bluuebunny/crossref_metadata_2025 huggingface dataset:
Streptomyces coelicolorGenesftsLanddivICPlay a Role in Cell Division but Are Dispensable for Colony Formation
Authors: Bennett Jennifer A. , Aimino Rachel M. , McCormick Joseph R.
Published: October 2007

We have characterized homologues of the bacterial cell division genesftsLanddivICin the gram-positive mycelial bacteriumStreptomyces coelicolorA3(2). We show by deletion-insertion mutations thatftsLanddivICare dispensable for growth and viability inS. coelicolor. When mutant strains were grown on a conventional rich medium (R2YE, containing high sucrose), inactivation of eitherftsLordivICresulted in the formation of aerial hyphae with partially constricted division sites but no clear separation of prespore compartments. Surprisingly, this phenotype was largely suppressed when strains were grown on minimal medium or sucrose-free R2YE, where division sites in many aerial hyphae had finished constricting and chains of spores were evident. Thus, osmolarity appears to affect the severity of the division defect. Furthermore, double mutant strains deleted for bothftsLanddivICare viable and have medium-dependent phenotypes similar to that of the single mutant strains, suggesting that functions performed by FtsL and DivIC are not absolutely required for septation during growth and sporulation. Alternatively, another division protein may partially compensate for the loss of both FtsL and DivIC on minimal medium or sucrose-free R2YE. Finally, based on transmission electron microscopy observations, we propose that FtsL and DivIC are involved in coordinating symmetrical annular ingrowth of the invaginating septum.
TheSalmonellaSPI1 Type Three Secretion System Responds to Periplasmic Disulfide Bond Status via the Flagellar Apparatus and the RcsCDB System
Authors: Lin Dongxia , Rao Christopher V. , Slauch James M.
Published: October 2007

Upon contact with intestinal epithelial cells,Salmonella entericaserovar Typhimurium injects a set of effector proteins into the host cell cytoplasm via theSalmonellapathogenicity island 1 (SPI1) type III secretion system (T3SS) to induce inflammatory diarrhea and bacterial uptake. The master SPI1 regulatory genehilAis controlled directly by three AraC-like regulators: HilD, HilC, and RtsA. Previous work suggested a role for DsbA, a periplasmic disulfide bond oxidase, in SPI1 T3SS function. RtsA directly activatesdsbA, and deletion ofdsbAleads to loss of SPI1-dependent secretion. We have studied thedsbAphenotypes by monitoring expression of SPI1 regulatory, structural, and effector genes. Here we present evidence that loss of DsbA independently affects SPI1 regulation and SPI1 function. ThedsbA-mediated feedback inhibition of SPI1 transcription is not due to defects in the SPI1 T3SS apparatus. Rather, the transcriptional response is dependent on both the flagellar protein FliZ and the RcsCDB system, which also affectsfliZtranscription. Thus, the status of disulfide bonds in the periplasm affects expression of the SPI1 system indirectly via the flagellar apparatus. RcsCDB can also affect SPI1 independently of FliZ. All regulation is through HilD, consistent with our current model for SPI1 regulation.
Identification of Two Gene Clusters and a Transcriptional Regulator Required for
Pseudomonas aeruginosa
Glycine Betaine Catabolism
Authors: Wargo Matthew J. , Szwergold Benjamin S. , Hogan Deborah A.
Published: October 2007

Glycine betaine (GB), which occurs freely in the environment and is an intermediate in the catabolism of choline and carnitine, can serve as a sole source of carbon or nitrogen in
Pseudomonas aeruginosa
. Twelve mutants defective in growth on GB as the sole carbon source were identified through a genetic screen of a nonredundant PA14 transposon mutant library. Further growth experiments showed that strains with mutations in two genes,
gbcA
(PA5410) and
gbcB
(PA5411), were capable of growth on dimethylglycine (DMG), a catabolic product of GB, but not on GB itself. Subsequent nuclear magnetic resonance (NMR) experiments with 1,2-
13
C-labeled choline indicated that these genes are necessary for conversion of GB to DMG. Similar experiments showed that strains with mutations in the
dgcAB
(PA5398-PA5399) genes, which exhibit homology to genes that encode other enzymes with demethylase activity, are required for the conversion of DMG to sarcosine. Mutant analyses and
13
C NMR studies also confirmed that the
soxBDAG
genes, predicted to encode a sarcosine oxidase, are required for sarcosine catabolism. Our screen also identified a predicted AraC family transcriptional regulator, encoded by
gbdR
(PA5380), that is required for growth on GB and DMG and for the induction of
gbcA
,
gbcB
, and
dgcAB
in response to GB or DMG. Mutants defective in the previously described
gbt
gene (PA3082) grew on GB with kinetics similar to those of the wild type in both the PAO1 and PA14 strain backgrounds. These studies provided important insight into both the mechanism and the regulation of the catabolism of GB in
P. aeruginosa
.
Transmembrane Helix 12 of the
Staphylococcus aureus
Multidrug Transporter QacA Lines the Bivalent Cationic Drug Binding Pocket
Authors: Hassan Karl A. , Skurray Ronald A. , Brown Melissa H.
Published: October 2007

