Unveiling the Enhancement of Spontaneous Emission at Exceptional Points

Exceptional points (EPs), singularities of non-Hermitian physics where complex spectral resonances degenerate, are one of the most exotic features of nonequilibrium open systems with unique properties. For instance, the emission rate of quantum emitters placed near resonators with EPs is enhanced (compared to the free-space emission rate) by a factor that scales quadratically with the resonance quality factor. Here, we verify the theory of spontaneous emission at EPs by measuring photoluminescence from photonic-crystal slabs that are embedded with a high-quantum-yield active material. While our experimental results verify the theoretically predicted enhancement, they also highlight the practical limitations on the enhancement due to material loss. Our designed structures can be used in applications that require enhanced and controlled emission, such as quantum sensing and imaging.

Concealed intraventricular conduction in the human heart

Concealed intraventricular conduction is defined and the following classification of the manifestations of concealed conduction into the bundle branch system is proposed. 1. Trans-septal retrograde concealed intraventricular conduction responsible for (a) perpetuation of functional bundle branch block initiated by a premature supraventriculra impluse; (b) alternation of aberrant ventricular conduction in supraventricular bigeminy; (c) normalization of intraventricular conduction with acceleration or rate in bradycardia-dependent bundle branch block, and (d) prevention of the manifestation of Wenchbach periods of conduction in a bundle branch or fascicle. 2. Antegrade concealed intraventricular conduction responsible for (a) prevention of expected aberrant ventricular conduction when a short cycle follows a long one, and (b) exceptions to the "rule of bigeminy". 3. Retrograde concealed intraventricular conduction of a ventricular escape in association with unidirectional bundle branch or fasciular block responsible for (a) resumption of AV conduction in "paroxysmal AV block" with bundle branch block, and (b) facilitation (due to supernormality) of conduction in type II AV block due to bilateral bundle branch block. 4. Concealed intraventricular conduction of a premature ventricular impulse responsible for (a) initiation or termination of a re-entrant ventricular tachycardia; (b) resetting of an idioventricular pacemaker, and (c) pseudo-intraventricular or pseudo-AV block.

A simplified method of harvesting and dilating the radial artery achieves acceptable clinical outcomes

BACKGROUND

The recent successful revival of the radial artery as a coronary-bypass conduit has been attributed to a minimally traumatic harvesting technique without diathermy, combined with long-term oral calcium antagonist therapy. We describe a simplified technique of harvesting the radial artery, which reduces procurement time and maintains conduit relaxation.

METHODS

Radial arteries were harvested using diathermy and topical glyceryl trinitrate-verapamil dilator solution. Postoperatively, intravenous glyceryl trinitrate, but no calcium antagonist was used. The clinical results in the first 100 consecutive patients receiving radial artery grafts (RA group), procured using this technique, were compared with a group of 100 patients receiving saphenous vein conduits (SV group) immediately prior to the introduction of the radial artery at our institution.

RESULTS

There were no demographic differences between the two groups, other than the SV group being slightly older. There was one intraoperative death in each group. There was no difference in the rate of peri-operative myocardial infarction or length of stay in the intensive care unit. At a median follow-up time of 16 months for the RA group, and 25 months for the SV group, the survival rates were 97 and 94%, respectively. All survivors were in the New York Heart Association class I. In the SV group, two postoperative angioplasties were performed.

CONCLUSIONS

These early results suggest that this method of procuring the radial artery using diathermy, glyceryl trinitrate and no postoperative calcium antagonists, is rapid, safe and effective. The continued use of this technique is justified, while awaiting the results of long-term angiographic studies.

Pulmonary arteriovenous fistula: presentation, diagnosis, and treatment

Pulmonary arteriovenous fistulas (PAVFs) are rare vascular malformations of the lung. There is a strong association with Rendu-Osler-Weber disease. Although most patients are asymptomatic, PAVFs can cause dyspnea from a right-to-left shunt. They can also bleed and result in hemoptysis and hemothorax. Because of paradoxical emboli, various central nervous system complications have been described including stroke, and brain abscess. Currently, spiral computed tomography offers the most practical method for establishing the presence of PAVFs. Most patients should be treated. Therapeutic options include angiographic embolization with metal coils or balloon occlusion and surgical excision. Angiographic treatment has become the mainstay of therapy for most patients during the last decade. It is less invasive and can be repeated easily. Surgery, which usually consists of a conservative lung resection, is associated with low morbidity and a low recurrence rate. Both therapeutic approaches are discussed. The Mayo Clinic surgical experience of the last 20 years for PAVFs is presented.

