bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of pasture vs. concentrate diet on CLA isomer distribution in different tissue lipids of beef cattle
Authors: Dannenberger Dirk , Nuernberg Karin , Nuernberg Gerd , Scollan Nigel , Steinhart Hans , Ender Klaus
Published: November 2006

This study examined the effects of feeding pasture vs. concentrate on the distribution of CLA isomers in the lipids of longissimus and semitendinosus muscle, liver and heart muscle, and subcutaneous fat in beef bulls. Sixty‐four German Holstein and German Simmental bulls were randomly allocated to either an indoor concentrate system or periods of pasture feeding followed by a finishing period on a concentrate containing linseed to enhance their beef content of n−3 PUFA and CLA. The concentrations of CLA isomers in the different tissues were determined by GC and silver ion HPLC. The diet affected the distribution of individual CLA isomers in the lipids of the different tissues. The concentration (mg/100 g fresh tissue) of the most prominent isomer, cis‐9,trans‐11 18∶2, was increased up to 1.5 times in liver and heart tissue of bulls fed on pasture as compared with concentrate. However, no diet effect was observed for cis‐9,trans‐11 18∶2 in the lipids of longissimus muscle and subcutaneous fat. In all tissues, the second‐most abundant CLA isomer in concentratefed bulls was trans‐7,cis‐9 18∶2. In contrast, trans‐11,cis‐13 18∶2 was the second‐most abundant CLA isomer in all investigated tissue lipids of pasture‐fed bulls. The concentration of the trans‐11,cis‐13 18∶2 isomer was up to 15 times higher in tissues of pasture‐fed bulls as compared with concentrate‐fed animals. Furthermone, diet affected the concentrations of the CLA trans,trans 18∶2 isomers. Pasture feeding significantly increased the concentrations of some trans,trans 18∶2 isomers as compared with concentrate, predominantly trans‐12,trans‐14 18∶2 and trans‐11,trans‐13 18∶2. Overall, pasture feeding resulted in significantly increased concentrations of the sum of CLA isomers in the lipids of longissimus, muscle, subcutaneous fat, heart and liver muscle of German Holstein and German Simmental bulls, but not in semitendinosus muscle.
Kinetics of 14C distribution after tracer dose of 14C‐lutein in an adult woman
Authors: de Moura Fabiana F. , Ho Charlene C. , Getachew Girma , Hickenbottom Sabrina , Clifford Andrew J.
Published: November 2006

Lutein is an oxygenated carotenoid (xanthophyll) found in dark green leafy vegetables. High intakes of lutein may lower the risk of age‐related macular degeneration. Current understanding of human lutein metabolism as it might occur in vivo is incomplete. Therefore, we conducted a feasibility study where we dosed a normal adult woman with 14C‐lutein (125 nmol, 36 nCi 14C), dissolved in olive oil (0.5 g/kg body weight) and mixed in a banana shake. Blood, urine, and feces collected before the dose was administered served to establish baseline values. There‐after, blood was collected for 63 d following the dose, while feces and urine were collected for 2 wk post‐dose. The 14C contents in plasma, urine, and feces were measured by accelerator MS. The 14C first appeared in plasma 1 h after dosing and reached its highest level,≈2.08% of dose/L plasma, at 14 h post‐dose. The plasma pattern of 14C did not include a chylomicrons/VLDL (intestinal) peak like that when the same subject received 14C‐β‐carotene (a previous test), suggesting that lutein was handled differently from β‐carotene by plasma lipoproteins. Lutein had an elimination half‐life (t1/2) of≈10 d. Forty‐five percent of the dose of 14C was eliminated in feces and 10% in urine in the first 2 d after dosing. Quantifying human lutein metabolism is a fertile area for future research.
Inhibition of 12‐ and 15‐lipoxygenase activities and protection of human and tilapia low density lipoprotein oxidation by I‐Tiao‐Gung (Glycine tomentella)
Authors: Chen Tsui‐Yao , Shiao Ming‐Shi , Pan Bonnie Sun
Published: November 2006

I‐Tiao‐Gung, Glycine tomentella, has been used extensively as a traditional herbal medicine to relieve physical pain, but its bioactivity has not been studied systematically. Ninety‐five percent ethanol extracts of G. tomentella (GT‐E) showed antioxidant activity in human plasma by prolonging the lag phase (+Tlag) of Cu2+‐induced, LDL oxidation and were dose dependent. The+Tlag of LDL combined with 3.2 μg/mL GT‐E was similar to that with 2.0 μM (ca. 0.5 μg/mL) Trolox. A similar inhibitory effect was found toward tilapia plasma LDL. In addition, GT‐E inhibited tilapia thrombocyte (nucleated platelet), 5‐, 12‐, and 15‐lipoxygenase (LOX). The IC50 values were 0.43, 0.72, and 0.42 μg/mL, respectively, whereas the IC50 values for nordihydroguaiaretic acid (NDGA) on 5‐, 12‐, and 15‐LOX were 2.3, 1.6, and 1.7 μg/mL, respectively. The IC50 value for cyclooxygenase‐2 (COX‐2) inhibition by GT‐E was 42.0 μg/mL, whereas the IC50 value by indomethacin as a positive control was 0.61 μg/mL. The prevention of LDL oxidation and the dual inhibition of LOX and COX‐2 are indicative of the possible roles of I‐Tiao‐Gung in antiatherosclerosis and anti‐inflammation.
Influence of stearic acid on postprandial lipemia and hemostatic function
Authors: Sanders Thomas A. B. , Berry Sarah E. E.
Published: November 2006

