bluuebunny/crossref_metadata_2025 huggingface dataset:
Stage‐specific germ‐somatic cell interaction directs the primordial folliculogenesis in mouse fetal ovaries
Authors: Lei Lei , Zhang Hua , Jin Shiying , Wang Fengchao , Fu Maoyong , Wang Haibin , Xia Guoliang
Published: June 2006

The mechanism regulating primordial follicle formation remains largely unexplored because of the developmental particularity of female germ cells and their ultimate functional structure as follicles. Using an in vitro follicle reconstitution culture model, we explored, in the present study, the possibility of producing transgenetic follicles in vitro. We found that mouse fetal ovarian germ cells progressively lose the flexibility for gene manipulation with their oogonia‐oocyte transformation upon entering meiosis, the borderline of which was at around embryonic age of 13.5 days post coitus (dpc). Interestingly, we further observed that fetal ovarian cells, only at this age or beyond achieve the capacity to reform the follicles in culture. Screening of well‐known marker gene (Zp1‐3, Figα, and Cx43) expression in cultured fetal ovarian cells of various developmental ages revealed that Figα is one of the determining factors for normal primordial follicle formation. By conducting reciprocal follicle reconstitution experiments, we provided further evidence that a synchronized germ‐somatic cell interaction determines the normal duration of primordial folliculogenesis. Besides uncovering a potentially important regulatory mechanism for normal oocyte differentiation and follicle formation, this observation offers an alternative approach to produce transgenic oocytes/follicles, and thus animal models. J. Cell. Physiol. 208: 640–647, 2006. © 2006 Wiley‐Liss, Inc.
Sexual Functioning in Patients With End-Stage Liver Disease Before and After Transplantation
Authors: Sorrell James H. , Brown Jill R.
Published: June 2006

The effects of end-stage liver disease (ESLD) on sexual functioning are complex and often overlooked in the context of chronic illness and the transplantation evaluation. The aim of the present study is to report on the prevalence of sexual dysfunction in patients with ESLD presenting for liver transplantation evaluation, as well as to examine a cohort after transplantation. Participants included 173 consecutive adult outpatients with ESLD who presented for orthotopic liver transplantation evaluation. All transplant candidates underwent a psychiatric evaluation, and a sexual history was taken by the transplant psychiatrist. Patients who received a liver transplant were contacted by telephone for follow-up (n = 39). The following domains were explored: sexual frequency, satisfaction, ability to orgasm, sexual interest, and, for men, erectile dysfunction. Before transplantation, high levels of sexual dysfunction were found, with women showing higher levels of dysfunction than men. Increased age and more severe liver disease were related to lower sexual frequency and satisfaction. Contrary to previous work, the cause of disease (alcoholic liver disease) was not related to sexual functioning before transplantation. Those with erectile dysfunction before transplantation showed continued dysfunction after transplantation. An additional finding was an age and gender bias against taking a sexual history from older women. Overall, for both men and women, the findings point to continued and persistent sexual dysfunction after transplantation. Findings may help transplant teams routinely inquire into the sensitive domain of sexual functioning early on and thereby provide an opportunity for treatment.
Liver Transpl 12:1473-1477, 2006.

© 2006 AASLD.
33S NMR spectroscopy 3. substituent effects on 33S NMR parameters in 2‐substituted ethanesulfonates
Authors: Musio Roberta , Sciacovelli Oronzo
Published: June 2006

33S NMR parameters (chemical shifts and linewidths) in 2‐substituted sodium ethanesulfonates, XCH2CH2SO3Na (X = H, CH3, OH, SH, NH2, Cl, Br, NH3+) depend upon the electronic properties of substituents. To explain experimental results and obtain additional information on the origin of the observed substituent effect (SE), sulfur isotropic absolute shielding constants have been calculated at DFT level of theory (B3LYP/6‐311 + + G(2d,p)) by gauge‐including atomic orbitals (GIAO) method. Data have been interpreted with the aid of natural bond orbital (NBO) method and natural chemical shielding (NCS) analysis. It has been demonstrated that in the class of compounds considered the diamagnetic contribution to sulfur‐shielding constant is constant and the observed upfield shift of 33S resonance induced by electron‐withdrawing substituents (reverse chemical shift effect) can be related to variations of the paramagnetic contribution. Substituents with different electronic properties cause variations in the polarization of SC and SO bonds of the CSO3− moiety thus determining changes of the electron density at sulfur nucleus and consequently the expansion or contraction of 3p sulfur orbitals. Also oxygen lone‐pairs and sulfur core 2p electrons can play an active role in determining the paramagnetic contribution to sulfur shielding. With regard to linewidth variations, they can be ascribed primarily to changes in the nuclear quadrupole coupling constant values. B3LYP/6‐311 + + G(2d,p) method allows obtaining a good reproducibility of SE on the electric field gradient (EFG) at sulfur, although its values tend to be underestimated significantly. Moreover, 17O shielding constants have been calculated. Copyright © 2006 John Wiley & Sons, Ltd.
Effusion and solid lymphomas have distinctive gene and protein expression profiles in an animal model of primary effusion lymphoma
Authors: Yanagisawa Y , Sato Y , Asahi‐Ozaki Y , Ito E , Honma R , Imai J , Kanno T , Kano M , Akiyama H , Sata T , Shinkai‐Ouchi F , Yamakawa Y , Watanabe S , Katano H
Published: June 2006

