bluuebunny/crossref_metadata_2025 huggingface dataset:
Microbial Methylation of Metalloids: Arsenic, Antimony, and Bismuth
Authors: Bentley Ronald , Chasteen Thomas G.
Published: January 2003

A significant 19th century public health problem was that the inhabitants of many houses containing wallpaper decorated with green arsenical pigments experienced illness and death. The problem was caused by certain fungi that grew in the presence of inorganic arsenic to form a toxic, garlic-odored gas. The garlic odor was actually put to use in a very delicate microbiological test for arsenic. In 1933, the gas was shown to be trimethylarsine. It was not until 1971 that arsenic methylation by bacteria was demonstrated. Further research in biomethylation has been facilitated by the development of delicate techniques for the determination of arsenic species. As described in this review, many microorganisms (bacteria, fungi, and yeasts) and animals are now known to biomethylate arsenic, forming both volatile (e.g., methylarsines) and nonvolatile (e.g., methylarsonic acid and dimethylarsinic acid) compounds. The enzymatic mechanisms for this biomethylation are discussed. The microbial conversion of sodium arsenate to trimethylarsine proceeds by alternate reduction and methylation steps, with S-adenosylmethionine as the usual methyl donor. Thiols have important roles in the reductions. In anaerobic bacteria, methylcobalamin may be the donor. The other metalloid elements of the periodic table group 15, antimony and bismuth, also undergo biomethylation to some extent. Trimethylstibine formation by microorganisms is now well established, but this process apparently does not occur in animals. Formation of trimethylbismuth by microorganisms has been reported in a few cases. Microbial methylation plays important roles in the biogeochemical cycling of these metalloid elements and possibly in their detoxification. The wheel has come full circle, and public health considerations are again important.
Signal Transduction and Regulatory Mechanisms Involved in Control of the σS(RpoS) Subunit of RNA Polymerase
Authors: Hengge-Aronis Regine
Published: January 2003

The σS(RpoS) subunit of RNA polymerase is the master regulator of the general stress response in Escherichia coli and related bacteria. While rapidly growing cells contain very little σS, exposure to many different stress conditions results in rapid and strong σSinduction. Consequently, transcription of numerous σS-dependent genes is activated, many of which encode gene products with stress-protective functions. Multiple signal integration in the control of the cellular σSlevel is achieved by rpoS transcriptional and translational control as well as by regulated σSproteolysis, with various stress conditions differentially affecting these levels of σScontrol. Thus, a reduced growth rate results in increased rpoS transcription whereas high osmolarity, low temperature, acidic pH, and some late-log-phase signals stimulate the translation of already present rpoS mRNA. In addition, carbon starvation, high osmolarity, acidic pH, and high temperature result in stabilization of σS, which, under nonstress conditions, is degraded with a half-life of one to several minutes. Important cis-regulatory determinants as well as trans-acting regulatory factors involved at all levels of σSregulation have been identified. rpoS translation is controlled by several proteins (Hfq and HU) and small regulatory RNAs that probably affect the secondary structure of rpoS mRNA. For σSproteolysis, the response regulator RssB is essential. RssB is a specific direct σSrecognition factor, whose affinity for σSis modulated by phosphorylation of its receiver domain. RssB delivers σSto the ClpXP protease, where σSis unfolded and completely degraded. This review summarizes our current knowledge about the molecular functions and interactions of these components and tries to establish a framework for further research on the mode of multiple signal input into this complex regulatory system.
Critical Role of Human T-Lymphotropic Virus Type 1 Accessory Proteins in Viral Replication and Pathogenesis
Authors: Albrecht Björn , Lairmore Michael D.
Published: January 2003

Human T-cell lymphotropic virus type 1 (HTLV-1) infection is associated with a diverse range of lymphoproliferative and neurodegenerative diseases, yet pathogenic mechanisms induced by the virus remain obscure. This complex retrovirus contains typical structural and enzymatic genes but also unique regulatory and accessory genes in four open reading frames (ORFs) of the pX region of the viral genome (pX ORFs I to IV). The regulatory proteins encoded by pX ORFs III and IV, Tax and Rex, respectively, have been extensively characterized. In contrast the contribution of the four accessory proteins p12
I
, p27
I
, p13
II
, and p30
II
, encoded by pX ORFs I and II, to viral replication and pathogenesis remained unclear. Proviral clones that are mutated in either pX ORF I or II, while fully competent in cell culture, are severely limited in their replicative capacity in a rabbit model. Emerging evidence indicates that the HTLV-1 accessory proteins are critical for establishment of viral infectivity, enhance T-lymphocyte activation, and potentially alter gene transcription and mitochondrial function. HTLV-1 pX ORF I expression is critical to the viral infectivity in resting primary lymphocytes, suggesting a role for p12
I
in lymphocyte activation. The endoplasmic reticulum and cis-Golgi localizing p12
I
, encoded from pX ORF I, activates NFAT, a key T-cell transcription factor, through calcium-mediated signaling pathways and may lower the threshold of lymphocyte activation via the JAK/STAT pathway. In contrast p30
II
localizes to the nucleus and represses viral promoter activity, but may regulate cellular gene expression through p300/CBP or related coactivators of transcription. p13
II
targets mitochondrial proteins, where it alters the organelle morphology and may influence energy metabolism. Collectively, studies of the molecular functions of the HTLV-1 accessory proteins provide insight into strategies used by retroviruses that are associated with lymphoproliferative diseases.
Evolutionary Conservation of Reactions in Translation
Authors: Ganoza M. Clelia , Kiel Michael C. , Aoki Hiroyuki
Published: January 2003

