Wind loads on open truss structures: applications of blockage to historic transporter bridges.

The overall aim of this study is to compare and contrast the design of the two remaining working examples of early twentieth-century transporter bridges in the UK, namely, those at Newport and Middlesbrough. With the aid of modern finite-element analysis, the behaviour of the structures under loading is investigated, likely modes of failure determined and the efficiency of each structure evaluated. The important horizontal load component due to wind at the exposed locations of the bridges is examined using 'current blockage', ideas transferred from recent work on wave-current-structure interaction for space-frame structures in offshore engineering. This article is part of the theme issue 'Environmental loading of heritage structures'.

Second-order statistics and 'designer' waves for violent free-surface motion around multi-column structures.

Extreme wave-structure interactions are investigated using second-order diffraction theory. The statistics of surface elevation around a multi-column structure are collected using Monte Carlo-type simulations for severe sea states. Within the footprint of a realistic four-column structure, we find that the presence of the structure can give rise to extreme crest elevations greater than twice those at the same return period in the incident wave field. Much of this extra elevation is associated with the excitation of second-order near-trapped modes. A 'designer' incident wave can be defined at each point around the structure for a given sea state as the average input wave to produce extreme crest elevations at a given return period, and we show that this wave can be simply vertically scaled to estimate the response at other return periods.

Onset and limiting amplitude of yaw instability of a submerged three-tethered buoy.

In this paper the dynamics of a submerged axi-symmetric wave energy converter are studied, through mathematical models and wave basin experiments. The device is disk-shaped and taut-moored via three inclined tethers which also act as a power take-off. We focus on parasitic yaw motion, which is excited parametrically due to coupling with heave. Assuming linear hydrodynamics throughout, but considering both linear and nonlinear tether geometry, governing equations are derived in 6 degrees of freedom (DOF). From the linearized equations, all motions, apart from yaw, are shown to be contributing to the overall power absorption. At higher orders, the yaw governing equation can be recast into a classical Mathieu equation (linear in yaw), or a nonlinear Mathieu equation with cubic damping and stiffness terms. The well-known stability diagram for the classical Mathieu equation allows prediction of onset/occurrence of yaw instability. From the nonlinear Mathieu equation, we develop an approximate analytical solution for the amplitude of the unstable motions. Comparison with regular wave experiments confirms the utility of both models for making relevant predictions. Additionally, irregular wave tests are analysed whereby yaw instability is successfully correlated to the amount of parametric excitation and linear damping. This study demonstrates the importance of considering all modes of motion in design, not just the power-producing ones. Our simplified 1 DOF yaw model provides fundamental understanding of the presence and severity of the instability. The methodology could be applied to other wave-activated devices.

Guanosine 3',5'-monophosphate: a central nervous system regulator of analgesia.

The dibutyryl derivative of guanosine 3',5'-monophosphate (cyclic GMP), administered centrally, totally abolishes response to noxious stimuli without depressing the central nervous system. Analgesic properties of the nucleotide are not reversed by naloxone. Microinjected intracerebrally into different sites, dibutyryl cyclic GMP does not mimic the action of morphine. Pharmacological effects of dibutyryl cyclic GMP suggest that endogenous cyclic GMP modulates an inhibitory pain pathway distinct from that on which morphine acts.

Transverse motion instability of a submerged moored buoy.

Wave energy converters and other offshore structures may exhibit instability, in which one mode of motion is excited parametrically by motion in another. Here, theoretical results for the transverse motion instability (large sway oscillations perpendicular to the incident wave direction) of a submerged wave energy converter buoy are compared to an extensive experimental dataset. The device is axi-symmetric (resembling a truncated vertical cylinder) and is taut-moored via a single tether. The system is approximately a damped elastic pendulum. Assuming linear hydrodynamics, but retaining nonlinear tether geometry, governing equations are derived in six degrees of freedom. The natural frequencies in surge/sway (the pendulum frequency), heave (the springing motion frequency) and pitch/roll are derived from the linearized equations. When terms of second order in the buoy motions are retained, the sway equation can be written as a Mathieu equation. Careful analysis of 80 regular wave tests reveals a good agreement with the predictions of sub-harmonic (period-doubling) sway instability using the Mathieu equation stability diagram. As wave energy converters operate in real seas, a large number of irregular wave runs is also analysed. The measurements broadly agree with a criterion (derived elsewhere) for determining the presence of the instability in irregular waves, which depends on the level of damping and the amount of parametric excitation at twice the natural frequency.

Decadal variability of extreme wave height representing storm severity in the northeast Atlantic and North Sea since the foundation of the Royal Society.

