Optical interferometry-based array of seafloor environmental sensors using a transoceanic submarine cable.

Optical fiber-based sensing technology can drastically improve Earth observations by enabling the use of existing submarine communication cables as seafloor sensors. Previous interferometric and polarization-based techniques demonstrated environmental sensing over cable lengths up to 10,500 kilometers. However, measurements were limited to the integrated changes over the entire length of the cable. We demonstrate the detection of earthquakes and ocean signals on individual spans between repeaters of a 5860-kilometer-long transatlantic cable rather than the whole cable. By applying this technique to the existing undersea communication cables, which have a repeater-to-repeater span length of 45 to 90 kilometers, the largely unmonitored ocean floor could be instrumented with thousands of permanent real-time environmental sensors without changes to the underwater infrastructure.

Comparing ultrastable lasers at 7 × 10-17 fractional frequency instability through a 2220 km optical fibre network.

Ultrastable lasers are essential tools in optical frequency metrology enabling unprecedented measurement precision that impacts on fields such as atomic timekeeping, tests of fundamental physics, and geodesy. To characterise an ultrastable laser it needs to be compared with a laser of similar performance, but a suitable system may not be available locally. Here, we report a comparison of two geographically separated lasers, over the longest ever reported metrological optical fibre link network, measuring 2220 km in length, at a state-of-the-art fractional-frequency instability of 7 × 10-17 for averaging times between 30 s and 200 s. The measurements also allow the short-term instability of the complete optical fibre link network to be directly observed without using a loop-back fibre. Based on the characterisation of the noise in the lasers and optical fibre link network over different timescales, we investigate the potential for disseminating ultrastable light to improve the performance of remote optical clocks.

Test of Special Relativity Using a Fiber Network of Optical Clocks.

Phase compensated optical fiber links enable high accuracy atomic clocks separated by thousands of kilometers to be compared with unprecedented statistical resolution. By searching for a daily variation of the frequency difference between four strontium optical lattice clocks in different locations throughout Europe connected by such links, we improve upon previous tests of time dilation predicted by special relativity. We obtain a constraint on the Robertson-Mansouri-Sexl parameter |α|≲1.1×10^{-8}, quantifying a violation of time dilation, thus improving by a factor of around 2 the best known constraint obtained with Ives-Stilwell type experiments, and by 2 orders of magnitude the best constraint obtained by comparing atomic clocks. This work is the first of a new generation of tests of fundamental physics using optical clocks and fiber links. As clocks improve, and as fiber links are routinely operated, we expect that the tests initiated in this Letter will improve by orders of magnitude in the near future.

Note: A high-performance, low-cost laser shutter using a piezoelectric cantilever actuator.

We report the design and characterization of an optical shutter based on a piezoelectric cantilever. Compared to conventional electro-magnetic shutters, the device has intrinsically low power and is acoustically quiet. The cantilever position is controlled by a high-voltage op-amp circuit for easy tuning of the range of travel, and mechanical slew rate, which enables a factor of 30 reduction in mechanical noise compared to a rapidly switched device. We achieve shuttering rise and fall times of 11 µs, corresponding to mechanical slew rates of 1.3 ms-1, with a timing jitter of less than 1 µs. When used to create optical pulses, we achieve minimum pulse durations of 250 µs. The reliability of the shutter was investigated by operating continuously for one week at 10 Hz switching rate. After this period, neither the shutter delay or actuation speed had changed by a measurable amount.

Influences of aquatic plants on the fate of the pyrethroid insecticide lambda-cyhalothrin in aquatic environments.

Aquatic exposure assessments for pesticides are generally based on laboratory studies performed in water alone or water sediment systems. Although aquatic macrophytes, which include a variety of bryophytes, macroalgae, and angiosperms, can be a significant component of many aquatic ecosystems, their impact on pesticide fate is generally not included in exposure assessments. To investigate the influence of aquatic plants on the fate and behavior of the pyrethroid insecticide lambda (lambda)-cyhalothrin, two laboratory experiments (to assess adsorption and degradation) and an indoor microcosm study (to assess fate under semirealistic conditions) were conducted. In the laboratory studies, adsorption to macrophytes was extensive and essentially irreversible, and degradation occurred rapidly by cleavage of the ester bond. In the indoor microcosm, which contained water, sediment, and macrophytes from a pond, degradation was also rapid, with DT50 and DT90 values of less than 3 and 19 h, respectively, for dissipation from the water column and of less than 3 and 56 h, respectively, for the whole system. For adsorptive and readily degraded pesticides like lambda-cyhalothrin, we conclude that macrophytes have considerable influence on fate and behavior in surface waters.