It has been suggested that fats rich in stearic acid may result in exaggerated postprandial lipenia and have adverse effects on hemostatic function. The effects of test meals containing different saturated and monounsaturated FA were compared in healthy subjects in a series of studies to investigate this hypothesis. Stearic acid, when present as cocoa butter, resulted in similar postprandial lipemia and factor VII activation compared with a meal containing high‐oleic sunflower oil. Stearic acid when presented as shea butter or as randomized stearate‐rich TAG resulted in decreased postprandial lipemia and decreased postprandial activation of factor VII. Stearic acid‐rich test meals did not result in impaired fibrinolytic activity compared with either a lowfat meal or a meal high in oleate. The difference in responses between the different stearic acid‐rich fats appears to be due to varying solid fat contents of the fats at 37°C.
Dietary long‐chain PUFA in the form of TAG or phospholipids influence lymph lipoprotein size and composition in piglets
Authors: Amate Laura , Gil Angel , Ramírez María
Published: November 2006

Several sources of long‐chain PUFA (LCP) are currently available for infant formula supplementation. These oils differ in their FA composition, the chemical form of the FA esters [TAG or phospholipids (PL)], and presence of other lipid components. These differences may affect LCP absorption, distribution, and metabolic fate after ingestion. The purpose of this study was to evaluate the influence of different chemical forms of dietary LCP on the composition of lymph lipoproteins. Eighteen pigs (5 d old) were bottle‐fed different diets for 2 wk: a control diet (C), a diet containing LCP as TAG from tuna and fungal oils (TF‐TAG), or a diet containing LCP as PL from egg yolk (E‐PL). We measured lipid and FA composition of lymph, main lymph fractions (TAG or PL), and the particle size of lymph lipoproteins. The average diameter of lymph lipoproteins was significantly lower in the E‐PL group compared with the control and TF‐TAG groups (C: 3902±384 Å; TF‐TAG: 3773±384 Å; E‐PL: 2370±185 Å). Arachidonic acid and DHA contents in lymph and lymph‐TAG were significantly higher in the TF‐TAG group compared to the E‐PL group (0.50±0.03 and 0.24±0.03 g/100 g vs. 0.29±0.04 and 0.12±0.03 g/100 g, respectively). The addition to the diet of LCP in the form of TAG or PL affected the size of intestinal lipoproteins and also led to a different distribution of these FA in lymph lipoproteins.
Lipase‐catalyzed hydrolysis of TG containing acetylenic FA
Authors: Lie Ken Iie Marcel S. F. , Fu Xun , Lau Maureen M. L. , Chye M. L.
Published: November 2006

Hydrolysis of symmetrical acetylenic TG of type AAA [viz., glycerol tri‐(4‐decynoate), glycerol tri‐(6‐octadecynoate), glycerol tri‐(9‐octadecynoate), glycerol tri‐(10‐undecynoate), and glycerol tri‐(13‐docosynoate)] in the presence of eight microbial lipases was studied. Novozyme 435 (Candida antarctica), an efficient enzyme for esterification, showed a significant resistance in the hydrolysis of glycerol tri‐(9‐octadecynoate) and glycerol tri‐(13‐docosynoate). Hydrolysis of acetylenic TG with Lipolase 100T (Humicola lanuginosa) was rapidly accomplished. Lipase PS‐D (Pseudomonas cepacia) showed a fair resistance toward the hydrolysis of glycerol tri‐(6‐octadecynoate) only, which reflected its ability to recognize the Δ6 positional isomer of 18∶1. Lipase CCL (Candida cylindracea, syn. C. rugosa) and AY‐30 (C. rugosa) were able to catalyze the release of 10‐undecynoic acid and 9‐octadecynoic acid from the corresponding TG, but less readily the 13‐docosynoic acid in the case of glycerol tri‐(13‐docosynoate). The two lipases CCL and AY‐30 were able to distinguish the small difference in structure of fatty acyl moieties in the TG substrate. To confirm this trend, three regioisomers of mixed acetylenic TG of type ABC (containing one each of Δ6, Δ9, and Δ13 acetylenic FA in various positions) were prepared and hydrolyzed with CCL and AY‐40. The results reconfirmed the observation that AY‐30 and CCL were able to distinguish the slight differences in the molecular structure (position of the acetylenic bond and chain length) of the acyl groups in the TG during the hydrolysis of such TG substrates.
Gas chromatographic quantification of fatty acid methyl esters: Flame ionization detection vs. Electron impact mass spectrometry
Authors: Dodds Eric D. , McCoy Mark R. , Rea Lorrie D. , Kennish John M.
Published: November 2006

The determination of FAME by GC is among the most commonplace analyses in lipid research. Quantification of FAME by GC with FID has been effectively performed for some time, whereas detection with MS has been used chiefly for qualitative analysis of FAME. Nonetheless, the sensitivity and selectivity of MS methods advocate a quantitative role for GC‐MS in FAME analysis—an approach that would be particularly advantageous for FAME determination in complex biological samples, where spectrometric confirmation of analytes is advisable. To assess the utility of GC‐MS methods for FAME quantification, a comparative study of GC‐FID and GC‐MS methods has been conducted. FAME in prepared solutions as well as a biological standard reference material were analyzed by GC‐FID and GC‐MS methods using both ion trap and quadrupole MS systems. Quantification by MS, based on total ion counts and processing of selected ions, was investigated for FAME ionized by electron impact. Instrument precision, detection limits, calibration behavior, and response factors were investigated for each approach, and quantitative results obtained by each technique were compared. Although there were a number of characteristic differences between the MS methods and FID with respect to FAME analysis, the quantitative performance of GC‐MS compared satisfactorily with that of GC‐FID. The capacity to combine spectrometric examination and quantitative determination advances GC‐MS as a powerful alternative to GC‐FID for FAME analysis.
Low pH enhances the transfer of carotene from carrot juice to olive oil
Authors: Rich Gillian T. , Fillery‐Travis Annette , Parker Mary L.
Published: November 2006

