Visualizing moiré ferroelectricity via plasmons and nano-photocurrent in graphene/twisted-WSe2 structures

Ferroelectricity, a spontaneous and reversible electric polarization, is found in certain classes of van der Waals (vdW) materials. The discovery of ferroelectricity in twisted vdW layers provides new opportunities to engineer spatially dependent electric and optical properties associated with the configuration of moiré superlattice domains and the network of domain walls. Here, we employ near-field infrared nano-imaging and nano-photocurrent measurements to study ferroelectricity in minimally twisted WSe2. The ferroelectric domains are visualized through the imaging of the plasmonic response in a graphene monolayer adjacent to the moiré WSe2 bilayers. Specifically, we find that the ferroelectric polarization in moiré domains is imprinted on the plasmonic response of the graphene. Complementary nano-photocurrent measurements demonstrate that the optoelectronic properties of graphene are also modulated by the proximal ferroelectric domains. Our approach represents an alternative strategy for studying moiré ferroelectricity at native length scales and opens promising prospects for (opto)electronic devices.

Negative refraction in hyperbolic hetero-bicrystals

We visualized negative refraction of phonon polaritons, which occurs at the interface between two natural crystals. The polaritons-hybrids of infrared photons and lattice vibrations-form collimated rays that display negative refraction when passing through a planar interface between the two hyperbolic van der Waals materials: molybdenum oxide (MoO₃) and isotopically pure hexagonal boron nitride (h¹¹BN). At a special frequency ω₀, these rays can circulate along closed diamond-shaped trajectories. We have shown that polariton eigenmodes display regions of both positive and negative dispersion interrupted by multiple gaps that result from polaritonic-level repulsion and strong coupling.

Nano-spectroscopy of excitons in atomically thin transition metal dichalcogenides

Excitons play a dominant role in the optoelectronic properties of atomically thin van der Waals (vdW) semiconductors. These excitons are amenable to on-demand engineering with diverse control knobs, including dielectric screening, interlayer hybridization, and moiré potentials. However, external stimuli frequently yield heterogeneous excitonic responses at the nano- and meso-scales, making their spatial characterization with conventional diffraction-limited optics a formidable task. Here, we use a scattering-type scanning near-field optical microscope (s-SNOM) to acquire exciton spectra in atomically thin transition metal dichalcogenide microcrystals with previously unattainable 20 nm resolution. Our nano-optical data revealed material- and stacking-dependent exciton spectra of MoSe2, WSe2, and their heterostructures. Furthermore, we extracted the complex dielectric function of these prototypical vdW semiconductors. s-SNOM hyperspectral images uncovered how the dielectric screening modifies excitons at length scales as short as few nanometers. This work paves the way towards understanding and manipulation of excitons in atomically thin layers at the nanoscale.

Nanoscale lattice dynamics in hexagonal boron nitride moiré superlattices

Twisted two-dimensional van der Waals (vdW) heterostructures have unlocked a new means for manipulating the properties of quantum materials. The resulting mesoscopic moiré superlattices are accessible to a wide variety of scanning probes. To date, spatially-resolved techniques have prioritized electronic structure visualization, with lattice response experiments only in their infancy. Here, we therefore investigate lattice dynamics in twisted layers of hexagonal boron nitride (hBN), formed by a minute twist angle between two hBN monolayers assembled on a graphite substrate. Nano-infrared (nano-IR) spectroscopy reveals systematic variations of the in-plane optical phonon frequencies amongst the triangular domains and domain walls in the hBN moiré superlattices. Our first-principles calculations unveil a local and stacking-dependent interaction with the underlying graphite, prompting symmetry-breaking between the otherwise identical neighboring moiré domains of twisted hBN.

Here, the authors investigate the lattice dynamics of twisted hexagonal boron nitride layers via nano-infrared spectroscopy, showing local and stacking-dependent variations of the optical phonon frequencies associated to the interaction with the graphite substrate.

Flash glucose monitoring: Impact on markers of glycaemic control and patient-reported outcomes in individuals with type 1 diabetes mellitus in the real-world setting

AIMS

We aimed to evaluate both glycaemic parameters and patient-reported outcomes in patients prescribed FGM based on the local criteria at our institution.