Long-term estimation of extreme wave height remains a key challenge because of the short duration of available wave data, and also because of the possible impact of climate variability on ocean waves. Here, we analyse storm-based statistics to obtain estimates of extreme wave height at locations in the northeast Atlantic and North Sea using the NORA10 wave hindcast (1958-2011), and use a 5 year sliding window to examine temporal variability. The decadal variability is correlated to the North Atlantic oscillation and other atmospheric modes, using a six-term predictor model incorporating the climate indices and their Hilbert transforms. This allows reconstruction of the historic extreme climate back to 1661, using a combination of known and proxy climate indices. Significant decadal variability primarily driven by the North Atlantic oscillation is observed, and this should be considered for the long-term survivability of offshore structures and marine renewable energy devices. The analysis on wave climate reconstruction reveals that the variation of the mean, 99th percentile and extreme wave climates over decadal time scales for locations close to the dominant storm tracks in the open North Atlantic are comparable, whereas the wave climates for the rest of the locations including the North Sea are rather different.

Identification of estrogen receptor beta2, a functional variant of estrogen receptor beta expressed in normal rat tissues.

The effects of estrogen and estrogen agonists can be mediated by estrogen receptor alpha (ER alpha) and estrogen receptor beta (ER beta). We now report the identification and initial characterization of several novel isoforms of rat ER beta messenger RNA (mRNA). The most abundant of these mRNA variants we have called ER beta2. ER beta2 had an in-frame insertion of 54 nucleotides that resulted in the predicted insertion of 18 amino acids within the ligand binding domain. We demonstrated by semiquantitative RT-PCR and RNase protection that ER beta2 mRNA was expressed at levels equal to those of the previously published ER beta (ER beta1) in ovary, prostate, pituitary, and muscle. In tissues of the nervous system, including frontal cortex, hippocampus, and hypothalamus, ER beta1 was present in a 2- to 6-fold greater abundance than ER beta2. We have also detected variants of both ER beta1 and ER beta2 mRNAs that contained deletions of 117 bp encompassing the region encoding the second zinc finger of the DNA binding domain. All four mRNA species were efficiently translated into functional protein in a heterologous system. ER beta2 bound estradiol with a lower affinity (Kd 5.1 nM) than either ER alpha (0.19 nM) or ER beta1 (0.14 nM). The binding of ER beta2 was selective in that cortisol, testosterone, aldosterone, and progesterone among other agents did not compete for estradiol binding. However, a variety of known estrogenic agents, including physiological estrogens (estrone and estriol), plant and environmental estrogens (genistein, coumestrol, bisphenol A, methoxychlor), and pharmocological agents (tamoxifen, 4-hydroxytamoxifen) did effectively compete for estradiol binding to both ER beta1 and ER beta2. Interestingly, the binding pharmacology differed among the agents tested. For example, genistein competed effectively for estradiol binding to ER beta1 but was > 150-fold weaker at competing from ER beta2. In contrast, 4-hydroxytamoxifen competed equally well at both receptors. We have also demonstrated by a gel shift assay that both ER beta1 and ER beta2 bound specifically to DNA containing a consensus estrogen response element. ER beta1 and ER beta2 could heterodimerize with each other and with ER alpha. Both ER beta1 and ER beta2 activated transcription in response to estradiol, however, ER beta2 required a 1000-fold greater estradiol concentration for activity than did ER beta1. Cotransfection of ER beta2 had no effect on ER beta1 activation when used in a equal ratio. A 10-fold excess of ER beta2 did raise the half-maximal dose of estradiol required for transcriptional activation, whereas the maximal level of induction did not change. The ER beta complementary DNAs deleted within the DNA binding domain could not bind to DNA or activate transcription from this reporter in the cell backgrounds tested. In conclusion, although the physiological significance of these ER beta variants warrants further investigation, ER beta2 mRNA encodes a specific, functional receptor for estradiol and estrogenic agents. We propose that ER beta2 should also be considered in addition to ER beta1 and ER alpha when describing the effects of estrogen, estrogen agonists/antagonists, or environmental estrogens.

A prospective study of bile leaks after laparoscopic cholecystectomy.

Since laparoscopic cholecystectomy rapidly became the gold standard, there is an increased morbidity of 1% to 3% for clinically significant bile leaks with this procedure, as compared with open cholecystectomy (<1%). The identification of subclinical bile leaks using cholescintigraphy occurs in the range from 31.4% to 40% after elective open cholecystectomy. At this writing, no studies exist that document the rate of subclinical bile leaks after elective laparoscopic cholecystectomy. In this study, 71 patients were evaluated using cholescintigraphy after elective laparoscopic cholecystectomy. This study represents the first prospective look at the rate of subclinical bile leaks after laparoscopic cholecystectomy in elective cases, and the findings show an overall incidence of 7.3%, as compared with historical reports of 30% to 44% for open cholecystectomy.