Quantification of acetochlor degradation in the unsaturated zone using two novel in situ field techniques: comparisons with laboratory-generated data and implications for groundwater risk assessments.

Degradation of the herbicide acetochlor in the unsaturated zone was quantified using two unique in situ field techniques. The DT50 values generated at two different sites on surface soil and two subsoil depths using these techniques were compared with values generated under aerobic laboratory-incubation conditions (typically 20 degrees C, 40% maximum water holding capacity). Additionally, laboratory-degradation data were generated on surface and subsoils from four other sites. All subsoils were treated with acetochlor at 5% of the surface soil application rate. Acetochlor degradation in both field- and laboratory-incubated subsoils was rapid and often exceeded surface soil rates. Field and laboratory DT50 values from all sites ranged from 2 to 88 days in subsoil, compared with a range of 1 to 18 days in surface soils. The DT50 results from in situ field techniques were comparable with those generated from laboratory incubations in the same soils, confirming the validity of performing laboratory-based degradation studies to determine pesticide DT50 values in subsoils. Microbiological characterisation of selected soils revealed that subsoils had a viable and active population, although direct counts of bacteria were consistently lower in subsoil (10(8)-10(9) g-1 dry soil) compared with surface soils (10(10) g-1 dry soil). The leaching models used to perform groundwater risk assessments (e.g. PELMO, PESTLA, MACRO-DB, PRZM and the FOCUS EU leaching scenarios) have provision for inclusion of subsoil degradation rates. However, conservative default estimates are typically used, as no other alternative is available. Results presented here show that these default values may significantly underestimate true subsoil degradation contributions, and therefore not accurately predict pesticide concentrations in groundwater. The degradation data generated for acetochlor were applied to the mathematical model PELMO to demonstrate the importance of the inclusion of subsoil degradation data in groundwater risk assessment models and thereby in the registration of pesticides in Europe.

Determination of protection from serum nuclease activity by DNA-polyelectrolyte complexes using an electrophoretic method.

Polyelectrolyte complexes between cationic polymers and DNA have emerged as potential nonviral vectors for DNA delivery. For successful in vivo delivery, methods for analyzing their ability to prevent digestion of the DNA payload by serum nucleases are essential. We report here a simple assay to determine degradation of DNA in these complexes using standard electrophoretic techniques. The assay is based on a high pH buffer which can dissociate the complexes under standard electrophoretic conditions. This assay can be used qualitatively to determine the time taken for degradation to occur. Alternatively, with a standard gel analysis program it can be used quantitatively to investigate rates of DNA degradation from complexes in the presence of serum nucleases. We have shown that it can distinguish between different formulations with the same polymer, and also to distinguish between the time taken to degradation and the rates of degradation of DNA in complexes formed with two structurally related, linear polyamidoamine polymers. The assay could also distinguish between the time to degradation using poly-l-lysine complexes, although these were less well dissociated by the electrophoresis buffer, and could not be analyzed quantitatively. This assay will be of value in investigating and developing polyelectrolyte formulations for parenteral administration.

Polymer chemical structure is a key determinant of physicochemical and colloidal properties of polymer-DNA complexes for gene delivery.

Polyplexes are now emerging as potentially useful vectors for gene therapy. To improve our understanding of how the chemical structure of the polymer affects the properties of these systems, a series of structurally related polymers, the linear poly(amidoamine)s (PAAs), have been examined for their abilities to form complexes with DNA. Structure-dependent differences in DNA binding are shown by gel electrophoretic retardation of DNA and thermal transition analyses. Two PAAs, NG28 and NG30, stand out as having high affinity DNA binding characteristics, similar to the model homopolypeptide, poly-L-lysine. In addition, differences in complex formation, particle size and surface charge are displayed for the different polymer-DNA systems. Electron microscopy studies showed that the polymers condensed DNA into similar unit structures but only complexes with NG30 did not undergo agglomeration. This was attributed to an excess of complexed polymer forming a shell of uncomplexed polymer chain segments around a condensed DNA-polymer core. The transfection activities of these polymer complexes differ greatly, and some of these differences can be explained in a multifactorial way by the physicochemical and colloidal properties. It is concluded that polymer chemical structure dictates the apparent affinity of DNA binding, and also several of the important colloidal characteristics of the resulting complexes.

In vitro cytotoxicity of poly(amidoamine)s: relevance to DNA delivery.