METHODS

This retrospective observational study included patients aged > 18 years with a diagnosis of type 1 diabetes mellitus (T1DM) who were prescribed FreeStyle Libre FGM (n = 90). Quantitative data on glycaemic parameters was collected pre- and post-initiation of FGM in addition to patient-reported outcome measures (PROMs). The primary outcome was change in pre- and post-FGM levels of glycosylated haemoglobin (HbA1C).

RESULTS

There was a mean reduction in HbA_1c of -7.29 ± 10.76 mmol/mol (p < 0.001, CI_95% 4.94-9.64) sustained to the latest reading. There was also a mean reduction in the number of hypoglycaemic episodes per week of 3.20 (percentage reduction 51.86%, p < 0.001, CI_95% 1.64-4.77). A significant improvement in quality of life scores was noted in all five domains of the abbreviated DDS between before and after starting FGM (p < 0.001). Key themes highlighted in inductive content analysis include 'life-changing', 'positive experience', and 'convenient'.

CONCLUSION

Flash glucose monitoring is associated with significant improvement in HbA_1c to a mean follow-up of 4.6 months. Additionally, patients reported positive experiences of FGM with significant improvement in all aspects of a focussed Diabetes Distress Scale.

A GIS-based methodology for selecting stormwater disconnection opportunities

The purpose of this paper is to introduce a geographic information system (GIS)-based decision support tool that assists the user to select not only areas where (retrofit) sustainable drainage systems (SuDS) could be implemented within a large catchment (>100 ha), but also to allow discrimination between suitable SuDS techniques based on their likely feasibility and effectiveness. The tool is applied to a case study catchment within London, UK, with the aim of increasing receiving water quality by reducing combined sewer overflow (CSO) spill frequency and volume. The key benefit of the tool presented is to allow rapid assessment of the retrofit SuDS potential of large catchments. It is not intended to replace detailed site investigations, but may help to direct attention to sites that have the greatest potential for retrofit SuDS implementation. Preliminary InfoWorks CS modelling of 'global disconnections' within the case study catchment, e.g. the removal of 50% of the total impervious area, showed that CSO spill volume could be reduced by 55 to 78% during a typical year. Using the disconnection hierarchy developed by the authors, the feasibility of retrofit SuDS deployment within the case study catchment is assessed, and the implications discussed.

Alcohol ethoxylates mediate their bacteriostatic effect by altering the cell membrane of Escherichia coli NCTC 8196

The minimum inhibitory concentration (MIC) of a homologous series of alcohol ethoxylates with the same head group size (E6) but differing in the number of carbon atoms in their 'tail group' from 10 to 16 was determined for Staphylococcus aureus NCTC 4163 and Escherichia coli NCTC 8196 using a turbidimetric assay. All the surfactants tested demonstrated bacteriostatic activity against both organisms. A tetrazolium assay showed that C14E6 and C16E6 had little effect on the membrane-bound dehydrogenase enzyme activity of E. coli NCTC 8196 compared with C10E6 and C12E6. C10E6 caused leakage both of K(+) and nucleotides in a concentration-dependent manner above its MIC of 0.2 mM. C12E6 caused some leakage at concentrations below its MIC (0.12 mM).

Hope makes a difference

Hope. It is a word that is often used but one which we do not stop to think intentionally about. It may be difficult to define, and frequently many come to know it more by its absence. Nurses espouse the value of hope, but it is a concept that often seems elusive when one is trying to put it into practice. The author suggests that hope is at the heart of psychiatric nursing practice and provides insights and reflections about how it has made a difference in the lives of individuals.

A comparison of neustonic plastic and zooplankton at different depths near the southern California shore

Previous studies of neustonic debris have been limited to surface sampling. Here we conducted two trawl surveys, one before and one shortly after a rain event, in which debris and zooplankton density were measured at three depths in Santa Monica Bay, California. Surface samples were collected with a manta trawl, mid-depth samples with a bongo net and bottom samples with an epibenthic sled, all having 333 micron nets. Density of debris was greatest near the bottom, least in midwater. Debris density increased after the storm, particularly at the sampling site closest to shore, reflecting inputs from land-based runoff and resuspended matter. The mass of plastic collected exceeded that of zooplankton, though when the comparison was limited to plastic debris similar to the size of most zooplankton, zooplankton mass was three times that of debris.

