Fermion Masses from SO(10) Hermitian Matrices

Masses of fermions in the SO(10) 16-plet are constructed using only the 10, 120 and 126 scalar multiplets. The mass matrices are restricted to be hermitian and the theory is constructed to have certain assumed quark masses, charged lepton masses and CKM matrix in accord with data. The remaining free parameters are found by fitting to light neutrino masses and MSN matrices result as predictions.Comment: 23 pages. Small textual additions for clarification; formalism and results unchanged. Version to appear in Phys. Rev.

Broadband characterisation of in-duct acoustic sources using an equivalent source approach

This paper is concerned with the development of an experimental method capable of independently characterising low Mach number, in-duct fluid machines, such as pumps, fans, etc. The aim is to propose and test a source characterisation method that is suitable for acoustic simulation and the construction Virtual Acoustic Prototypes. Such a requirement demands that the source characterisation be (a) independent, so that components can be virtually (re)combined within different assemblies and (b) valid over a wide frequency range so as to enable the output of a virtual assembly to be auralised. In this regard, standard methods based on sound power are not suitable. An equivalent source approach is proposed, based on a two-stage measurement procedure in which source strengths are obtained by solving an inverse problem. The experimental application of the procedure is illustrated as part of a case study where a high speed compressor unit is independently characterised and the resulting source data used to predict the operational response in a new assembly. Three frequency ranges are identified based on plane wave, modal and statistical behavior within the duct. The same measured data is used within each regime but subject to different processing according to different assumptions. Predictions are shown to be in good agreement with the directly measured response over a broad frequency range (100 Hz–10 kHz)

An Exact Calculation of the Energy Density of Cosmological Gravitational Waves

In this paper we calculate the Bogoliubov coefficients and the energy density of the stochastic gravitational wave background for a universe that undergoes inflation followed by radiation domination and matter domination, using a formalism that gives the Bogoliubov coefficients as continous functions of time. By making a reasonable assumption for the equation of state during reheating, we obtain in a natural way the expected high frequency cutoff in the spectral energy density.Comment: 12 pages+5 figures, uuencoded file,DF/IST-2.9

Single Channel Analysis of Conductance and Rectification in Cation-selective, Mutant Glycine Receptor Channels

Members of the ligand-gated ion channel superfamily mediate fast synaptic transmission in the nervous system. In this study, we investigate the molecular determinants and mechanisms of ion permeation and ion charge selectivity in this family of channels by characterizing the single channel conductance and rectification of α1 homomeric human glycine receptor channels (GlyRs) containing pore mutations that impart cation selectivity. The A-1'E mutant GlyR and the selectivity double mutant ([SDM], A-1'E, P-2'Δ) GlyR, had mean inward chord conductances (at −60 mV) of 7 pS and mean outward conductances of 11 and 12 pS (60 mV), respectively. This indicates that the mutations have not simply reduced anion permeability, but have replaced the previous anion conductance with a cation one. An additional mutation to neutralize the ring of positive charge at the extracellular mouth of the channel (SDM+R19'A GlyR) made the conductance–voltage relationship linear (14 pS at both 60 and −60 mV). When this external charged ring was made negative (SDM+R19'E GlyR), the inward conductance was further increased (to 22 pS) and now became sensitive to external divalent cations (being 32 pS in their absence). The effects of the mutations to the external ring of charge on conductance and rectification could be fit to a model where only the main external energy barrier height for permeation was changed. Mean outward conductances in the SDM+R19'A and SDM+R19'E GlyRs were increased when internal divalent cations were absent, consistent with the intracellular end of the pore being flanked by fixed negative charges. This supports our hypothesis that the ion charge selectivity mutations have inverted the electrostatic profile of the pore by introducing a negatively charged ring at the putative selectivity filter. These results also further confirm the role of external pore vestibule electrostatics in determining the conductance and rectification properties of the ligand-gated ion channels

Cation-selective Mutations in the M2 Domain of the Inhibitory Glycine Receptor Channel Reveal Determinants of Ion-Charge Selectivity