An acidic residue in transmembrane segment (TMS) 10 is important for recognition of bivalent cationic substrates by the QacA multidrug transporter. Remarkably, an acidic residue in TMS 12 compensated for the absence of such a residue in TMS 10, suggesting that TMS 12 is a component of the bivalent cation-binding region.
Incidence of respiratory sensitisation and allergy to enzymes among employees in an enzyme producing plant and the relation to exposure and host factors
Authors: Larsen A I , Johnsen C R , Frickmann J , Mikkelsen S
Published: October 2007

Objectives:

Belonging to the group of high molecular weight respiratory sensitisers, microbial enzymes have been reported as a well known cause of occupational allergy, typically manifesting itself as rhinitis and/or asthma. High exposure to such high molecular weight sensitisers, and possibly also peak exposures, implies a higher risk than low exposure, but the exact relation between exposure, sensitisation and clinical allergy remains to be clarified. The authors sought to estimate the risk of respiratory enzyme allergy in an enzyme producing plant and to assess the relation between exposure indices and allergy.

Methods:

Retrospective follow-up study based upon data gathered from health surveillance since 1970. 1207 employees from production and laboratories were included. The level of enzyme exposure in the relevant departments was estimated retrospectively into five exposure levels based on 10-fold increments/decrements of the threshold limit value and other exposure information. The risk was estimated in an exponential regression survival model fitted with constant intensity for subperiods of time using maximum likelihood estimation.

Results:

During the first three years of a persons employment, the enzyme sensitisation and allergy incidence rates were 0.13 and 0.03 per person-year at risk, respectively. In the fitted models, exposure class did not correlate with the outcome variables. The risk of sensitisation decreased along the three decades, whereas the risk of allergy remained unchanged. The risk of sensitisation and allergy was doubled among smokers. Pre-employment atopy was only associated with sensitisation risk.

Conclusion:

Sensitisation to enzymes decreased during the study period, possibly reflecting improvements in the working environment. A similar decrease could not be demonstrated for allergy to enzymes. Neither of the two outcomes correlated with exposure estimates, possibly because of the low precision of the estimates.
Exposures and reported symptoms associated with occupational deployment to the Buncefield fuel depot fire, England 2005
Authors: Morgan O , Verlander N Q , Kennedy F , Moore M , Birch S , Kearney J , Lewthwaite P , Lewis R , O’Brian S , Osman J , Reacher M
Published: October 2007

Objectives:

An explosion at the Buncefield fuel depot outside London occurred on 11 December 2005. We conducted a retrospective cohort study of airborne exposures and health status for workers deployed.

Methods:

Deployed individuals were identified through their occupational health departments. We sent a self-completion questionnaire asking about health symptoms during the burn and post-burn phases. The prevalence of health symptoms in workers was compared to symptoms in local residents not under the smoke plume.

Results:

Of 1949 eligible individuals, 815 returned questionnaires (response rate 44). Respiratory protection was used by 39. Symptoms were reported by 41 of individuals during the burn phase compared with 26 in the post-burn phase. In a final multivariable model, reporting of any symptoms was associated with deployment inside the inner fire cordon during the burn phase (OR 2.07, 95 CI 1.24 to 3.47) and wearing a face mask (OR 2.33, 95 CI 1.67 to 3.26). Compared with the general public, eye irritation (prevalence ratio (PR) 2.1, 95 CI 1.5 to 3.0), coughing (PR 1.3, 95 CI 1.0 to 1.8) and headaches (PR 1.7, 95 CI 1.2 to 2.5) were more common in workers deployed during the burn phase but not the post-burn phase.

Conclusions:

Increased reporting of symptoms close to the fire during the burn phase was consistent with increased exposure to products of combustion, although no major acute illness was reported. That only a minority of individuals used face masks, which were not protective for symptoms, raises questions about the availability of adequate respiratory protection for such incidents.
Arterial structure and function and environmental exposure to cadmium
Authors: Schutte R , Nawrot T , Richart T , Thijs L , Roels H A , Van Bortel L M , Struijker-Boudier H , Staessen J A
Published: October 2007

Objectives:

Few studies have addressed the effect of cadmium toxicity on arterial properties.

Methods:

We investigated the possible association of 24 h urinary cadmium excretion (an index of lifetime exposure) with measures of arterial function in a randomly selected population sample (n  557) from two rural areas with low and high environmental exposure to cadmium.

Results:

24 h urinary cadmium excretion was significantly higher in the high compared with the low exposure group (p<0.001). Even though systolic (p  0.42), diastolic (p  0.14) and mean arterial pressure (p  0.68) did not differ between the high and low exposure groups, aortic pulse wave velocity (p  0.008), brachial pulse pressure (p  0.026) and femoral pulse pressure (p  0.008) were significantly lower in the high exposure group. Additionally, femoral distensibility (p<0.001) and compliance (p  0.001) were significantly higher with high exposure. Across quartiles of 24 h urinary cadmium excretion (adjusted for sex and age), brachial (p for trend  0.015) and femoral (p for trend  0.018) pulse pressure significantly decreased and femoral distensibility (p for trend  0.008) and compliance (p for trend  0.007) significantly increased with higher cadmium excretion. After full adjustment, the partial regression coefficients confirmed these associations. Pulse wave velocity (β  −0.79±0.27; p  0.004) and carotid (β  −4.20±1.51; p  0.006), brachial (β  −5.43±1.41; p  0.001) and femoral (β  −4.72±1.74; p  0.007) pulse pressures correlated negatively, whereas femoral compliance (β  0.11±0.05; p  0.016) and distensibility (β  1.70±0.70; p  0.014) correlated positively with cadmium excretion.