A comparison of neustonic plastic and zooplankton abundance in southern California's coastal waters

The density of neustonic plastic particles was compared to that of zooplankton in the coastal ocean near Long Beach, California. Two trawl surveys were conducted, one after an extended dry period when there was little land-based runoff, the second shortly after a storm when runoff was extensive. On each survey, neuston samples were collected at five sites along a transect parallel to shore using a manta trawl lined with 333 micro mesh. Average plastic density during the study was 8 pieces per cubic meter, though density after the storm was seven times that prior to the storm. The mass of plastics was also higher after the storm, though the storm effect on mass was less than it was for density, reflecting a smaller average size of plastic particles after the storm. The average mass of plastic was two and a half times greater than that of plankton, and even greater after the storm. The spatial pattern of the ratio also differed before and after a storm. Before the storm, greatest plastic to plankton ratios were observed at two stations closest to shore, whereas after the storm these had the lowest ratios.

Comparability of bioaccumulation within the sanddab guild in coastal Southern California

Most assessments of fish contamination in Southern California use ecologically different species from different sites. Use of ecologically similar species (a guild) might provide better assessments of fish contamination across different sites and depths. In July-August 1997, we collected samples of four sanddab guild species at 22 sites where species pairs co-occurred and determined total DDT concentrations in homogenized whole fish composites. Log-transformed DDT concentrations were highly correlated among all species pairs within this guild. All relationships were linear over the range observed, with slopes not statistically different from unity. The variability in response among species was about four times the variability encountered among replicates within species, but 15 times smaller than the variability among sites. Together, these results suggest that the sanddab guild, widespread on soft bottoms of the Southern California coastal shelf, can be used as a "superspecies" in bathymetrically diverse regional assessments of fish tissue contamination.

Activation of metabotropic glutamate receptors by repetitive stimulation in auditory cortex

To determine whether metabotropic glutamate receptors (mGluRs) contribute to the responses of neurons to repetitive stimulation in the rat auditory cortex in vitro, five stimulus pulses were delivered at 2-100 Hz which elicited five depolarizing synaptic responses, f-EPSPs: f-EPSPs(1-5). Stimulus pulses 2-5 delivered at low frequencies (2-10 Hz) elicited f-EPSPs(2-5) that were about 15% smaller than the response elicited by the first pulse (f-EPSP(1)). In the presence of the nonspecific mGluR agonist, ACPD, the amplitude of all f-EPSPs was 40% smaller than predrug responses. APV, CNQX, or bicuculline (antagonists of NMDA-, AMPA/kainate-, and GABA(A)-receptors, respectively) did not change this effect of ACPD. The mGluR antagonist, MCPG, had no effect on f-EPSPs but did reduce the effect of ACPD. High-frequency stimulation (50-100 Hz) elicited f-EPSPs that were smaller with each successive stimulus. In ACPD, f-EPSP(1) was 40% smaller than predrug, but f-EPSPs(3-5) were not changed compared to pre-ACPD f-EPSPs(3-5), indicating that ACPD occludes the effect of repetitive stimulation. MCPG increased f-EPSP(5) by 15%, indicating that a portion of the reduction of f-EPSPs during high-frequency stimulation is mediated by mGluRs. MCPG also partially blocked the effect of ACPD. In CNQX, ACPD only decreased EPSPs, but APV or bicuculline did not change the effect of ACPD. These results suggest that the successive reduction of f-EPSPs during a high-frequency train is partially a result of mGluR activation.

A comparison of plastic and plankton in the north Pacific central gyre

The potential for ingestion of plastic particles by open ocean filter feeders was assessed by measuring the relative abundance and mass of neustonic plastic and zooplankton in surface waters under the central atmospheric high-pressure cells of the North Pacific Ocean. Neuston samples were collected at 11 random sites, using a manta trawl lined with 333 u mesh. The abundance and mass of neustonic plastic was the largest recorded anywhere in the Pacific Ocean at 334271 pieces km2 and 5114 g km2, respectively. Plankton abundance was approximately five times higher than that of plastic, but the mass of plastic was approximately six times that of plankton. The most frequently sampled types of identifiable plastic were thin films, polypropylene/monofilament line and unidentified plastic, most of which were miscellaneous fragments. Cumulatively, these three types accounted for 99% of the total number of plastic pieces.