A current model for carotenoid transport and absorption in the gut proposes an initial solubilization in the oil phase of dietary emulsions followed by incorporation of the carotenoids in mixed bile salt micelles. To assess the relevance of the first stage of this model to what is observed in vivo we have examined the transfer of carotene from carrot juice to olive oil. Increased acidity enhanced the transfer from both whole juice and carotene crystals isolated from both whole juice and carotene crystals isolated from carrot chromoplasts. The transfer was significantly slower from whole juice. By using exogenous β‐carotene and measuring its transfer to oil in the presence and absence of carrot juice we have demonstrated that the inhibition of the transfer in juice arises, at least in part, from soluble juice factors. The inhibition is relieved by a fall in pH, which leads to lowering of the electric potential at the oil/aqueous phase interface and aggregation of carrot tissue including crystalline carotene. Under conditions of low pH, oil droplets adhere to the tissue aggregates, allowing carotene to pass into the oil. Our results provide an explanation for why carotene absorption in vivo is depressed by conditions of low gastric acidity.
GD3 and GM2 synthase activities in rat testes during the period of sexual development
Authors: Gamallo Juana L. G. T. , Trindade Vera M. T. , Bernard Elena A.
Published: November 2006

Activities of two key enzymes of gangliosides biosynthesis were determined in rat testes during development. GD3 synthase activity was low and showed small variations with age. GM2 synthase activity increased 10‐fold in testes from 10‐ to 30‐d‐old animals, showing a maximum activity at 30 d, followed by a small decrease until 45 d and then a constant activity up to adulthood. These developmental changes in the activity of both glycosyltransferases were related to the increasing complexity in the ganglioside pattern observed in rats testes during the period of sexual development.
Visfatin is present in bovine mammary epithelial cells, lactating mammary gland and milk, and its expression is regulated by cAMP pathway
Authors: Yonezawa Tomo , Haga Satoshi , Kobayashi Yosuke , Takahashi Tatsuyuki , Obara Yoshiaki
Published: November 2006

Visfatin was originally identified as a growth factor for immature B cells, and recently demonstrated to bind insulin receptor. Visfatin mRNA and protein were detected by RT‐PCR and Western blot analysis in cloned bovine mammary epithelial cells, lactating bovine mammary gland and human breast cancer cell line, MCF‐7. Immunocytochemical staining localized the visfatin protein in the cytosol and nucleus of both cells. Quantitative‐RT‐PCR analysis revealed that the expression of the visfatin mRNA was significantly elevated when treated with forskolin (500 μM), isopreterenol (1–10 μM) and dibutyric cyclic AMP (1 mM) for 24 h, and significantly reduced when treated with insulin (5–50 ng/ml) and dexsamethasone (0.5–250 nM) for 24 h. These results indicate that mammary epithelial cells express the visfatin protein and secrete them into the milk.
LEVELS AND DIFFERENTIALS IN CHILDHOOD MORTALITY IN SOUTH AFRICA, 1977–1998
Authors: NANNAN NADINE , TIMÆUS IAN M. , LAUBSCHER RIA , BRADSHAW DEBBIE
Published: November 2006

This study uses the 1996 Census and the 1998 Demographic and Health Survey (DHS) to investigate the level of and trend in infant and child mortality and their covariates in South Africa. Census estimates of childhood mortality are higher than those from the DHS. Analysis suggests that the former overestimate mortality while the latter are probably slightly too low. Both inquiries document a reversal of the trend toward lower mortality in the 1990s. Under-five mortality increased by about a third during the five years up to early 1998. By then the infant mortality rate was about 55 per 1000 and under-five mortality 72 per 1000. Other factors may explain the tapering off of the decline in mortality after the late 1980s but AIDS deaths account for its increase. Inequalities in childhood mortality between population groups, rooted in past discriminatory apartheid policies, shrank between the late-1970s and mid-1990s. However, they remain substantial and are largely unaccounted for by province, metropolitan residence and inter-group differences in mothers’ education. The HIV/AIDS epidemic is likely to offset the beneficial impact of post-apartheid pro-poor policies and may exacerbate racial differences in childhood mortality in South Africa. There is an urgent need to improve the routine collection of statistics to monitor child mortality so as to assess progress towards the Millennium Development Goals and track inequalities.
Extending from PARs inCaenorhabditis elegansto homologues inHaemonchus contortusand other parasitic nematodes
Authors: NIKOLAOU S. , GASSER R. B.
Published: November 2006

Signal transduction molecules play key roles in the regulation of developmental processes, such as morphogenesis, organogenesis and cell differentiation in all organisms. They are organized into ‘pathways’ that represent a coordinated network of cell-surface receptors and intracellular molecules, being involved in sensing environmental stimuli and transducing signals to regulate or modulate cellular processes, such as gene expression and cytoskeletal dynamics. A particularly important group of molecules implicated in the regulation of the cytoskeleton for the establishment and maintenance of cell polarity is the PAR proteins (derived frompartition defective in asymmetric cell division). The present article reviews salient aspects of PAR proteins involved in the early embryonic development and morphogenesis of the free-living nematodeCaenorhabditis elegansand some other organisms, with an emphasis on the molecule PAR-1. Recent advances in the knowledge and understanding of PAR-1 homologues from the economically important parasitic nematode,Haemonchus contortus, of small ruminants is summarized and discussed in the context of exploring avenues for future research in this area for parasitic nematodes.
Abdominal aortic aneurysm in association with horseshoe kidney
Authors: Papavassiliou  , Douvas  , Xanthopoulos  , Loupou  , Dervisis  , Arvanitis
Published: November 2006