Current X-ray diffraction and cryoelectron microscopic data of ribosomes of eubacteria have shed considerable light on the molecular mechanisms of translation. Structural studies of the protein factors that activate ribosomes also point to many common features in the primary sequence and tertiary structure of these proteins. The reconstitution of the complex apparatus of translation has also revealed new information important to the mechanisms. Surprisingly, the latter approach has uncovered a number of proteins whose sequence and/or structure and function are conserved in all cells, indicating that the mechanisms are indeed conserved. The possible mechanisms of a new initiation factor and two elongation factors are discussed in this context.
MECHANICAL PROPERTIES OF GREAT ARTERIAL WALL AND CLINICAL IMPLICATION
Authors: PALLOTTI G. , PETTAZZONI P. , BIGI A. , ROVERI N.
Published: January 2003

X-ray diffraction and microscopic analysis investigate the morphological organization of the structural components in the dog carotid wall. Histological analysis confirms an anisotropic morphology of smooth muscle cells and elastic fibers in the tissue. Collagen fibers, as revealed by X-ray diffraction technique, are organized in an isotropic network in the unstretched carotid media. Collagen fibers stretch without a preferential direction of orientation when a carotid segment is deformed in the physiological range under intraluminal pressure. A mathematical model, which takes into account the isotropic distribution of the collagen fibers, is developed. The validity of this model has been tested by computing several mechanical parameters using Anliker's data on the axial and radial oscillation obtained for carotids of living dogs. In spite of the anisotropic morphology of the main constituents of the carotid media layer, from a mechanical point of view the tissue can be considered as an isotropic material for the random distribution of the collagen fibers, which represent the component of higher tensile strength.
THE ADDITION OF SARCOMERES IN SERIES IS THE MAIN PROTECTIVE MECHANISM FOLLOWING ECCENTRIC EXERCISE
Authors: MORGAN DAVID L. , TALBOT JASON A.
Published: January 2003

Sore muscles following unaccustomed eccentric exercise is a common experience. One remarkable aspect of this is the rapid training. A single bout of exercise can provide significant protection against muscle damage and soreness from subsequent bouts. Several studies have shown that such training also increases the optimum muscle length and/or the number of sarcomeres. The present study aimed to test whether this accounts for all the protection. Rats were trained for up to 30 minutes per day on a treadmill, either inclined to 16° (concentrically biased exercise) or declined to 16° (eccentrically biased exercise) for one week. The decline rats were found to have smaller optimum knee angles, or longer muscle lengths, for torque generation by vastus intermedius muscles than the incline rats. When test eccentric contractions were given over the same range of knee angles for each training group, the decline rats showed less damage. When the differences in the optimum length were accounted for and the eccentric contractions were given over the same portion of the torque angle curve, there was no difference between the two groups in the amount of damage that they suffered, suggesting that the shift in optimum was responsible for all of the protection.
THE TENSEGRITY-TRUSS AS A MODEL FOR SPINE MECHANICS: BIOTENSEGRITY
Authors: LEVIN STEPHEN M.
Published: January 2003

The commonly accepted "tower of blocks" model for vertebrate spine mechanics is only useful when modeling a perfectly balanced, upright, immobile spine. Using that model, in any other position than perfectly upright, the forces generated will tear muscle, crush bone and exhaust energy. A new model of the spine uses a tensegrity-truss system that will model the spine right side up, upside-down or in any position, static or dynamic. In a tensegrity-truss model, the loads distribute through the system only in tension or compression. As in all truss systems, there are no levers and no moments at the joints. The model behaves non-linearly and is energy efficient. Unlike a tower of blocks, it is independent of gravity and functions equally well on land, at sea, in the air or in space and models the spines of fish and fowl, bird and beast.
APONEUROSIS LENGTH AND FASCICLE INSERTION ANGLES OF THE BICEPS BRACHII
Authors: ASAKAWA DEANNA S. , PAPPAS GEORGE P. , DRACE JOHN E. , DELP SCOTT L.
Published: January 2003

Magnetic resonance images and ultrasound images were used to examine the architecture of the distal biceps brachii muscle in 12 unimpaired subjects. The distal biceps brachii tendon continued as an internal aponeurosis that spanned 34± 4% of the length of the biceps brachii long head muscle on average. The distal muscle fascicles inserted at angles to this aponeurosis; fascicles anterior to the aponeurosis inserted at a significantly greater (p ≤ 0.05) angle (17°) than the fascicles posterior to the aponeurosis (14°) in the distal 2 cm of muscle when the elbow was extended. Mean fascicle insertion angles were on average 3–4° greater with the elbow flexed 90° against a 5% maximum voluntary contraction load as compared to their values with the elbow extended. These data provide the basis for designing experiments to measure muscle and tendon motion in vivo.
EXTRACTION OF MINUTE GAS BUBBLES FROM LIQUIDS FLOWING IN A SIMULATED CARDIOPULMONARY BYPASS SYSTEM BY A VENTURI-ASPIRATOR UNIT
Authors: YANG WEN-JEI , EID AMR , ECHIGO R.
Published: January 2003

An experimental study is performed to extract minute gas bubbles from liquids flowing in a simulated cardiopulmonary bypass system using a Venturi-aspirator unit. In other words, oxygen bubbles in oxygenated blood are simulated by air bubbles in water with AP30 (about same viscosity as whole blood). This study is intended to determine the feasibility of using a Venturi aspirator unit to extract minute gas bubbles from a simulated cardiopulmonary bypass system. Testing of the Venturi-type bubble extraction is carried out using three different test sections. Two Venturis are used, and a straight tube configuration is used as a control. The two Venturis are similar, with the exception that one has a longer inlet cone which causes the entering liquid to accelerate at a slower rate. Results are obtained for effectiveness of the aspirator unit as functions of total flow rate, extraction suction, suction pressure difference, and hydraulic head. It is concluded from the study that:

(i) The effectiveness of the Venturis is typically between 90 and 100 percent. It increases with an increase in suction or suction pressure difference but decreases with an increase in total flow rate.