Lymphoma usually forms solid tumours in patients, and high expression levels of adhesion molecules are observed in these tumours. However, Kaposi's sarcoma‐associated herpesvirus (KSHV)‐related primary effusion lymphoma (PEL) does not form solid tumours and adhesion molecule expression is suppressed in the cells. Inoculation of a KSHV‐associated PEL cell line into the peritoneal cavity of severe combined immunodeficiency mice resulted in the formation of effusion and solid lymphomas in the peritoneal cavity. Proteomics using two‐dimensional difference gel electrophoresis and DNA microarray analyses identified 14 proteins and 105 genes, respectively, whose expression differed significantly between effusion and solid lymphomas. Five genes were identified as having similar expression profiles to that of lymphocyte function‐associated antigen 1, an important adhesion molecule in leukocytes. Among these, coronin 1A, an actin‐binding protein, was identified as a molecule showing high expression in solid lymphoma by both DNA microarray and proteomics analyses. Western and northern blotting showed that coronin 1A was predominantly expressed in solid lymphomas. Moreover, KSHV‐encoded lytic proteins, including viral interleukin‐6, were highly expressed in effusion lymphoma compared with solid lymphoma. These data demonstrate that effusion and solid lymphomas possess distinctive gene and protein expression profiles in our mouse model, and suggest that differences in gene and protein expression between effusion and solid lymphomas may be associated with the formation of effusion lymphoma or invasive features of solid lymphoma. Furthermore, the results obtained using this combination of proteomics and DNA microarray analyses indicate that protein synthesis partly reflects, but does not correlate strictly with, mRNA production. Copyright © 2006 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.
Molecular architecture and rheological characterization of novel intramolecularly crosslinked polystyrene nanoparticles
Authors: Tuteja Anish , Mackay Michael E. , Hawker Craig J. , Van Horn Brooke , Ho Derek L.
Published: June 2006

Novel polystyrene nanoparticles were synthesized by the controlled intramolecular crosslinking of linear polymer chains to produce well‐defined single‐molecule nanoparticles of varying molecular mass, corresponding directly to the original linear precursor chain. These nanoparticles are ideal to study the relaxation dynamics/processes of high molecular mass polymer melts, as the high degree of intramolecular crosslinking potentially inhibits entanglements. Both the nanoparticles and their linear analogs were characterized by measuring their intrinsic viscosity, hydrodynamic radius (Rh), and radius of gyration (Rg). The ratio Rg/Rh was computed to characterize the molecular architecture of the nanoparticles in solution, revealing a shift toward the constant density sphere limit with increasing crosslink density and molecular mass. Further, confirming particulate behavior, Kratky plots obtained from neutron scattering data show a shift toward particle‐like nature. The rheological behavior of the particles was found to be strongly dependent on both the extent of intramolecular crosslinking and molecular mass, with a minimal viscosity change at low crosslinking levels and a gel‐like behavior evident for a large degree of crosslinking. These and other results suggest the presence of a secondary mode of polymer relaxation/movement besides reptation, which in this case, is influenced by the total number of crosslinked loops present in the nanoparticle. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 1930–1947, 2006
Investigation of sulfonated poly(ether ether ketone sulfone)/heteropolyacid composite membranes for high temperature fuel cell applications
Authors: Wang Zhe , Ni Hongzhe , Zhao Chengji , Li Xianfeng , Fu Tiezhu , Na Hui
Published: June 2006

The sulfonated poly(ether ether ketone sulfone) (SPEEKS)/heteropolyacid (HPA) composite membranes with different HPA content in SPEEKS copolymers matrix with different degree of sulfonation (DS) were investigated for high temperature proton exchange membrane fuel cells. Composite membranes were characterized by Fourier transfer infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). FTIR band shifts suggested that the sulfonic acid groups on the copolymer backbone strongly interact with HPA particles. SEM pictures showed that the HPA particles were uniformly distributed throughout the SPEEKS membranes matrix and particle sizes decreased with the increment of copolymers' DS. The holes were not found in SPEEKS‐4/HPA30 (consisting of 70% SPEEKS copolymers with DS = 0.8 and 30% HPA) composite membrane after composite membranes were treated with boiling water for 24 h. Thermal stabilities of the composite membranes were better than those of pure sulfonated copolymers membranes. Although the composite membranes possessed lower water uptake, it exhibited higher proton conductivity for SPEEKS‐4/HPA30 especially at high temperature (above 100 °C). Its proton conductivity linearly increased from 0.068 S/cm at 25 °C to 0.095 S/cm at 120 °C, which was higher than 0.06 S/cm of Nafion 117. In contrast, proton conductivity of pure SPEEKS‐4 membrane only increased from 0.062 S/cm at 25 °C to 0.078 S/cm at 80 °C. At 120 °C, proton conductivity decreased to poor 0.073 S/cm. The result indicated that composite membranes exhibited high proton conductivity at high temperature. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 1967–1978, 2006
Effect of crosslink on the characteristic length of glass transition of network polymers
Authors: Sasaki Takashi , Uchida Tadashi , Sakurai Kensuke
Published: June 2006