Effect of sternotomy direction on the incidence of inadvertent pleurotomy

OBJECTIVE

Median sternotomy was performed by 2 different techniques in order to determine whether there was a difference in the incidence of inadvertent pleural entry.

EXPERIMENTAL DESIGN

Patients were prospectively evaluated and reviewed at a mean follow-up interval of 8.2 months.

PATIENTS AND METHODS

Ninety five consecutive patients underwent primary sternotomy at a single tertiary referral center.

MEASURES

Planned outcome measures included, incidence of pleural entry, length of hospitalization, and chest tube site related postoperative morbidity.

RESULTS

Group 1 (n=49) had sternotomy undertaken from the sternal notch proceeding downwards. Group 2 (n=46) underwent sternotomy performed from the xiphoid upwards. Mediastinal evaluation revealed a significant reduction in the incidence of pleural violation for group 1 (3) versus group 2 (11) (p=0.014). This difference was not found to be surgeon specific.

CONCLUSIONS

Sternotomy undertaken from the sternal notch proceeding downwards is shown to be associated with a reduced incidence of inadvertent pleural entry. Potential advantages for this approach also include reduced respiratory morbidity, less chest tube site complications and a trend to reduced length of hospitalization.

Role of apoptosis in failure of beta-cell mass compensation for insulin resistance and beta-cell defects in the male Zucker diabetic fatty rat

To define the mechanisms involved in the evolution of diabetes in the Zucker diabetic fatty (ZDF) rat, beta-cell mass and replication rates were determined by immunochemistry, point-counting morphometry, and 6-h 5-bromo-2'-deoxyuridine (BrdU) incorporation. The beta-cell mass in 5- to 7-week-old prediabetic ZDF rats (4.3 +/- 0.06 mg) was similar to age-matched insulin-resistant Zucker fatty (ZF) rats (3.7 +/- 0.05 mg) and greater than that in Zucker lean control (ZLC) rats (1.9 +/- 0.3, P < 0.05). At 12 weeks (after diabetes onset), beta-cell mass in the ZDF rats (8.1 +/- 1.7 mg) was significantly lower than the ZF rats (15.7 +/- 1.8 mg). The mass in the ZF rats was significantly greater than in the ZLC rats (4.3 +/- 0.8 mg, P < 0.05). The beta-cell proliferation rate (mean of both time points) was significantly greater in the ZDF rats (0.88 +/- 0.1%) compared with the ZF and ZLC rats (0.53 +/- 0.07%, 0.62 +/- 0.07%, respectively, P < 0.05), yet ZDF rats have a lower beta-cell mass than the ZF rats despite a higher proliferative rate. Morphological evidence of neogenesis and apoptosis is evident in the ZF and ZDF rats. In addition, even at 5-7 weeks a modest defect in insulin secretion per beta-cell unit was found by pancreas perfusion. These studies provide evidence that the expansion of beta-cell mass in response to insulin resistance and insulin secretory defects in diabetic ZDF rats is inadequate. This failure of beta-cell mass expansion in the ZDF rat does not appear to be from a reduction in the rate of beta-cell proliferation or neogenesis, suggesting an increased rate of cell death by apoptosis.

Home nutrition survey in the UK: The patient's perspective

A detailed survey questionnaire compiled by the executive committee of Patients on Intravenous and Nasogastric Nutrition Therapy (PINNT) was circulated in November 1991 to the postal addresses of all full (patient) members of PINNT in the UK. The objective of the survey was to identify current practices and problems of home nutrition support as seen from the patients perspective. 128 questionnaires were distributed. 87 (68%) analysable questionnaires were completed and returned. 77 were for parenteral nutrition (HPN) patients and 10 for patients on enteral nutrition (HEN). Areas of concern for patients include the practicalities of administration of lipid and additives, and problems associated with the appearance of air in infusion bags. Although most patients appeared happy with the home nutrition support services 18% commented on particular negative aspects. This survey highlights such areas which may not be identified during routine patient/clinician contact.

The effect of selective decontamination of the digestive tract on gastrointestinal enterococcal colonization in ITU patients

OBJECTIVE

The effect of selective decontamination of the digestive tract (SDD) on Intensive Therapy Unit (ITU)-acquired enterococcal infection and colonization was studied. Changes in the predominant species isolated and resistance patterns to antimicrobial agents were also studied.

DESIGN

Three groups were investigated: historical control (HC), contemporaneous control (CC) and patients receiving SDD (topical polymyxin, amphotericin B and tobramycin throughout ITU stay with intravenous ceftazidime for the first 3 days only).

SETTING

Adult general ITU with 7 beds.