Mirizzi syndrome.

Compression of the common bile duct by a stone impacted in the cystic duct is an uncommon cause of obstructive jaundice. We present a case study and review of the literature pertaining to the presentation, diagnosis, and surgical treatment of Mirizzi Syndrome.

Formation and inhibition of chloroaromatic micropollutants formed in incineration processes.

The formation pathways for chlorinated aliphatic and chlorinated aromatic compounds in technical incineration processes are reviewed. It is shown that acetylene is converted to chloroaromatic compounds including PCDD/F in a special flow reactor by catalytic activity of CuCl2 in the temperature regime of a post-combustion zone of technical incinerators. Mechanistic pathways begin with chlorination of acetylene. Dichloroacetylene is further condensed to C-4 and C-6 units. Hexachlorobenzene is the dominant aromatic compound and a likely precursor to chlorinated phenols and PCDD/F. Two specific mechanisms of formation of chlorinated aromatic compounds including PCDD/F have been advanced. Both mechanisms begin with the formation of dichloroacetylene from flame pyrolysis products like acetylene. Condensation of dichloroacetylene is mediated by copper species via metallacyclic intermediates and/or a catalytic cycle involving copper stabilized trichlorovinyl radicals. The final pathways of conversion of chlorinated benzenes to PCDD/F via chlorophenols are under active investigation.

Copper-catalyzed chlorination and condensation of acetylene and dichloroacetylene.

The chlorination and condensation of acetylene at low temperatures is demonstrated using copper chlorides as chlorinated agents coated to model borosilicate surfaces. Experiments with and without both a chlorine source and borosilicate surfaces indicate the absence of gas-phase and gas-surface reactions. Chlorination and condensation occur only in the presence of the copper catalyst. C2 through C8 organic products were observed in the effluent; PCDD/F were only observed from extraction of the borosilicate surfaces. A global reaction model is proposed that is consistent with the observed product distributions. Similar experiments with dichloroacetylene indicate greater reactivity in the absence of the copper catalyst. Reaction is observed in the gas-phase and in the presence of borosilicate surfaces at low temperatures. The formation of hexachlorobenzene is only observed in the presence of a copper catalyst. PCDD/F were only observed from extraction of the borosilicate surfaces. A global reaction model is proposed for the formation of hexachlorobenzene from dichloroacetylene.

Kinetic studies of the reaction of hydroxyl radicals with trichloroethylene and tetrachloroethylene.

Rate coefficients are reported for the gas-phase reaction of the hydroxyl radical (OH) with C2HCl3 (k(1)) and C2Cl4 (k2) over an extended temperature range at 740+/-10 Torr in a He bath gas. These absolute rate measurements were accomplished using a laser photolysis/laser-induced fluorescence (LP/LIF) technique under slow flow conditions. The simple Arrhenius equation adequately describes the low temperature data for k1 (<650 K) and the entire data set for k2 and is given by (in units of cm3 molecule(-1) s(-1)): k1(291 - 650 K) = (9.73+/-1.15) x 10(-13) exp (158.7+/-44.0)/T, k2(293 - 720 K ) = (1.53+/-0.14) x 10(-12) exp (-688.2+/-67.5)/T. Error limits are 2sigma values. The room temperature values for k1 and k2 are within +/-2sigma of previous data using different techniques. The Arrhenius activation energies for k1 and k2 are a factor of 2-3 lower than previously reported values. The experimental measurements for both k1 and k2 in conjunction with transition state and variation transition state theory calculations infer an OH addition mechanism. The lack of a measurable kinetic isotope effect for k1 is consistent with this mechanism. Insight into the subsequent reactions of the chemically activated intermediate are presented in the form of potential energy diagrams derived from ab initio calculations.

Rupture of the round window membrane.

A case of sudden deafness due to rupture of the round window membrane is presented. Nineteen similar cases have previously been reported in the literature. In a review of these twenty patients, it is noted that a history of concurrent physical effort or barotrauma was present in eighteen. This supports the view that the injury is produced by pressure changes acting either along the cochlear aqueduct (the explosive route) or, directly on the middle ear structures (the implosive route). At operation, the rupture may be difficult to see, and a separate leak from the oval window may be present. The timing of any surgical intervention is important. The authors recommend that this should be deferred for one week after the onset of symptoms, as the fistula may heal spontaneously. If no definite improvement has occurred at the end of this time, then tympanotomy should be undertaken during the next week.