The characteristic length of the glass transition temperature was evaluated for crosslinked bulk polystyrenes and poly(methyl methacrylate)s by differential scanning calorimetry. The characteristic length, which corresponds to a length scale of the cooperative rearrangement due to polymer segmental relaxation, was revealed to decrease with increase in the degree of crosslink. The relative values of configurational entropy for crosslinked polymers were evaluated based on a simple polymer network model on a cubic lattice. As a result, the configurational entropy of the smallest cooperatively rearranging region was revealed to decrease with increase in the degree of crosslink, which is responsible for the above behavior of the characteristic length. The effects of crosslink on the characteristic length and the glass transition temperature were found to be stronger for crosslinked poly(methyl methacrylate)s than for crosslinked polystyrenes, which reflects the difference in the structure of crosslink segment. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 1958–1966, 2006
Oscillating spectra of polar IO and SO phonons and electron–IO and SO phonon couplings in a freestanding wurtzite quantum wire
Authors: Zhang Li , Shi Jun‐jie
Published: June 2006

By employing the transfer matrix method, the polar interface optical (IO) and surface optical (SO) phonon modes and the corresponding Fröhlich electron–phonon interaction Hamiltonians in a freestanding multishell wurtzite cylindrical quantum wire (QWR) are derived and studied under the dielectric continuum approximation and Loudon's uniaxial crystal model. The present theoretical scheme can be looked on as a generalization of the previous studies regarding the IO phonon modes in quasi‐one‐dimensional (Q1D) wurtzite QWRs with a certain layer‐number. Numerical calculations on a freestanding wurtzite GaN/AlN QWR are performed. The degenerating behaviors of the IO and SO phonon modes in the freestanding wurtzite QWR seem prominent in contrast to the situation of Q1D wurtzite QWR with infinite polar matrix. The calculations of the electron–phonon coupling function show that the high‐frequency IO phonon branch and SO mode play a more important role in the electron–phonon interaction. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Magnon energy gap and the magnetically structural symmetry in a three‐layer ferrimagnetic superlattice
Authors: Qiu Rong‐ke , Zhang Zhi‐dong , Guo Lian‐quan , Ying Cai‐hong , Liang Jing
Published: June 2006

The magnon energy band in a ferrimagnetic superlattice with three layers in a unit cell is studied by employing retarded Green's functions and the spin‐wave method. Two modulated energy gaps Δω 13 and Δω 23 are evaluated systematically, which exist in the magnon energy band along the Kx ‐direction perpendicular to the plane of the superlattice. It is revealed that the energy gap Δω 13 has a direct relation with the symmetry among the spin quantum numbers and the interlayer exchange couplings, while the energy gap Δω 23 relates to the symmetry among these spin quantum numbers only. These symmetries differ from the symmetry of crystallographic point groups. We define the magnetically structural symmetry that is dominated mainly by the magnetic parameters. The absence of the energy gap at a certain condition means that the system has a high magnetically structural symmetry. The magnetically structural symmetry of the superlattice, which is an intrinsic property, strongly affects the magnon energy band structure and thus the magnetic behaviors of the system. Furthermore, two complete bandgaps are observed to extend through the Brillouin zone (referred to as “magnonic crystal”) in this superlattice system. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
EPR of VHal centres in SrS
Authors: Seeman V. , Danilkin M. , Must M. , Ots A. , Pärnoja E. , Pung L. , Tarkpea K.
Published: June 2006

VHal centres were studied by EPR in SrS doped with halogens after X‐raying the samples at 77 K. VHal centre arises when a hole is captured by sulphide‐ion next to a cation vacancy with a halogen ion substituting the opposite sulphide‐ion. EPR parameters and thermal decay characteristics are measured for VCl, VBr, and VI centres. The efficiency of different halogens to produce and stabilise cation vacancies is shown to vary for different alkaline earth sulphides. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Development of electronic nose method for evaluation of residual solvents in low‐density polyethylene films
Authors: Yüzay Isinay E. , Selke Susan
Published: June 2006

Flexible packaging films containing high levels of residual volatile organic compounds (VOCs) can alter the flavour and odour of packaged foods. Currently, a range of gas chromatographic techniques and sensory evaluations are used for assessing the residual VOCs in packaging films. An objective method for assessing the residual solvents from low‐density polyethylene (LDPE) was developed using an Alpha MOS Fox 3000 electronic nose (e‐nose) equipped with 12 metal oxide semiconductor sensors. Three VOCs, ethyl acetate, ethyl alcohol and toluene, were chosen as models for solvents of interest in flexible food packaging analysis. LDPE film samples were spiked with single and binary mixtures of solvents and analysed using the e‐nose and by GC–FID (HP 6890; Hewlett‐Packard Co., Wilmington, DE). The responses obtained from the e‐nose were processed using principal component analysis (PCA) and discriminate factorial analysis (DFA) in order to identify the residual solvents. Partial least squares analysis (PLS) was also used to quantify the amount of residual solvent and to correlate the e‐nose results with gas chromatography, which is currently the standard method for determining residual VOCs in packaging films. There was good agreement between the e‐nose responses and gas chromatography results for single solvents (r = 0.90–0.98). The technique also worked for binary solvent mixtures (r = 0.84–0.99). The electronic nose can be a viable alternative to traditional techniques while providing simplicity and objectivity, which would be extremely advantageous in routine quality control of residual solvents. Copyright © 2006 John Wiley & Sons, Ltd.
Gray‐scale ultrasound morphology in the presence or absence of intrauterine fluid and vascularity as assessed by color Doppler for discrimination between benign and malignant endometrium in women with postmenopausal bleeding
Authors: Epstein E. , Valentin L.
Published: June 2006

Objective

To determine if gray‐scale ultrasound morphology in the presence or absence of intrauterine fluid and endometrial vascular morphology as assessed by color Doppler ultrasonography can discriminate between benign and malignant endometrium in women with postmenopausal bleeding.

