Intracerebroventricular Infusion of Vasoactive Intestinal Peptide Rescues the Luteinizing Hormone Surge in Middle-Aged Female Rats

Reproductive aging is characterized by delayed and attenuated luteinizing hormone (LH) surges apparent in middle-aged rats. The suprachiasmatic nucleus (SCN) contains the circadian clock that is responsible for the timing of diverse neuroendocrine rhythms. Electrophysiological studies suggest vasoactive intestinal peptide (VIP) originating from the SCN excites gonadotropin-releasing hormone (GnRH) neurons and affects daily patterns of GnRH–LH release. Age-related LH surge dysfunction correlates with reduced VIP mRNA expression in the SCN and fewer GnRH neurons with VIP contacts expressing c-fos, a marker of neuronal activation, on the day of the LH surge. To determine if age-related LH surge dysfunction reflects reduced VIP availability or altered VIP responsiveness under estradiol positive feedback conditions, we assessed the effect of intracerebroventricular (icv) VIP infusion on c-fos expression in GnRH neurons and on LH release in ovariohysterectomized, hormone-primed young and middle-aged rats. Icv infusion of VIP between 1300 and 1600 h significantly advanced the time of peak LH release, increased total and peak LH release, and increased the number of GnRH neurons expressing c-fos on the day of the LH surge in middle-aged rats. Surprisingly, icv infusion of VIP in young females significantly reduced the number of GnRH neurons expressing c-fos and delayed and reduced the LH surge. These observations suggest that a critical balance of VIP signaling is required to activate GnRH neurons for an appropriately timed and robust LH surge in young and middle-aged females. Age-related LH surge changes may, in part, result from decreased availability and reduced VIP-mediated neurotransmission under estradiol positive feedback conditions

Ectopic expression of the phosphomimic mutant version of Arabidopsis response regulator 1 promotes a constitutive cytokinin response phenotype

Background Cytokinins control numerous plant developmental processes, including meristem formation and activity, nutrient distribution, senescence timing and responses to both the abiotic and biotic environments. Cytokinin signaling leads to the activation of type-B response regulators (RRBs), Myb-like transcription factors that are activated by the phosphorylation of a conserved aspartate residue in their response receiver domain. Consistent with this, overexpression of RRBs does not substantially alter plant development, but instead leads to cytokinin hypersensitivity. Results Here we present comparative analysis of plants overexpressing Arabidopsis RRB 1 (ARR1) or a phosphomimic ARR1D94E mutant in which the conserved aspartate-94 (D94) is replaced by the phosphomimic residue glutamate (E). The D94E substitution causes a 100-fold increase in response activation and instigates developmental and physiological changes that characterize wild-type plants treated with cytokinins or transgenic plants with increased cytokinin content. Conclusion The current model of cytokinin signaling emphasizes the essential role of conserved aspartate residue phosphorylation of RRBs in promoting cytokinin responses. Our comparative analyses of developmental and physiological traits of ARR1 and ARR1D94E overexpressing plants revealed that the ARR1D94E protein is indeed a constitutive and wide-spectrum cytokinin response activator

High stress monitoring of prestressing tendons in nuclear concrete vessels using fibre-optic sensors

Maintaining the structural health of prestressed concrete nuclear containments is a key element in ensuring nuclear reactors are capable of meeting their safety requirements. This paper discusses the attachment, fabrication and characterisation of optical fibre strain sensors suitable for the prestress monitoring of irradiated steel prestressing tendons. The all-metal fabrication and welding process allowed the instrumented strand to simultaneously monitor and apply stresses up to 1300 MPa (80% of steel's ultimate tensile strength). There were no adverse effects to the strand's mechanical properties or integrity. After sensor relaxation through cyclic stress treatment, strain transfer between the optical fibre sensors and the strand remained at 69%. The fibre strain sensors could also withstand the non-axial forces induced as the strand was deflected around a 4.5 m bend radius. Further development of this technology has the potential to augment current prestress monitoring practices, allowing distributed measurements of short- and long-term prestress losses in nuclear prestressed-concrete vessels

Asymmetry of bifurcated features in radio pulsar profiles

High-quality integrated radio profiles of some pulsars contain bifurcated, highly symmetric emission components (BECs). They are observed when our line of sight traverses through a split-fan shaped emission beam. It is shown that for oblique cuts through such a beam, the features appear asymmetric at nearly all frequencies, except from a single `frequency of symmetry' nu_sym, at which both peaks in the BEC have the same height. Around nu_sym the ratio of flux in the two peaks of a BEC evolves in a way resembling the multifrequency behaviour of J1012+5307. Because of the inherent asymmetry resulting from the oblique traverse of sightline, each minimum in double notches can be modelled independently. Such a composed model reproduces the double notches of B1929+10 if the fitted function is the microscopic beam of curvature radiation in the orthogonal polarisation mode. These results confirm our view that some of the double components in radio pulsar profiles directly reveal the microscopic nature of the emitted radiation beam as the microbeam of curvature radiation polarised orthogonally to the trajectory of electrons.Comment: 10 pages, 7 figures, printed in MNRA

