bluuebunny/crossref_metadata_2025 huggingface dataset:
Micropatterning organosilane self-assembled monolayers with plasma etching and backfilling techniques
Authors: Harant Adam W. , Whipple Stephen G. , Douglas Kenneth , Bowman Christopher N.
Published: April 2005

Organosilane self-assembled monolayers (SAMs) were micropatterned using standard photoresist-based lithographic and plasma etching techniques. Etched regions were backfilled with a second SAM containing a different organic substituent. By repeating the patterning process, a complex, multifunctional patterned surface composed of three different SAMs (amino-, methyl-, and thiol-terminated) was formed. Since two distinct etching steps are used, the backfilled SAMs can be deposited in trenches of different depths. Multifunctional, micropatterned SAMs were visualized by friction mode scanning probe microscopy (SPM). Gold-coated SPM tips yielded high contrast friction images from surfaces patterned with thiol-terminated SAMs.
Emission statistics for Si and HfC emitter arrays after residual gas exposure
Authors: Nicolaescu D. , Nagao M. , Sato T. , Filip V. , Kanemaru S. , Itoh J.
Published: April 2005

Field emission arrays (FEAs) comprising 100 Si or HfC coated Si emitters have been fabricated. The FEAs emission properties were measured in ultra high vacuum conditions and after being subject to Ar and O2 residual gases with partial pressures in the range 10−6 to 10−4Pa. The influence of residual gases on the FEAs field emission properties has been comparatively assessed using the model parameter extraction method. The array field emission model uses equations that describe the electron emission current from individual emitters of given radius R and work function ϕ together with nonuniform distribution functions giving the dispersion of these parameters within the array. A simplified relationship for the array emission current depending on a single integral instead of a double one has been derived. A nonlinear extraction algorithm using partial derivatives of the objective function is used, which gives fast and accurate results. Both Si and HfC emitters exhibit (to a different degree) tightening of the radius distribution with time and more uniform emission, when exposed to O2 residual gas. The current degradation of Si and HfC arrays, when exposed to Ar residual gas, is mostly associated with the work function increase. HfC emitters have higher emission currents, lower noise level, and better stability of the emission than Si emitters. These properties are discussed in terms of the array parameter statistics.
Field-emission based vacuum device for the generation of terahertz waves
Authors: Lin Ming-Chieh , Huang Kuo-Hua , Lu Pu-Shih , Lin Pei-Yi , Jao Ruei-Fu
Published: April 2005

Terahertz (THz), waves i.e., electromagnetic radiation in the frequency extending from 0.1 to 10 THz (wavelengths of 3 mm down to 0.03 mm), have been used to characterize the electronic, vibrational, and compositional properties of solid, liquid, and gas phase materials during the past decade. More and more applications in imaging science and technology call for the well development of THz wave sources. Amplification and generation of a high frequency electromagnetic wave are a common interest of field emission based devices. In the present work, we propose a vacuum electronic device based on field emission mechanism for the generation of THz waves. To verify our thinking and designs, the cold tests and the hot tests have been studied via the simulation tools, SUPERFISH and MAGIC. In the hot tests, two types of electron emission mechanisms are considered. One is the field emission and the other is the explosive emission. The preliminary design of the device is carried out and tested by the numerical simulations. The simulation results show that an electronic efficiency up to 4% can be achieved without employing any magnetic circuits.
Shot noise power spectrum of planar field emitters
Authors: Rangaswamy K. , Cahay M. , Jensen K. L.
Published: April 2005

A quantum-mechanical wave impedance approach is used to calculate the shot noise power spectrum of the emission current from planar metallic cathodes. The formalism takes into account the effects of the image force potential in front of the cathode. For metals with low work function, the Fano factor which characterizes the reduction of the shot noise power SI below the Schottky result 2 q IA (where q is the magnitude of the charge of the electron and IA is the time average of the anode current) is calculated as a function of the applied external electric field. Simple analytical expressions for the Fano factor are derived for the cathode operated in the thermionic (Richardson) and tunneling (Fowler–Nordheim) regimes. The value of the Fano factor is found to be reduced substantially below the value calculated when the effects of the image charge potential are neglected.
Surface morphology of epitaxial LiF(110) and CaF2(110) layers
Authors: Sugawara Akira , Mae K.
Published: April 2005

Regular ridge-and-valley surface structures were spontaneously formed by the homoepitaxial growth of LiF(110) and CaF2(110). The surface structure was examined by in situ reflection high-energy electron diffraction (RHEED) and ex situ atomic force microscopy (AFM). The LiF(110) homoepitaxial surfaces exhibited regular ridge-and-valley structures composed of {100} facets and [001] macrosteps, and the ridge spacings increased with growth temperature. The CaF2(110) surfaces also exhibited regular ridge-and-valley structures composed of {111} facets and [11¯0] macrosteps when deposited above 400 °C. Annealing alone did not produce a well-developed ridge-and-valley structure. The highly mobile admolecules supplied during deposition played a central role on the morphological evolution of the surfaces. The heteroepitaxial growth of LiF and CaF2 on {100}-faceted NaCl(110) substrates was also examined. Although the LiF(110) exhibited a regular ridge-and-valley structure, CaF2(110) formed arrays of islands at the bottom of the grooves.
Fermi level pinning on Si0.83Ge0.17 surface by inductively coupled plasma treatment
Authors: Kim Iee-Gon , Choi Kyoung Jin , Lee Jong-Lam
Published: April 2005