Conclusion:

Increased cadmium body burden is associated with lower aortic pulse wave velocity, lower pulse pressure throughout the arterial system, and higher femoral distensibility.
Occupation and bladder cancer in a hospital-based case–control study in Spain
Authors: Samanic C M , Kogevinas M , Silverman D T , Tardón A , Serra C , Malats N , Real F X , Carrato A , García-Closas R , Sala M , Lloreta J , Rothman N , Dosemeci M
Published: October 2007

Objectives:

We investigated the association between occupation and bladder cancer in a hospital-based case–control study conducted in Spain.

Methods:

1219 patients with transitional cell carcinoma of the urinary bladder and 1271 controls selected from 18 hospitals in Spain between June 1998 and September 2000 provided detailed information on life-time occupational history, smoking habits, medical history, and other factors. We used unconditional logistic regression to calculate odds ratios (OR) and 95% confidence intervals (CI) for each occupation and industry, adjusting for age, hospital region, smoking duration, and employment in a high-risk occupation for bladder cancer.

Results:

Statistically significant increased risks were observed among men employed as machine operators in the printing industry (OR 5.4; 95% CI 1.6 to 17.7), among men employed in the transportation equipment industry (OR 1.6; 95% CI 1.1 to 2.6) and among those who had worked for ⩾10 years in the electrical/gas/sanitary services (OR 3.9; 95% CI 1.5 to 10.4) and in hotels and other lodgings (OR 3.1; 95% CI 1.3 to 7.3). Men who worked as miscellaneous mechanics and repairers (OR 2.0; 95% CI 1.1 to 3.6) and as supervisors in production occupations (OR 2.1; 95% CI 1.2 to 3.6) also had excess risks for bladder cancer. Male farmers and those who worked in crop and livestock production had decreased risks for bladder cancer. We found no significant associations between occupation or industry and bladder cancer risk among women.

Conclusions:

We did not observe excess bladder cancer risk for many of the occupations identified as being a priori at high risk. Examination of more detailed job exposure information should help clarify these associations.
HEISENBERG OPERATORS, INVARIANT DOMAINS AND HEISENBERG EQUATIONS OF MOTION
Authors: ARAI ASAO
Published: October 2007

An abstract operator theory is developed on operators of the form AH(t) := eitHAe-itH, t ∈ ℝ, with H a self-adjoint operator and A a linear operator on a Hilbert space (in the context of quantum mechanics, AH(t) is called the Heisenberg operator of A with respect to H). The following aspects are discussed: (i) integral equations for AH(t) for a general class of A; (ii) a sufficient condition for D(A), the domain of A, to be left invariant by e-itH for all t ∈ ℝ; (iii) a mathematically rigorous formulation of the Heisenberg equation of motion in quantum mechanics and the uniqueness of its solutions; (iv) invariant domains in the case where H is an abstract version of Schrödinger and Dirac operators; (v) applications to Schrödinger operators with matrix-valued potentials and Dirac operators.
ON NONLEPTONIC Σ+ → pπ0 DECAY IN THE EFFECTIVE QUARK MODEL WITH CHIRAL U(3) × U(3) SYMMETRY
Authors: YA. BERDNIKOV A. , BERDNIKOV YA. A. , FABER M. , IVANOV A. N. , IVANOVA V. A. , NIKITCHENKO A. V. , TROITSKAYA N. I.
Published: October 2007

Within the effective quark model with chiral U (3) × U (3) symmetry we calculate the S-wave and P-wave amplitudes of the nonleptonic decay Σ+ → pπ0, the partial width and the dynamical polarization of the proton in the dependence on the polarization of the Σ+-hyperon. The theoretical results agree well with the experimental data.
IS THE f0(600) MESON A DYNAMICALLY GENERATED RESONANCE? — A LESSON LEARNED FROM THE O(N) MODEL AND BEYOND
Authors: XIAO L. Y. , GUO ZHI-HUI , ZHENG H. Q.
Published: October 2007

O(N) linear σ model is solvable in the large N limit and hence provides a useful theoretical laboratory to test various unitarization approximations. We find that the large Nc limit and the mσ→∞ limit do not commute. In order to get the correct large Nc spectrum one has to first take the large Nc limit. We argue that the f0(600) meson may not be described as generated dynamically. On the contrary, it is most appropriately described at the same level as the pions, i.e. both appear explicitly in the effective Lagrangian. Actually it is very likely the σ meson responsible for the spontaneous chiral symmetry breaking in a Lagrangian with linearly realized chiral symmetry.
THREE-DIMENSIONAL TOPOLOGICAL FIELD THEORY INDUCED FROM GENERALIZED COMPLEX STRUCTURE
Authors: IKEDA NORIAKI
Published: October 2007