Methods

In a prospective study 95 consecutive women with postmenopausal bleeding and endometrial thickness ≥ 4.5 mm as measured by transvaginal ultrasound were included. Gray‐scale and color Doppler ultrasound examination of the endometrium was performed. The ultrasound examiner characterized the morphology of the endometrium before and during saline infusion and assessed the endometrial vascular tree using a predetermined classification protocol without suggesting a diagnosis. A histopathological diagnosis was obtained by operative hysteroscopy, dilatation and curettage or hysterectomy.

Results

There were no statistically significant differences in ultrasound findings between benign and malignant endometria of uterine cavities without fluid. Heterogeneous echogenicity, irregular surface, and both heterogeneous echogenicity and irregular surface of a focal lesion (or of the endometrium in the absence of focal lesions) in a uterine cavity filled with fluid (spontaneous or infused) were significantly more common in malignant than in benign endometrium. The sensitivity, false positive rate, positive and negative likelihood ratios of these findings were as follows: heterogeneous echogenicity, 80%, 29%, 2.74, 0.28, P = 0.003; irregular surface, 89%, 33%, 2.70, 0.17, P = 0.002; and both, 78%, 12%, 6.59, 0.25, P < 0.001. Two or more vessels were found in 67% (8/12) of the malignant endometria vs. 51% (40/79) of the benign endometria (non‐significant difference). Vascular branching tended to be more common in malignant endometria (10/11; 91%) than in benign endometria (39/61; 64%), P = 0.09.

Conclusion

Heterogeneous echogenicity and an irregular surface of a focal lesion or of the endometrium in a fluid‐filled uterine cavity are useful ultrasound criteria for predicting endometrial malignancy. Assessment of vascular morphology using color Doppler ultrasound is of limited — if any — value for discrimination between benign and malignant endometrium. Copyright © 2006 ISUOG. Published by John Wiley & Sons, Ltd.
Non‐compaction cardiomyopathy in an adult with hereditary spherocytosis
Authors: Alter Peter , Maisch Bernhard
Published: June 2006

A 23‐year old male (199 cm, 88 kg) presented muscular weakness due to skeletal myopathy and symptoms of heart failure NYHA functional class II. Total creatine kinase was increased up to 830 U/l, but troponin was negative. Prior episodes of intermittent atrial fibrillation were reported and 6 years ago splenectomy was performed due to hereditary spherocytosis. Cardiac magnetic resonance imaging revealed the spongy appearance of non‐compacted left ventricular myocardium. This impaired fetal morphogenesis occurred predominantly in the apical to midventricular anterior, lateral and inferior segments. Non‐compaction cardiomyopathy was initially described in paediatric patients. Occasional associations with other congenital disorders are known, e.g., Barth syndrome, which is an X‐linked disease characterized by cardio‐skeletal myopathy of variable severity and neutropenia. To our knowledge, combined occurrence of non‐compaction cardiomyopathy, skeletal myopathy and hereditary spherocytosis has not previously been reported.
PolydA and polyrA self‐structured by a europium and amino acid complex
Authors: Zhang Haiyuan , Yu Haijia , Ren Jinsong , Qu Xiaogang
Published: June 2006

Different DNA selectivity was found for the newly synthesized europium–l‐valine complex. Unexpected DNA and RNA selection results showed that europium–l‐valine complex can cause single‐stranded polydA and polyrA to self‐structure. The sigmoidal melting curve profiles indicate the transition is cooperative, similar to the cooperative melting of a duplex DNA. This is different from another europium amino acid complex, europium–l‐aspartic acid complex which can induce B‐Z transition under the low salt condition. To our knowledge, there is no report to show that a metal–amino acid complex can cause the self‐structuring of single‐stranded DNA and RNA.
Stillbirth in developing countries
Authors: McClure E.M. , Nalubamba‐Phiri M. , Goldenberg R.L.
Published: June 2006

Objective: To conduct a systematic review of the literature on stillbirths in developing countries.

Method Review of the English literature for all articles related to stillbirth in developing countries published from 1975 to 2005.

Results Because almost half of the deliveries in developing countries occur at home, under‐reporting of stillbirths is a huge problem, and reliable data about rates and causes are difficult to obtain. Hospital stillbirth data are often subject to substantial bias and the ability to generalize from these data is unknown. Nevertheless, at least 4 million stillbirths occur yearly, the vast majority in developing countries, with rates in many developing countries ten‐fold higher than elsewhere. Prolonged and obstructed labor, preeclampsia and various infections, all without adequate treatment, account for the majority of stillbirths.