Cholinergic synaptic potentials in the supragranular layers of auditory cortex

Receptive-field plasticity within the auditory neocortex is associated with learning, memory, and acetylcholine (ACh). However, the interplay of elements involved in changing receptive-fields remains unclear. Herein, we describe a depolarizing and a hyperpolarizing potential elicited by repetitive stimulation (20-100 Hz, 0.5-2 sec) and dependent on ACh, which may be involved in modifying receptive-fields. These potentials were recorded, using whole cell techniques, in layer II/III pyramidal cells in the rat auditory cortex in vitro. Stimulation at low stimulus intensities can give rise to a hyperpolarizing response and stimulation at higher stimulus intensities can elicit a depolarizing response. The depolarizing response had a reversal potential of -35 mV, and was reduced by the combination of AMPA/kainate and NMDA glutamate receptor antagonists (AMPA/kainate: CNQX, DNQX, and GYKI 52466; NMDA: APV, MK-801) and by the muscarinic ACh receptor antagonist atropine. The hyperpolarizing response had a reversal potential of -73 mV and could be reduced by atropine, GABA(A) receptor antagonists (bicuculline and a Cl(-) channel blocker picrotoxin), and to a small extent a GABA(B) receptor antagonist (saclofen). This suggests that the hyperpolarizing response is likely to be mediated by ACh acting on GABAergic interneurons. Extracellular recordings, also made from layer II/III of cortical slices, yielded a negative-going potential which was reduced by ionotropic glutamate receptor antagonists (same as above) and by the ACh receptor antagonists atropine and scopolamine, suggesting that this potential was the extracellular representation of the depolarizing response.

Intraosseous hemangioma of the zygoma: CT and MR findings

Intraosseous hemangiomas are uncommon, constituting less than 1% of all osseous tumors. The most frequent sites are the calvaria and the vertebral column. Involvement of the facial bones is rare, and occurs most commonly in the maxilla, mandible, and nasal bones. Only 20 cases of zygomatic involvement have been reported in the English-language literature. We report a case of an intraosseous hemangioma of the zygoma documented by CT and MR studies.

Composition and distribution of beach debris in Orange County, California

Many studies have quantified debris collected on beaches around the world. Only a few of those studies have been conducted in the United States, and they are largely limited to semi-quantitative efforts performed as part of volunteer clean-up activities. This study quantifies the distribution and composition of beach debris by sampling 43 stratified random sites on the Orange County, California coast, from August to September 1998. We estimated that approximately 106 million items, weighing 12 metric tons, occur on Orange County beaches. The most abundant items were pre-production plastic pellets, foamed plastics, and hard plastics. Debris density on the remote rocky shoreline was greater than that on high-use sandy beaches for most debris items. This finding partially reflects the periodic clean-up of high-use beaches by local municipalities, and also indicates that a high percentage of the observed debris was transported to the site from waterborne sources.

Imaging of musculoskeletal and spinal tuberculosis

The diagnosis of tuberculosis of the musculoskeletal system is difficult for many reasons. As Walker states, to diagnose tuberculosis one must consider the possibility. The uncommonness of osteoarticular MTb results in clinician inexperience, which leads to overlooking the diagnosis. Subtle early manifestations may elude detection. Negative skin tests and normal chest films do not exclude the consideration of tuberculosis. The most conclusive means of reaching the diagnosis (biopsy and culture) necessitate invasive procedures that are not always definitive, and may require repeated attempts. Management and surgical decisions, however, rely on prompt diagnosis; diagnostic delay has prognostic implications and results in significant morbidity. Musculoskeletal tuberculosis produces no pathognomonic imaging signs, and in advanced stages mimics other disease processes. Despite these difficulties, the diagnostician's goal is to catch the disease as early as possible, because antibiotic treatment can lead to resolution and obviate more radical management. The radiologist must be aware of the groups at greatest risk, and typical and atypical presentations at imaging. The eventual eradication of MTb is conceivable, although not presently within our grasp. Maintaining reasonable suspicion and developing cognizance of the patterns of presentation allow the radiologist to diagnose efficiently the patient who presents with osteoarticular tuberculosis.