We have examined the cytotoxicity of a number of poly(amidoamine) polymers which have been proposed for use as DNA delivery systems and compared them to the charged polyamino acid polylysine. Most of the poly(amidoamine)s tested were shown to be remarkably non-toxic to both HepG2 and HL60 cell lines. However, one of the structures (NG30, co-monomers methylene bisacrylamide, dimethylethylene diamine) did show cytotoxicity similar to that of polylysine. A second PAA structure (NG37, NG38, NG39, co-monomers bisacryloyl piperazine, 2-methyl piperazine) showed mild cytotoxicity towards both cell lines, related to the degree of polymerisation. The results support the idea that the cytotoxicity of polycations has a strong structural basis rather than being an effect due only to charge. As a consequence of their general reduced level of cytotoxicity, poly(amidoamine)s appear to have possible advantages for complexation with DNA over some other cationic polymers as a key component of DNA delivery systems.

Arrhythmogenic right ventricular dysplasia (ARVD): an overlooked and underdiagnosed condition?

We present three cases of arrhythmogenic right ventricular dysplasia causing or contributing to sudden death. These cases serve to highlight the range of clinical presentations and histological features seen in this rare and poorly understood condition. Arrhythmogenic right ventricular dysplasia (ARVD) is a cardiomyopathy characterized by a normal or mild increase in heart weight with right-sided heart dilatation. Typically a proportion of the right ventricular muscle is replaced by fat and fibrous tissue. Clinically, the condition is characterized by episodes of ventricular tachycardia and global dyskinesia of the right ventricle. It may cause ventricular fibrillation and sudden death, especially in young persons engaged in strenuous exercise or who experience severe emotional outburst. The aetiology of the condition is unknown, although it has been noted to show familial clustering in some cases.

Reactions to particles in smoke.

Smoke is a mixture of particles and gaseous chemicals of varying physical and chemical properties. When inhaled these produce the characteristic features of smoke-inhalational injury. Although heat is produced in fires it is the chemical agents which cause the damage to the airways and the lungs. Mortality and morbidity are closely related to pulmonary injury and thus to the particulate and chemical nature of smoke. Moreover, there seems to be a potentiating effect, in that the particles worsen the toxicity of the chemicals present.

Early development of accelerated graft coronary artery disease: risk factors and course.

OBJECTIVES: This study assessed the time of first appearance of angiographic graft coronary artery disease in relation to clinical and laboratory variables and clinical events in heart transplant recipients. BACKGROUND: Graft coronary artery disease is the main factor limiting long-term survival after heart transplantation, and it is important to understand its natural history. METHODS: One hundred thirty-nine consecutive patients who developed angiographic coronary artery disease after heart transplantation were classified according to early (< or = 2 years) versus late (> 2 years) posttransplantation initial detection of coronary artery disease. These subgroups were analyzed for differences in clinical and laboratory demographics, incidence of progression to ischemic events and incidence of antecedent cytomegalovirus infection. RESULTS: The early-onset group (64 patients) had more rapid progression to ischemic events than the late-onset group (75 patients), with 59% of the late group and only 35% of the early group free from ischemic events by 5 years after initial detection (p = 0.02), but there were no significantly correlated clinical or laboratory predictors of ischemic events. The early group had a significantly higher incidence of antecedent cytomegalovirus infection. CONCLUSIONS: We conclude that 1) accelerated graft coronary artery disease develops at variable times after heart transplantation; 2) the early appearance of graft coronary artery disease may be a marker of intrinsically more aggressive disease; 3) cytomegalovirus infection is associated with earlier onset of graft coronary artery disease. Patients with early development of graft coronary artery disease should potentially be given priority for interventional strategies as they are developed.

A comparison of the fate and effects of two pyrethroid insecticides (lambda-cyhalothrin and cypermethrin) in pond mesocosms.

: The fate and effects of two pyrethroid insecticides (lambda-cyhalothrin and cypermethrin) were investigated in replicated 25 m(3) pond mesocosms. Three pesticide treatments which simulated spray drift deposition were examined: 0.7 g a.i. ha(-1) cypermethrin and 0.17 and 1.7 g a.i. ha(-1) lambda-cyhalothrin. Based on the use rate and pesticidal activity of the chemicals, the cypermethrin and lower lambda-cyhalothrin rates were approximately equivalent. After applications, pyrethroid residues in the water column declined rapidly. Treatment-related effects were observed on some macroinvertebrate taxa, most notably the Asellidae and Gammaridae. Surfacedwelling insects also suffered initial knock-down, particularly in the 1.7 g a.i. ha(-1) lambda-cyhalothrin treatment, but there was recovery after the spray period. No adverse effects occurred on algae, macrophytes or zooplankton, but there were occasional enhancements (e.g. algal biomass and abundances of copepod nauplii and Rotifera) which may have been indirect effects. An overall comparison of the treatments indicated that the higher lambda-cyhalothrin rate had the greatest effects, whilst the cypermethrin application had a somewhat greater impact than the lower lambda-cyhalothrin treatment rate (due to effects on peracarid crustaceans). The study indicated that should spray drift occur at the levels expected for either pyrethroid's normal use patterns, potential impacts on natural aquatic ecosystems would be minor and transient.