Conclusion Despite the large number of stillbirths worldwide, the topic of stillbirths in developing countries has received very little research, programmatic or policy attention. Better access to appropriate obstetric care, especially during labor, should reduce developing country stillbirth rates dramatically.
Late manifestation of a pseudoaneurysm in the descending thoracic aorta
Authors: Gurkan  , Sunar  , Canbaz  , Duran
Published: June 2006

Rupture of the descending aorta following deceleration trauma is a catastrophic event because it has a high mortality. Prompt surgical treatment is generally considered to be mandatory. However, a few injured patients may leave the hospital with an undiagnosed aortic rupture which may give rise to a chronic pseudoaneurysm. In this report, a 28-year-old man is presented in whom a pseudoaneurysm of the descending thoracic aortic was diagnosed six months after a car accident.
Abdominal aortic aneurysm in a patient presenting with ischemic colitis
Authors: Tatebe  , Kashimura  , Uehara  , Shinonaga  , Kuraoka
Published: June 2006

A 76-year-old man with an abdominal aortic aneurysm (AAA) initially presented with ischemic colitis, which was improved by conservative treatment. Preoperative assessment by computerized axial tomography scanning and aortography revealed an infrarenal type AAA with mural thrombus, stenoses of the right common iliac artery and the left internal iliac artery. The patient underwent aortoiliac bypass surgery with resection of the stenoses, and reconstruction of the left internal iliac artery. No complications including bowel ischemia, were noted postoperatively. This case emphasized the potential benefits of the extraperitoneal approach to the aorta, reconstruction of both internal iliac arteries, and use of prostaglandin E1.
Area-pressure relationship of lower limb main veins in man
Authors: Chauveau  , Bassez  , Tra  , Scherrer
Published: June 2006

Background: The mechanical properties of human veins remain incompletely known. However they play an important part in number of physiological and pathological situations, as hemodynamic adjustment to orthostasis, deep venous thrombosis (DVP) and chronic venous insufficiency (CVI). The aim of the study was to describe the pressure/volume (area) relationship of some important conduit veins of the human’s lower limb. Probands and methods: We investigated the area/pressure relationship of the femoral vein (FV) at mid thigh, the great saphenous vein (GSV) at lower third of the leg, and a deep leg vein (DLV), either the peroneal or posterior tibial vein, in fifteen healthy young men. The cross section areas were measured with B-mode ultrasound while various positive and negative venous pressures were generated by body’s tilting. Results: Over the range of pressures investigated, the area/pressure relationship was roughly linear, the classical sigmoid relation did not emerge from our data. The relative compliance of FV, GSV and DLV was 0.0312, 0.0118, and 0.0147 mmHg-1, respectively. Conclusions: The relative compliance of FV is more than two times higher than the relative compliance of both the DLV and the GSV.
Influence of HMG-CoA-Reductase Inhibitors on the body fat status
Authors: Bucek  , Reiter  , Wirth  , Pourazim  , Minar
Published: June 2006

Background: While the literature has conclusively shown a significant decrease of plasma lipids after intake of HMG-CoA reductase inhibitors, there is no detailed information provided about their effects on the body fat status. Patients and methods: We performed a retrospective analysis of a prospective randomized controlled trial including consecutive patients with suspected arterial occlusive disease. Normolipidemic patients served as the control group and hyperlipidemic patients were randomized to either 20 mg atorvastatin or to 40 mg simvastatin. At baseline, after 6 weeks and after 6 months we assessed the relative body fat, the waist circumference and the body mass index (BMI) as well as plasma total cholesterol (chol), low-densitiy lipoprotein cholesterol (LDL) and triglycerides (TG). Results: In total we included 129 patients in our analysis. The body fat status remained unchanged in the control group as well as in the atorvastatin group (all p > 0.05) for the whole study period, while simvastatin treatment led to a slight, but significant increase of the relative body fat (+ 4.2%) between the 6 weeks and 6 months assessment (p = 0.013). Conclusions: Long-term intake of statins seems to have no positive influence on parameters of the body fat status and therefore misses one important goal in the cardiovascular risk prevention.
A decade of exploring a submarine intraplate volcano: Hydrothermal manganese and iron at Lō'ihi volcano, Hawai'i
Authors: Malahoff Alexander , Kolotyrkina Irina Ya. , Midson Brian P. , Massoth Gary J.
Published: June 2006

Decadal time series observations of hydrothermal fluid emissions from Lō'ihi volcano were initiated in 1992 using a combination of submersible and shipboard sampling strategies. Magmatic‐tectonic processes associated with a spectacular seismic event in July–August 1996 led to the collapse of Pele's Vents (31°C) near the volcano summit into a new pit crater (Pele's Pit) inundated by high‐temperature (Tmax = 198°C) focused and lower‐temperature (<95°C) diffuse fluid discharge. Variations in the concentrations and relative abundances of vented Fe and Mn characterize the precollapse, summit collapse, and postcollapse periods. The precollapse plume emanating from Pele's Vents had a low rise height (∼35 m) and concentration intensity (<5 nmol/L TDMn, 70 nmol/L TDFe, ∼1.8 km distant) and dispersed to the southwest. Plumes coeval with the 1996 summit collapse were characterized by extreme metal concentrations within Pele's Pit (up to ∼10,000 nmol/L DMn and 400,000 nmol/L TDFe) and nearby East Pit (∼34,000 nmol/L DMn and 120,000 nmol/L TDFe). An intense hydrothermal plume dispersed predominantly to the southwest of the several hundred meter deep pits with concentration anomalies as high as 236 nmol/L DMn and 3,800 nmol/L TDFe measured 9 km distant. Iron and Mn concentrations within the pits decreased >30‐ to 200‐fold ∼1.5 months postcollapse and, during the following year, decreased a further twofold to threefold at Pele's Pit and ∼30‐fold at East Pit. While a steady concentration of ∼400 nmol/L TDFe prevailed throughout the remaining years of this study at Pele's Pit, a gradual and threefold decrease in the concentration of DMn to about 15 nmol/L was observed. High‐temperature fluids (128–198°C 1997–1999, ∼90°C 2001) venting simultaneously from different orifices within Pele's Pit had distinguishable Fe/Mn ratios that can be attributed to different subseafloor origins. Fe/Mn ratios characteristic of fluids moderated by high‐temperature water‐rock reaction had low values in 1997–1998 (1.6 ± 0.7), increasing to about 7 in 1999. Fluids moderated by magmatic degassing of CO2 had much higher Fe/Mn ratios, increasing from 24 ± 15 in 1997–1998 to 50 in 1999 and 63–87 in 2001. Fe/Mn values of dispersing plumes at Lō'ihi reflect an admixture of these sources and a relative Fe abundance that is consistently high compared to mid‐ocean ridge systems. The pulsed injection of Mn and Fe into the surrounding ocean associated with the 1996 tectonic‐magmatic event at Lō'ihi was massive. Our decadal observations confirm that Mn and Fe are useful markers of the magnitude and evolution of the effects of magmatic perturbation on hydrothermal systems influenced by chronic magmatic degassing.
Hurricanes, submarine groundwater discharge, and Florida's red tides
Authors: Hu Chuanmin , Muller‐Karger Frank E. , Swarzenski Peter W.
Published: June 2006

