting the grounded realities of the experience of depression and (2) stimulate discussion on the need to provide holistic care pathways that are responsive to the uniqueness of this lived experience and finally to (3) encourage further research on key psycho‐social factors associated with depression and the concurring advancement of nursing care. This paper has been completed in the context of an ongoing study into the grounded experience of ‘Depression’ and the development of a psychiatric nursing theory of connectivity.
The effects of diagnosis and non‐compliance attributions on therapeutic alliance processes in adult acute psychiatric settings
Authors: FORSYTH A.
Published: January 2007

To investigate the effects of the diagnoses of borderline personality disorder (BPD) and major depressive disorder (MDD), together with reasons for client non‐compliance with therapy tasks, on mental health workers’ helping, empathy and anger reactions. Utilizing a 2 × 2 × 2 factorial design, mental health nurses were asked to read a series of vignettes and complete a 15‐item rating scale for helping, empathy and anger reactions to each of the vignettes. Eight clinical vignettes were constructed and contained a combination of controllable/uncontrollable and stable/unstable attributional dimensions for service users who failed to complete a therapy task. The diagnoses of BPD and MDD were added to the vignettes to determine whether diagnoses affected alliance factors. A total of 26 mental health workers participated in the study and there were main effects for those workers to be angrier when causes were perceived as due to controllable factors; to be more helpful to service users’ with a diagnosis of MDD; and less helpful when causes were perceived to be due to stable factors. Results show some support for Weiner’s model of helping behaviour. It is suggested that there is an important role to explore the attributions of mental health workers working with service users with BPD. A role for case conceptualization is discussed to facilitate therapeutic engagement with service users with a diagnosis of BPD.