Does rapidity of development of transplant coronary artery disease portend a worse prognosis?

We postulated that transplant coronary artery disease with rapid progression to more than 50% stenosis within a 1-year interval may have a different prognosis from transplant coronary artery disease with a more indolent rate of progression. Annual coronary angiograms of 139 consecutive patients who underwent transplantation between January 1968 and February 1990 who survived at least 1 year after transplantation and in whom angiographically apparent transplant coronary artery disease developed were included in the study. Of this group, 45 patients progressed from a normal angiogram to the presence of 50% or greater stenosis in one or more major vessels within 1 year (fulminant group); 94 did not (indolent group). Mean posttransplantation follow-up time was 5.3 +/- 4.1 years for patients with fulminant progression of disease and 6.6 +/- 3.7 years for those with indolent progression. A highly significant difference was found in the time-related incidence of ischemic events (myocardial infarction, congestive heart failure, sudden death, and retransplantation) between the indolent and the fulminant groups after initial detection of transplant coronary artery disease. At 1, 3, and 5 years after initial detection of transplant coronary artery disease, 50%, 33%, and 16% of patients in the fulminant group and 89%, 70%, and 60% of patients in the indolent group were free of ischemic events (p < 0.0001). The fulminant group of patients had a mean of 2.9 +/- 1.5 rejection episodes, and the indolent group a mean of 2.3 +/- 1.4 episodes (p = 0.02) during the first year after transplantation.(ABSTRACT TRUNCATED AT 250 WORDS)

Influence of graft rejection on incidence of accelerated graft coronary artery disease: a new approach to analysis.

Conflicting data exist on the role of graft rejection as a risk factor for later development of accelerated graft coronary artery disease. We analyzed 126 consecutive heart transplant recipients treated with cyclosporine-based immunosuppressive regimens and devised an arbitrary method to incorporate the number, duration, and severity of myocardial rejection episodes during the first postoperative year, resulting in a rejection score for each patient. We then correlated the later incidence (mean follow-up, 4 years) of angiographic accelerated graft coronary artery disease with this rejection score and with its components: number, duration, and severity of rejection; number and duration of untreated rejection; and incidence and duration of delayed rejection therapy. Accelerated graft coronary artery disease developed in 60 patients (48%). The rejection score was 96.7 for patients in the "no accelerated graft coronary artery disease" group and 110.4 for those in the "accelerated graft coronary artery disease" group (p = NS). No significant difference was noted between patients with and without disease in any of the other seven rejection parameters analyzed, and no significant difference in time to occurrence of disease was noted between groups divided at the median rejection score. Donor age was older and fasting triglyceride blood level was higher in patients with accelerated graft coronary artery disease than in those without disease. All other clinical characteristics, including HLA mismatches, ischemic time, blood pressure, lipid profile, and drug therapy, did not differ between the two groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Particulate matter of smoke inhalation.

Smoke inhalational injury is a common event, which often complicates cutaneous burns, markedly increasing mortality, especially when it is associated with facial burning. The primary source of injury in the upper respiratory tract is heat, but thermal injury does not usually extend beyond the bifurcation of the trachea. Within the lung, it is the deposition of particles, derived from the substrate burnt, together with the toxic gases given off which causes the injury. The way in which the injuries are caused is not completely understood, but it appears to be a direct response to the stimulation of the inflammatory response. This seems to give rise to a feedback mechanism. The continued presence of particulate matter may lead to continuing damage and thus to impaired respiratory function in survivors. The nature of the particulate matter, like the toxic fumes given off, reflects the chemical nature of the substances burnt, and is not as is commonly assumed, merely carbon.

An analysis of factors impeding passenger escape from aircraft fires.

The aviation world has long recognised that fires in aircraft are potentially very dangerous, being the cause of considerable mortality and morbidity even in otherwise survivable accidents. The evidence accumulated in the British Airtours Boeing 737 accident at Manchester International Airport on 22 August 1985, and the information acquired as a result of this investigation, reinforce the long held view that protection for passengers is needed. Heat, smoke, and toxic fumes can incapacitate people very rapidly. The time it took for people to die cannot be accurately assessed, but it is likely that all died within 4.5 min of the emergency being declared and probably within 2 min of smoke and flames entering the fuselage. Thus, it is obvious that new measures will have to be taken if lives are to be saved in future events of this nature.