We construct a three-dimensional topological sigma model which is induced from a generalized complex structure on a target generalized complex manifold. This model is constructed from maps from a three-dimensional manifold X to an arbitrary generalized complex manifold M. The theory is invariant under the diffeomorphism on the worldvolume and the b-transformation on the generalized complex structure. Moreover the model is manifestly invariant under the mirror symmetry. We derive from this model the Zucchini's two-dimensional topological sigma model with a generalized complex structure as a boundary action on ∂X. As a special case, we obtain three-dimensional realization of a WZ-Poisson manifold.
PERTURBED SELF-SIMILAR MASSLESS SCALAR FIELD IN SPHERICALLY SYMMETRIC SPACE–TIMES
Authors: SHARIF M.
Published: October 2007

In this paper, we investigate the linear perturbations of the spherically symmetric space–times with kinematic self-similarity of the second kind. The massless scalar field equations are solved which yield the background and an exact solutions for the perturbed equations. We discuss the boundary conditions of the resulting perturbed solutions. The possible perturbation modes turn out to be stable as well as unstable. The analysis leads to the conclusion that there does not exist any critical solution.
THE ORBIFOLDS OF PERMUTATION-TYPE AS PHYSICAL STRING SYSTEMS AT MULTIPLES OF c = 26 II: THE TWISTED BRST SYSTEMS OF ${\hat c} = 52$ MATTER
Authors: HALPERN M. B.
Published: October 2007

This is the second in a series of papers which consider the orbifolds of permutation-type as candidates for new physical string systems at higher central charge. In the first paper, I worked out the extended actions of the twisted sectors of those orbifolds — which exhibit new permutation-twisted worldsheet gravities and correspondingly extended diffeomorphism groups. In this paper I begin the study of these systems as operator string theories, limiting the discussion for simplicity to the strings with [Formula: see text] matter (which are those governed by ℤ2-twisted permutation gravity). In particular, I present here a construction of the twisted reparametrization ghosts and new twisted BRST systems of all [Formula: see text] strings. The twisted BRST systems also imply new extended physical state conditions, whose analysis for individual [Formula: see text] strings is deferred to the next paper of the series.
PARITY DOUBLING IN PARTICLE PHYSICS
Authors: AFONIN S. S.
Published: October 2007

Parity doubling in excited hadrons is reviewed. Parity degeneracy in hadrons was first experimentally observed 40 years ago. Recently new experimental data on light mesons caused much excitement and renewed interest to the phenomenon, which still remains to be enigmatic. The present retrospective review is an attempt to trace the history of parity doubling phenomenon, thus providing a kind of introduction to the subject. We begin with early approaches of 1960's (Regge theory and dynamical symmetries) and end up with the latest trends (manifestations of broader degeneracies and AdS/QCD). We show the evolution of various ideas about parity doubling. The experimental evidence for this phenomenon is scrutinized in the nonstrange sector. Some experiments of 1960's devoted to the search for missing nonstrange bosons are reexamined and it is argued that the results of these experiments are encouraging from the modern perspective.
A COSMOLOGICAL MODEL WITH DARK SPINOR SOURCE
Authors: GU YING-QIU
Published: October 2007

In this paper, we discuss the system of Friedman–Robertson–Walker (FRW) metric coupling with massive nonlinear dark spinors in detail, where the thermodynamic movement of spinors is also taken into account. The results show that, the nonlinear potential of the spinor field can provide a tiny negative pressure, which resists the universe to become singular. The solution is oscillating in time and closed in space, which approximately takes the form: [Formula: see text], with [Formula: see text] light year, and δ = 0.96 ~ 0.99. The present time is about t ~ 18°.
ABSENCE OF DIQUARKS IN S-WAVE BARYONS
Authors: ANTUNES ANTONIO CARLOS BAPTISTA , ANTUNES LEILA JORGE
Published: October 2007

We analyze the dynamics of diquark formation in baryons containing one light and two heavy quarks. Due to the slower motion of the heavy quarks, we consider the motion of the light quark in a reference frame fixed in the two heavy ones. The potential of the light quark interacting with the two heavy quarks is derived from the quark–antiquark potential in mesons. This potential has a repulsive barrier between the two heavy quarks. A variational approach similar to that used in the study of the hydrogen molecule is applied to determine the two lowest energy eigenvalues and eigenfunctions of the light quark. The time-dependent wave function obtained describes the oscillation of the light quark along the direction defined by the two heavy quarks. We observe that the energy of this oscillating state is higher than the repulsive barrier between the two heavy quarks. There is no tunneling in the oscillation of the light quark, so we conclude that there is not formation of clusters or metastable states of a heavy and a light quark in this kind of baryons.
ENHANCEMENT OF SECOND HARMONIC GENERATION IN ONE-DIMENSIONAL FERROELECTRIC-METALLIC PHOTONIC CRYSTALS
Authors: ZHAO LI-MING , GU BEN-YUAN , YANG GUO-ZHEN
Published: October 2007

We investigate second harmonic generation (SHG) in one-dimensional (1D) ferroelectric-metallic photonic crystals (PCs) which are composed of alternatively inverting poled ferroelectric domains with metallic insert layers. We observe a giant enhancement of SHG conversion efficiency due to high reflectivity of metallic layers, which form resonant cavities and lead to substantial increase of fundamental wave (FW) field in nonlinear medium layers.
POLARON IN A QUANTUM DOT UNDER AN ELECTRIC FIELD
Authors: LIU MIAN , MA WENDONG , LI ZIJUN
Published: October 2007