A Karenia brevis Harmful Algal Bloom affected coastal waters shallower than 50 m off west‐central Florida from January 2005 through January 2006, showing a sustained anomaly of ∼1 mg chlorophyll m−3 over an area of up to 67,500 km2. Red tides occur in the same area (approximately 26–29°N, 82–83°W) almost every year, but the intense 2005 bloom led to a widespread hypoxic zone (dissolved oxygen <2 mg L−1) that caused mortalities of benthic communities, fish, turtles, birds, and marine mammals. Runoff alone provided insufficient nitrogen to support this bloom. We pose the hypothesis that submarine groundwater discharge (SGD) provides the missing nutrients, and indeed can trigger and support the recurrent red tides off west‐central Florida. SGD inputs of dissolved inorganic nitrogen (DIN) in Tampa Bay alone are ∼35% of that discharged by all central Florida rivers draining west combined. We propose that the unusual number of hurricanes in 2004 resulted in high runoff, and in higher than normal SGD emerging along the west Florida coast throughout 2005, initiating and fueling the persistent HAB. This mechanism may also explain recurrent red tides in other coastal regions of the Gulf of Mexico.
A study of the currents of the outer shelf and upper slope from a decade of shipboard ADCP observations in the Middle Atlantic Bight
Authors: Flagg Charles N. , Dunn Maureen , Wang Dong‐Ping , Rossby H. Thomas , Benway Robert L.
Published: June 2006

Since 1992, upper ocean ADCP current data between New York and Bermuda have been gathered from the container ship Oleander to identify long‐term changes in the shelf, slope, Gulf Stream and Sargasso Sea. Temperature and surface salinity data have been been collected along this route since 1978 by NOAA/NMFRC. The first ten years of ADCP data from which the effects of warm ring have been removed are used to describe processes within the shelfbreak frontal sub‐region. The Eulerian mean velocity structure shows an along‐isobath shelfbreak jet with maximum speeds of O(0.15 m s−1) offshore of which is a ∼30 km wide relatively quiescent region. There is also an offshore slope current 40 to 50 km wide extending vertically to 300 m, with similar velocities as those found in the shelfbreak jet. The mean shelfbreak jet transport is 0.4 Sv while the slope current adds another 2.5 Sv. Maximum shelfbreak transport occurs in the fall and winter while the slope current reaches its maximum during the spring. In stream coordinates, the shelfbreak jet has maximum speeds of 0.35 m s−1, a width of ∼30 km and a vertical decay scale of ∼50 m. The maximum Rossby number within the jet, defined by ∣dU/dy∣max/f, is about 0.2. Significant interannual fluctuations occur in upper ocean temperature, salinity and currents, some of which appear related to changes in the NAO index. Seasonal changes in the slope current appear to be related to seasonal changes in the wind stress curl over the slope sea.
Sap flux–upscaled canopy transpiration, stomatal conductance, and water use efficiency in an old growth forest in the Great Lakes region of the United States
Authors: Tang Jianwu , Bolstad Paul V. , Ewers Brent E. , Desai Ankur R. , Davis Kenneth J. , Carey Eileen V.
Published: June 2006

Combining sap flux and eddy covariance measurements provides a means to study plant stomatal conductance and the relationship between transpiration and photosynthesis. We measured sap flux using Granier‐type sensors in a northern hardwood‐dominated old growth forest in Michigan, upscaled to canopy transpiration, and calculated canopy conductance. We also measured carbon and water fluxes with the eddy covariance method and derived daytime gross primary production (GPP). The diurnal patterns of sap flux and canopy transpiration were mainly controlled by vapor pressure deficit (D) and photosynthetically active radiation (PAR). Daily sums of sap flux and canopy transpiration had exponential relationships to D that saturated at higher D and had linear relationships to PAR. Sugar maple (Acer saccharum) and yellow birch (Betula alleghaniesis) had higher sap flux per unit of sapwood area than eastern hemlock (Tsuga canadensis), while sugar maple and hemlock had higher canopy transpiration per unit of leaf area than yellow birch. Sugar maple dominated canopy transpiration per ground area. Canopy transpiration averaged 1.57 mm d−1, accounting for 65% of total evapotranspiration in the growing season. Canopy conductance was controlled by both D and PAR, but the day‐to‐day variation in canopy conductance mainly followed a negatively logarithmic relationship with D. By removing the influences of PAR, half‐hourly canopy conductance was also negatively logarithmically correlated with D. Water use efficiency (WUE) had a strong exponential relationship with D on a daily basis and approached a minimum of 4.4 mg g−1. WUE provides an alternative to estimate GPP from measurements of sap flux.
Gaseous mercury in background forest soil in the northeastern United States
Authors: Sigler Jeffrey M. , Lee Xuhui
Published: June 2006