Sudden deafness following chromic acid application to a perforation of the tympanic membrane.

It is current practice in the treatment of many ear diseases to instil locally into the ear potentially ototoxic agents. It is now becoming increasingly clear that some of these agents may pass from the middle to the inner ear despite the presence of intact labyrinthine windows and hence produce deafness. This paper reports a case of severe sensorineural deafness which developed following the application of chromic acid to a perforation of the tympanic membrane--a hitherto unrecognized complication. Therefore, the risks outlined above should be carefully considered prior to local therapy with any such agents and they should be applied with extreme caution.

Cerebrospinal fluid otorrhoea and otorhinorrhoea following closed head injury.

A discussion of acute traumatic CSF otorrhoea and otorhinorrhoea is presented. The incidence of meningeal infection is reviewed and the management of these cases is outlined with special emphasis on the indications for surgical intervention and the otological procedures available. Two patients who sustained transverse fractures of the petrous temporal bone are described in whom subsequent attacks of meningitis were prevented by a new, simple yet effective operation.

Glossopharyngeal neuralgia with syncope.

Thirty-two cases of glossopharyngeal neuralgia complicated by syncope, cardiac arrhythmias or convulsions, singly or together, have been reported in the world literature. A further case is described and the clinical features of these thirty-three are reviewed. It is recommended that treatment should be undertaken as a matter of urgency. In the first place, Carbamezapine, with often the addition of Atropine, may prove effective. However, surgical intervention appears to give a better chance of permanent relief. Four alternative methods of surgery are discussed and the cervical or the intracranial approach recommended. Surgery should not be delayed in patients who fail to respond to medical treatment or in whom recurrence of symptoms occurs.

An algorithmic approach to aspergillus sinusitis.

The effective management of paranasal sinus aspergillosis requires early diagnosis, histological classification, surgery and where appropriate, chemotherapy. Fungal sinusitis may be easily missed unless a high index of suspicion is maintained and specific culture and histology requested. The disease is classified into invasive and noninvasive types, each being divided into two subgroups: invasive aspergillosis may be either fulminant or indolent and noninvasive disease localized or allergic. The literature is reviewed and an algorithmic approach to aspergillus sinusitis proposed. The importance of histologically differentiating invasive from noninvasive aspergillosis prior to selecting the appropriate treatment options is stressed. CT scan should precede definitive surgery, and be used in follow-up. Close and prolonged follow-up is essential.

Primary non-Hodgkin's lymphoma of the larynx in an AIDS patient.

A case of primary non-Hodgkin's lymphoma of the larynx in an AIDS patient is presented with a review of the literature. Non-Hodgkin's lymphomas in AIDS patients are common but the primary laryngeal presentation is very rare. The symptoms usually include dysphonia and progressive airway obstruction requiring tracheostomy. As with laryngeal non-Hodgkin's laryngeal lymphomas in non-HIV positive patients the majority are of B cell lineage and respond well to radiotherapy. Our patient had a high grade lymphoma of B cell lineage which showed a good response to radiotherapy. The role of chemotherapy and surgery is not yet established. We suggest that the diagnosis of AIDS should not influence the management of these patients unless the individual is in the terminal disease stage.

Investigation of waste incineration of fluorotelomer-based polymers as a potential source of PFOA in the environment.

In light of the widespread presence of perfluorooctanoic acid (PFOA) in the environment, a comprehensive laboratory-scale study has developed data requested by the U.S. Environmental Protection Agency (EPA) to determine whether municipal and/or medical waste incineration of commercial fluorotelomer-based polymers (FTBPs) at end of life is a potential source of PFOA that may contribute to environmental and human exposures. The study was divided into two phases (I and II) and conducted in accordance with EPA Good Laboratory Practices (GLPs) as described in the quality assurance project plan (QAPP) for each phase. Phase I testing determined that the PFOA transport efficiency across the thermal reactor system to be used in Phase II was greater than 90%. Operating at 1000°C over 2s residence time with 3.2-6.6mgdscm(-1) hydrogen fluoride (HF), corrected to 7% oxygen (O2), and continuously monitored exhaust oxygen of 13%, Phase II testing of the FTBP composites in this thermal reactor system yielded results demonstrating that waste incineration of fluorotelomer-based polymers does not result in the formation of detectable levels of PFOA under conditions representative of typical municipal waste combustor (MWC) and medical waste incinerator (MWI) operations in the U.S. Therefore, waste incineration of these polymers is not expected to be a source of PFOA in the environment.