Consensus under Misaligned Orientations

This paper presents a consensus algorithm under misaligned orientations, which is defined as (i) misalignment to global coordinate frame of local coordinate frames, (ii) biases in control direction or sensing direction, or (iii) misaligned virtual global coordinate frames. After providing a mathematical formulation, we provide some sufficient conditions for consensus or for divergence. Besides the stability analysis, we also conduct some analysis for convergence characteristics in terms of locations of eigenvalues. Through a number of numerical simulations, we would attempt to understand the behaviors of misaligned consensus dynamics.Comment: 23 pages, 9 figure

WTC2005-63773 VAPOR PHASE LUBRICATION OF GOLD/GOLD INTERFACES

ABSTRACT The extension of current micro-satellite development efforts calls for a reduction in size by up to two orders of magnitude. Such a reduction in size necessitates the development of novel actuators, switches, and sensors operating on the micron length scale. The leading technology for creating such devices involves microfabrication processes currently used in the production of integrated circuits. Devices generated by these means are referred to as Micro-ElectroMechanical Systems (MEMS). While many challenges remain in the design and production of MEMS, a critical aspect of their successful deployment involves lubrication of the devices to prevent wear and permanent, undesired adhesion (seizure) of the miniature moving parts. Results from research addressing the vapor phase lubrication of gold-gold contacts, modeling interfaces expected to be encountered in future RF MEMS devices, will be presented. Such interfaces will require high frequency intermittent contact, the absence of irreversible interfacial adhesion, the general absence of sliding within the contact, and the requirement of electrical conductivity upon contact. Work in this area has focused on the use of alklythiols as a means of controlling interfacial adhesion. Experiments have been carried out using atomic force microscopy to characterize adhesion as a function of alkylthiol chain length. In addition, these experiments have incorporated the simultaneous measurement of interfacial currents to explore load versus conductivity relationships. These measurements have been supported through measurements of surface composition through correlated quartz crystal microbalance (QCM) and X-ray photoelectron spectroscopy (XPS) measurements. INTRODUCTION There have been a number of methods to lubricate MEMS devices proposed and tested and several review articles have been published describing these efforts

Boost-Invariant Running Couplings in Effective Hamiltonians

We apply a boost-invariant similarity renormalization group procedure to a light-front Hamiltonian of a scalar field phi of bare mass mu and interaction term g phi^3 in 6 dimensions using 3rd order perturbative expansion in powers of the coupling constant g. The initial Hamiltonian is regulated using momentum dependent factors that approach 1 when a cutoff parameter Delta tends to infinity. The similarity flow of corresponding effective Hamiltonians is integrated analytically and two counterterms depending on Delta are obtained in the initial Hamiltonian: a change in mu and a change of g. In addition, the interaction vertex requires a Delta-independent counterterm that contains a boost invariant function of momenta of particles participating in the interaction. The resulting effective Hamiltonians contain a running coupling constant that exhibits asymptotic freedom. The evolution of the coupling with changing width of effective Hamiltonians agrees with results obtained using Feynman diagrams and dimensional regularization when one identifies the renormalization scale with the width. The effective light-front Schroedinger equation is equally valid in a whole class of moving frames of reference including the infinite momentum frame. Therefore, the calculation described here provides an interesting pattern one can attempt to follow in the case of Hamiltonians applicable in particle physics.Comment: 24 pages, LaTeX, included discussion of finite x-dependent counterterm

WTC2005-63773 VAPOR PHASE LUBRICATION OF GOLD/GOLD INTERFACES

ABSTRACT The extension of current micro-satellite development efforts calls for a reduction in size by up to two orders of magnitude. Such a reduction in size necessitates the development of novel actuators, switches, and sensors operating on the micron length scale. The leading technology for creating such devices involves microfabrication processes currently used in the production of integrated circuits. Devices generated by these means are referred to as Micro-ElectroMechanical Systems (MEMS). While many challenges remain in the design and production of MEMS, a critical aspect of their successful deployment involves lubrication of the devices to prevent wear and permanent, undesired adhesion (seizure) of the miniature moving parts. Results from research addressing the vapor phase lubrication of gold-gold contacts, modeling interfaces expected to be encountered in future RF MEMS devices, will be presented. Such interfaces will require high frequency intermittent contact, the absence of irreversible interfacial adhesion, the general absence of sliding within the contact, and the requirement of electrical conductivity upon contact. Work in this area has focused on the use of alklythiols as a means of controlling interfacial adhesion. Experiments have been carried out using atomic force microscopy to characterize adhesion as a function of alkylthiol chain length. In addition, these experiments have incorporated the simultaneous measurement of interfacial currents to explore load versus conductivity relationships. These measurements have been supported through measurements of surface composition through correlated quartz crystal microbalance (QCM) and X-ray photoelectron spectroscopy (XPS) measurements. INTRODUCTION There have been a number of methods to lubricate MEMS devices proposed and tested and several review articles have been published describing these efforts