(ii) The Venturi is most suitable for extraction of minute gas bubbles, especially for use with AP30 (whole blood), which yields substantially higher effectiveness than water.

(iii) It is anticipated that a Venturi-aspirator unit can be superior to other bubble separation device as the cardiopulmonary bypass system for applications in extra corporeal blood oxygenation.
Marijuana Use and Prior Injury among Injured Problem Drinkers
Authors: Woolard Robert , Nirenberg Ted D. , Becker Bruce , Longabaugh Richard , Minugh P. Allison , Gogineni Aruna , Carty Kathleen , Clifford Patrick R.
Published: January 2003

Objectives: The purpose of this paper is to better understand marijuana use among injured problem drinkers in the emergency department (ED). The specific objectives are: 1) to assess the prevalence of marijuana use; 2) to identify factors associated with marijuana use; 3) to determine whether prior injury is associated with marijuana use; and 4) to determine whether marijuana‐using problem drinkers want to change behaviors. Methods: The authors conducted a post‐hoc analysis on data obtained prospectively. Subjects had injury and problem drinking: either measurable alcohol level (blood alcohol concentration, BAC), report of drinking, or an Alcohol Use Disorders Identification Test (AUDIT) score of ≥8. The study was conducted on weekend nights; 3,776 injured ED patients were screened, 383 refused, 578 were enrolled, and 433 had complete data. Results: Of the 433 subjects, 48.3% reported using marijuana in the three months prior. Marijuana‐using problem drinkers had more hazardous drinking, higher AUDIT scores (14.0 vs. 11.4, p < 0.001), and higher risk‐taking scores (12.4 vs. 10.1, p < 0.001). More used other drugs (69.7% vs. 30.3%, p < 0.001). In regression analyses, marijuana use remained an independent predictor of prior injury (OR = 2.16, 95% CI = 1.25 to 3.75), particularly prior alcohol‐related (OR = 2.26, 95% CI = 1.45 to 3.53) and motor‐vehicle‐related (OR = 1.69, 95% CI = 1.03 to 2.79) injury. Readiness‐to‐change scores were similar (4.14 vs. 4.22, p = 0.21) between users and nonusers. Conclusions: Marijuana use among injured problem drinkers is prevalent. Their risk of prior injury is increased. Counseling for alcohol and injury should address marijuana use.
Interactions Between Suspended Nanowires and Patterned Surfaces
Authors: Martin B.R. , Angelo S.K.St. , Mallouk T.E.
Published: December 2002

Gold nanowires, 350 nm in diameter and 3–6 μm in length, were derivatized by using positively and negatively charged self‐assembled monolayers. The interactions between these particles and surfaces were investigated as a function of their surface chemistry and topography. Electrostatically repulsive sulfonate–sulfonate interactions resulted in mobile particles on the surface, whereas electrostatically attractive interactions between polyamines and sulfonates immobilized the particles. Patterned surfaces were selectively derivatized with particles using these attractive and repulsive interactions. By lithographically defining surface wells that were commensurate with the length of the nanowires, nanowire bundles were assembled in the wells.
Oriented Free‐Standing Three‐Dimensional Silicon Inverted Colloidal Photonic Crystal Microfibers
Authors: Míguez H. , Yang S.M. , Tétreault N. , Ozin G.A.
Published: December 2002

Inverse colloidal photonic crystals (see Figure and cover) can be fashioned in the form of free‐standing, oriented rectangular‐ and V‐shaped microfibers via a self‐assembly strategy. Microspectroscopy of these microfibers is consistent with the existence of a complete photonic bandgap near 1.5 μm, making these microfiber constructions interesting as optical components of microphotonic crystal circuits.
Chemistry of Phosphine–Borane Adducts at Platinum Centers: Synthesis and Reactivity of PtII Complexes with Phosphinoborane Ligands
Authors: Jaska Cory A. , Dorn Hendrik , Lough Alan J. , Manners Ian
Published: December 2002

Reaction of [Pt(PEt3)3] with the primary and secondary phosphine–borane adducts PhRPH⋅BH3 (R=H, Ph) resulted in oxidative addition of a PH bond at the Pt0 center to afford the complexes trans‐[PtH(PPhR⋅BH3)(PEt3)2] (1: R=H; 2: R=Ph). The products 1 and 2 were characterized by 1H, 11B, 13C, 31P, and 195Pt NMR spectroscopy, and the molecular structures were verified by X‐ray crystallography. In both cases, a trans arrangement of the hydride ligand with respect to the phosphidoborane ligand was observed. When 2 was treated with PhPH2⋅BH3, a novel phosphidoborane ligand‐exchange reaction occurred which yielded 1 and Ph2PH⋅BH3. Treatment of 2 with one equivalent of depe (depe=1,2‐bis(diethylphosphino)ethane) resulted in the formation of the complex cis‐[PtH(PPh2⋅BH3)(depe)] (3), in which the hydride ligand and the phosphidoborane ligand are in a cis arrangement. Treatment of 3 with PhPH2⋅BH3 was found to result in an exchange of the phosphidoborane ligands to give the complex cis‐[PtH(PPhH⋅BH3)(depe)] (4) and Ph2PH⋅BH3. Complex 4 was found to undergo further reaction in the presence of PhPH2⋅BH3 to give meso‐cis‐[Pt(PPhH⋅BH3)2(depe)] (5) and rac‐cis‐[Pt(PPhH⋅BH3)2(depe)] (6).
A Family of Low‐Molecular‐Weight Hydrogelators Based on L‐Lysine Derivatives with a Positively Charged Terminal Group
Authors: Suzuki Masahiro , Yumoto Mariko , Kimura Mutsumi , Shirai Hirofusa , Hanabusa Kenji
Published: December 2002

