Light scattering and random lasing in aqueous suspensions of hexagonal boron nitride nanoflakes.

Liquid phase exfoliation allows large scale production of 2D materials in solution. The particles are highly anisotropic and strongly scatter light. While spherical particles can be accurately and precisely described by a single parameter-the radius, 2D nanoflakes, however, cannot be so easily described. We investigate light scattering in aqueous solutions of 2D hexagonal boron nitride nanoflakes in the single and multiple scattering regimes. In the single scattering regime, the anisotropic 2D materials show a much stronger depolarization of light when compared to spherical particles of similar size. In the multiple scattering regime, the scattering as a function of optical path for hexagonal boron nitride nanoflakes of a given lateral length was found to be qualitatively equivalent to scattering from spheres with the same diameter. We also report the presence of random lasing in high concentration suspensions of aqueous h-BN mixed with Rhodamine B dye. The h-BN works as a scattering agent and Rhodamine B as a gain medium for the process. We observed random lasing at 587 nm with a threshold energy of 0.8 mJ.

Nurse Triage in an Irish Out-of-hours General Practice Co-Operative.

Specially trained triage nurses play a crucial role in the operation of out-of-hours GP co-operatives. This study aimed to establish the proportion of all patient contacts with the out-of-hours GP co-operative based in the Mid-West of Ireland (Shannondoc), which were managed by triage nurses. A retrospective, descriptive analysis was conducted on the database of contacts to the Shannondoc urgent, out-of-hours primary care co-operative. Of the 110,039 contacts to the service in 2013, 19,147 (17.4%) were classified as being managed by nurses and 14.2% were managed by nurse telephone triage alone. Twenty-four percent of the 19,147 calls managed by nurses involved children under six years. Triage nurses play an important role in administering safe medical advice over the phone. This has implications for the training of triage nurses and the future planning of urgent out-of-hours primary care services.

Exploring diastolic pressure ratio to fractional flow reserve discordance and a hypothesis on tailoring diastolic pressure ratio cut-off values to improve diagnostic accuracy in the mid- and distal-LAD.

Previous studies have identified a higher rate of discordance between non-hyperaemic pressure ratios and FFR in the LAD when compared to the other two coronary arteries. We hypothesised that in keeping with recently published data, we would identify a higher discordance rate between diastolic pressure ratio (DPR) and FFR in the LAD compared to the RCA or LCx. In our study, 12.7% of LAD lesions had discordant results compared with 2.4% of non-LAD lesions. This represents a statistically significant increased rate of discordance in LAD lesions compared to non-LAD lesions (p = 0.04986). Note was made of a tendency for non-proximal LAD lesions to be associated with false-positive DPR results in the borderline range (0.88 and 0.89). In a speculative, hypothesis generating post-hoc analysis, we found an improved diagnostic accuracy of DPR when the cut-off value for a positive DPR in the non-proximal LAD was changed to ≤0.87. It is fathomable that improvements in the diagnostic accuracy of DPR for FFR may be improved by tailoring DPR cut-offs to the location of the lesion assessed.

The rise of the angiosperms: a genecological factor.

In the primitive angiosperms, closed carpels are believed to have evolved as protection for ovules, which would otherwise be injured by animal pollinators. The hypothesis is presented that, whatever the origin and other functions of angiosperms, insect pollination and closed carpels may, in combination, reduce the influence of random variation on pollen tube competition, thus enhancing the ability of natural selection to act on the gametophytic phase of the life cycle. The microgametophytic phase represented by vast numbers of haploid individuals can then serve, by insect pollination and closed carpels, as a screen against any genome not functioning with a high degree of metabolic vigor. Poorly balanced genomes could thus be eliminated at relatively little cost. Insect-pollinated angiosperms would therefore benefit from positive aspects of sexual recombination. Such a system may have allowed the angiosperms to undergo their rise to dominance.

A Correlation between Gametophytic and Sporophytic Characteristics in Zea mays L.

If a mixture of types of corn pollen, identified by genetic markers, is applied to the silks of other inbred lines, the rate of pollen tube growth often varies with type of pollen. This gametophytic differential is correlated with a sporophytic differential-relatively heavier seeds in seed mixtures result from fertilization by gametes from faster growing tubes. The increased seed weight is due to greater competitive ability of the zygotes thus formed.