Although the soil gaseous mercury (Hg) reservoir is an important component of the soil Hg emission process, little is known of the behavior of gaseous Hg in soil pores and the processes governing the ultimate evasion of Hg from soil surfaces. In this study, gaseous Hg in background forest soil in the northeastern United States was examined during 2003 and 2004 using a novel flask sampling technique. This represents the first detailed study of gaseous Hg concentration within the soil profile. Soil gaseous Hg varied seasonally with soil temperature, and highest concentrations consistently occurred in the O‐ and upper A‐horizons. The study revealed clear gradients in gaseous Hg concentrations, which bore striking resemblance to gradients in bound Hg. In addition, measurements of soil Hg flux were correlated with soil gaseous Hg concentrations at 2 cm depth. These results indicate that the upper soil layers, rich in bound Hg, act as a source of gaseous Hg that may ultimately be emitted to the atmosphere. Large changes in soil gaseous Hg over shallow layers underscore the importance of fine vertical resolution of measurements, and therefore the utility of flask sampling.
Surface refractive index field estimation from multiple radars
Authors: Hao Yonggang , Goeckel Dennis , Janaswamy Ramakrishna , Frasier Stephen
Published: June 2006

Retrieval of surface layer refractivity via the method of Fabry et al. (1997) is considered. A mathematical framework is constructed, and signal processing algorithms are derived that facilitate refractivity retrieval from the returns from multiple radars viewing a common geographical area. In particular, an approximate discrete model is derived to relate the measured phases to the surface layer refractivity fields, and a modified least squares estimation algorithm is then proposed for the resulting, often ill‐conditioned, inversion problem. Because the measurement technique is subject to modulo 2π uncertainties which impact retrievals, a novel algorithm which jointly estimates the unwrapped phases and refractive index (RI) field is also provided. Numerical results indicate the effectiveness of the derived algorithms in both the single‐ and multiple‐radar cases, as well as clearly establishing that having multiple views of the same geographical area from separate radars provides for significant improvement of the RI field estimates.
Improved positioning by addition of atmospheric corrections to local area differential GPS
Authors: Singh Malkiat , Reilly Michael H.
Published: June 2006

A local area differential GPS (DGPS) method applies corrections from a reference GPS receiver to improve positioning accuracy for a roaming GPS receiver. Increasing separation between reference and roaming receivers dilutes this improvement, largely because ionospheric and tropospheric effects differ between their two locations. We correct differential corrections for this difference and determine the improvement with this “atmospheric” DGPS method at roaming receiver positions that are separated from a Coast Guard reference receiver at Annapolis, Maryland, by 44, 67, and 228 km. For ionospheric corrections we use our Raytrace–Ionospheric conductivity and electron density–Bent–Gallagher ionospheric propagation model with driving parameters obtained from two‐frequency data of surveyed reference GPS receivers. For tropospheric corrections we use the Hopfield model and weather station data for surface temperature, pressure, and relative humidity. Internet delivery of atmospheric differential corrections is used to avoid blockage or range cutoff of radio transmissions. Some comparisons are made with Wide Area Augmentation System GPS receiver performance.
Anomalous F region response to moderate solar flares
Authors: Smithtro C. G. , Sojka J. J. , Berkey T. , Thompson D. , Schunk R. W.
Published: June 2006

Ionograms recorded with a dynasonde at Bear Lake Observatory, Utah, during moderate solar x‐ray flares exhibit characteristic enhancements to the E and F1 region ionosphere. However, during these same flares, the peak electron density of the ionosphere (NmF2) unexpectedly decreases, recovering after the flare ends. In order to reconcile this anomalous behavior with expected increases to the total electron content (TEC), we undertake a modeling effort using the Time‐Dependent Ionospheric Model (TDIM) developed at Utah State University. For solar input, a simple flare time irradiance model is created, using measurements from the Solar EUV Experiment instrument on the TIMED spacecraft. TDIM simulations show that the anomalous NmF2 response can be explained by assuming a rapid electron temperature increase, which increases the O+ scale height, moving plasma to higher altitudes. The model results are able to reproduce both the decreasing NmF2 as well as the expected TEC enhancement.
Counterclockwise rotation of late Eocene–Oligocene fore‐arc deposits in southern Peru and its significance for oroclinal bending in the central Andes
Authors: Roperch Pierrick , Sempere Thierry , Macedo Orlando , Arriagada César , Fornari Michel , Tapia Claudio , García Marcelo , Laj Carlo
Published: June 2006