A family of L‐lysine‐based low‐molecular‐weight compounds with various positively charged terminals (pyridinium and imidazolium derivatives) was synthesized and its gelation behavior in water was investigated. Most of the compounds can be very easily synthesized in high yields (total yields >90 %), and they function as excellent hydrogelators that form hydrogels below 1 wt %; particularly, Nε‐lauroyl‐Nα‐[11‐(4‐tert‐butylpyridinium)undecanoyl]‐L‐lysine ethyl ester (2 c) and Nε‐lauroyl‐Nα‐[11‐(4‐phenylpyridinium)undecanoyl]‐L‐lysine ethyl ester (2 d), which are able to gel water at concentration of only 0.2 wt %. This corresponds to a gelator molecule that entraps more than 20 000 water molecules. All hydrogels are very stable and maintain the gel state for at least 9 months. TEM observations demonstrated that these hydrogelators self‐assemble into a nanoscaled fibrous structure; a three‐dimensional network is then formed by the entanglement of the nanofibers. An FTIR study in [D6]DMSO/D2O and in CHCl3 revealed the existence of intermolecular hydrogen bonding between the amide groups. This was further supported by a 1H NMR study in [D6]DMSO/H2O. A luminescence study, in which ANS (1‐anilino‐8‐naphtharenesulfonic acid) was used as a probe, indicated that the hydrogelators self‐assemble into nanostructures possessing hydrophobic pockets at a very low concentration. Consequently, it was found that the driving forces for self‐assembly into a nanofiber are hydrogel bonding and hydrophobic interactions.
Convenient Syntheses of Fluorous Aryl Iodides and Hypervalent Iodine Compounds: ArI(L)n Reagents That Are Recoverable by Simple Liquid/Liquid Biphase Workups, and Applications in Oxidations of Hydroquinones
Authors: Rocaboy Christian , Gladysz John A.
Published: December 2002

Iodinations of the ortho, meta, and para fluorous arenes (Rf8CH2CH2CH2)2C6H4 (Rf8=(CF2)7CF3) with I2/H5IO6 in AcOH/H2SO4/H2O give 3,4‐(Rf8CH2CH2CH2)2C6H3I (5) and the analogous 2,4‐ (6) and 2,5‐ (7) isomers, respectively. Spectroscopic yields are >90 %, but 5 and 7 must be separated by chromatography from by‐products (yields isolated: 70 %, 97 %, 61 %). Reaction of 1,3,5‐(Rf8CH2CH2CH2)3C6H3 with PhI(OAc)2/I2 gives 2,4,6‐(Rf8CH2CH2CH2)3C6H2I (8) on multigram scales in 97 % yield. The CF3C6F11/toluene partition coefficients of 5–8 (24 °C: 69.5:30.5 (5), 74.7:25.3 (6), 73.9:26.1 (7), 98.0:2.0 (8)) are lower than those of the precursors, but CF3C6F11/MeOH gives higher values (97.0:3.0 (5), 98.6:1.4 (6), 98.0:2.0 (7), >99.3:<0.3 (8)). Reactions of 5–8 with excess NaBO3 in AcOH yield the corresponding ArI(OAc)2 species 9–12 (9, 85 % as a 90:10 9/5 mixture; 10, 97 %; 11, 95 %; 12, 93 % as a 95:5 12/8 mixture). These rapidly oxidize 1,4‐hydroquinones in MeOH. Subsequent additions of CF3C6F11 give liquid biphase systems. Solvent removal from the CF3C6F11 phases gives 5–8 in >99–98 % yields, and solvent removal from the MeOH phases gives the quinone products, normally in >99–95 % yields. The recovered compounds 5–8 are easily reoxidized to 9–12 and used again.
Cover Picture: ChemPhysChem 1/2003
Authors: Petry Renate , Schmitt Michael , Popp Jürgen
Published: December 2002

The cover picture shows a picture of a Mentha × piperita plant, which has a high pharmaceutical relevance. Raman spectra of extremely high spatial resolution have been recorded of this plant by applying etched and silver‐coated glass fiber tips; a method which has been developed in our group within the scope of a BMBF project FKZ 13N7511 located in the framework of Laser‐Biodynamik. On the right, a picture of such a glass fiber tip illuminated by the Raman laser is shown. The fiber tip is brought extremely close to the sample area to be investigated. The picture also shows the Raman spectrum obtained by applying this fiber‐tip technique. This method allows the recording of Raman spectra of biologically relevant samples with an extremely high spatial resolution (200 nm).
Nitric oxide mediates metabolism as well as respiratory and cardiac responses to hypoxia in the snail lymnaea stagnalis
Authors: Taylor Barbara E. , Harris Michael B. , Burk Michele , Smyth Kim , Lukowiak Ken , Remmers John E.
Published: December 2002

Lymnaea stagnalis were exposed to hypoxic and chemical challenges while ventilation, heart rate and metabolism were monitored. Hypoxia increased ventilatory behavior, but this response was eliminated by immersion in 0.75 mM nitric oxide synthase (NOS) inhibitor, 7‐nitroindazole (7 NI). 7 NI also suppressed ventilatory behavior under normoxia. 10.0 mM L‐arginine (ARG, the NOS substrate) increased ventilatory behavior under normoxia, but dampened the hypoxic response. The heart‐rate response to NOS inhibition exhibited dose‐dependent contradictory characteristics. Under both normoxia and hypoxia 0.25 mM 7 NI increased heart rate, while 0.75 mM 7 NI suppressed it. The effect of 0.50 mM 7 NI depended on whether normoxia or hypoxia was coincident; under normoxia 0.50 mM 7 NI increased heart rate, while under hypoxia this concentration suppressed heart rate. Exposure to ARG did not elicit dose‐dependent contradictory responses. Heart rate increased when treated with 10.0 mM ARG under normoxia and hypoxia, while 1.0 mM ARG increased heart rate only under hypoxia. Metabolic responses to NOS inhibition also exhibited dose‐dependent contradictory changes. V·O2 decreased over 60% in response to 0.75 mM 7 NI, and baseline V·O2 was restored when exposure ceased. In contrast, 0.25 mM 7 NI increased V·O2 10%, and the increase continued after exposure ceased. 0.50 mM 7 NI decreased V·O2 40%, but V·O2 increased when exposure ceased. ARG had only the effect of increasing V·O2, and only at 10.0 mM concentration. Based on these results and on NO's known role as a neuromodulator, we conclude that the cardio‐respiratory responses to hypoxia are, in part, mediated by NO. J. Exp. Zool. 295A:37–46, 2003. © 2003, Wiley‐Liss, Inc.
“Some like it shallower” – p‐type doping in SiC
Authors: Deák Peter , Aradi Bálint , Gali Adam , Gerstmann Uwe
Published: December 2002