PATIENTS

Patients with a nasogastric tube in situ and who were likely to remain in ITU for 48 h or longer were recruited.

RESULTS

Enterococcal infections occurred in 3 of 84 HC patients and 2 of 91 CC patients. There were no unit-acquired enterococcal infections in the SDD group. There were 140 episodes of enterococcal colonization occurring in 112 patients, with significantly more in the SDD and CC groups (p < 0.05. There were no significant differences in antibiotic sensitivities between the three groups. Enterococcus faecalis was the most frequently isolated species.

CONCLUSION

SDD does not predispose to enterococcal infection but does encourage colonization in patients receiving the regimen and other patients in ITU at the same. There is a complex interaction of factors which influence faecal flora and the likelihood of patients becoming colonized or infected with enterococci.

A controlled trial of selective decontamination of the digestive tract in intensive care and its effect on nosocomial infection

Nosocomial infection is a major problem in intensive therapy units (ITUs) and a significant cause of mortality. Selective decontamination of the digestive tract (SDD) has been advocated as a means to reduce ITU morbidity and mortality. Ninety-one patients in a general ITU underwent SDD, consisting of topical polymyxin E, tobramycin and amphotericin B administered throughout the unit stay together with parenteral ceftazidime for the first three days, and were compared with 84 historical and 92 contemporaneous control patients who were treated conventionally. Twenty-seven historical and 32 contemporaneous control patients developed unit-acquired infections, in comparison with only three patients in the SDD group (P less than 0.01). Mortality in the SDD group (36%) was not significantly different from that in the other two groups (historical control 40%, contemporaneous control 43%). Screening specimens revealed a significantly higher rate of colonization with resistant Acinetobacter spp. in the contemporaneous control than in the other two groups of patients; infection caused by resistant bacteria did not occur. SDD did not lead to a significant reduction in the use of systemically-administered antibiotics when compared with either control group. SDD may be used selectively in an ITU without ill effects on those patients not receiving SDD; nevertheless, microbiological monitoring is needed to detect emergence of resistant bacteria in the unit.

Human artificial insemination: donors in Melbourne. From our medical schools

Donors are crucial to any artificial insemination by donor (AID) programme but information about them is limited. This paper discusses the sources, characteristics and processing of semen donors.

Chromatography tubes: a novel RIA technique

We describe a novel radioimmunoassay in which separation of free and antibody-bound antigen is achieved by passive means. The separation is carried out by a modified form of inverted dry column chromatography on a column, or 'chromatography tube', consisting of a small polystyrene tube packed with a dry, insoluble, hydrophilic resin. Using the radioimmunoassay or digoxin as an example, an exceptionally simple procedure is described with sensitivity, accuracy and precision suitable for clinical purposes. Advantages of the chromatography tube method are discussed.

Effects of stable and changing rates and premature ventricular beats on transient tachycardia-, pseudobradycardia-, and bradycardia-dependent bundle branch block alternans

New circumstances under which bundle block (BBB) alternans may appear or disappear are described. 1) Tachycardia-dependent as well as bradycardia-dependent BBB alternans may begin after constant BBB is interrupted by a premature ventricular beat. Tachycardia- and bradycardia- dependence may be differentiated by the shape of the first beat after the pause. 2) When BBB alternans disappears during a constant ventricular rate, tachycardia-dependent BBB alternans changes to persistent normal or more normal intraventricular conduction, whereas bradycardia-dependent BBB alternans changes to a persistently greater degree of BBB. 3) BBB alternans appears to be tachycardia- or pseudobradycardia-dependent in relation to the cycle length and antegrade and retrograde refractory periods in the involved bundle branch. 4) BBB alternans may be recognized during persistent irregular ventricular action in atrial fibrillation. Here the recognition of BBB alternans depends upon the sequence of contours as well as upon the cycle lengths.

A characteristic precordial repolarization abnormality with intermittent left bundle-branch block

We reviewed electrocardiograms of 23 patients with intermittent left bundle-branch block. A characteristic electrocardiographic pattern consisting of right and mid-precordial deep symmetrical T-wave inversions was detected during normal conduction in 19 of the 23. Of the seven patients who had cardiac catheterization, only two had findings suggestive or organic heart disease and only one had significant obstructive coronary disease. Thus we conclude that patients with intermittent left bundle-branch block frequently have T-wave inversions in right and mid-precordial leads during normal conduction that do not necessarily reflect coronary disease. These T-wave changes are similar to those after termination of chronic right ventricular pacing (left bundle-branch pattern), suggesting that both patterns of abnormal ventricular activation can produce abnormal repolarization when activation returns to normal.