We report the preoperative diagnosis and surgical treatment of an abdominal aortic aneurysm (AAA) in association with a horseshoe kidney (HSK) in a 70-year-old man. Through a median laparotomy a vascular tube graft was successfully used for repair the AAA. The extensive parenchymal isthmus overlying the aneurysm remained intact.
Akute Extremitätenischämie als Erstsymptom eines gedeckt rupturierten, thrombosierten Pseudoaneurysmas eines undifferenziertem pleomorphen high grade Sarkoms der Arteria iliaca externa
Authors: Karl  , Nagel  , Storck
Published: November 2006

Eine sehr seltene Ursache einer akuten Extremitätenischämie stellen maligne, primäre Gefäßwandtumoren dar. Aufgrund der Rarität des Krankheitsbildes und der unspezifischen Symptomatik wird die Diagnose meist erst postoperativ oder post mortem gestellt. Maligne Gefäßwandtumoren sollten daher insbesondere bei Patienten mit einer akuten Ischämie ohne typische Anamnese und fehlende kardiovaskuläre Risikofaktoren in die differentialdiagnostischen Überlegungen miteinbezogen werden. Die Prognose maligner Gefäßwandtumoren ist schlecht. Ein kurativer Therapieansatz besteht nur in der radikalen chirurgischen Exstirpation und gleichzeitiger Wiederherstellung der arteriellen Gefäßstrombahn. Multimodale Therapiekonzepte sollten im Rahmen einer adjuvanten oder palliativen Behandlung im Rahmen einer Tumorkonferenz festgelegt werden. Wir berichten erstmals über den Fall eines gedeckt rupturierten « Pseudoaneurysmas « der Arteria iliaca externa aufgrund eines undifferenzierten pleomorphen high- grade Sarkoms der Arterienwand als Ursache einer akuten Extremitätenischämie bei einem 70-jährigen männlichen Patienten. Bereits zum Zeitpunkt der Erstoperation bestand eine diffuse Skelettmetastasierung, die jedoch erst im Rahmen der postoperativen Staging Untersuchungen diagnostiziert wurde. Aufgrund der bereits bestehenden Metastasierung sowie des weiteren Verlaufs wurde keine Chemotherapie durchgeführt. Der Patient verstarb 5 Monate postoperativ an den Folgen der disseminierten Tumorerkrankung mit Lungen- und Lebermetastasen.
Depth‐to‐the‐bottom optimization for magnetic data inversion: Magnetic structure of the Latium volcanic region, Italy
Authors: Caratori Tontini F. , Cocchi L. , Carmisciano C.
Published: November 2006

We present an algorithm for the linear inversion of two‐dimensional (2‐D) surface magnetic data to obtain 3‐D models of the susceptibility of the source. The forward model is discretized by a mesh of prismatic cells with constant magnetization that allows the recovery of a complete 3‐D generating source. As the number of cells are normally greater than the amount of available data, we have to solve an underdetermined linear inverse problem. A Tikhonov regularization of the solution is introduced as a depth‐weighting function adapted from Li and Oldenburg (1996) to close the source toward the bottom. The main novelty of this method is a first‐stage optimization that gives information about the depth to the bottom of the generating source. This parameter permits both the evaluation of the appropriate vertical extension of the mesh and the definition of the shape of the regularizing depth‐weighting distribution. After discussing the performance of this method by showing the results of various synthetic tests, we invert the magnetic anomalies of the volcanic edifices in the Latium region in central Italy to define their 3‐D source distribution.
Characterization of terminal impedance and radiation properties of a horizontal VLF antenna over Antarctic ice
Authors: Chevalier T. W. , Inan U. S. , Bell T. F.
Published: November 2006

Measurements of the input impedance of two very low frequency (VLF) transmitters in Antarctica are used to validate existing dielectric models for the ice substrate at these frequencies. Using a finite difference time domain approach, Maxwell's equations are solved in the presence of dispersive media, representing the layers of ice which form the Antarctic ice sheet as a single‐pole Debye material. This model provides simulated input impedance values in good agreement with measured data for both the South Pole beacon and the former Siple Station VLF transmitters. Using the validated simulation tool, the radiation characteristics of the South Pole beacon VLF transmitter are characterized. Results for the radiation resistance, efficiency, and far‐field pattern are provided for the current South Pole transmitter. The power pattern for a two‐element array is also determined.
Temporal and spatial changes of permafrost in Canada since the end of the Little Ice Age
Authors: Zhang Yu , Chen Wenjun , Riseborough Daniel W.
Published: November 2006

Climate warming was significant from the mid‐19th century to the mid‐20th century and in recent decades at most northern high latitudes. Climate warming could induce permafrost degradation, which may have important impacts on hydrological, ecological, and biogeochemical processes and on northern communities and infrastructure. To assess the effects of climate change on permafrost, a process‐based model of Northern Ecosystem Soil Temperature (NEST) was developed and utilized to simulate the ground thermal regime of the Canadian landmass at a resolution of a half‐degree latitude‐longitude since the end of the Little Ice Age (circa 1850). The simulated southern boundary of the permafrost for recent decades is similar to that of the current published map, and the simulated active layer thickness and the depth to permafrost base are comparable to site measurements. Simulation results show that climate change since the end of the Little Ice Age, especially during the 20th century, has induced degradation of permafrost in most of Canada: From the 1850s to the 1990s, the area underlain by permafrost was reduced by 5.4%; for those areas where permafrost existed in all the years throughout the period 1850–2002, the mean depth to the base of permafrost decreased (became shallower) by 3 m; the mean active layer thickness increased by 0.21 m, or 34%; and the mean depth to permafrost table increased by 0.39 m. Results also show that suprapermafrost taliks were formed and became larger and more frequent with climate warming in the southern permafrost region, which greatly enhanced permafrost thaw from the top and could have severe impacts on the landscape, hydrology, and ecosystems.
1
∕
f
noise in metallic and semiconducting carbon nanotubes
Authors: Reza Shahed , Huynh Quyen T. , Bosman Gijs , Sippel-Oakley Jennifer , Rinzler Andrew G.
Published: November 2006