Effects of inductively coupled plasma (ICP) treatment on Fermi level pinning on the surface of Si0.83Ge0.17 was studied by current–voltage and x-ray photoemission spectroscopy measurements. ICP treatment induced the growth of silicon oxide, suggesting that Si vacancies are generated under the oxide. From linear fitting of Schottky barrier heights with metal work functions, it was found that surface state density increased from 6.60×1012to1.13×1013∕cm2eV by the ICP treatment, leading to the pinning of surface Fermi level about EC∼0.53eV. From this, it is suggested that the Si vacancies are the main surface states in pinning Fermi level on the ICP-treated surface.
Ion-beam morphological conditioning of carbon field emission cathode surfaces
Authors: Hunt Charles E. , Chakhovskoi Andrei G. , Wang Yu
Published: April 2005

Samples of reticulated vitreous carbon (RVC) and paste graphite film have been evaluated for field-emission properties both before and after surface modification. The RVC has been treated using an open-air laser method. The graphite has been treated using an Ar-ion flood bombardment method. Both methods result in a change in surface morphology of the emission cathode which physically resembles results obtained using current or voltage stress treatment methods. Emission properties become more uniform, exhibit less noise, and, in the best cases, match results seen from carbon nanotubes or ultra-nanocrystalline diamond cathodes. The results demonstrate a method for obtaining large total currents at optimal extraction voltages, from large-area, low-cost cathodes. This method is useful for applications, such as field-emission lamps and x-ray tubes, which do not require nanofabricated, lithographically-patterned cathode structures.
Influence of electric field intensity on the copper catalyst-mediated crystallization of amorphous silicon
Authors: Kim Young-Bae , Kim Chul-Ho , Kim Hyun-Chul , Kim Young-Woong , Jeon Hyun-Pyo , Choi Duck-Kyun
Published: April 2005

The effects of electric field intensity on the crystallization of amorphous silicon (a-Si) using the field-aided lateral crystallization (FALC) process have been studied in the range of 0–180 V∕cm. The crystallization velocity increases as the electric field intensity increases. Moreover, the better quality of polycrystalline silicon resulted in the films that crystallized faster. The activation energy of the metal-induced lateral crystallization process calculated from the Arrhenius plot is 1.79 eV (±0.03 eV), whereas that of the FALC process is 1.65 eV (±0.04 eV) regardless of the electric field intensities. It is also shown that the electric field affects both the enhancement of the preexponential factor in the Arrhenius equation and the decrease in the energy barrier height for the crystallization. In particular, the effect is almost the same in the temperature range of 400–500 °C. The increase in the crystallization velocity is attributed to the field-enhanced diffusion of copper ions in the Cu3Si crystallization mediator and the amorphous Si.
Characterization of an advanced high-efficiency electron emission device
Authors: Negishi Nobuyasu , Nakada Tomonari , Sakemura Kazuto , Okuda Yoshiyuki , Satoh Hideo , Watanabe Atsushi , Yoshikawa Takamasa , Ogasawara Kiyohide , Koshida Nobuyoshi
Published: April 2005

As previously reported, the emission characteristics of metal-insulator-semiconductor (MIS) electron emission devices could be significantly improved by introducing microdimple structures into the emission sites. In this paper, we describe the characteristics of efficient cold electron emitters from a viewpoint of application to flat panel display (FPD). First, the forming operation for the device to activate the dynamic emission is discussed on a basis of the experimental analyses of the electrical properties and output electron energy spectra. Next it is demonstrated that the device has some desirable features as an excitation source of FPD: a high emission current density, a low operation voltage, emission uniformity, and stable emission with small angle dispersion. It is also shown from the result of lifetime evaluation that the device shows a half-life of 3000 h, and that the deteriorated emission can be recovered by the dc reactivation treatment.
Low temperature burnable carbon nanotube paste component for carbon nanotube field emitter backlight unit
Authors: Lee Sora , Im Won Bin , Kang Jong Hyuk , Jeon Duk Young
Published: April 2005

A new component of carbon nanotube (CNT) paste is explored with an attempt to develop a carbon nanotube field emitter backlight unit (CNT-FE BLU) fabricated by the screen-printing method. To reduce the residual organic binder materials on the surface of single-wall carbon nanotube (SWCNT), the P(MMA-co-BMA) random copolymer is developed as a new binder material. The weight of the residue after burning process at 350 °C was measured by thermo gravimetric analysis (TGA). The percentage of residue was 0.015% of the initial weight, which is only a quarter of the residual percentage of commercial binder material. The measured field emission property demonstrated that the developed P(MMA-co-BMA) was effective in reducing the residue on the surface of the CNT, which is critically important for improving the field emission property of CNT-FE BLU fabricated by the screen-printing method.
Ideally ordered 10 nm channel arrays grown by anodization of focused-ion-beam patterned aluminum
Authors: Peng C. Y. , Liu C. Y. , Liu N. W. , Wang H. H. , Datta A. , Wang Y. L.
Published: April 2005