Adsorption to fish sperm of vertically transmitted fish viruses.

More than 99 percent of a vertically transmitted fish rhabdovirus, infectious hematopoietic necrosis virus, was removed from suspension in less than 1 minute by adsorption to the surface membrane of sperm from two genera of salmonid fishes. The vertically transmitted, infectious pancreatic necrosis virus adsorbed to a lesser degree, but no adsorption occurred with a second fish rhabdovirus that is not vertically transmitted. Such adsorption may be involved in vertical transmission of these viruses.

Gametophytic self-incompatibility reexamined.

The conventional hypothesis of gametophytic self-incompatibility in the angiosperms involves one to four multiallelic incompatibility loci and the positive inhibition of incompatible pollen tubes. However, this concept does not accommodate recent experimental data indicating that there may be many loci. An alternative hypothesis which incorporates many loci and complementary pollen-style interactions suggests that there may be no S gene, as previously thought, and that gametophytic self-incompatibility is perhaps merely one aspect of extensive pollen-style interactions.

Pollen Tube Growth Rates in Zea mays: Implications for Genetic Improvement of Crops.

Speed of pollen tube growth is positively correlated with the quality of the resultant sporophytic generation. Therefore, gametophytic competition may be an important adaptive mechanism. Furthermore, pollen tube growth rates may be used to predict the quality of F(1) crosses in crop species.

The Global Genome Biodiversity Network (GGBN) Data Standard specification.

Genomic samples of non-model organisms are becoming increasingly important in a broad range of studies from developmental biology, biodiversity analyses, to conservation. Genomic sample definition, description, quality, voucher information and metadata all need to be digitized and disseminated across scientific communities. This information needs to be concise and consistent in today's ever-increasing bioinformatic era, for complementary data aggregators to easily map databases to one another. In order to facilitate exchange of information on genomic samples and their derived data, the Global Genome Biodiversity Network (GGBN) Data Standard is intended to provide a platform based on a documented agreement to promote the efficient sharing and usage of genomic sample material and associated specimen information in a consistent way. The new data standard presented here build upon existing standards commonly used within the community extending them with the capability to exchange data on tissue, environmental and DNA sample as well as sequences. The GGBN Data Standard will reveal and democratize the hidden contents of biodiversity biobanks, for the convenience of everyone in the wider biobanking community. Technical tools exist for data providers to easily map their databases to the standard.Database URL: http://terms.tdwg.org/wiki/GGBN_Data_Standard.

Ischemia in the ambulatory setting--the total ischemic burden: relation to exercise testing and investigative and therapeutic implications.

To establish the relation between treadmill exercise testing and ambulatory St segment monitoring in the detection of ischemia in patients with coronary artery disease, and to assess whether standard medical therapy affects any such relation, 277 patients with stable angina and angiographically documented coronary artery disease were studied with treadmill exercise testing and 48 h ambulatory ST segment monitoring. One hundred forty-six patients (52%) were studied while receiving no routine antianginal therapy, and 131 (48%) while receiving standard medical therapy. In 187 patients (67%) the exercise test was positive for ischemia. During 11,964 h of ambulatory monitoring, 881 episodes of ischemia (645 [73%] silent) were recorded, of which 809 (92%) occurred in patients with a positive exercise test. The mean heart rate at the onset of ischemic episodes during ambulatory monitoring was significantly less than that at the onset of 1 mm ST segment depression during exercise testing (94.5 versus 105.9 beats/min, p less than 0.0001). However, the frequency of ambulatory ischemic episodes was strongly related to a positive exercise test (p less than 0.001), and this relation was similar for both silent and painful ischemia (p less than 0.0001 for both) and in patients who were and were not receiving therapy (p less than 0.0001 for both). The total duration of ischemia was similarly related to a positive exercise test (p less than 0.0001). Only one patient with a negative exercise test had frequent (greater than 5/day) episodes of ischemia on ambulatory monitoring and had documented coronary artery spasm. Thus, exercise testing identifies the majority of patients likely to have significant ischemia during their daily activities.(ABSTRACT TRUNCATED AT 250 WORDS)

Blood pressure changes during transient myocardial ischemia: insights into mechanisms.