Metabotropic glutamate receptors modify ionotropic glutamate responses in neocortical pyramidal cells and interneurons

In neocortex glutamate activates ionotropic and metabotropic receptors (mGluRs). Whole-cell current-clamp recordings in the in vitro rat auditory cortex at 32 degrees C were used to explore the role that mGluRs have in regulation of AMPA/kainate, NMDA, and GABA receptor-mediated synaptic transmission. Our findings are: (a) The fast EPSP (AMPA/kainate), slow EPSP (NMDA), and IPSPs (GABAA, GABAB), elicited in pyramidal neurons are reduced in the presence of (1S,3R)-ACPD (mGluR agonist) with greatest effect on the slow IPSP>fast IPSP>>fast EPSP. The effect is likely the result of ACPD acting at presynaptic mGluRs because the probability of release of glutamate and GABA is reduced in the presence of ACPD, intracellular infusion of a G protein antagonist (GDPPS) did not block the effect of ACPD, nor were iontophoretic kainic acid or NMDA-induced depolarizations reduced by ACPD. (b) The slow EPSP is enhanced following washout of ACPD and enhancement is not due to disinhibition because it is present in the absence of IPSPs, but if IPSPs are present, its magnitude can be influenced. Iontophoretic NMDA responses are enhanced in the presence of ACPD, an effect blocked by GDPbetaS and heparin (intracellular inositol 1,4,5-trisphosphate receptor antagonist). Taken together, this evidence suggests that enhancement is a result of group I postsynaptic mGluR activation. (c) In fast-spiking cells ACPD reduces the EPSP (AMPA/kainate and NMDA-mediated). This action is likely presynaptic because it persists when GDPbetaS is in the cells. (d) The rate of spike discharge recorded from fast-spiking cells is accelerated in ACPD but does not change in the presence of GDPbetaS, suggesting a postsynaptic effect. Our data indicate that mGluRs can influence neocortical synaptic transmission in complex ways by acting presynaptically and postsynaptically.

Central versus peripheral mediation of naloxone's perfusion effects in endotoxic rats

Opioid receptor antagonists can act centrally and peripherally. It is unclear if these 2 pathways differentially mediate the perfusion-associated effects of opioid antagonism during endotoxemia. Male, Sprague-Dawley rats (340-390 g) were surgically prepared with left ventricular, tail artery, and jugular vein catheters 24 h before experiments were begun. Conscious, unrestrained rats were challenged with Escherichia coli lipopolysaccharide (LPS; 2 mg/kg/hr over 30 min) infusion. Measurements of regional blood flows were made using radioactive microspheres prior to (baseline), and at 60 and 120 min after LPS infusion. Saline (1 mL/kg bolus + 0.5 mL/kg/h infusion), naloxone (Nlx; 4 mg/kg bolus + 2 mg/kg/h infusion), or naloxone methyl bromide (Nlx-mb; 4.64 mg/kg, bolus + 2.32 mg/kg/h infusion) were administered 40 min after LPS infusion was begun. Nlx-mb does not cross the blood-brain barrier, and was thus used to differentiate central from peripherally mediated responses. At the end of each experiment, blood samples were collected for determination of ET-1 and nitric oxide metabolites (NOx = NO3 + NO2) using enzyme-linked immunosorbent assay (ELISA) and Griess reaction methods, respectively. Endotoxemia produced a significant decrease in cardiac output and an increase in systemic vascular resistance. Treatment with Nlx or Nlx-mb significantly attenuated the endotoxin-induced elevation in systemic vascular resistance and the decrease in cardiac output at 60 min after induction of endotoxemia compared with their respective baseline values. Nlx and Nlx-mb also attenuated the endotoxin-induced increases in hepatic portal and skeletal vascular resistances. These observations suggested that the ameliorative effect of Nlx on endotoxemia-induced regional vascular resistance alterations was mediated via peripheral opioid receptor mechanisms. However, although Nlx attenuated the endotoxin-induced decreases in the blood flow to the stomach and pancreas, Nlx-mb attenuated the endotoxin-induced decreases in the blood flow to the small intestine and cecum, in addition to the pancreas and, to some extent, the stomach. As such, separate central and peripherally mediated actions of opioid receptor antagonism were indicated. Nlx also resulted in an increase in the plasma levels of ET-1 only, whereas Nlx-mb increased the plasma levels of ET-1 and NOx. These observations suggest that separate central and peripheral effects of opioids during endotoxemia play a role in the associated circulatory alterations, and may differentially affect the release and/or synthesis of vasoactive mediators that might be related to their varied hepatosplanchnic vascular response during endotoxemia.