Arrays of ideally ordered alumina nanochannels with unprecedented ∼10nm pore size, 40–50 nm interpore spacing, and improved channel uniformity have been fabricated by anodizing an aluminum substrate with a guiding pattern on its surface. The pattern is an array of hexagonally close-packed concaves fabricated by focused ion beam direct sputtering; and its lattice constant is carefully matched to the conditions of the subsequent anodization process in order to achieve effective guiding in the growth of the nanochannels and therefore the ordering of an array.
Selective growth of carbon nanotubes on silicon protrusions
Authors: Sato Hideki , Hata Koichi , Miyake Hideto , Hiramatsu Kazumasa , Saito Yahachi
Published: April 2005

Selective growth of carbon nanotubes (CNTs) to required positions is a matter of importance for an application to electron sources for field emitter arrays. Although some techniques have been proposed concerning the selective growth of carbon nanotubes, they have complex processes and difficulties in reliability and controllability. We have developed the selective CNT growth technique, which consists of fabrication of pyramid-shaped protrusion arrays on silicon (Si) substrate by a liftoff process, selective deposition of metal catalyst film on the vertexes of the protrusions, and growth of the CNTs on the metal catalyst by chemical vapor deposition (CVD). Here we report the detailed growth characteristics of CNTs selectively grown by thermal CVD (TCVD) on vertexes of pyramid-shaped protrusions fabricated on Si substrate. The growth of CNTs by TCVD gave long, randomly oriented and dispersed CNT growth, which was completely different from growth regimes given by plasma enhanced CVD (PECVD), i.e., vertically aligned and bundled growth. The array of the CNTs grown by TCVD gave better field emission characteristics than that with the CNTs grown by PECVD. That was presumably because the CNTs grown by TCVD gave longer and more dispersive CNT growth than PECVD and consequently gave higher field enhancement on the CNTs. It is also shown that the single growth of the CNT is successfully performed using this process.
Field emission from teepee-shaped carbon nanotube bundles
Authors: Busta H. , Tolt Z. , Montgomery J. , Feinerman A.
Published: April 2005

Randomly, but perpendicular to the surface, oriented carbon nanotubes of about 5 μm in height and submicrometer spacing were coated with 3.5 μm plasma enhanced CVD silicon dioxide. Subsequent removal of the oxide in buffered HF, followed by de-ionized water rinse and nitrogen blow drying resulted in the formation of a peculiar pattern of nanotubes similar in shape to teepees or the hair cells of the inner ear. Since several nanotubes can supply current to the apexes of these bundles and since the spacing between the apexes is increased, thus reducing the electrostatic screening effect, these structures might have interesting field emission properties. Field emission measurements were performed at pressures of about 1×10−8Torr. Room temperature emission was poor with turn-on fields of about 30 V/μm due to surface contamination effects. Turn-on fields of about 15 V/μm and macroscopic current densities of 50mA∕cm2 were obtained when the measurements were performed at 170 °C.
Process method to suppress the effect of phase errors in alternating phase shift masks
Authors: Singh Navab , Roy Moitreyee M. , Mehta Sohan S. , Adeyeye A. O.
Published: April 2005

We have developed a process method to suppress the effect of phase errors in alternating phase shift masks. Our method uses double exposure at reversed focus offsets to nullify the intensity imbalance caused by the phase errors. We have evaluated our technique using 120nm half-pitch line space patterns and found it very successful with remarkable improvement in usable depth of focus without loosing exposure latitude. We also observed that our technique could bring immunity against the lens aberrations such as defocus and astigmatism.
The Surprising Impact of Seat Location on Student Performance
Authors: Perkins Katherine K. , Wieman Carl E.
Published: April 2005

Every physics instructor knows that the most engaged and successful students tend to sit at the front of the class and the weakest students tend to sit at the back. However, it is normally assumed that this is merely an indication of the respective seat location preferences of weaker and stronger students. Here we present evidence suggesting that in fact this may be mixing up the cause and effect. It may be that the seat selection itself contributes to whether the student does well or poorly, rather than the other way around. While a number of studies have looked at the effect of seat location on students, the results are often inconclusive, and few, if any, have studied the effects in college classrooms with randomly assigned seats.1 In this paper, we report on our observations of a large introductory physics course in which we randomly assigned students to particular seat locations at the beginning of the semester. Seat location during the first half of the semester had a noticeable impact on student success in the course, particularly in the top and bottom parts of the grade distribution. Students sitting in the back of the room for the first half of the term were nearly six times as likely to receive an F as students who started in the front of the room. A corresponding but less dramatic reversal was evident in the fractions of students receiving As. These effects were in spite of many unusual efforts to engage students at the back of the class and a front-to-back reversal of seat location halfway through the term. These results suggest there may be inherent detrimental effects of large physics lecture halls that need to be further explored.
Teaching E = mc2: Mass Without Mass
Authors: Hobson Art
Published: April 2005

The mass-energy relation is, according to Einstein, the most important result of the special theory of relativity.1 Many educators have called for the inclusion of more such “modern” (post-1900) physics in our introductory courses.2 Although we frequently treat E = mc2 as a simple numerical relation, useful for solving nuclear physics problems, it is more important to discuss what this equation means. What can it tell us about the nature of energy and matter? Does rest mass arise purely from the energy of force fields? It seems not to be widely recognized that the answer to this last question is now known, at least for 90% of the mass of ordinary matter, to be “yes.”
Prescribing Eyeglasses for Myopia and Hyperopia
Authors: Ruiz Michael J.
Published: April 2005