Ligand-gated ion channel receptors mediate neuronal inhibition or excitation depending on their ion charge selectivity. An investigation into the determinants of ion charge selectivity of the anion-selective α1 homomeric glycine receptor (α1 glycine receptor [GlyR]) was undertaken using point mutations to residues lining the extra- and intracellular ends of the ion channel. Five mutant GlyRs were studied. A single substitution at the intracellular mouth of the channel (A-1′E GlyR) was sufficient to convert the channels to select cations over anions with PCl/PNa = 0.34. This result delimits the selectivity filter and provides evidence that electrostatic interactions between permeating ions and pore residues are a critical factor in ion charge selectivity. The P-2′Δ mutant GlyR retained its anion selectivity (PCl/PNa = 3.81), but it was much reduced compared with the wild-type (WT) GlyR (PCl/PNa = 27.9). When the A-1′E and the P-2′Δ mutations were combined (selectivity double mutant [SDM] GlyR), the relative cation permeability was enhanced (PCl/PNa = 0.13). The SDM GlyR was also Ca2+ permeable (PCa/PNa = 0.29). Neutralizing the extracellular mouth of the SDM GlyR ion channel (SDM+R19′A GlyR) produced a more Ca2+-permeable channel (PCa/PNa = 0.73), without drastically altering monovalent charge selectivity (PCl/PNa = 0.23). The SDM+R19′E GlyR, which introduces a negatively charged ring at the extracellular mouth of the channel, further enhanced Ca2+ permeability (PCa/PNa = 0.92), with little effect on monovalent selectivity (PCl/PNa = 0.19). Estimates of the minimum pore diameter of the A-1′E, SDM, SDM+R19′A, and SDM+R19′E GlyRs revealed that these pores are larger than the α1 GlyR, with the SDM-based GlyRs being comparable in diameter to the cation-selective nicotinic acetylcholine receptors. This result provides evidence that the diameter of the ion channel is also an important factor in ion charge selectivity

A Single P-loop Glutamate Point Mutation to either Lysine or Arginine Switches the Cation–Anion Selectivity of the CNGA2 Channel

Cyclic nucleotide-gated (CNG) channels play a critical role in olfactory and visual transduction. Site-directed mutagenesis and inside-out patch-clamp recordings were used to investigate ion permeation and selectivity in two mutant homomeric rat olfactory CNGA2 channels expressed in HEK293 cells. A single point mutation of the negatively charged pore loop (P-loop) glutamate (E342) to either a positively charged lysine or arginine resulted in functional channels, which consistently responded to cGMP, although the currents were generally extremely small. The concentration–response curve of the lysine mutant channel was very similar to that of wild-type (WT) channels, suggesting no major structural alteration to the mutant channels. Reversal potential measurements, during cytoplasmic NaCl dilutions, showed that the lysine and the arginine mutations switched the selectivity of the channel from cations (PCl/PNa = 0.07 [WT]) to anions (PCl/PNa = 14 [Lys] or 10 [Arg]). Relative anion permeability sequences for the two mutant channels, measured with bi-ionic substitutions, were NO3− > I− > Br− > Cl− > F− > acetate−, the same as those obtained for anion-selective GABA and glycine channels. The mutant channels also seem to have an extremely small single-channel conductance, measured using noise analysis of about 1–2 pS, compared to a WT value of about 29 pS. The results showed that it is predominantly the charge of the E342 residue in the P-loop, rather than the pore helix dipoles, which controls the cation–anion selectivity of this channel. However, the outward rectification displayed by both mutant channels in symmetrical NaCl solutions suggests that the negative ends of the pore helix dipoles may play a role in reducing the outward movement of Cl− ions through these anion-selective channels. These results have potential implications for the determinants of anion–cation selectivity in the large family of P-loop–containing channels

History of scoria-cone eruptions on the eastern shoulder of the Kenya–Tanzania Rift revealed in the 250-ka sediment record of Lake Chala near Mount Kilimanjaro