OBJECTIVES: We investigated the contribution of changes in systemic blood pressure to the genesis of spontaneous myocardial ischemia. BACKGROUND: Although increases in heart rate often precede the development of spontaneous myocardial ischemia, it remains a subject of controversy whether these are accompanied by simultaneous changes in blood pressure. METHODS: Using an ambulatory monitoring device that triggered blood pressure recordings from the level of the ST segment, we documented systolic and diastolic blood pressure and heart rate changes related to episodes of ST segment depression in 17 patients with stable coronary artery disease. RESULTS: Systolic blood pressure and heart rate, but not diastolic pressure, increased significantly before the onset of ST segment depression and persisted throughout the ischemic episode. There was a significant correlation between the changes in heart rate and systolic blood pressure during episodes of myocardial ischemia (r = 0.5, p = 0.0005) and between heart rate and systolic blood pressure changes at 1-mm ST segment depression during treadmill exercise testing and ambulatory monitoring (r = 0.73, p = 0.0005 for heart rate; r = 0.77, p = 0.0008 for systolic blood pressure), indicating that patients with a low heart rate threshold during ischemic episodes also had a lower systolic blood pressure threshold before ischemia during both tests. Circadian changes in systolic blood pressure paralleled the variations in heart rate and ischemic episodes, with the lowest values at night. CONCLUSIONS: Significant increases in myocardial oxygen demand, including systolic blood pressure, occur during episodes of spontaneous myocardial ischemia. Patients with a lower heart rate threshold during ischemic episodes had a lower systolic blood pressure threshold during both ambulatory monitoring and treadmill exercise. The effects of antianginal therapy on blood pressure changes during ischemia need to be explored further.

Patterns and behavior of transient myocardial ischemia in stable coronary disease are the same in both men and women: a comparative study.

OBJECTIVES: This study sought to compare the circadian variations in transient ischemic activity, mean heart rate and ischemic threshold between women and men with coronary artery disease. BACKGROUND: There is a circadian variation in ischemic activity, onset of myocardial infarction and sudden cardiac death in patients with coronary artery disease, but studies assessing ischemia have incorporated predominantly male subjects. METHODS: Thirty-one women and 45 men underwent at least 48 h of ambulatory ST segment monitoring. RESULTS: There was a similar and significant circadian variation in ischemic activity in both women and men (p < 0.0001 and p < 0.0001, respectively), with a trough at night, a surge in the morning and a peak between 1 and 2 PM, corresponding to a similar circadian variation in mean hourly heart rate (p < 0.0001) that was not different between men and women (p = 0.28, power to detect a shift 99.9%). Mean heart rate at onset of ischemia (ischemic threshold) had similar variability in women and men (p = 0.96), and harmonic regression analysis confirmed a significant circadian variation (p < 0.0001), with a trough at night and a peak during activity hours. Heart rate increased significantly in the 5 min before ischemia throughout the 24 h (p < 0.0001), with no gender differences in the pattern of preonset to onset heart rate changes over time (p = 0.52); the smallest differences were recorded in the middle of the night. The majority of ischemic episodes (80%) had a heart rate increase > 5 beats/min in the 5 min before ischemia, but there were no gender differences. CONCLUSIONS: Women with coronary artery disease have a pattern of ischemic activity and underlying pathophysiologic mechanisms very similar to men. The importance of increase in myocardial oxygen demand in the genesis of ischemia in both men and women is reflected by similar magnitude of heart rate increases before ischemia. The lower ischemic threshold during the nocturnal hours, when blood pressure is also lower, is consistent with a circadian variation in underlying coronary vascular tone.

Nitric oxide activity in the atherosclerotic human coronary circulation.