Most eyeglass prescriptions are given for patients with one of two common visual problems: myopia and hyperopia. Myopia is the condition where the eye cannot clearly focus on far objects; e.g., one can't easily see the blackboard from the back of the room. Hyperopia refers to problems seeing close up, e.g., difficulty reading the newspaper. Physics enables us to estimate the prescription of eyeglasses quickly from data anyone can gather. The beauty of the method derives from the fact that you do not need to know anything about the detailed structure of the eye's compound lens system and biological media. This is due to the fact that eyeglasses are corrective.
The Dizzying Depths of the Cylindrical Mirror
Authors: DeWeerd Alan J. , Hill S. Eric
Published: April 2005

A typical introduction to geometrical optics treats plane and spherical mirrors. At first glance, it may be surprising that texts seldom mention the cylindrical mirror, except for the occasional reference to use in fun houses and to viewing anamorphic art.1,2 However, even a cursory treatment reveals its complexity. Holzberlein used an extended object to qualitatively illustrate that images are produced both before and behind a concave cylindrical mirror.3 He also speculated on how this extreme astigmatism results in an observer's dizziness. By considering a simple point object, we make a more detailed analysis of the cylindrical mirror and the dizziness it induces. First, we illustrate how rays from a point object reflect to form not one point image but two line images. Next, we describe how an observer perceives a likeness of the object. Finally, we suggest how confusing depth cues induce dizziness. Although we focus on the concave cylindrical mirror, the discussion is easy to generalize to the convex cylindrical mirror.
Use of Thioredoxin as a Reporter To Identify a Subset of
Escherichia coli
Signal Sequences That Promote Signal Recognition Particle-Dependent Translocation
Authors: Huber Damon , Boyd Dana , Xia Yu , Olma Michael H. , Gerstein Mark , Beckwith Jon
Published: April 2005

We have previously reported that the DsbA signal sequence promotes efficient, cotranslational translocation of the cytoplasmic protein thioredoxin-1 via the bacterial signal recognition particle (SRP) pathway. However, two commonly used signal sequences, those of PhoA and MalE, which promote export by a posttranslational mechanism, do not export thioredoxin. We proposed that this difference in efficiency of export was due to the rapid folding of thioredoxin in the cytoplasm; cotranslational export by the DsbA signal sequence avoids the problem of cytoplasmic folding (C. F. Schierle, M. Berkmen, D. Huber, C. Kumamoto, D. Boyd, and J. Beckwith, J. Bacteriol.
185
:
5706-5713, 2003). Here, we use thioredoxin as a reporter to distinguish SRP-dependent from non-SRP-dependent cleavable signal sequences. We screened signal sequences exhibiting a range of hydrophobicity values based on a method that estimates hydrophobicity. Successive iterations of screening and refining the method defined a threshold hydrophobicity required for SRP recognition. While all of the SRP-dependent signal sequences identified were above this threshold, there were also a few signal sequences above the threshold that did not utilize the SRP pathway. These results suggest that a simple measure of the hydrophobicity of a signal sequence is an important but not a sufficient indicator for SRP recognition. In addition, by fusing a number of both classes of signal sequences to DsbA, we found that DsbA utilizes an SRP-dependent signal sequence to achieve efficient export to the periplasm. Our results suggest that those proteins found to be exported by SRP-dependent signal sequences may require this mode of export because of their tendency to fold rapidly in the cytoplasm.
A Glimpse into the Expanded Genome Content of
Vibrio cholerae
through Identification of Genes Present in Environmental Strains
Authors: Purdy Alexandra , Rohwer Forest , Edwards Rob , Azam Farooq , Bartlett Douglas H.
Published: April 2005

Vibrio cholerae
has multiple survival strategies which are reflected both in its broad distribution in many aquatic environments and its high genotypic diversity. To obtain additional information regarding the content of the
V. cholerae
genome, suppression subtractive hybridization (SSH) was used to prepare libraries of DNA sequences from two southern California coastal isolates which are divergent or absent in the clinical strain
V. cholerae
O1 El Tor N16961. More than 1,400 subtracted clones were sequenced. This revealed the presence of novel sequences encoding functions related to cell surface structures, transport, metabolism, signal transduction, luminescence, mobile elements, stress resistance, and virulence. Flanking sequence information was determined for loci of interest, and the distribution of these sequences was assessed for a collection of
V. cholerae
strains obtained from southern California and Mexican environments. This led to the surprising observation that sequences related to the toxin genes
toxA
,
cnf1
, and
exoY
are widespread and more common in these strains than those of the cholera toxin genes which are a hallmark of the pandemic strains of
V. cholerae
. Gene transfer among these strains could be facilitated by a 4.9-kbp plasmid discovered in one isolate, which possesses similarity to plasmids from other environmental vibrios. By investigating some of the nucleotide sequence basis for
V. cholerae
genotypic diversity, DNA fragments have been uncovered which could promote survival in coastal environments. Furthermore, a set of genes has been described which could be involved in as yet undiscovered interactions between
V. cholerae
and eukaryotic organisms.
Inactivation of a Predicted Leader Peptidase Prevents Photoautotrophic Growth of
Synechocystis
sp. Strain PCC 6803
Authors: Zhbanko Maria , Zinchenko Vladislav , Gutensohn Michael , Schierhorn Angelika , Klösgen Ralf Bernd
Published: April 2005