We conducted a theoretical study on the properties of a polaron with electron-LO phonon strong-coupling in a cylindrical quantum dot under an electric field using linear combination operator and unitary transformation methods. The changing relations between the ground state energy of the polaron in the quantum dot and the electric field intensity, restricted intensity, and cylindrical height were derived. The numerical results show that the polar of the quantum dot is enlarged with increasing restricted intensity and decreasing cylindrical height, and with cylindrical height at 0 ~ 5 nm , the polar of the quantum dot is strongest. The ground state energy decreases with increasing electric field intensity, and at the moment of just adding electric field, quantum polarization is strongest.
PZT NANOCOMPOSITES REINFORCED BY SMALL AMOUNT OF MgO
Authors: LI FAXIN , YI XIAOXING , CONG ZHIQI , FANG DAINING
Published: October 2007

To enhance the fracture toughness of brittle lead titanate zirconate (PZT) ceramics, PZT nanocomposites with 0.1, 0.5 and 1.0 vol% MgO were fabricated by means of a conventional industrial fabrication method. Through scanning electron microscopy (SEM) observation, indentation tests and D–E hysteresis measurement, the properties of PZT/ MgO nanocomposites are characterized. With the increase of additional MgO , the fracture mode of PZT/ MgO nanocomposites gradually changes from intergranular to transgranular fracture and the fracture toughness is fairly enhanced. The electric coercive fields of PZT/ MgO nanocomposites decrease gradually while the piezoelectric constant d33 hardly changes except that of PZT-1.0 vol% MgO which decreases about 13% compared with the monolithic PZT.
FIRST PRINCIPLES STUDY OF EFFECT OF 3d TRANSITION METAL-DOPED ZINC OXIDE ON GAS SENSITIVITY
Authors: QIU ZHIYONG , MURAKAMI RI-ICHI
Published: October 2007

Two series models were developed in order to investigate the gas sensitivity of 3d transition metal-doped zinc oxide (ZnO) materials. Software based on a discrete variation method (DVM) within the framework of density functional theory was used to calculate the electronic structures of the models. It was possible to determine gas sensitivity using the calculated results, from which a relationship between electronic properties and gas sensitivity was formed. The results showed that doping the transition metals greatly affected the gas sensitivity of ZnO -based materials. The main effect was attributed to the change in carrier concentration. On the contrary, the doping of transition metals had a negligible effect on the mobility of ZnO -based materials. Titanium or iron doped- ZnO is thus expected to have the best gas sensitivity of all of the 3d transition metal-doped ZnO materials.
STUDY OF PLASMA FOCUS AS A HARD X-RAY SOURCE FOR NON-DESTRUCTIVE TESTING
Authors: HUSSAIN S. , ZAKAULLAH M.
Published: October 2007

An experimental study on pulse duration, source size and intensity of hard X-ray pulses emitted from a low-energy plasma focus device geared to enhance X-ray yield by using lead inserted copper tapered anode is reported, regarding its application for non-destructive testing. It is found that the radiation intensity in a single shot is high enough to obtain good resolution radiographs of test objects located outside the vacuum chamber about 27 ± 0.1 cm away from the focus region in a very short exposure. The high contrast radiograph clearly shows the efficacy of the system for two different absorbing materials that need different photon energies. It is established that this plasma focus operated in argon is a suitable hard X-ray source for non-destructive testing of compound objects consisting of metal and plastic.
STUDIES ON THE EPR g FACTORS FOR THE ORTHORHOMBIC NdBa2Cu3O7
Authors: WU SHAO-YI , ZHANG HUA-MING , ZHANG ZHI-HONG , WEI LI-HUA
Published: October 2007

The perturbation formulas of the EPR g factors for a 4f3 ion in orthorhombic symmetry are established, by considering the contributions from the admixtures of various states. The formulas are applied to the studies of the g factors for the orthorhombic NdBa 2 Cu 3 O 7. The related crystal-field parameters in the calculations are obtained from the superposition model and the local structural data of the orthorhombic Nd 3+ site in NdBa 2 Cu 3 O 7. The calculated g factors are in reasonable agreement with the observed values. The theoretical results are discussed.
Rainwater-fed peat as a precursor of coal
Authors: Clymo R. S.
Published: October 2007

About 3% of the Earth’s land surface is peat-covered at present. Most peat forms where there is waterlogging, because oxygen diffuses down through water more slowly than it is consumed by micro-organisms. The anaerobic micro-organisms in peat continue the decay process, but only slowly.

A great variety of rheotrophic (usually minerotrophic and eutrophic) peats form if the waterlogging is caused by groundwater. Of greater extent, but less varied, are the ombrotrophic peats which are dependent on precipitation. Most of these peatlands are in Russia, Canada, Fennoscandia and the British Isles. The main peat-forming plants in such places are bogmosses (
Sphagnum
), sedges and heaths, with pines (
Pinus
) and larch (
Larix
) in some places. These peats may be analogous to those which formed the Permian coals of Australia. In western Malesia are large areas of coastal ombrotrophic forest-bogs. These tropical forest peats may be analogous to those which formed the Carboniferous coals. The organic chemistry of newly dead plants differs considerably amongst all these plant groups, and they in turn may be very different from the majority of plants which formed the starting materials for the formation of coals in the past.