The usual p‐type dopants of SiC, B, and Al, do not produce really shallow levels. In fact, boron can give rise to a secondary very deep acceptor level as well. The picture is complicated by hydrogen which is readily incorporated during in‐growth doping into p‐type material and can passivate both dopants but to a different degree. First principle calculations are reported regarding the interaction of hydrogen with B and Al in SiC. The results explain why hydrogen is incorporated in much higher amounts into B‐doped than into Al‐doped samples, and also reveal the influences of hydrogen on boron to produce the shallower acceptor. It will be shown that hydrogen incorporation during growth does not influence Al. Finally an Al–N–Al complex is proposed as a shallower acceptor in SiC.
Residual donors in wurtzite GaN homoepitaxial layers and heterostructures
Authors: Neu G. , Teisseire‐Doninelli M. , Morhain C. , Semond F. , Grandjean N. , Beaumont B. , Frayssinet E. , Knap W. , Witowski A. M. , Sadowski M. L. , Leszczynski M. , Prystawko P.
Published: December 2002

Shallow donors in GaN epilayers grown by metalorganic chemical vapour deposition (MOCVD) and by molecular beam epitaxy (MBE) on sapphire, SiC and GaN substrates have been studied by selectively excited photoluminescence (SPL) and far‐infrared (FIR) absorption. The spectroscopic studies of neutral donor bound excitons allow us to determine the D0X rotational excited state spectra in a large domain of tensile and compressive strain fields depending on the substrates used for the growth. The energy transitions between the ground state and the n = 2 states of residual donors are determined from the spectra of the two‐electron replica of D0X lines in accordance with resonant electronic Raman scattering results. The comparison between FIR results and the two‐electron spectroscopy shows, that silicon is the main residual donor (Ed = 30.4 meV in strain‐free samples) in both MOVPE and MBE layers. A second unknown donor (Ed = 31.8 meV) is frequently found in GaN/SiC grown by MOCVD. A third deeper level (Ed = 33.1 meV) is rarely detected by two‐electron spectroscopy but could be associated with a weak neutral‐donor bound exciton shifted down by 0.9 meV from the main SiGa related D0X line in MBE homoepitaxial layers.
Dynamics of trapping on donors and relaxation of the B‐exciton in GaN
Authors: Korona K. P. , Wysmołek A. , Stępniewski R. , Potemski M. , Kuhl J. , Baranowski J. M. , Martinez G. , Grzegory I. , Porowski S.
Published: December 2002

There are three exciton branches in wurzite‐GaN: A, B and C. Here, time‐resolved photoluminescence and magneto‐optic spectroscopy of the B‐exciton are presented, both free (FXB) and bound to donor (D0XB) in homoepitaxial GaN. The free B‐exciton has an energy of about 3.483 eV and a very short lifetime of about 20 ps. The B‐exciton bound to donor (D0XB) has an energy of 3.475 eV and a lifetime longer than the free excitons but shorter than the lifetime of the A‐exciton bound to donor. It is shown that a simple model based on an invariant expression describes properly the behavior of D0XA and D0XB in a magnetic field. Results of resonance excitation experiments suggest that in many cases the process of binding a free exciton to a donor conserves the exciton type and that the relaxation of B‐ to A‐exciton takes place later. Moreover, thermal excitation of D0XA to D0XB has been observed.
The discrimination of the response pattern of inter-phylum phytoplankton diversity to long-term eutrophication trends in Lake Kasumigaura, Japan
Authors: Sugiura N. , Wei B. , Maekawa T.
Published: December 2002

To study the response pattern of phytoplankton to eutrophication, the long-term water chemistry and biological data spanning three phytoplankton phyla and 19 genera were investigated in Lake Kasumigaura, a eutrophic lake in Japan. Fisher' s linear discrimination functions in combination with ecological indexes and a similarity index were used to analyze the relationship between the eutrophic levels (representing with dissolved inorganic nitrogen and total dissolved phosphorus) and the response of the inter-phylum phytoplankton diversity. The algal similarity index was found to characterize the change of eutrophication levels well. Almost 80 percent of eutrophic lake water samples can be correctly discriminated based on the logarithmic cells of phytoplankton genera. However, the ecological indices (number of genera, Margalef' s index, Menhinick' s index, McNaughton' s index, as well as the Shannon' s index and evenness index) failed to predict the change of eutrophic state.
Age Estimates of Globular Clusters in the Milky Way: Constraints on Cosmology
Authors: Krauss Lawrence M. , Chaboyer Brian
Published: January 2003