To establish the role of the two putative type I leader peptidases (LepB1 and LepB2) encoded in the genome of the cyanobacterium
Synechocystis
sp. strain PCC 6803, we generated independent knockout mutants for both genes by introducing kanamycin resistance cassettes into the two open reading frames (sll0716 [
lepB1
] and slr1377 [
lepB2
], respectively). Although the insertion was successful in both instances, it was not possible to select homozygous mutant cells for
lepB2
, suggesting that the function of this gene is essential for cell viability. In contrast, LepB1 is apparently essential only for photoautotrophic growth, because homozygous
lepB1
::Km
r
cells could be propagated under heterotrophic conditions. They were even capable to some extent of photosynthetic oxygen evolution. However, the photosynthetic activity decreased gradually with extended incubation in the light and was particularly affected by high light intensities. Both features were indicative of photooxidative damage, which was probably caused by inefficient replacement of damaged components of the photosynthetic machinery due to the lack of a leader peptidase removing the signal peptides from photosynthetic precursor proteins. Indeed, processing of the PsbO precursor polypeptide to the corresponding mature protein was significantly affected in the mutant, and reduced amounts of other proteins that are synthesized as precursors with signal peptides accumulated in the cells. These results strongly suggest that LepB1 is important for removal of the signal peptides after membrane transport of the components of the photosynthetic machinery, which in turn is a prerequisite for the biogenesis of a functional photosynthetic electron transport chain.
Plasmid-Encoded Regulator of Extracellular Proteases inBacillus anthracis
Authors: Aronson Arthur I. , Bell Chris , Fulroth Ben
Published: April 2005

Bacillus anthracisSterne cured of the pXO1 plasmid had enhanced secreted protease activity during the postexponential phase but no change in hemolytic or lecithinase activities. A zymogen profile revealed at least six proteases, including serine, metal, and perhaps cysteine types. There were similar amounts of protease secreted by the closely related speciesBacillus cereusandBacillus thuringiensis, but the patterns differed. Among the pXO1 plasmid-encoded proteins, there is a tetratricopeptide protein designated Cot43 that is related to the Rap proteins ofBacillus subtilisand the PlcR pleiotropic regulator of secreted enzymes and toxins inB. thuringiensis. A disruption of thecot43gene resulted in overproduction of several proteases to a somewhat greater extent than in the plasmid-cured strain. Transformation of either of these strains with a clone of thecot43gene resulted in the inhibition of accumulation of some of the proteases and induction of at least one. On the basis oflacZfusions, transcription of thecot43gene increased in late exponential cells at the time of protease accumulation. The expression oflacZfusions to the upstream regions of twoB. anthracisextracellular protease genes was greater in the strain with the disruption ofcot43than in the Sterne strain, indicating regulation at the level of transcription. InB. anthracis, a pXO1 plasmid-encoded protein directly modulates or indirectly regulates the transcription of genes for several chromosomally encoded extracellular proteases.
Novel Roles of
ohrR
-
ohr
in
Xanthomonas
Sensing, Metabolism, and Physiological Adaptive Response to Lipid Hydroperoxide
Authors: Klomsiri Chananat , Panmanee Warunya , Dharmsthiti Saovanee , Vattanaviboon Paiboon , Mongkolsuk Skorn
Published: April 2005

Lipid hydroperoxides are highly toxic to biological systems. Here, the
Xanthomonas campestris
pv. phaseoli sensing and protective systems against linoleic hydroperoxide (LOOH) were investigated by examining the phenotypes, biochemical and regulatory characteristics of various
Xanthomonas
mutants in known peroxide resistance pathways. Analysis of LOOH resistance levels indicates that both alkyl hydroperoxide reductase (AhpC) and organic hydroperoxide resistance enzyme (Ohr) have important and nonredundant roles in the process. Nonetheless, inactivation of
ohr
leads to a marked reduction in LOOH resistance levels. The regulatory characteristics of an
ohr
mutant add further support to its primary role in LOOH protection. Northern analysis shows that LOOH had differential effects on induction of
ahpC
and
ohr
expression with the latter being more sensitive to the inducer. Analysis of the
ahpC
and
ohr
promoters confirmed that the LOOH-dependent induction of these promoters is mediated by the transcription regulators OxyR and OhrR, respectively. Using the in vivo promoter assays and the in vitro gel mobility shift assay, we show that LOOH directly oxidized OhrR at the sensing residue Cys-22 leading to its inactivation. In addition, physiological analysis shows that pretreatment of
X. campestris
pv. phaseoli with a sublethal dose of LOOH induced high levels of resistance to subsequent exposure to lethal concentrations of LOOH. This novel LOOH-induced adaptive response requires a functional
ohrR-ohr
operon. These data illustrate an important novel physiological role for the
ohrR-ohr
system in sensing and inactivating lipid hydroperoxides.
Evidence based guidelines for the prevention, identification, and management of occupational asthma
Authors: Nicholson P J , Cullinan P , Newman Taylor A J , Burge P S , Boyle C
Published: April 2005

Background:Occupational asthma is the most frequently reported work related respiratory disease in many countries. This work was commissioned by the British Occupational Health Research Foundation to assist the Health and Safety Executive in achieving its target of reducing the incidence of occupational asthma in Great Britain by 30% by 2010.