OBJECTIVES: We determined the activity of nitric oxide at rest and after acetylcholine in the atherosclerotic human coronary circulation. BACKGROUND: Although responses to acetylcholine, an endothelium-dependent vasodilator, are abnormal in patients with coronary atherosclerosis, whether this reflects abnormal nitric oxide activity in humans in vivo has not been investigated previously. METHODS: We investigated the effects of intracoronary L-NG-monomethyl arginine (L-NMMA), a specific antagonist of nitric oxide synthesis, on coronary vascular resistance and epicardial coronary artery diameter at rest and after acetylcholine in 24 patients with coronary artery disease and in 12 subjects with angiographically normal coronary arteries who were free from atherosclerotic risk factors. RESULTS: With L-NMMA, the 13 +/- 4% (mean +/- SEM) increase in coronary vascular resistance and the 4 +/- 1% lumen diameter narrowing in atherosclerotic patients were lower than the 38 +/- 9% increase in resistance and the 15 +/- 2% decrease in diameter (both p < 0.01) observed in normal control subjects, indicating reduced basal nitric oxide activity in atherosclerosis. The degree of angiographic atherosclerotic narrowing did not correlate with the magnitude of diameter reduction. Acetylcholine-induced coronary epicardial and microvascular dilation was also depressed in atherosclerotic patients (32.2 +/- 9% reduction in coronary vascular resistance with 10(-6) mol/liter acetylcholine) compared with normal control subjects (65.5 +/- 2% decrease, p < 0.01). L-NMMA inhibited acetylcholine-induced epicardial and microvascular vasodilation in both patient groups, but the inhibition was greater in normal control subjects than in atherosclerotic patients, indicating that stimulation of nitric oxide activity by acetylcholine is reduced in atherosclerotic patients compared with normal control subjects. Coronary vascular dilation with sodium nitroprusside was similar in both groups and was not suppressed by L-NMMA. Furthermore, L-arginine reversed the constrictor effects of L-NMMA, indicating that the action of L-NMMA is specifically caused by inhibition of nitric oxide production from L-arginine. CONCLUSIONS: These findings indicate that 1) there is a reduced basal activity of nitric oxide in the human atherosclerotic epicardial and microvascular coronary circulation; and 2) acetylcholine-induced coronary vascular dilation is at least partly due to stimulation of the activity of nitric oxide, and the reduced response to acetylcholine is due to attenuation in the stimulated activity of nitric oxide in patients with atherosclerosis.

Percutaneous transluminal coronary angioplasty in chronic coronary artery occlusion.

OBJECTIVES: This study was conducted to determine the procedural success rate, complication rate and long-term outcome of percutaneous transluminal coronary angioplasty in chronically occluded coronary arteries. BACKGROUND: Coronary angioplasty of chronically occluded vessels has a lower success rate than has angioplasty of nonoccluded vessels, but it is frequently considered safe because the target vessel is already occluded. The purpose of this study was to determine the reliability of these assumptions at our institution, with the objectives stated above. METHODS: We identified from the angioplasty data base at our institution 100 consecutive coronary angioplasty procedures performed between 1987 and 1991 for chronic total occlusion, defined as complete occlusion (Thrombolysis in Myocardial Infarction [TIMI] grades 0 and 1 flow) for > or = 3 months. The records of the 95 patients who underwent these procedures were reviewed to determine procedural outcome and medium-term results. RESULTS: Procedural success was obtained in 47 occluded vessels (47%). Significantly fewer successes were obtained in the right coronary artery (26.8%) than in either the left anterior descending (57.1%) or the left circumflex (45%) coronary artery (p < 0.05). A procedural failure without serious adverse consequences occurred in 45 procedures (45%), but in eight patients (right coronary artery in five, left anterior descending artery in three) attempted recanalization was complicated by extensive coronary dissection with acute myocardial ischemia, and one of these patients died. There were no emergency operations, but elective coronary artery bypass surgery was undertaken in 26 patients (in 3 after extensive dissection, in 7 after an apparently good result and in 16 in whom the procedure failed). At 12 months after the procedure, 64.1% of those with a procedural success were event free compared with 32.6% of those whose procedure was both unsuccessful and uncomplicated (p < 0.025) and 25% of those in whom it was unsuccessful and complicated by coronary dissection (p < 0.025). CONCLUSIONS: In this series of recanalization of chronically occluded coronary arteries, there was a low procedural success rate, particularly for the right coronary artery. However, when procedural success was obtained, the long-term outlook was good. The overall risk of coronary dissection was comparable to the risk in nonoccluded vessels but was particularly high in the right coronary artery (13%).

A pseudoautosomal random amplified polymorphic DNA marker for the sex chromosomes of Silene dioica.