Reconstructions of the timing and frequency of past eruptions are important to assess the propensity for future volcanic activity, yet in volcanic areas such as the East African Rift only piecemeal eruption historiesexist. Understanding thevolcanichistory of scoria‐conefields, whereeruptionsare often infrequentand deposits strongly weathered, is particularly challenging. Here we reconstruct a history of volcanism from scoria cones situated along the eastern shoulders of the Kenya–Tanzania Rift, using a sequence of tephra (volcanic ash) layers preserved in the ~250‐ka sediment record of Lake Chala near Mount Kilimanjaro. Seven visible and two non‐visible (crypto‐) tephra layers in the Lake Chala sequence are attributed to activity from the Mt Kilimanjaro (northern Tanzania) and the Chyulu Hills (southern Kenya) volcanic fields, on the basis of their glass chemistry, textural characteristics and known eruption chronology. The Lake Chala record of eruptions from scoria cones in the Chyulu Hills volcanic field confirms geological and historical evidence of its recent activity, and provides first‐order age estimates for seven previously unknown eruptions. Long and well‐resolved sedimentary records such as that of Lake Chala have significant potential for resolving regional eruption chronologies spanning hundreds of thousands of years.NERC (NE/ P011969/1

Benefits of Exergy-Based Analysis for Aerospace Engineering Applications—Part I

This paper compares the analysis of systems from two different perspectives: an energy-based focus and an exergy-based focus. A complex system was simply modeled as interacting thermodynamic systems to illustrate the differences in analysis methodologies and results. The energy-based analysis had combinations of calculated states that are infeasible. On the other hand, the exergy-based analyses only allow feasible states. More importantly, the exergy-based analyses provide clearer insight to the combination of operating conditions for optimum system-level performance. The results strongly suggest changing the analysis/design paradigm used in aerospace engineering from energy-based to exergy-based. This methodology shift is even more critical in exploratory research and development where previous experience may not be available to provide guidance. Although the models used herein may appear simplistic, the message is very powerful and extensible to higher-fidelity models: the 1st Law is only a necessary condition for design, whereas the 1st and 2nd Laws provide the sufficiency condition

The diet of red-throated divers (Gavia stellata) overwintering in the German Bight (North Sea) analysed using molecular diagnostics

In Europe, the German Bight is one of the most important non-breeding areas for protected red-throated divers (Gavia stellata). It is unclear what attracts the birds to this area, especially as the food composition of seabirds outside the breeding season is notoriously difficult to study. To obtain information on prey species composition of red-throated divers in this area, faecal samples from 34 birds caught alive were analysed using DNA metabarcoding. Prey DNA was detected in 85% of the samples with a mean number of 4.2 ± 0.7 taxa per sample (n = 29). Altogether, we found a broad prey spectrum with 19 fish taxa from 13 families dominated by five groups: clupeids, mackerel, gadoids, flatfish and sand lances with clupeids being the most frequently detected prey. Our results indicate that red-throated divers are generalist opportunistic feeders in the German Bight, but pelagic schooling fish that aggregate at frontal zones and have a high energetic value might be favoured. Atlantic mackerel appears to be a more important prey for red-throated divers in this area than previously thought. The precision achievable using metabarcoding has revealed a number of prey species that are consumed by red-throated divers in the German Bight, which helps to explain the selection of this area by divers in winter and spring

Vector Meson Photoproduction with an Effective Lagrangian in the Quark Model

A quark model approach to the photoproduction of vector mesons off nucleons is proposed. Its starting point is an effective Lagrangian of the interaction between the vector meson and the quarks inside the baryon, which generates the non-diffractive s- and u- channel resonance contributions. Additional t-channel $\pi^0$ and $\sigma$ exchanges are included for the $\omega$ and $\rho^0$ production respectively to account for the large diffractive behavior in the small $t$ region as suggested by Friman and Soyeur. The numerical results are presented for the $\omega$ and $\rho$ productions in four isospin channels with the same set of parameters, and they are in good agreement with the available data not only in $\omega$ and $\rho^0$ productions but also in the charged $\rho$ productions where the additional t-channel $\sigma$ exchange does not contribute so that it provides an important test to this approach. The investigation is also extended to the $\phi$ photoproduction, and the initial results show that the non-diffractive behavior of the $\phi$ productions in the large $t$ region can be described by the s- and u- channel contributions with significantly smaller coupling constants, which is consistent with the findings in the similar studies in the QHD framework. The numerical investigation has also shown that polarization observables are essential for identifying so-called "missing resonances".Comment: 36 pages, 10 PS figures, extended version of nucl-th/9711061 and nucl-th/9803021, submitted to PR