Aim:The guidelines aim to improve the prevention, identification, and management of occupational asthma by providing evidence based recommendations on which future practice can be based.

Methods:The literature was searched systematically using Medline and Embase for articles published in all languages up to the end of June 2004. Evidence based statements and recommendations were graded according to the Royal College of General Practitioner’s star system and the revised Scottish Intercollegiate Guidelines Network grading system.

Results:A total of 474 original studies were selected for appraisal from over 2500 abstracts. The systematic review produced 52 graded evidence statements and 22 recommendations based on 223 studies.

Discussion:Evidence based guidelines have become benchmarks for practice in healthcare and the process used to prepare them is well established. This evidence review and its recommendations focus on interventions and outcomes to provide a robust approach to the prevention, identification, and management of occupational asthma, based on and using the best available medical evidence. The most important action to prevent cases of occupational asthma is to reduce exposure at source. Thereafter surveillance should be performed for the early identification of symptoms, including occupational rhinitis, with additional functional and immunological tests where appropriate. Effective management of workers suspected to have occupational asthma involves the identification and investigation of symptoms suggestive of asthma immediately they occur. Those workers who are confirmed to have occupational asthma should be advised to avoid further exposure completely and early in the course of their disease to offer the best chance of recovery.
Short Stent Implantation for Routine Use Is Feasible in a High Proportion of Coronary Interventions and Yields a Low Restenosis Rate
Authors: Dietz Ulrich , Holz Nina , Dauer Cheryl , Meinert Rolf , Lambertz Heinz
Published: April 2005

Stent length predicts restenosis. The feasibility of using a short stent (<10 mm) routinely was investigated in 331 consecutive patients treated for 424 coronary artery lesions. A single short stent provided suitable coverage and achieved a residual stenosis <30%, with or without predilatation, in 252/424 lesions (59.4%). Longer stents were implanted in 58/424 lesions (13.7%), while only percutaneous transluminal coronary angioplasty was performed in 114/242 lesions (26.9%). Angiographic success and procedural success were achieved in 250/252 lesions (99.2%). Restenosis occurred in 36/231 lesions (15.6%) after short stenting, in 10/53 lesions (18.9%) after long stents, in 21/88 lesions (23.9%) after percutaneous transluminal coronary angioplasty, and in 67/372 lesions (18.0%) controlled angiographically. Only small vessel diameter predicted restenosis after short stenting. Thus, a single short stent implanted directly or after predilatation is sufficient to achieve an acceptable angiographic result in more than in nearly 60% of all treated lesions. Short stenting results in a low restenosis rate.
Positron Emission Tomography Does Not Add to Computed Tomography for the Diagnosis and Staging of Pancreatic Cancer
Authors: Lytras D. , Connor S. , Bosonnet L. , Jayan R. , Evans J. , Hughes M. , Garvey C.J. , Ghaneh P. , Sutton R. , Vinjamuri S. , Neoptolemos J.P.
Published: April 2005

Background: Positron emission tomography (PET) has been proposed for pancreatic cancer diagnosis and staging. Methods: 112 patients with suspected pancreatic cancer underwent 18F-fluoro-2-deoxy-D-glucose gamma camera PET and computed tomography (CT), of whom 62 also had laparoscopic ultrasonography and 70 underwent abdominal exploration for potential resection. The final diagnosis was malignancy in 78 and benign disease in 34 patients (25 with chronic pancreatitis). Results: The diagnostic sensitivity and specificity for PET were 73 and 60% compared to 89 and 65% for CT respectively (Cohen’s ĸ = 0.59). In 30 patients CT was equivocal with cancer in 14 and benign disease in 16. PET correctly diagnosed 13 of these patients (cancer in 6 and benign disease in 7), interpreted 4 as equivocal (cancer in 3 and benign disease in 1) but was incorrect in the remaining 13 patients (cancer in 5 and benign disease in 8). The sensitivity and specificity for detecting small volume metastatic disease were 20 and 94% for CT and 22 and 91% for PET, respectively. Conclusion: PET had a similar accuracy to that of CT for imaging pancreatic cancer but it did not provide any additional information in patients with equivocal CT findings and currently would seem of little benefit for the staging of pancreatic cancer.
Rectal Cancer: The Role of Radiotherapy
Authors: Lidder Paul G. , Hosie Ken B.
Published: April 2005

Surgery is the definitive tool in the management of patients with rectal carcinoma. Early failure of treatment remains problematic and is manifest in local recurrence. Development of surgical techniques and inclusion of other treatment modalities aim to reduce the incidence of local recurrence and improve survival. This article examines the role of radiotherapy in the management of patients with rectal carcinoma and explores the controversies that exist in its application. The evidence for the use and benefits of radiotherapy in adjuvant and neoadjuvant settings is reviewed, and its application in association with total mesorectal excision considered.
Fatness Is a Better Predictor of Cardiovascular Disease Risk Factor Profile Than Aerobic Fitness in Healthy Men
Authors: Christou Demetra D. , Gentile Christopher L. , DeSouza Christopher A. , Seals Douglas R. , Gates Phillip E.
Published: April 2005

Background—

The prevalence of cardiovascular disease (CVD) is partly attributable to an inactive and/or overweight population. However, the independent association of body fatness and aerobic fitness with CVD risk factors is uncertain. We sought to determine whether fatness or fitness better predicted traditional CVD risk factors in men with broad fatness, aerobic fitness, and age ranges using 3 expressions of adiposity.