In spite of these differences the study of present-day moss and sedge bogs may be helpful and particularly in the study of Permian coals. There is usually a two-layered structure. In the 5–50 cm thick surface layer aerobic decay may remove as much as 90% of the original matter and do so selectively. Below is the much thicker waterlogged anaerobic layer in which microbial decay is of a different sort and is much slower. But there is evidence that it continues for thousands of years at least. The extent to which peat is a product of microbial activity operating on a slowly changing substrate is unknown. Equally unknown is the balance between microbially mediated and chemical changes. One consequence of bacterial decay is that there seems to be an inherent limit to the depth of such peat-forming systems. At least one (unusual) case is known which has resulted in the production of a lignitic peat, which breaks with a conchoidal fracture, and which is barely 12 000 years old. The limiting depth, assessed from growth during the last 10 000 years, seems to be too little to account for the observed thickness of coals.
Coal, climate and terrestrial productivity: the present and early Cretaceous compared
Authors: Ziegler A. M. , Raymond A. L. , Gierlowski T. C. , Horrell M. A. , Rowley D. B. , Lottes A. L.
Published: October 2007

At the present time, rainfall sufficient and consistent enough for swamp formation and peat preservation occurs in the equatorial and temperate belts. Evaporite deposits and aeolian sandstones occur in the consistently dry areas, while the intermediate areas of seasonal rainfall tend not to have any of these climatically significant sediments. In the Cretaceous, the temperate belts are well represented by coals as today, but the tropical belt is not, and the same can be said of other Mesozoic and early Cenozoic periods. Instead, the tropics are represented by low diversity floras and sediments, like the Nubian Sandstone, which can be interpreted as representative of climates in which precipitation was markedly seasonal. The inference is that the Intertropical Convergence Zone was less latitudinally confined during the warmer ‘greenhouse’ periods, and that this might have been due to weaker polar fronts.
Facies studies of coal and coal-bearing strata
Authors: McCabe Peter J.
Published: October 2007

Prior to 1960 most discussions on the depositional environment of coal-bearing strata were related to theories of the origin of cyclothems. Work during the 1960s on modern deltas, particularly the Mississippi, led to the interpretation of the classic cyclothem as deltaic in origin, with coals originating in delta-top swamps. During the 1970s and early 1980s, detailed models of depositional environments were developed for coal-bearing strata. Coals have now been described in association with virtually all types of terrestrial depositional environments.

There are surprisingly few published examples of facies analyses of coal-bearing strata. Detailed measured sections and meticulous descriptions of sedimentary structures are necessary for geologists to make independent assessments of published environmental interpretations and to make comparisons between various coal-bearing formations. The coal industry could benefit from more predictive facies models, which will require greater integration of coal and clastic facies studies.

In most mires close to areas of active clastic deposition, ash content of peat is too high for them to be precursors of coal. Most coal must have originated as peats in raised mires or in low-lying mires well removed from active clastic environments. In the latter case, a significant hiatus in deposition may be represented by the contact of coal with underlying sediments. Subsurface studies, which allow an understanding of the three-dimensional character of coal-bearing strata, may provide clues as to the type of swamp in which a coal was deposited. Recent studies in the Upper Cretaceous of Alberta, for example, provide clear evidence that coals originated in mires well removed from contemporaneous clastic depositional systems.
Implications of vegetational change through the geological record on models for coal-forming environments
Authors: Collinson Margaret E. , Scott Andrew C.
Published: October 2007

Two broad categories of peat-forming environments, those dominated by arborescent lycopsids (Carboniferous) and those dominated by taxodiaceous conifers (Cretaceous to Recent) are used to compare some features of plant biology and plant association which would influence peat formation. Significant differences between the two categories indicate that modern analogues for ancient coal-forming environments should always take account of such plant features. Some of the more obvious implications for interpretation of coal-forming environments are discussed. A fuller appreciation of these implications requires greater understanding of the ancient plants and plant communities involved. In particular, both the individual plants and plant assemblages should be taken into account when making environmental interpretations of coal petrological studies and in the calculation of peat to coal compression ratios.
Mineral matter in coals, with special reference to the Pennine Coalfields
Authors: Spears D. A.
Published: October 2007

The minerals present in coals are grouped as either detrital or diagenetic. The detrital minerals undergo diagenetic modifications however, and provide one of the sources for elements incorporated into diagenetic minerals. The detrital minerals are present either dispersed or concentrated in the coal seams. The overall composition of the detrital minerals is a function of grain size and thus of current velocity. Clay mineral composition varies with the maturity of the sediment, and in particular whether this is reworked from within the basin or is more representative of the upland source. Dirt partings (intraseam mudrocks) represent either an increase in detrital sediment input or a reduction in the rate of organic accumulation, or even loss of organic matter. Wind blown sediment in coals are best represented by altered volcanic ashes, tonsteins, providing a means of correlation and minerals for absolute age determinations. The alteration of ash to kaolinite both in the peat and in the associated sediments demonstrates which clay mineral is stable in the pore waters. Diagenetic kaolinite, probably formed from elements organically derived, is also recognized, particularly in low ash coals. The elements present in diagenetic silicates, sulphides and carbonates originated from within the peat and also from mudrocks in the sequence. The diagenetic sequence of minerals in the cleat is equated with that of other clastic sediments and is similarly interpreted as a burial depth sequence. The residual, diagenetic porefluids resulting from burial diagenesis are the source of economically important, high Cl concentrations in the coal.
Genesis of the Warwickshire Thick Coal: a group of long-residence histosols
Authors: Fulton I. M.
Published: October 2007