Studies on metal-organic frameworks of Cu(II) with isophthalate linkers for hydrogen storage

Hydrogen (H2) is a promising alternative energy carrier due to its environmental benefits, high energy density and its abundance. However, development of a practical storage system to enable the “Hydrogen Economy” remains a huge challenge. Metal-organic frameworks (MOFs) are an important class of crystalline coordination polymers constructed by bridging metal centers with organic linkers, and show promise for H2 storage due to their high surface area and tuneable properties. We summarize our research on novel porous materials with enhanced H2 storage properties, and describe frameworks derived from 3,5-substituted dicarboxylates (isophthalates) that serve as versatile molecular building blocks for the construction of a range of interesting coordination polymers with Cu(II) ions. A series of materials has been synthesised by connecting linear tetracarboxylate linkers to {Cu(II)2} paddlewheel moieties. These (4,4)-connected frameworks adopt the fof-topology in which the Kagomé lattice layers formed by {Cu(II)2} paddlewheels and isophthalates are pillared by the bridging ligands. These materials exhibit high structural stability and permanent porosity, and the pore size, geometry and functionality can be modulated by variation of the organic linker to control the overall H2 adsorption properties. NOTT-103 shows the highest H2 storage capacity of 77.8 mg g−1 at 77 K, 60 bar among the fof-type frameworks. H2 adsorption at low, medium and high pressures correlates with the isosteric heat of adsorption, surface area and pore volume, respectively. Tri-branched C3-symmetric hexacarboxylate ligands with Cu(II) give highly porous (3,24)-connected frameworks incorporating {Cu(II)2} paddlewheels. These ubt-type frameworks comprise three types of polyhedral cage: a cuboctahedron, truncated tetrahedron and a truncated octahedron which are fused in the solid state in the ratio 1:2:1, respectively. Increasing the length of the hexacarboxylate struts directly tunes the porosity of the resultant material from micro- to mesoporosity. These materials show exceptionally high H2 uptakes owing to their high surface area and pore volume. NOTT-112, the first reported member of this family reported, adsorbs 111 mg g−1 of H2 at 77 K , 77 bar. More recently, enhanced H2 adsorption in these ubt-type frameworks has been achieved using combinations of polyphenyl groups linked by alkynes to give an overall gravimetric gas capacity for NU-100 of 164 mg g−1 at 77 K, 70 bar. However, due to its very low density NU-100 shows a lower volumetric capacity of 45.7 g L-1 compared with 55.9 g L-1 for NOTT-112, which adsorbs 2.3 wt% H2 at 1 bar, 77K. This significant adsorption of H2 at low pressures is attributed to the arrangement of the {Cu24(isophthalate)24} cuboctahedral cages within the polyhedral structure. Free metal coordination positions are the first binding sites for D2, and in these ubt-type frameworks there are two types of Cu(II) centres, one with its vacant site pointing into the cuboctahedral cage and another pointing externally. D2 molecules bind first at the former position, and then at the external open metal sites. However, other adsorption sites between the cusp of three phenyl groups and a Type I pore window in the framework are also occupied. Ligand and complex design feature strongly in enhancing and maximising H2 storage, and, although current materials operate at 77 K, research continues to explore routes to high capacity H2 storage materials that can function at higher temperatures

Platelet Factor XIIIa Release During Platelet Aggregation and Plasma Clot Strength Measured by Thrombelastography in Patients with Coronary Artery Disease Treated with Clopidogrel.

It has been estimated that up to half of circulating Factor XIIIa (FXIIIa) is stored in platelets. The release of FXIIIa from platelets upon stimulation with ADP in patients with coronary artery disease treated with dual antiplatelet therapy has not been previously examined. Samples from 96 patients with established coronary artery disease treated with aspirin and clopidogrel were examined. Platelet aggregation was performed by light transmittance aggregometry (LTA) in platelet rich plasma (PRP) with platelet poor plasma (PPP) as reference and ADP 5μM as agonist. Kaolin activated TEG was performed in citrate PPP. PRP after aggregation was centrifuged and plasma supernatant (PSN) collected. FXIIIa was measured in PPP and PSN.Platelet aggregation after stimulation with ADP 5μM resulted in 24% additional FXIIIa release in PSN as compared to PPP (99.3 ± 27 vs. 80.3 ± 24 %, p<0.0001). FXIIIa concentration in PSN correlated with maximal plasma clot strength (TEG-G) (r=0.48, p<0.0001), but not in PPP (r=0.15, p=0.14). Increasing quartiles of platelet derived FXIIIa were associated with incrementally higher TEG-G (p=0.012). FXIIIa release was similar between clopidogrel responders and non-responders (p=0.18). In summary, platelets treated with aspirin and clopidogrel release a significant amount of FXIIIa upon aggregation by ADP. Platelet derived FXIIIa may contribute to differences in plasma TEG-G, and thus in part provide a mechanistic explanation for high clot strength observed as a consequence of platelet activation. Variability in clopidogrel response does not significantly influence FXIIIa release from platelets