Methods and Results—

In 135 carefully screened healthy men, we measured 18 established CVD risk factors, body mass index, total percent body fat, waist circumference, and maximal aerobic capacity. Body mass index, percent body fat, and waist circumference were consistently associated with all metabolic risk factors (
r
=−0.44 to 0.51,
P
<0.05) after partialling out the effects of aerobic fitness and age. Body mass index and waist circumference were also independently associated with selective hemodynamic risk factors (
r
=0.20 to 0.30,
P
≤0.01). In contrast, aerobic fitness was independently associated with only selective metabolic risk factors (
r
=−0.21 to 0.19,
P
<0.05) and was not associated with any hemodynamic risk factors (
P
>0.05). Both aerobic fitness and body fatness were independently associated with selective hemostatic risk factors (
r
=−0.22 to −0.26,
P
≤0.01;
r
=−0.32 to 0.48,
P
<0.05, respectively). Overall, fatness was more strongly and consistently associated with CVD risk factors than aerobic fitness.

Conclusions—

Body fatness is a better predictor of CVD risk factor profile than aerobic fitness in healthy men. Although habitual physical activity is an effective strategy for preventing CVD, elevated body fatness is associated with an adverse CVD risk factor profile independently of aerobic fitness.
Variation of C-Reactive Protein Levels in Adolescents
Authors: Larkin Emma K. , Rosen Carol L. , Kirchner H. Lester , Storfer-Isser Amy , Emancipator Judith L. , Johnson Nathan L. , Zambito Anna Marie V. , Tracy Russell P. , Jenny Nancy S. , Redline Susan
Published: April 2005

Background—

There is increasing evidence that sleep-disordered breathing (SDB) is an independent risk factor for cardiovascular disease (CVD) in adults. C-reactive protein (CRP), a marker of systemic inflammation, is an important predictor of future cardiovascular events. The goal of this study was to quantify the associations of SDB, sleep duration, and CRP in adolescents to better understand the role of SDB in CVD risk.

Methods and Results—

Adolescents (n=143; age, 13 to 18 years; 36% black; 50% female) with a wide range of SDB severity underwent polysomnography and measurement of high-sensitivity CRP. SDB was quantified with the apnea hypopnea index (AHI) and oxygen desaturation measures. Sleep duration was estimated from 7-day actigraphy. The independent and dose-response associations of SDB with CRP were addressed through linear mixed-effects models. Forty-eight percent were overweight or obese, and 12% had SDB (AHI ≥5). CRP levels varied with increasing body mass index and SDB. After adjustment for body mass index , age, sex, and race, mean CRP levels were 0.50, 0.43, 0.97, and 1.66 mg/L for SDB severity levels of AHI <1, 1 to 4.9, 5 to 14.9, and ≥15, respectively (
P
=0.0049, AHI ≥15 versus <1). Adjusted mean CRP levels demonstrated a dose response with SDB above a threshold AHI of 5. This association was partially explained by overnight hypoxemia and less so by sleep duration.

Conclusions—

In adolescents free of known CVD, an AHI ≥5 is associated with increasing levels of CRP, suggesting that pediatric SDB may confer additional CVD risk beyond that of obesity.
Inflammatory Cytokines Interleukin-6 and Oncostatin M Induce Plasminogen Activator Inhibitor-1 in Human Adipose Tissue
Authors: Rega G. , Kaun C. , Weiss T.W. , Demyanets S. , Zorn G. , Kastl S.P. , Steiner S. , Seidinger D. , Kopp C.W. , Frey M. , Roehle R. , Maurer G. , Huber K. , Wojta J.
Published: April 2005

Background—

Adipose tissue is a prominent source of plasminogen activator inhibitor-1 (PAI-1), the primary physiological inhibitor of plasminogen activation. Increased PAI-1 expression acts as a cardiovascular risk factor, and plasma levels of PAI-1 strongly correlate with body mass index (BMI). Elevated serum levels of interleukin-6 (IL-6), an inflammatory cytokine and a member of the glycoprotein 130 (gp130) ligand family, are found in obese patients and might indicate low-grade systemic inflammation. Another gp130 ligand, oncostatin M (OSM), upregulates PAI-1 in cardiac myocytes, astrocytes, and endothelial cells. We used tissue explants and primary cultures of preadipocytes and adipocytes from human subcutaneous and visceral adipose tissue to investigate whether IL-6 and OSM affect PAI-1 expression in fat.

Methods and Results—

Human subcutaneous and visceral adipose tissue responded to treatment with IL-6 and OSM with a significant increase in PAI-1 production. Human preadipocytes were isolated from subcutaneous and visceral adipose tissue. Adipocyte differentiation was induced by hormone supplementation. All cell types expressed receptors for IL-6 and OSM and produced up to 12-fold increased levels of PAI-1 protein and up to 9-fold increased levels of PAI-1 mRNA on stimulation with IL-6 and OSM. AG-490, a janus kinase/signal transducer and activator of transcription inhibitor, abolished the OSM-dependent PAI-1 induction almost completely.