The Warwickshire Thick Coal is of Westphalian B age, and it developed at the southern margin of the Pennine Basin in central England. It usually consists of three to five leaves of coal which can total up to 8.5 m in thickness. Palynological analysis of the leaves has revealed the presence of four miospore types which occur in similar successions in each leaf. These coals are interpreted as long-residence histosols. Comparable successions have been recognized by other authors and a variety of mechanisms advanced for their formation. The model proposed to account for their origin is change in vegetation due to variations in water table (hydroseral growth), which occur during the development of ombrotrophic bogs similar to those found in the Far East. Many inter-related factors are believed to affect water table variation including climate, topography and raising of the bog surface (the latter controlled by both differential rate of subsidence and accumulation of plant debris). It is probable that the model proposed may be applicable to other coal seams, and this has implications for coal exploration. Estimation of regional rates of subsidence may help in the location of thick long-residence histosols, and examination of miospore cycles within leaves of coal may be useful in predicting the proximity of seam splits.
Coal geology and exploration of part of the Tertiary Kutei Basin in East Kalimantan, Indonesia
Authors: Land D. H. , Jones C. M.
Published: October 2007

Geological survey of some 700 km
2
of Miocene coal-bearing strata in Borneo, near Samarinda, E Kalimantan, Indonesia, identified 1000 Mt of recoverable reserves of coal, ranging in rank from lignite A to high-volatile C bituminous, in 43 seams between 1.5 and 13 m thick. Environments of deposition are paralic and include shoreline, deltaic and alluvial flood-plain. Strata studied are divided into four newly-defined lithological formations, the Loa Duri, Loa Kulu, Prangat and Kamboja formations, in a section totalling over 3000 m thick. The survey included drilling 72 cored boreholes, between 200 and 350 m deep, of which 60 each proved at least one coal seam over 2 m thick. The coals have low ash, high moisture and generally low sulphur.
AdWords and generalized online matching
Authors: Mehta Aranyak , Saberi Amin , Vazirani Umesh , Vazirani Vijay
Published: October 2007

How does a search engine company decide what ads to display with each query so as to maximize its revenue? This turns out to be a generalization of the online bipartite matching problem. We introduce the notion of a trade-off revealing LP and use it to derive an optimal algorithm achieving a competitive ratio of 1−1/
e
for this problem.
Low distortion embeddings for edit distance
Authors: Ostrovsky Rafail , Rabani Yuval
Published: October 2007

We show that {0, 1}

d

endowed with edit distance embeds into ℓ
1
with distortion 2

O

(√log
d
log log
d
). We further show efficient implementation of the embedding that yield solutions to various computational problems involving edit distance. These include sketching, communication complexity, nearest neighbor search. For all these problems, we improve upon previous bounds.
Lossless abstraction of imperfect information games
Authors: Gilpin Andrew , Sandholm Tuomas
Published: October 2007

Finding an equilibrium of an extensive form game of imperfect information is a fundamental problem in computational game theory, but current techniques do not scale to large games. To address this, we introduce the
ordered game isomorphism
and the related
ordered game isomorphic abstraction transformation
. For a multi-player sequential game of imperfect information with observable actions and an ordered signal space, we prove that any Nash equilibrium in an abstracted smaller game, obtained by one or more applications of the transformation, can be easily converted into a Nash equilibrium in the original game. We present an algorithm,
GameShrink
, for abstracting the game using our isomorphism exhaustively. Its complexity is
õ
(
n
2
), where
n
is the number of nodes in a structure we call the signal tree. It is no larger than the game tree, and on nontrivial games it is drastically smaller, so
GameShrink
has time and space complexity
sublinear
in the size of the game tree. Using
GameShrink
, we find an equilibrium to a poker game with 3.1 billion nodes—over four orders of magnitude more than in the largest poker game solved previously. To address even larger games, we introduce approximation methods that do not preserve equilibrium, but nevertheless yield (
ex post
) provably close-to-optimal strategies.
A bisimulation for type abstraction and recursion
Authors: Sumii Eijiro , Pierce Benjamin C.
Published: October 2007

We present a bisimulation method for proving the contextual equivalence of packages in λ-calculus with full existential and recursive types. Unlike traditional logical relations (either semantic or syntactic), our development is “elementary,” using only sets and relations and avoiding advanced machinery such as domain theory, admissibility, and TT-closure. Unlike other bisimulations, ours is complete even for existential types. The key idea is to consider
sets
of relations—instead of just relations—as bisimulations.
Embedded systems security co-design
Authors: Eby Matthew , Werner Jan , Karsai Gabor , Ledeczi Akos
Published: October 2007

There is an ever increasing concern about security threats as embedded systems are moving towards networked applications. Model based approaches have proven to be effective techniques for embedded systems design. However, existing modeling tools were not designed to meet the current and future security challenges of networked embedded systems. In this paper, we propose a framework to incorporate security modeling into embedded system design. We've developed a security analysis tool that can easily integrate with existing tool chains to create co-design environments that addresses security, functionality and system architecture aspects of embedded systems concurrently.
Towards the security and privacy analysis of patient portals
Authors: Mathe Janos L. , Duncavage Sean , Werner Jan , Malin Bradley A. , Ledeczi Akos , Sztipanovits Janos
Published: October 2007