Aging and meaning in life: examining the concept

To make sense of their existence in the face of adversity and chaos or during times of relative calm, human beings seek meaning. Meaning has been identified as a significant factor in health and well-being in later years. Engaging in an intensive literature search about meaning in later life constituted the beginning step for a qualitative research study. By studying how older people experience meaning in their lives, we may learn more about the human experiences of joy and hope and their capacity to respond to opportunities and manage problems in their lives.

MR imaging of the biceps muscle-tendon complex

The anatomy of the biceps brachii muscle-tendon complex is reviewed. Particular attention is given to the tendon of the long head. Pathologic conditions affecting the biceps are discussed with respect to clinical features and current ideas regarding pathogenesis, which are correlated with the appearance at MR imaging.

A phenomenological study of meaning in life in suicidal older adults

The purpose of this hermeneutical phenomenological study was to explore how older adults who were suicidal experienced meaning in their lives. Eleven older persons between the ages of 64 and 92 years were interviewed about their subjective experiences of feeling suicidal. Data were analysed using van Manen's (1990) method of hermeneutical analysis. Three main themes evolved as characteristic of the fundamental thematic structure of the participants' experiences of meaning. These themes were conceptualized under a broader theme of alienation, a theme which was characterized by broken connections with individuals and meaningful activities. The question of meaning in life for these older persons was reflected not only from the perspective of meaningfulness, but also from the viewpoint of meaninglessness. Their narratives contribute to a deepened understanding of what it is like to be old, suicidal, and to feel like life has no meaning and purpose.

An 80 Kb P1 clone from chromosome 3p21.3 suppresses tumor growth in vivo

High frequencies of allelic loss on the short arm of chromosome 3 in small cell lung cancer (SCLC) and a number of other tumors suggest the existence of a tumor suppressor gene(s) within the deleted regions. Two small cell lung cancer lines, NCI H740 and GLC20, have been described which have homozygous deletions in the region 3p21.3. The deleted region overlaps with a 2 Mb fragment of human DNA present in the interspecies hybrid HA(3)BB9F, that suppresses tumor formation by mouse A9 fibrosarcoma cells. Human sequences from this cell hybrid were isolated using inter Alu PCR. From this starting point, a P1 contig was developed for the region of 450 Kb that is common to the homozygous deletions seen in the SCLC lines NCI H740 and GLC20 and is also present in HA(3)BB9F, the suppressed A9 hybrid. Individual P1 clones were assayed for their ability to suppress the tumorigenicity of the mouse fibrosarcoma cell line A9 as assayed by injection of transfected A9 cells into athymic nude mice. The introduction of one of the P1 clones into A9 cells resulted in suppression of tumor growth whereas two other P1 clones from the contig failed to suppress tumor formation in athymic nude mice. These data functionally delimit a tumor suppressor locus to a region of 80 kb within a P1 clone at 3p21.3.

CT evaluation of infradiaphragmatic air in patients treated with mechanically assisted ventilation: a potential source of error

OBJECTIVE

The purpose of this study was to describe the CT features of infradiaphragmatic air that may develop in patients after mechanically assisted ventilation, its location, its pathway of transdiaphragmatic dissection, and its extension into the abdomen.

MATERIALS AND METHODS

We retrospectively evaluated six consecutive adult patients with pneumomediastinum associated with positive end-expiratory pressure therapy who developed intraabdominal air and were imaged with CT in our institution-between 1993 and 1995. Abdominal CT examinations were reviewed and correlated with the clinical findings, follow-up examinations, and exploratory laparotomies in four patients.