The charge transport and noise properties of three terminal, gated devices containing multiple single-wall metallic and semiconducting carbon nanotubes were measured at room temperature. Applying a high voltage pulsed bias at the drain terminal the metallic tubes were ablated sequentially, enabling the separation of measured conductance and 1∕f noise into metallic and semiconducting nanotube contributions. The relative low frequency excess noise of the metallic tubes was observed to be two orders of magnitude lower than that of the semiconductor tubes.
Characterization of indium tin oxide surfaces and interfaces using low intensity x-ray photoemission spectroscopy
Authors: Yi Y. , Lyon J. E. , Beerbom M. M. , Schlaf R.
Published: November 2006

Ultraviolet photoemission spectroscopic (UPS) and x-ray photoemission spectroscopic (XPS) characterizations of indium tin oxide (ITO) surfaces prepared in ambient environment significantly lower the work function of the ITO surface. This artifact complicates the investigation of ITO surfaces and interfaces using XPS and UPS. The presented results demonstrate that, while the exposure of the sample surface to standard UPS UV sources results in a reduction of the work function within a second or less, XPS measurements show a more gradual work function change over the course of hundreds of seconds. This allowed the design of a measurement protocol based on low intensity x-ray photoelectron spectroscopy work function measurements, which do not cause significant work function changes during the exposure time needed for characterization. Applying this technique, the orbital lineup between the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital of the semiconducting polymer poly(3-hexylthiophene) (P3HT) and the valence and conduction bands of ITO were determined. The results indicate that it is appropriate to describe the ITO/P3HT junction as semiconductor heterojunction, and that hole injection most likely occurs between ITO conduction band minimum and P3HT HOMO.
Kinetic properties and magnetic susceptibility of La0.825Sr0.175MnO3 under hydrostatic pressure
Authors: Itskevich E. S. , Kraĭdenov V. F. , Kuz’min S. M.
Published: November 2006

The magnetic susceptibility χ, thermopower α, and resistivity ρ of single crystals of the manganate La0.825Sr0.175MnO3 are investigated in the temperature interval 77–300K and at pressures to 14kbar. All of these measurements reveal the presence of a transition to a ferromagnetic metallic state at TC≈280K and a structural transition at Tstr≈200K. The pressure coefficients of these transition temperatures are found to be ∂TC∕∂P=+1.3K∕kbar and ∂Tstr∕∂P=−6.3K∕kbar. The thermopower α(T) is everywhere positive, has a domelike shape, and decreases with increasing pressure. On the χ(T) curve at T≈100K there is a feature that is shifted to lower temperatures under pressure (∂TM∕∂P=−5.8K∕kbar). The physical cause of this feature is discussed.
Double-pulse THz radiation bursts from laser-plasma acceleration
Authors: Bosch R. A.
Published: November 2006

A model is presented for coherent THz radiation produced when an electron bunch undergoes laser-plasma acceleration and then exits axially from a plasma column. Radiation produced when the bunch is accelerated is superimposed with transition radiation from the bunch exiting the plasma. Computations give a double-pulse burst of radiation comparable to recent observations. The duration of each pulse very nearly equals the electron bunch length, while the time separation between pulses is proportional to the distance between the points where the bunch is accelerated and where it exits the plasma. The relative magnitude of the two pulses depends upon by the radius of the plasma column. Thus, the radiation bursts may be useful in diagnosing the electron bunch length, the location of the bunch’s acceleration, and the plasma radius.
New diamond cell for single-crystal x-ray diffraction
Authors: Boehler Reinhard
Published: November 2006

A new design for a high-precision diamond cell is described. Two kinematically mounted steel disks are elastically deflected to generate pressure. This principle provides higher precision in the diamond anvil alignment than most sliding piston-cylinder or guide-pin devices at significantly lower cost. With this new diamond cell conical diamond anvils with an x-ray aperture of 85° were successfully tested to over 50GPa using helium as a pressure medium. Anvil thickness of less than 1.4mm provides high x-ray transmission and low background, a significant improvement compared to beryllium or diamond-disk backing plates. Because the diamond anvils are supported by tungsten carbide seats, samples and pressure media can be annealed by external or laser heating to provide hydrostatic pressure conditions.
Manipulating spin-dependent interactions in rotationally excited cold molecules with electric fields
Authors: Tscherbul T. V. , Krems R. V.
Published: November 2006

We use rigorous quantum mechanical theory to study collisions of magnetically oriented cold molecules in the presence of superimposed electric and magnetic fields. It is shown that electric fields suppress the spin-rotation interaction in rotationally excited Σ2 molecules and inhibit rotationally elastic and inelastic transitions accompanied by electron spin reorientation. We demonstrate that electric fields enhance collisional spin relaxation in Σ3 molecules and discuss the mechanisms for electric field control of spin-changing transitions in collisions of rotationally excited CaD(Σ2) and ND(Σ3) molecules with helium atoms. The propensities for spin depolarization in the rotationally excited molecules are analyzed based on the calculations of collision rate constants at T=0.5K.
Effect of hydrogenation on the memory properties of Si nanocrystals obtained by inductively coupled plasma chemical vapor deposition
Authors: Cha Young-Kwan , Park Sangjin , Park Youngsoo , Yoo In-Kyeong , Cha Daigil , Shin Jung H. , Choi Suk-Ho
Published: November 2006