Clinical information systems (CIS) significantly influence the quality and efficiency of health care delivery. However, CIS are complex environments that integrate information technologies, human stakeholders, and patient-specific data. Given the sensitivity of patient data, federal regulations require healthcare providers to adopt policy, as well as technology, protections for patient data. Ad hoc system design and implementation of CIS can cause unforeseen and unintended privacy and security breaches. The introduction of model-based design techniques combined with the development of high-level modeling abstractions and analysis methods provide a mechanism to investigate these concerns by conceptually simplifying CIS without losing expressive power. This work introduces the Model-based Design Environment for Clinical Information Systems (MODECIS) - a graphical design environment that assists CIS architects in formalizing CIS systems as well-defined services. MODECIS leverages Service-Oriented Architectures to create realistic system models at an abstract level. By modeling CIS using abstractions, we enable the analysis of legacy architectures, as well as the design and simulation of, future CIS. We present the feasibility of MODECIS via modeling certain functions, such as the authentication process of the MyHealth@Vanderbilt patient portal.
Testing linear dependence of hyperexponential elements
Authors: Li Ziming , Wu Min , Zheng Dabin
Published: October 2007

A Wronskian (resp. Casoratian) criterion is useful to test linear dependence of elements in a differential (resp. difference) field over constants. We generalize this criterion for invertible hyperexponential elements in a differential-difference ring extension over a field
F
. The generalization also enables us to connect similarity and
F
-linear dependence of invertible hyperexponential elements.
The design and programming of a powerful short wordlength processor using context-dependent machine instructions
Authors: Hor T. M. , Yuen C. K.
Published: October 2007

Context-dependent machine instructions were used to extend the capability of instruction set of a short wordlength processor. By freeing instruction bits for other purposes, a more powerful machine instruction set can be designed. Programming examples were given to illustrate the benefit obtained from the design. Less CPU time and memory space were required as compared with popular 8-bit CPUs.
Multiprocessor/distributed processing bibliography (in machine-readable form)
Authors: Miya E. N.
Published: October 2007

There is a lot of renewed interest in
parallel processing
. People parallel process, too. Human parallel processing tends to be cooperative rather than competitive. To this end, research literature uses bibliographies like road-maps to the field.
Dataflow architecture for EEG patient monitor
Authors: Hu Weiming
Published: October 2007

Much work is currently directed towards dataflow architectures. Most of the proposed architectures attempt to exploit fine grained parallelism. This paper describes an application specific dataflow architecture which exploits coarse grained parallelism. The application is that of a real-time patient monitor used to display patient data.
Speculations on the evolution of an architecture
Authors: Tagg A. G.
Published: October 2007

PRIME computers was formed in the early 1970s by a splinter group of hardware and software engineers from Honeywell. With them, they brought their ideas on minicomputers, based on their experience of Honeywell minis, and their experience of the MULTICS operating system.
Multi-processor system description and simulation using structured multi-programming languages
Authors: Van Oost E. M. J. C.
Published: October 2007

Most of the multi-processor systems designed for real time control demand a high efficiency, compromising the simplicity of the system. If this requirement imposes a hardware implementation of most of the primitives of the system, a complicated hardware will result. In order to retain to some extent the ease of using structured multi-programming languages, e.g. Concurrent Pascal [1], we have used these languages for the description and simulation of the complex hardware, instead of using them for software implementation of parallelism.

This approach is explained with examples taken from an existing multi-processor system [2] developed at the Brussels Free University (V.U.B.).
Focal adhesion disassembly is an essential early event in hepatic stellate cell chemotaxis
Authors: Melton Andrew C. , Soon Russell K. , Park J. Genevieve , Martinez Luis , deHart Gregory W. , Yee Hal F.
Published: October 2007

Chemotaxis (i.e., directed migration) of hepatic stellate cells to areas of inflammation is a requisite event in the liver's response to injury. Previous studies of signaling pathways that regulate stellate cell migration suggest a key role for focal adhesions, but the exact function of these protein complexes in motility remains unclear. Focal adhesions attach a cell to its substrate and therefore must be regulated in a highly coordinated manner during migration. To test the hypothesis that focal adhesion turnover is an essential early event for chemotaxis in stellate cells, we employed a live-cell imaging technique in which chemotaxis was induced by locally stimulating the tips of rat stellate cell protrusions with platelet-derived growth factor-BB (PDGF). Focal adhesions were visualized with an antibody directed against vinculin, a structural component of the focal adhesion complex. PDGF triggered rapid disassembly of adhesions within 6.25 min, subsequent reassembly by 12.5 min, and continued adhesion assembly in concert with the spreading protrusion until the completion of chemotaxis. Blockade of adhesion disassembly by growing cells on fibronectin or treatment with nocodazole prevented a chemotactic response to PDGF. Augmentation of adhesion disassembly with ML-7 enhanced the chemotactic response to PDGF. These data suggest that focal adhesion disassembly is an essential early event in stellate cell chemotaxis in response to PDGF.