RESULTS

In four patients, air present in the anterior mediastinum (endothoracic fascia) was seen to extend into the anterior abdominal wall within the extraperitoneal space. In a fifth patient, the air was located extraperitoneally and intraperitoneally. In the remaining patient, air was present exclusively in the peritoneal cavity. In only two patients did we detect small amounts of air in the posterior retroperitoneum. In five patients, we also detected subcutaneous emphysema and/or air dissection into the muscle planes of the anterolateral abdominal wall.

CONCLUSION

In patients on mechanically assisted ventilation, anterior mediastinal air can dissect through the diaphragm into the anterior abdominal extraperitoneal space. This anterior pathway of infradiaphragmatic extension of air can be erroneously diagnosed as intraperitoneal air, which may lead to unnecessary exploratory laparotomies. Also, anterior mediastinal air can enter the peritoneal cavity, particularly in patients with a history of median sternotomy.

Rational suicide among older adults: a cause for concern?

Society is collectively having to examine questions it has never had to face before and nurses are frequently confronted with the difficult issue of whether suicide can or should be a rational choice for older adults. They may be faced with the question of whether an older person should ever be restrained from suicide. Arguments for and against rational suicide are highlighted and the author makes the case for a rational approach to the affirmation of life, rather than its rejection, even to the very end.

Catheter ablation of the atrioventricular junction using radiofrequency energy and a bilateral cardiac approach

Radiofrequency current catheter ablation was used successfully to create complete atrioventricular (AV) block in 60 of 61 patients (98%) with drug refractory supraventricular tachyarrhythmias. The remaining patient developed Mobitz I AV block and is clinically improved (clinical efficacy 100%). In 54 patients (89%), complete AV block was achieved using a right-sided approach. Patients aged > 60 years needed significantly fewer right-sided radiofrequency applications to produce complete AV block (5.3 +/- 5.3 vs 11.1 +/- 10.0; p = 0.009). In 6 of 7 patients with unsuccessful right-sided ablation, a left ventricular approach was used. In each case, 1 to 4 additional radiofrequency applications produced complete AV block. Patients with unsuccessful right-sided ablation were generally younger than those with successful ablation (50 +/- 16 vs 64 +/- 11; p = 0.007). It is concluded that catheter ablation using radiofrequency current is an extremely effective means of producing complete AV block. Older patients appear to be more susceptible to right-sided radiofrequency approaches. Left ventricular ablation easily produces complete AV block in patients refractory to right-sided attempts.

Analysis of Deaths in Patients with an Implantable Cardioverter Defibrillator

The cause of death and clinical characteristics of 26 patients that died after implantable cardioverter defibrillator placement were reviewed and compared to the 145 patients still living after a mean follow-up of 17 months. Operative mortality was 4% (7/171) and resulted from postoperative ventricular arrhythmias (four patients), heart failure (two patients), and respiratory failure (one patient). Operative mortality was significantly higher (1.7% vs 9.6%, P less than 0.05) following concomitant surgical procedures. Total late mortality was 11% (18/171). Thirteen deaths (75%) occurred in-hospital from progressive deterioration of left ventricular function (nine patients), arrhythmia (two patients), and noncardiac causes (two patients). Outpatient mortality was 3.5% (6/171) and resulted from presumed sudden cardiac death in five of six patients; two of the five had devices that were inactive, one had high defibrillation thresholds, and two had suspected bradyarrhythmic deaths. One postoperative death and one late in-hospital death were also considered sudden cardiac deaths for a total of seven patients with defibrillation system failures. By multivariant analysis, preoperative clinical characteristics associated with a worse prognosis following defibrillator implantation were identified: presentation as ventricular tachycardia (P less than 0.02), induction of sustained monomorphic ventricular tachycardia (P less than 0.05), poor left ventricular performance (P less than 0.01), poor functional status (P less than 0.001), and the use of diuretics (P less than 0.01). Frequent device discharges (P less than 0.001) and concomitant antitachycardia pacing systems (P less than 0.001) were markers for greater arrhythmia recurrence and were potent predictors of a worse prognosis and particularly sudden death.