Effect of hydrogenation on memory properties has been studied for metal-oxide-semiconductor (MOS) structures with Si nanocrystals fabricated using inductively coupled plasma chemical vapor deposition and subsequent annealing. Hydrogenation induces a drastic increase of a dip in the quasistatic capacitance-voltage (C-V) curve of the MOS capacitor, caused by the reduction of the interface states due to hydrogen passivation. This is consistent with high-frequency C-V measurements showing more well-defined curves with less distortion in hydrogenated samples. After hydrogenation, the MOS device shows a significantly larger decrease of flatband voltage shift in electron charging than in hole charging, indicating more effective passivation of the defect states related to the electron charging. A longer retention time is found for electron charging after hydrogenation, but almost no change of charge loss rate for hole charging. These results suggest that an asymmetry exists in the effect of hydrogenation between electron and hole storage.
An efficient molecular orbital approach for self-consistent calculations of molecular junctions
Authors: Nakamura Hisao , Yamashita Koichi
Published: November 2006

To model electron transport through a molecular junction, we propose an efficient method using an ab initio self-consistent nonequilibrium Green’s function theory combined with density functional theory. We have adopted a model close to the extended molecule approach, due to its flexibility, but have improved on the problems relating to molecule-surface couplings and the long-range potential via a systematic procedure for the same ab initio level as that of Green’s function. The resulting algorithm involves three main steps: (i) construction of the embedding potential; (ii) perturbation expansion of Green’s function in the molecular orbital basis; and (iii) truncation of the molecular orbital space by separating it into inactive, active, and virtual spaces. The above procedures directly reduce the matrix size of Green’s function for the self-consistent calculation step, and thus, the algorithm is suitable for application to large molecular systems.
Compact, low-cost, and high-resolution interrogation unit for optical sensors
Authors: Kiesel Peter , Schmidt Oliver , Mohta Setu , Johnson Noble , Malzer Stefan
Published: November 2006

Compact wavelength detectors that resolve wavelength changes in the subpicometer range over a broad spectral range are presented. A photodiode array or position sensor device is coated with a linear variable filter that converts the wavelength of the incident light into a spatial intensity distribution. The centroid of the spatial distribution is determined by a differential readout of the two elements of the photodiode array or the position sensor device. The device can interrogate any optical sensor that produces a wavelength shift in response to a stimulus. The potential of this device was tested by interrogating fiber-Bragg-grating sensors.
Structural and Electronic Properties of Iron(II) Complexes of 2-(1,2,4-Triazol-3-yl)pyridine and Substituted Derivatives
Authors: Sugiyarto KH , Craig DC , Rae AD , Goodwin HA
Published: November 2006

Iron(II) and nickel(II) tris(ligand) complexes of 2-(triazol-3-yl)pyridine and the substituted derivatives 2-(1(N)-methyltriazol-3-yl)pyridine and -(1,5-dimethyltriazol-3-yl)pyridine have been prepared. Coordination of the dimethyl -substituted ligand via N(4) of the triazolyl moieties is confirmed by structure determination of [FeL3] [BF4]2, which has the mer configuration. Tris (2-(1,5-dimethyltriazol-3-yl)pyridine)iron(II) bis ( tetrafluoroborate ): orthorhombic, space group Pbca, a 11.568(3), b 19.442(4), c 30.551(8) Ǻ, Z 8. The methyl substituents appear to have only a minor influence on the donor properties of the ligands, all three of which have field strengths in the iron(II) quintet ↔ singlet crossover region. Temperature-induced singlet ↔ quintet transitions occur in salts of the [FeN6]2+ derivatives in both the solid and solution states. Mossbauer effect studies reveal the complexity of the solid state properties of salts of the iron complex of 2-(1(N)-methyltriazol-3-yl)pyridine and suggest that there is a fundamental change with time in the geometry of the complex cation. The metastable form of the complex hexafluorophosphate salt shows virtually no quadrupole splitting in the spectrum for the quintet state species, which implies high symmetry for the metal ion environment. Mossbauer studies further reveal the presence of multiple iron(II) sites in the lattice for salts containing either the N-methyl or the unsubstituted ligand.
The Ring Size Influence on 29Si N.M.R. Chemical Shifts of Some Spirocyclic Tetra- and Penta-coordinate Diolato Silicates
Authors: Kemmitt T , Milestone NB
Published: November 2006

A series of tetracoordinate spirocyclic silicates has been prepared from the reaction of a range of diols with tetraethoxysilane, Si ( OEt )4. The silicates can be converted into anionic pentacoordinate silicates by reaction with KOBut/18-crown-6 in toluene. Alternatively, the pentacoordinate spirocycles can be prepared directly without prior preparation of a tetracoordinate spiro silicate. 29Si n.m.r. studies have demonstrated that the chemical shifts are sensitive to both coordination number and ring size. Ring contributions to the 29Si chemical shifts are apparent for the five- membered ring spiro silicates, those for the pentcoordinate species being less than those for the tetracoordinate species. Acyclic and six- membered ring spiro silicates are virtually indistinguishable by 29Si n.m.r. spectroscopy, which demonstrates that no ring contribution to the chemical shift is apparent for this ring size.
Characterization of Three 'Active' Rhodium(III) Hydroxides
Authors: Crimp SJ , Spiccia L
Published: November 2006