Recent observations of stellar globular clusters in the Milky Way Galaxy, combined with revised ranges of parameters in stellar evolution codes and new estimates of the earliest epoch of globular cluster formation, result in a 95% confidence level lower limit on the age of the Universe of 11.2 billion years. This age is inconsistent with the expansion age for a flat Universe for the currently allowed range of the Hubble constant, unless the cosmic equation of state is dominated by a component that violates the strong energy condition. This means that the three fundamental observables in cosmology—the age of the Universe, the distance-redshift relation, and the geometry of the Universe—now independently support the case for a dark energy–dominated Universe.
Holocene Deglaciation of Marie Byrd Land, West Antarctica
Authors: Stone John O. , Balco Gregory A. , Sugden David E. , Caffee Marc W. , Sass Louis C. , Cowdery Seth G. , Siddoway Christine
Published: January 2003

Surface exposure ages of glacial deposits in the Ford Ranges of western Marie Byrd Land indicate continuous thinning of the West Antarctic Ice Sheet by more than 700 meters near the coast throughout the past 10,000 years. Deglaciation lagged the disappearance of ice sheets in the Northern Hemisphere by thousands of years and may still be under way. These results provide further evidence that parts of the West Antarctic Ice Sheet are on a long-term trajectory of decline. West Antarctic melting contributed water to the oceans in the late Holocene and may continue to do so in the future.
Escherichia coli
and
Salmonella
2000: the View From Here
Authors: Schaechter Moselio ,   The View From Here Group
Published: January 2003

Five years after the publication of the second edition of the reference book Escherichia coli and Salmonella: Cellular and Molecular Biology, and on the eve of launching a successor venture, the editors and colleagues examine where we stand in our quest for an understanding of these organisms. The main areas selected for this brief inquiry are genomics, evolution, molecular multifunctionality, functional backups, regulation of gene expression, cell biology, sensing of the environment, and ecology.
Sodium Ion Cycle in Bacterial Pathogens: Evidence from Cross-Genome Comparisons
Authors: Häse Claudia C. , Fedorova Natalie D. , Galperin Michael Y. , Dibrov Pavel A.
Published: January 2003

Analysis of the bacterial genome sequences shows that many human and animal pathogens encode primary membrane Na
+
pumps, Na
+
-transporting dicarboxylate decarboxylases or Na
+
-translocating NADH:ubiquinone oxidoreductase, and a number of Na
+
-dependent permeases. This indicates that these bacteria can utilize Na
+
as a coupling ion instead of or in addition to the H
+
cycle. This capability to use a Na
+
cycle might be an important virulence factor for such pathogens as Vibrio cholerae, Neisseria meningitidis, Salmonella enterica serovar Typhi, and Yersinia pestis. In Treponema pallidum, Chlamydia trachomatis, and Chlamydia pneumoniae, the Na
+
gradient may well be the only energy source for secondary transport. A survey of preliminary genome sequences of Porphyromonas gingivalis, Actinobacillus actinomycetemcomitans, and Treponema denticola indicates that these oral pathogens also rely on the Na
+
cycle for at least part of their energy metabolism. The possible roles of the Na
+
cycling in the energy metabolism and pathogenicity of these organisms are reviewed. The recent discovery of an effective natural antibiotic, korormicin, targeted against the Na
+
-translocating NADH:ubiquinone oxidoreductase, suggests a potential use of Na
+
pumps as drug targets and/or vaccine candidates. The antimicrobial potential of other inhibitors of the Na
+
cycle, such as monensin, Li
+
and Ag
+
ions, and amiloride derivatives, is discussed.
Receptors and Entry Cofactors for Retroviruses Include Single and Multiple Transmembrane-Spanning Proteins as well as Newly Described Glycophosphatidylinositol-Anchored and Secreted Proteins
Authors: Overbaugh Julie , Miller A. Dusty , Eiden Maribeth V.
Published: January 2003

In the past few years, many retrovirus receptors, coreceptors, and cofactors have been identified. These molecules are important for some aspects of viral entry, although in some cases it remains to be determined whether they are required for binding or postbinding stages in entry, such as fusion. There are certain common features to the molecules that many retroviruses use to gain entry into the cell. For example, the receptors for most mammalian oncoretroviruses are multiple membrane-spanning transport proteins. However, avian retroviruses use single-pass membrane proteins, and a sheep retrovirus uses a glycosylphosphatidylinositol-anchored molecule as its receptor. For some retroviruses, particularly the lentiviruses, two cell surface molecules are required for efficient entry. More recently, a soluble protein that is required for viral entry has been identified for a feline oncoretrovirus. In this review, we will focus on the various strategies used by mammalian retroviruses to gain entry into the cell. The choice of receptors will also be discussed in light of pressures that drive viral evolution and persistence.
Human Telomerase and Its Regulation
Authors: Cong Yu-Sheng , Wright Woodring E. , Shay Jerry W.
Published: January 2003

The telomere is a special functional complex at the end of linear eukaryotic chromosomes, consisting of tandem repeat DNA sequences and associated proteins. It is essential for maintaining the integrity and stability of linear eukaryotic genomes. Telomere length regulation and maintenance contribute to normal human cellular aging and human diseases. The synthesis of telomeres is mainly achieved by the cellular reverse transcriptase telomerase, an RNA-dependent DNA polymerase that adds telomeric DNA to telomeres. Expression of telomerase is usually required for cell immortalization and long-term tumor growth. In humans, telomerase activity is tightly regulated during development and oncogenesis. The modulation of telomerase activity may therefore have important implications in antiaging and anticancer therapy. This review describes the currently known components of the telomerase complex and attempts to provide an update on the molecular mechanisms of human telomerase regulation.
MECHANICAL TEST PROTOCOLS TO EVALUATE POLYMERIC TRACHEOBRONCHIAL STENTS
Authors: LIM C. S. , ENG P. C. T. , CHIANG W. M. , ANG K. S.
Published: January 2003