The results of a paleomagnetic study along the fore arc of southern Peru (15–18°S) and northern Chile (18–19°S) are reported from middle to late Miocene ignimbrites (7 sites), late Oligocene to early Miocene ignimbrites (72 sites), Paleogene sediments (20 sites), and Mesozoic and Paleocene volcanics and intrusions (31 sites). Comparison of locality‐mean directions with expected paleomagnetic directions indicates vertical axis rotations ranging from 5.2 ± 11.3° clockwise to 55.6 ± 7.0° counterclockwise. Spatially, the magnitude of counterclockwise rotations increases northward from ∼0° within the Chilean fore arc south of 18°30′S to >45° north of 16°30′S. In southern Peru, paleomagnetic rotations recorded in Paleogene red beds decrease from late Eocene to late Oligocene, whereas Miocene ignimbrites display no evidence of rotation. These new results confirm that the rotations recorded in the fore arc of southern Peru were acquired at least before ∼15 Ma, and probably before 25 Ma, and thus prior to the late Neogene shortening of the sub‐Andes. The onset of major Andean shortening in the Eastern Cordillera during the latest Eocene–earliest Oligocene is interpreted to have triggered the bending of the Peruvian fore arc. The region of the Peruvian fore arc with the largest rotations appears to be the fore‐arc counterpart of the Abancay deflection, a remarkable NE‐SW offset in the axis of the Eastern Cordillera induced by a major regional preorogenic structure. We underline that the Abancay deflection should be seen as the northwestern boundary, and therefore as a key element, of the Bolivian Orocline.
Sharp interface, one‐dimensional seawater intrusion into a confined aquifer with controlled pumping: Analytical solution
Authors: Kacimov A. R. , Sherif M. M.
Published: June 2006

A rigorous, closed form solution for the hydraulic head, sharp interface shape, and position in a confined aquifer bordered on one side by a static interface with intruded sea water and on another side by a constant head boundary is obtained in terms of the Dupuit‐Forcheheimer model. Linear and nonlinear differential equations governing the hydraulic head variation with the horizontal coordinate contain a sink term, which is assumed to have a constant strength over the unintruded part of the catchment and linearly decreasing strength through the section overlying the interface. Solutions of the two equations are conjugated. For the length of the freshwater zone a quartic is obtained and solved. An explicit solvability condition is presented. The interface equation includes the commanding freshwater head, seawater level, density contrast between saline and fresh water, aquifer thickness and conductivity, and intensity of smeared losses, which model abstraction from the aquifer.
Vertical structure reveals eddy lifetime in the Greenland Sea
Authors: Ronski S. , Budéus G.
Published: June 2006

Recently observed coherent vortices in the central Greenland Sea are regarded as possible contributors to local deep water formation. Within them, winter convection distributes surface waters to considerably greater depths than elsewhere (up to 2700 m vs 1500 m). The lifetime of coherent vortices is an important open question, which determines the volume flux into deep waters. Here, we present previously lacking direct evidence for a lifetime of more than two years from a detailed analysis of the vertical structure within a vortex core on the base of hydrographic observations in 2005.
Frozen local hole approximation
Authors: Pahl Elke , Birkenheuer Uwe
Published: June 2006

The frozen local hole approximation (FLHA) is an adiabatic approximation which is aimed to simplify the correlation calculations of valence and conduction bands of solids and polymers or, more generally, of the ionization potentials and electron affinities of any large system. Within this approximation correlated local hole states (CLHSs) are explicitly generated by correlating local Hartree-Fock (HF) hole states, i.e., (N−1)-particle determinants in which the electron has been removed from a local occupied orbital. The hole orbital and its occupancy are kept frozen during these correlation calculations, implying a rather stringent configuration selection. Effective Hamilton matrix elements are then evaluated with the above CLHSs; diagonalization finally yields the desired correlation corrections for the cationic hole states. We compare and analyze the results of the FLHA with the results of a full multireference configuration interaction with single and double excitations calculation for two prototype model systems, (H2)n ladders and H–(Be)n–H chains. Excellent numerical agreement between the two approaches is found. Comparing the FLHA with a full correlation treatment in the framework of quasidegenerate variational perturbation theory reveals that the leading contributions in the two approaches are identical. In the same way it could be shown that a much less demanding self-consistent field (SCF) calculation around a frozen local hole fully recovers, up to first order, all the leading single excitation contributions. Thus, both the FLHA and the above SCF approximation are well justified and provide a very promising and efficient alternative to fully correlated wave-function-based treatments of the valence and conduction bands in extended systems.
Evaluation of efficiency of reference potential spatial warping algorithm in conformational sampling of peptides
Authors: Ishitani Ryuichiro , Shimizu Kentaro , Terada Tohru
Published: June 2006

Molecular dynamics (MD) simulation using the reference potential spatial warping algorithm (REPSWA) is a promising method for computing the conformational equilibrium of a system with a rugged energy surface. Its effectiveness has previously been demonstrated using only a simplified model system of a hydrocarbon chain omitting nonbonded interaction terms from the potential energy function. To evaluate the applicability of REPSWA MD simulation to more realistic problems, we applied it to small peptide systems in an aqueous environment. Difficulties were encountered, however, forcing us to devise several modifications. We investigated their effectiveness in comparison to conventional constant-temperature and multicanonical MD simulations. We found that the sampling efficiency of the modified REPSWA MD after a careful optimization of its parameters was better than that of the constant-temperature MD and comparable to that of the multicanonical MD in several cases.
Model for the free-volume distributions of equilibrium fluids
Authors: Krekelberg William P. , Ganesan Venkat , Truskett Thomas M.
Published: June 2006

We introduce and test via molecular simulation a simple model for predicting the manner in which interparticle interactions and thermodynamic conditions impact the single-particle free-volume distributions of equilibrium fluids. The model suggests a scaling relationship for the density-dependent behavior of the hard-sphere system. It also predicts how the second virial coefficients of fluids with short-range attractions affect their free-volume distributions.