Pure solutions of [ Rh (H2O)6]3+, dimer [Rh2(μ-OH)2(H2O)8]4+ and trimer [Rh3(μ-OH)4(H2O)10]5+ have been converted into their respective 'active' hydroxides by dropwise addition to an imidazole solution. These 'active' hydroxides have been analysed by a variety of techniques including rhodium determination, infrared spectroscopy, thermal analysis and powder X-ray diffraction. Purity determinations using ion-exchange chromatography showed that the three hydroxides consist primarily of the neutral forms of the starting aqua ion (>96%) with small amounts of species with higher nuclearity. Rhodium analysis and thermogravimetric measurements confirmed the composition of these hydroxides to be Rh (OH)3(H2O)3.H2O, Rh2(μ-OH)2(OH)4(H2O)4 and Rh3(μ-OH)4(OH)5(H2O)5.5H2O. A scheme for the thermal decomposition of each of the hydroxides has been proposed on the basis of the t.g . and d.t.a . data and the knowledge that the final product in each case is α-Rh2O3. Heating of the hydroxides in air resulted in oxidation of RhIII to RhIV (temperature 250-300°C) forming RhO2 which on further heating decomposed to α-Rh2O3 and dioxygen.
The Chemistry of 5-Oxodihydroisoxazoles. XIII. Reactions of the Imino Carbene Derived From Photolysis of Ethyl 5-Oxo-2-phenyl-2,5-dihydroisoxazole-4-carboxylate
Authors: Ang KH , Prager RH , Williams CM
Published: November 2006

Photolysis of ethyl 5-oxo-2-phenyl-2,5-dihydroisoxazole-4-carboxylate at 300 nm in acetonitrile gives a carbene which is captured efficiently by bromide, chloride, acetate and cyanate, and less efficiently by iodide, thiocyanate, cyclohexene and tetrahydrofuran. No hydrogen abstraction or reaction with double bonds was evident.
Studies in the Cycloproparene Series: Reactions With Radicals
Authors: Chai CLL , Christen D , Halton B , Neidlein R , Starr MAE
Published: November 2006

The behaviour of 1H-cyclopropabenzene (1) and 1H-cyclopropa[b]naphthalene (23) towards a variety of radicals results in opening of the three- membered ring to give ortho -substituted benzyl and 2-methylnaphthalene derivatives, e.g. (13) and (28), respectively. Ring expansion into the cycloheptatriene manifold by way of addition to the bridge bond and norcaradiene formation have not been observed. Analogous reactions with the methylidenecyclopropa [b] naphthalenes (33) and (34) lead to much decomposition, and provide little evidence for the C1cycloproparenyl radicals (35) and (36).
Synthetic Studies on Wedeligenin: Preparation of an A/B-Ring Intermediate
Authors: Macleod JK , Morris KB
Published: November 2006

In a new approach to the synthesis of wedeligenin , an A/B-ring intermediate (13a) has been synthesized. The β- keto ester (15) was readily prepared from Wieland-Meischer ketone in three steps. Baeyer-Villiger oxidation of (15) and subsequent methylenation provided an alkene (16) which contained the malonyl substituent, later to become the gem-diester of (13a). Regiospecific conversion of the alkene into a bromohydrin followed by cyclization afforded (13a). This provided an A/B-ring intermediate which could be further elaborated to allow C/D-ring annulation.
Cyclographin, a New Depsidone From the Lichen Catarraphia dictyoplaca
Authors: Elix JA , Elix JA , Naidu R , Naidu R , Thor G , Thor G
Published: November 2006

The new depsidone cyclographin (1) (methyl 2-chloro-4-formyl-3,7-dihydroxy-1,6,9-trimethyl-11-oxo-11H-dibenzo[ b,e ][1,4]dioxepin-8-carboxylate) has been isolated from the lichen Catarraphia dictyoplaca and the structure established by spectroscopic and degradative methods.
Experiments Directed Towards the Synthesis of Anthracyclinones. XXVI. The Preparation of Chiral Intermediates for Anthracyclinone Synthesis
Authors: Beauregard DA , Cambie RC , Dansted PC , Rutledge PS , Woodgate PD
Published: November 2006

(2′R)-1,5-Dimethoxy-2(2′-methyloxiran-2′-ylmethyl) anthraquinone (8), an intermediate for the synthesis of fridamycin E, has been prepared enantioselectively via the diol (15). The diol (15) was prepared in high yield by asymmetric cis-hydroxylation of the alkene (11). The analogous diol (22), a vineomycinone B2 precursor, was also prepared.
Copper Catalyzed Reactions of Penicillin Derivatives With t-Butyl Perbenzoate
Authors: Clark BM , Easton CJ , Watkins SK
Published: November 2006

The benzoyloxylation of penicillin derivatives at C5, on treatment with t-butyl perbenzoate in the presence of a copper catalyst, is facilitated by a phthalimido group at C6 when the substituents on the lactam ring are in the cis orientation, but hindered when the groups are trans substituted. In the absence of a C6 substituent, a competing reaction occurs in which the thiazolidine ring is cleaved.
Synthesis and Crystal Structure of 'Thorium Hydroxy Picrate Hexadecahydrate' ('Basic Thorium Picrate')
Authors: Harrowfield JM , Peachey BJ , Skelton BW , White AH
Published: November 2006

The title compound, crystallized from the solution produced by dissolution of thorium carbonate in hot, aqueous picric acid ( Hpic , 2,4,6-trinitrophenol) as pale yellow needles, has been the subject of a room-temperature single-crystal X-ray study and found to be [( pic )(H2O)6Th(μ-OH)2Th(OH2)6( pic )]( pic )4.20H2O. The compound is triclinic, Pī , a 14.651(4), b
12.877(6), c 11.838(2) Ǻ, α 69.71(3), β 75.93(2), γ 80.10(3); Z = 1 ( dimeric ) f.u .; conventional R on |F| at convergence was 0.032 for 8281 'observed' (I > 3σ(I)) reflections. The thorium is nine-coordinate Th (O- pic )(μ-O)2(OH2)6, the dimer being centrosymmetric and the coordination geometry about thorium being approximately that of a singly capped square antiprism , the capping atom (over a square face) being the slightly more remote of the bridging hydroxy groups. Th -μ-OH are 2.366(3), 2.381(3), Th-OH2 2.479(5)-2.534(4) and Th-O( pic ) 2.366(3) Ǻ.
Compilation and Critical Evaluation of Structure-Reactivity Parameters and Equations. I. Values of σm and σp Based on the Ionization of Substituted Benzoic Acids in Water at 25°C
Authors: Shorter J
Published: November 2006