Tracheobronchial stents are used in the treatment of inoperable stenoses of the respiratory tracts and their purpose is to restore patency to the stenosed conduits or to provide scaffolding to these channels when they are weak. In this paper, the laboratory protocols to evaluate the mechanical properties of polymeric tracheobronchial stents, such as migration, collapsibility, distending strength and surface finish, are described. These are issues of concern when applying polymeric tracheobronchial stents in the palliation of stenosed airways. Using these test methodologies, comparisons are made between the mechanical properties exhibited by two commercially available polymeric stents and a new prototype polymeric stent.
Synthesis of glucocorticoid-induced leucine zipper (GILZ) by macrophages: an anti-inflammatory and immunosuppressive mechanism shared by glucocorticoids and IL-10
Authors: Berrebi Dominique , Bruscoli Stefano , Cohen Nicolas , Foussat Arnaud , Migliorati Graziella , Bouchet-Delbos Laurence , Maillot Marie-Christine , Portier Alain , Couderc Jacques , Galanaud Pierre , Peuchmaur Michel , Riccardi Carlo , Emilie Dominique
Published: December 2002

Glucocorticoids and interleukin 10 (IL-10) prevent macrophage activation. In murine lymphocytes, glucocorticoids induce expression of glucocorticoid-induced leucine zipper (GILZ), which prevents the nuclear factor κB (NF-κB)–mediated activation of transcription. We investigated whether GILZ could account for the deactivation of macrophages by glucocorticoids and IL-10. We found that GILZ was constitutively produced by macrophages in nonlymphoid tissues of humans and mice. Glucocorticoids and IL-10 stimulated the production of GILZ by macrophages both in vitro and in vivo. Transfection of the macrophagelike cell line THP-1 with the GILZ gene inhibited the expression of CD80 and CD86 and the production of the proinflammatory chemokines regulated on activation normal T-cell expressed and secreted (CCL5) and macrophage inflammatory protein 1α (CCL3). It also prevented toll-like receptor 2 production induced by lipopolysaccharide, interferonγ, or an anti-CD40 mAb, as well as NF-κB function. In THP-1 cells treated with glucocorticoids or IL-10, GILZ was associated with the p65 subunit of NF-κB. Activated macrophages in the granulomas of patients with Crohn disease or tuberculosis do not produce GILZ. In contrast, GILZ production persists in tumor-infiltrating macrophages in Burkitt lymphomas. Therefore, GILZ appears to play a key role in the anti-inflammatory and immunosuppressive effects of glucocorticoids and IL-10. Glucocorticoid treatment stimulates GILZ production, reproducing an effect of IL-10, a natural anti-inflammatory agent. The development of delayed-type hypersensitivity reactions is associated with the down-regulation of GILZ gene expression within lesions. In contrast, the persistence of GILZ gene expression in macrophages infiltrating Burkitt lymphomas may contribute to the failure of the immune system to reject the tumor.
Treatment models for those with severe mental illness and comorbid personality disorder
Authors: Tyrer Peter , Simmonds Shaeda
Published: December 2002

Background

Dual diagnosis of personality disorder and severe mental illness is an important clinical association that has been under-researched with regard to clinical management.

Aims

To compare the outcomes of differenttreatment models.

Method

The outcome of patients with this combined diagnosis was compared in a systematic review of three randomised controlled trials in which different forms of community outreach treatment or intensive case management were compared with standard care.

Results

The results from the three studies showed that the outcome of comorbid diagnoses was worse than that of single diagnoses. Although assertive approaches reduced in-patient care, they sometimes did so at the expense of increasing social dysfunction and behavioural disturbance.

Conclusions

For those with comorbid severe mental illness and personality disorder, the policy of assertive outreach and care in community settings may be inappropriate for both public and patients unless modified to take account of the special needs of this group.
Emergent Nanostructures: Water‐Induced Mesoscale Transformation of Surfactant‐Stabilized Amorphous Calcium Carbonate Nanoparticles in Reverse Microemulsions
Authors: Li M. , Mann S.
Published: December 2002

The water‐induced crystallization of alkylbenzenesulfonate‐coated amorphous calcium carbonate (ACC) nanoparticles in water‐in‐isooctane sodium bis(2‐ethylhexyl)sulfosuccinate (NaAOT) microemulsions at a [H2O]/[NaAOT] molar ratio (w) of 10:1 produces a range of organized hybrid surfactant–vaterite nanostructures depending on the water droplet/ACC nanoparticle number ratio,n = [H2O]/[CaCO3]. The crystalline nanostructures develop within primary aggregates of the surfactant‐stabilized ACC nanoparticles by in situ mesoscale transformation, which is mediated by the extent of coupling at the surfactant–inorganic interface. Strong coupling in the presence of low amounts of water (n = 34) gives monodisperse spheroidal aggregates of densely packed 5 nm diameter surfactant‐coated vaterite nanoparticles, whereas weak interactions atn = 3400 produce discrete vaterite nanoparticles, 130 nm in size. Significantly, intermediate levels of coupling produce anisotropic nanostructures such as spindle‐shaped aggregates of 18 nm sized surfactant‐coated vaterite nanoparticles (n = 170) and high‐aspect‐ratio bundles of co‐aligned 10 nm wide twisted vaterite nanofilaments (n = 340). Adding excess aqueous CO32–to the microemulsion droplets inhibits the growth of the nanofilaments, whereas excess Ca2+has no effect. The results show that the transformation pathways are determined by the extent of water penetration into the ACC cores and electrostatic interactions at the mineral–surfactant interface, and indicate that complex hybrid nanostructures can be assembled in situ when these processes are coupled synergistically at the mesoscopic level. Such observations could be of generic importance in nanochemistry and biomineralization.
Lasing From a Förster Transfer Fluorescent Dye Couple Dissolved in a Chiral Nematic Liquid Crystal
Authors: Chambers M. , Fox M. , Grell M. , Hill J.
Published: December 2002