Implantable cardioverter defibrillator implanted by nonthoracotomy approach: initial clinical experience with the redesigned transvenous lead system

Standard implantation procedure for the implantable cardioverter defibrillator (ICD) has traditionally required a thoracotomy approach. A newly revised nonthoracotomy defibrillator lead system that uses a single transvenous tripolar endocardial lead alone or in combination with a subcutaneous/submuscular patch lead was introduced into clinical trials in September, 1990. Fourteen patients requiring a cardioverter defibrillator for recurrent sustained ventricular tachycardia (eight patients) or aborted sudden cardiac death (six patients) were evaluated for implantation of this lead system. Primary successful lead system implantation was obtained in nine patients. The remaining five patients had unacceptably high defibrillation thresholds (DFTs) for implantation. One of the nine initially successful implants demonstrated unacceptable DFTs and cross-talk inhibition from a permanent pacemaker necessitating removal of the nonthoracotomy lead system and replacement with a conventional lead system via thoracotomy. All remaining primary implanted patients experienced successful conversion of induced ventricular fibrillation prior to hospital discharge. Continued follow-up and greater experience to confirm the durability and efficacy of the nonthoracotomy AICD lead system are needed.

Rhythm disturbances after cardiac surgery

The management of arrhythmias in the postoperative cardiac surgical patient often requires a combination of steps, correction of metabolic abnormalities, administration of antiarrhythmic agents, and precordial electrical shocks when necessary. Atrial, ventricular, or AV sequential pacing may also be required in conjunction with these other steps. Overdrive or underdrive pacing has also been used in the control and termination of various arrhythmias. In refractory arrhythmias, postoperative EPS can gear drug therapy more appropriately. In patients at increased risk of postoperative arrhythmias, preoperative EPS may identify these patients more readily. The placement of prophylactic ICD patches at the time of cardiac surgery in patients at increased risk can be performed safely and may obviate the need for subsequent thoracotomy. As clinicians, one should always be aware that any cardiac arrhythmia may occur following cardiac surgery, and that many modalities are available for their diagnosis and treatment.

The Neuman System Model applied to mental health nursing of older adults

As we move into the 21st century, nurses are facing the challenge of contributing to the health care of a society with an increasing proportion of ageing persons. This group of people become more heterogeneous as they age, bringing with them an extended life history of experiences of wellness and illness. They have been faced with numerous stressors and losses and have made successful or unsuccessful adaptation to those life experiences. One of the disconcerting stressors of the elderly is the promotion and maintenance of mental health. In this paper we will examine the application of the Neuman System Model to the mental health nursing of older adults.

ECT for major depression in a patient with acute brain trauma

A woman with depression and cerebral cortical laceration caused by a self-inflicted gunshot wound received ECT 3 weeks after wounding herself and had no untoward effects. The authors discuss relative contraindications to ECT based on head injury and posttraumatic seizures.

Binge eating - therapeutic response to diphenylhydantoin: case report

A high incidence of abnormal EEGs and response to anticonvulsant medication has been noted among binge eaters. We report the case of a young women with binge eating episodes and an abnormal EEG who responded to diphenylhydantoin therapy.

Assessment of affect in schizophrenia. Reliability data

Pathological affect--impairment of facial expressiveness and demeanor--is a common manifestation of the schizophrenic process. In this study, empirically defined and statistically independent concepts of affectual range, mobility, appropriateness, and communicability were rated by 30 professionals and paraprofessionals from special videotapes of 22 chronic schizophrenics. Reliability of the ratings, measured by correlations among and across parameters and rater types, averaged r = .70, notably better than that of the same raters using traditional subjective clinical judgment (r = .54). There was little disagreement among psychiatrists, psychology interns, junior medical students, or social workers/nurses, nor were any of those groups significantly more reliable than the average for all raters. Significant trends toward low reliability of the appropriateness parameter are pointed out and possible clinical relevance is discussed.

Satyriasis: a case study

Satyriasis is a term describing pathologic hypersexuality in males. A 24 year-old male presented with satyriasis. After a search for organic etiology proved unsuccessful, the patient was treated with medroxyprogesterone acetate and psychotherapy with good results. The differential diagnosis, psychodynamics, and treatment are discussed.