Data have been compiled for the pKa values in water at 25°C of about 60 meta- or para-substituted benzoic acids, with a view to proposing recommended values of Hammett substituent constants, σ. The number of substituents covered is about one-half of this number, but for certain substituents data are not available for both the meta and para position. The amount and the reliability of the data vary greatly from one acid to another. Critical appraisal leads to the classification of the substituents and their σ values as belonging to a First Division (with more reliable data) or a Second Division (with less reliable data). The substituents in the former category are: Me, NO2, OMe, F, Cl, and Br (each in both the meta and the para position). Recommended values of σ are tabulated for substituents in each Division, but for certain members of the Second Division there are caveats because the data show discrepancies.
The Preparation and Crystal Structure of Benzyl 3,4,6-Tri-O-methylsulfonyl-β-D-glucopyranoside
Authors: Carvalho CF , Kennard CHL , Lynch DE , Smith G , Wong A
Published: November 2006

A series of methylsulfonyl derivatives of benzyl β-D-glucopyranoside has been prepared and isolated and the crystal structure of one, benzyl 3,4,6-tri-O-methylsulfonyl-β-D-glucopyranoside (3), as a dimethyl sulfoxide solvate determined by X-ray diffraction and refined to a residual R 0.035 for 1714 observed reflections.
A Theoretical and Experimental Investigation of the Kinetics of Ring Closure of the 3-Methyl-3-azahex-5-enyl Radical
Authors: Della EW , Knill AM
Published: November 2006

Evaluation of the Arrhenius parameters for ring closure of the 3-methyl-3-azahex-5-enyl radical is reported. Cyclization of the radical is found to occur with high regioselectivity giving the exo -trig product exclusively with an activation energy of 22 kJ mol-1 and log A value of 11.1. The experimental activation barrier compares favourably with that determined by force field calculations which predict a value of 21 kJ mol-1. The 3-methyl-3-azahex-5-enyl radical is therefore found to undergo ring closure some 70 times faster than the parent hex-5-enyl radical, in accord with predictions based upon geometrical considerations.
Phylogenetic relationships of the cuscuses and brushtail possums (Marsupialia:Phalangeridae) using the nuclear gene BRCA1
Authors: Raterman Denise , Meredith Robert W. , Ruedas Luis A. , Springer Mark S.
Published: November 2006

The family Phalangeridae comprises approximately two dozen extinct and extant species that include the brushtail possums (Trichosurus), scaly-tailed possum (Wyulda) and cuscuses (Phalanger, Strigocuscus, Spilocuscus and Ailurops). Morphological studies have suggested that Ailurops ursinus is the sister taxon to all other phalangerids. Another species of interest is Strigocuscus celebensis, whose morphologically based taxonomic affinity has habitually been with trichosurins. Mitochondrial 12S rRNA results, however, found moderate support for an Ailurops and Strigocuscus celebensis clade and placed A. ursinus and S. celebensis as sister to Phalanger and Spilocuscus. This study uses nuclear sequence data from the breast cancer and ovarian cancer susceptibility gene 1 (BRCA1) to test previous mitochondrial DNA results and uses relaxed molecular clock methods to estimate divergence dates. The results support Ailurops as sister taxon to S. celebensis and this clade as sister to Phalangerini. Relaxed molecular-dating methods suggest a date of 23–29 million years for the split between Trichosurini and the remaining phalangerids and 19–24 million years for the split between Ailurops + Strigocuscus celebensis and Phalangerini. Several vicariant/dispersal events are necessary to explain the geographic distribution of the Phalangeridae and our estimated molecular divergence dates are congruent with previously proposed south-east Asian geological events.
A 50-kDa ERK-like protein is up-regulated by a dual altered peptide ligand that suppresses myasthenia gravis-associated responses
Authors: Ben-David Hava , Aruna Badiga Venkata , Seger Rony , Sela Michael , Mozes Edna
Published: November 2006

Myasthenia gravis (MG) and its animal model, experimental autoimmune MG (EAMG), are T cell-dependent antibody-mediated autoimmune diseases. A dual altered peptide ligand (APL) that is composed of the tandemly arranged two single amino acid analogues of two myasthenogenic peptides, p195–212 and p259–271, down-regulatedin vitroandin vivoMG-associated autoreactive responses. The dual APL was shown to exert its beneficial effects by up-regulating ERK1,2 in CD4+CD25+regulatory cells. In this study, we investigated a novel 50-kDa ERK-like protein (ERK-50) that is up-regulated significantly in addition to ERK1,2 after treatment with the dual APL. We report here that ERK-50 was up-regulated in LN cells and in LN-derived T cells of mice that were immunized with the myasthenogenic peptides and treated with the dual APL. Moreover, ERK-50 was up-regulated in dual-APL- treated mice that were immunized with theTorpedoacetylcholine receptor. ERK-50 was demonstrated to be recognized by antibodies directed against the C and N termini of ERK1, against the C terminus of ERK2, and against general ERK. The 50-kDa ERK was shown to be stimulated by Con A, and inhibition of MEK1 down-regulated the 50-kDa ERK as was shown for ERK1,2. However, 4β-phorbol 12-myristate 13-acetate (TPA) did not stimulate ERK-50. Finally, the activated ERK-50 was up-regulated in the dual-APL-induced CD4+CD25+regulatory cells. Thus, ERK-50 is suggested to be a novel ERK isoform, being up-regulated in response to treatment with the dual APL.