Conclusions—

We have for the first time established a link between the gp130 ligands, the proinflammatory mediators IL-6 and OSM, and the expression of PAI-1 in human adipose tissue. Thus, we speculate that IL-6 and OSM, by upregulating PAI-1 in adipose tissue, can contribute to the increased cardiovascular risk of obese patients.
Interaction of Body Mass Index and Framingham Risk Score in Predicting Incident Coronary Disease in Families
Authors: Mora Samia , Yanek Lisa R. , Moy Taryn F. , Fallin M. Daniele , Becker Lewis C. , Becker Diane M.
Published: April 2005

Background—

Siblings of individuals with premature coronary heart disease (CHD) have a marked excess risk of CHD risk factors and premature CHD. The impact of body mass index (BMI) on incident CHD in these families and the extent to which it may be mediated by associated risk factors are unknown. The aim of this study was to examine the effect of high BMI on incident CHD in white and black families with premature CHD and to estimate the heritability of BMI.

Methods and Results—

Risk factors, BMI, and Framingham Risk Score (FRS) were assessed at baseline and incident CHD was determined prospectively in 827 apparently healthy siblings of probands with premature CHD aged <60 years. During a mean follow-up of 8.7 years, 13.3% of siblings had incident CHD events. Event rates were higher in obese and overweight siblings than in those with normal weight (15.3% and 16.0% versus 8.1%, respectively;
P
=0.01). Multivariable Cox proportional hazards analyses demonstrated the independent prognostic value of BMI when added to FRS (
P
=0.02). A marked interaction between obesity (BMI ≥30 kg/m
2
) and high FRS (>20%) was seen for incident CHD (
P
for interaction=0.008), with an adjusted hazard ratio compared with low-FRS/normal-weight siblings of 14.63 (95% CI, 6.40 to 33.44;
P
<0.0001). BMI heritability (h
2
) was moderate for whites and low for blacks (52% and 29%, respectively).

Conclusions—

High BMI contributed independently and significantly to incident CHD, beginning in the overweight range, and was most notable for obese siblings with a high-risk FRS.
AVO for one- and two-fracture set models
Authors: Chen He , Brown Raymon L. , Castagna John P.
Published: April 2005

A theoretical comparison is made of PP and PS angle–dependent reflection coefficients at the top of two fractured-reservoir models using exact, general, anisotropic reflection coefficients. The two vertical-fracture models are taken to have the same total crack density. The primary issue investigated is determination of the fracture orientation using azimuthal AVO analysis. The first model represents a single-fracture set and the second model has an additional fracture set oblique to the first set at an angle of 60°. As expected, the PP-wave anisotropy is reduced when multiple fracture sets are present, making the determination of orientation more difficult than for the case of a single-fracture set. Long offsets are required for identification of dominant fracture orientations using PP-wave AVO. PS-wave AVO, however, is quite sensitive to fracture orientations, even at short offsets. For multiple-fracture sets, PS signals can potentially be used to determine orientations of the individual sets.
Routine 2D inversion of magnetotelluric data using the determinant of the impedance tensor
Authors: Pedersen L. B. , Engels M.
Published: April 2005

Recent developments in the speed and quality of data acquisition using the radiomagnetotelluric (RMT) method, whereby large amounts of broadband RMT data can be collected along profiles, have prompted us to develop a strategy for routine inverse modeling using 2D models. We build a rather complicated numerical model containing both 2D and 3D elements believed to be representative for shallow conductors in crystalline basement overlain by a thin sedimentary cover. We then invert the corresponding synthetic data on selected profiles, using both traditional MT approaches, as well as the proposed approach, which is based on the determinant of the MT impedance tensor. We compare the estimated resistivity models with the true models along the selected profiles and find that the traditional approaches often lead to strongly biased models and bad data fit, in contrast to those using the determinant. In this case, much of the bias is removed and the data fit is improved. The determinant of the impedance tensor is independent of the chosen strike direction, and once the a priori model is set, the best fitting model is found to be practically independent of the starting model used. We conclude that the determinant of the impedance tensor is a useful tool for routine inverse modeling.
Fluid effects on shear waves in finely layered porous media
Authors: Berryman James G.
Published: April 2005

Although there are five effective shear moduli for any layered transversely isotropic with a vertical symmetry axis (VTI) medium, one and only one effective shear modulus of the layered system (namely, the uniaxial shear) contains all the dependence of pore fluids on the elastic or poroelastic constants that can be observed in vertically polarized shear waves. Pore fluids can increase the magnitude of shear energy stored in this modulus by an amount that ranges from the smallest to the largest effective shear moduli of the VTI system. But since there are five shear moduli in play, the overall increase in shear energy due to fluids is reduced by a factor of about five in general. We can, therefore, give definite bounds on the maximum increase of overall shear modulus — about 20% of the allowed range as liquid is fully substituted for gas. An attendant increase of density (depending on porosity and fluid density) by approximately 5–10% decreases the shear-wave speed and thereby partially offsets the effect of this shear modulus increase. The final result is an increase of shear-wave speed on the order of 5–10%. This increase is shown to be possible under most favorable circumstances, that is, when the shear modulus fluctuations are large (resulting in strong anisotropy) and the medium behaves in an undrained fashion due to fluid trapping. At frequencies higher than seismic (such as sonic and ultrasonic waves for well logging or laboratory experiments), resulting short response times also produce the requisite undrained behavior; therefore, fluids also affect shear waves at high frequencies by increasing rigidity.