The segregation pattern of an 810-bp random amplified polymorphic DNA (RAPD) band in the F1 and backcross generations of a Silene dioica (L.) Clairv. family provides evidence that this molecular marker is located in the pseudoautosomal region (PAR) of the X and Y chromosomes. The marker was found through a combination of bulked segregant analysis (BSA) and RAPD techniques. Recombination rates between this pseudoautosomal marker and the differentiating portion of the Y chromosome are 15% in both generations. Alternative explanations involving nondisjunction or autosomal inheritance are presented and discussed. Chromosome counts provide evidence against the nondisjunction hypothesis, and probability calculations argue against the possibility of autosomal inheritance. This constitutes the first report of a pseudoautosomal DNA marker for plant sex chromosomes.

The use of uncemented extensively porous-coated femoral components in the management of Vancouver B2 and B3 periprosthetic femoral fractures.

We assessed the outcome of patients with Vancouver type B2 and B3 periprosthetic fractures treated with femoral revision using an uncemented extensively porous-coated implant. A retrospective clinical and radiographic assessment of 22 patients with a mean follow-up of 33.7 months was performed. The mean time from the index procedure to fracture was 10.8 years. There were 17 patients with a satisfactory result. Complications in four patients included subsidence in two, deep sepsis in one, and delayed union in one. Concomitant acetabular revision was required in 19 patients. Uncemented extensively porous-coated femoral stems incorporate distally allowing stable fixation. We found good early survival rates and a low incidence of nonunion using this implant.

Contribution of nitric oxide to reactive hyperemia: impact of endothelial dysfunction.

Our objectives were to (1) test the hypothesis that nitric oxide (NO) contributes to peak reactive hyperemia (RH) in the human peripheral vasculature, (2) examine the impact of atherosclerosis and its risk factors on RH, and (3) investigate whether L-arginine will improve RH in patients with endothelial dysfunction. The endothelium contributes to shear stress-mediated vasomotion by releasing a variety of dilating factors, including NO, but the contribution of NO to peak RH in patients with and without endothelial dysfunction is unknown. Endothelium-dependent and endothelium-independent function was assessed with intrafemoral arterial acetylcholine (ACh) and sodium nitroprusside. RH was produced by occlusion of blood flow to the leg for 3 minutes. The study was repeated after NG-monomethyl-L-arginine (L-NMMA) in 44 subjects and L-arginine in 9 patients with atherosclerosis. There were 15 normal control subjects without risk factors for atherosclerosis and 29 patients with risk factors or angiographic atherosclerosis. Microvascular vasodilation in response to ACh, but not to sodium nitroprusside, was lower in the patients with risk factors or atherosclerosis compared with normal control subjects, P=0.048, and the inhibition of ACh-induced microvascular dilation by L-NMMA was also greater in normal control subjects (P=0.045). Similarly, RH, including the peak response, was inhibited by L-NMMA in normal control subjects (P=0.0011) but not in patients with risk factors or atherosclerosis, suggesting that the contribution of NO to both ACh-induced dilation and RH was diminished in patients with risk factors or atherosclerosis. L-Arginine did not affect vasodilation in response to ACh, sodium nitroprusside, or RH. We concluded that (1) NO contributes to all phases of RH in the normal human peripheral vasculature, (2) patients with atherosclerosis or its risks have abnormal NO bioactivity in response to pharmacological and physiological stimulation, and (3) L-arginine does not improve RH in atherosclerosis. Reduced physiological vasodilation in atherosclerosis may contribute to or exacerbate hypertension and ischemia.

Pollen tetrads in the detection of environmental mutagenesis.

Although pollen viability promises to be a very sensitive indicator of environmental mutagenesis, its utility in this regard is confounded by the fact that it is influenced also by nonmutagenic environmental stress. However, with appropriately homozygous material, we may discriminate between mutagenic and nonmutagenic influences on pollen viability. Pollen inviability resulting from mutagenesis will exhibit a strong tendency to segregate, whereas stress induced inviability will not. When pollen grains are shed individually, evidence for genetic segregation is often lost, but with pollen in tetrads, this evidence, a specific indicator of environmentally induced mutation, is preserved. A further advantage of pollen in tetrads is that, again because evidence for genetic segregation is preserved, tetrads allow us to distinguish between pre- and postpachytene mutations. This capability eliminates the problem of mutant sectors whereby a single mutational event may give rise to a large number of mutant cells. Methods of examining pollen tetrads are discussed.