Förster exciton transfer from a ’sensitizer’ to an ’emitter’ dye allows for the decoupling of the excitation and emission processes in dye lasers. Here, we report on the lasing from a Förster transfer couple dissolved in an unconventional, mirrorless resonator; namely, a chiral nematic liquid crystal (CNLC). We found optically pumped lasing at a threshold as low as 2.1 J m–2. We also demonstrate simultaneous lasing at two widely separated wavelengths.
Non‐Covalent Chemistry on Surface‐Confined, Isolated Dendrimers
Authors: van Manen H.‐J. , Auletta T. , Dordi B. , Schönherr H. , Vancso G.J. , van Veggel F.C.J.M. , Reinhoudt D.N.
Published: December 2002

A “bottom‐up” fabrication of nanometer‐scale dendritic structures via the growth of isolated, nanosized supramolecular structures on gold surfaces is presented. A novel dendritic wedge containing peripheral pyridines and a focal dialkylsulfide chain (9) was synthesized and its coordination chemistry in solution was tested with a second‐generation Fréchet dendron functionalized with a focal SCS PdII pincer moiety (13). Replacement of the labile acetonitrile in 13 by the pyridine groups of 9 converts dendritic wedge 9 into fourth‐generation metallodendron 9 · 134 in one step. Based on these results the spatially confined growth on a gold surface was studied. The dendritic molecules with reactive pyridine groups at the periphery (9) were first spatially isolated by inserting them into decanethiol self‐assembled monolayers (SAMs) on a gold surface. Subsequently, the peripheral pyridines were reacted via metal–ligand coordinative interactions by exposing the monolayer to a solution of dendritic wedges containing focal SCS PdII pincer moieties (13). The isolated molecules inserted into the original SAM in the first step were resolved by ex‐situ tapping‐mode atomic force microscopy (TM‐AFM). The subsequent PdII–pyridine coordination resulted in a significant increase in size of the individually resolved molecules. Reference experiments demonstrated that the increased size of the isolated dendrimers on the gold substrate was a result of specific metal–ligand interactions. The methodology presented herein allows the creation of surface‐confined architectures and potentially provides a viable complement to currently employed “top‐down” methods in nanofabrication.
Fine‐Tuning of the Chromaticity of the Emission Color of Organic–Inorganic Hybrids Co‐Doped with EuIII, TbIII, and TmIII
Authors: Carlos L.D. , Sá Ferreira R.A. , Rainho J.P. , de Zea Bermudez V.
Published: December 2002

A fine‐tuning of the emission chromaticity from red to green is reported for organic–inorganic nanostructured hybrids co‐doped with Eu3+, Tb3+, and Tm3+. Raising the temperature from 200 to 300 K changes the color coordinates smoothly from the yellowish–green region of the chromaticity diagram towards the red. This is discussed in terms of thermally activated energy‐transfer mechanisms from Tb3+ energy states to the hybrid’s emitting levels.
Fabricating Ordered Voids in a Colloidal Crystal Film–Substrate System by Using Organic Liquid Patterns as Templates
Authors: Lu G. , Chen X. , Yao J. , Li W. , Zhang G. , Zhao D. , Yang B. , Shen J.
Published: December 2002

A colloidal crystal film–substrate system with ordered voids has been fabricated using a combination of microcontact printing, self‐organization of organic liquid on the patterned self‐assembled monolayers, and a vertical deposition technique. The Figure shows an SEM image of the bottom surface of a colloidal crystal film that had been peeled off the substrate after the solvent has evaporated.
A Combined Top–Down/Bottom–Up Approach to the Microscopic Localization of Metallic Nanodots
Authors: Spatz J.P. , Chan V.Z.‐H. , Mößmer S. , Kamm F.‐M. , Plettl A. , Ziemann P. , Möller M.
Published: December 2002

Periodic and aperiodic two‐dimensional nanostructures with hierarchical order have been prepared by a combined top–down/bottom–up approach. This method allows 7 nm nanoparticles to be positioned with a accuracy of 10 nm or less, with a separation distance of several micrometers. The Figure is an optical dark field microscopy image of a square arrangement of Au dots on a Si wafer.
Conjugated Polymer Inverse Opals for Potentiometric Biosensing
Authors: Cassagneau T. , Caruso F.
Published: December 2002

Colloidal crystals of poly(styrene) spheres can be used as templates to fabricate a conjugated polymer inverse opal potentiometric biosensor (see Figure) incorporating an enzyme. After core removal, a seven‐fold increase in sensitivity relative to conventional films is measured for analyte concentrations varying from 1 to 100 μM. The presence of large pores enables the formation of a Schottky junction, which governs the sensing response.
Growth and Optical Properties of Self‐Organized Au2Si Nanospheres Pea‐Podded in a Silicon Oxide Nanowire
Authors: Wu J.S. , Dhara S. , Wu C.T. , Chen K.H. , Chen Y.F. , Chen L.C.
Published: December 2002

Silicon‐based nanowires with embedded self‐assembled chains of gold silicide nanospheres (Au2Si@SiONW) have been prepared by annealing Si/Au bilayers. The diameter, number density, and length of the wires can be controlled by adjusting the bilayer thickness. The composite material displayed a new sharp photoluminescence peak thought to result from inter‐band transitions in the “pea‐podded” (see Figure) gold silicide crystals.
Surface‐Specific Zeolite‐Binding Proteins
Authors: Nygaard S. , Wendelbo R. , Brown S.
Published: December 2002

Proteins that distinguish the crystallographic planes of zeolites have been identified. On EMT zeolite the proteins obscure only the (001) face and are able to immobilize an enzyme with negligible loss of activity (see dye‐exclusion assay, Figure). A general method for isolating proteins able to distinguish spatial orientations of atoms on non‐biological surfaces is described.