Bistability in sine-Gordon: the ideal switch

The sine-Gordon equation, used as the representative nonlinear wave equation, presents a bistable behavior resulting from nonlinearity and generating hysteresis properties. We show that the process can be understood in a comprehensive analytical formulation and that it is a generic property of nonlinear systems possessing a natural band gap. The approach allows to discover that sine-Gordon can work as an it ideal switch by reaching a transmissive regime with vanishing driving amplitude.Comment: Phys. Rev. E, (to be published, May 2005

Risk factors associated with the severity of pneumonia in a cohort of hospitalised children in a rural setting

Paediatrics and Child Healt

Regioselective Synthesis of 3-Hydroxy-4,5-alkyl-Substituted Pyridines Using 1,3-Enynes as Alkynes Surrogates

The poor regioselectivity of the [4 + 2] cycloaddition of 3-azetidinones with internal alkynes bearing two alkyl substituents via nickel-catalyzed carbon–carbon activation is addressed using 1,3-enynes as substrates. The judicious choice of substitution on the enyne enables complementary access to each regioisomer of 3-hydroxy-4,5-alkyl-substituted pyridines, which are important building blocks in medicinal chemistry endeavors

A surprising method for polarising antiprotons

We propose a method for polarising antiprotons in a storage ring by means of a polarised positron beam moving parallel to the antiprotons. If the relative velocity is adjusted to $v/c \approx 0.002$ the cross section for spin-flip is as large as about $2 \cdot 10^{13}$ barn as shown by new QED-calculations of the triple spin-cross sections. Two possibilities for providing a positron source with sufficient flux density are presented. A polarised positron beam with a polarisation of 0.70 and a flux density of approximately $1.5 \cdot 10^{10}$/(mm$^2$ s) appears to be feasible by means of a radioactive $^{11}$C dc-source. A more involved proposal is the production of polarised positrons by pair production with circularly polarised photons. It yields a polarisation of 0.76 and requires the injection into a small storage ring. Such polariser sources can be used at low (100 MeV) as well as at high (1 GeV) energy storage rings providing a time of about one hour for polarisation build-up of about $10^{10}$ antiprotons to a polarisation of about 0.18. A comparison with other proposals show a gain in the figure-of-merit by a factor of about ten.Comment: 13 pages, 8 figures; v2: minor language and signification corrections v3: (14 pages, 12 figures) major error, nonapplicable polarisation transfer cross sections replaced by the mandatory spin-flip cross section

Cathode insert design for SC RF guns

The cathode inserts in superconducting SC RF guns are normal conducting devices attached to a SC RF gun cavity. They enable the photocathode replacement and, at the same time, preserve high quality factor and high fields in the RF guns. However, the insert may also limit the gun performance because of multipacting etc. The experience gathered in early designs at Wuppertal [1], and, more recently at BNL [2] and HZDR [3] is taken into account. We consider the design structure of the cathode insert worked out by BINP for 1 cell prototype of SC HZDR RF gun [4]. The detailed electric, mechanic, and thermal calculations of the initial [4] and the upgraded design are presented in this paper

The epidemiology of hypertension family practice in Cape Town

A prevalence study of hypertension in 8 family practices in low socio-economic areas of Cape Town examined 1046 patients over the age of 15 years. The crude prevalence rate of hypertension was 20,26%. There was no significant sex difference. Systolic pressure, diastolic pressure and hypertensive status increased with age and body mass index (BMI). There were complex relationships with regard to sex in that the female sex was predictive of hypertensive status after the age of 45 years unexplained by differences in BM!. After adjusting for age, BMI and sex differences, widowhood, poor education, obesity, a family history of hypertension or stroke and a past history of hypertension were significant predictors of hypertensive status. Smoking status, occupational social class or property ownership were not predictive. Fifty-one per cent of hypertensive subjects were treated. Of those receiving treatment, 30% were controlled resulting in a control prevalence of only 18%. Younger male subjects were better controlled by treatment. A strong need for improved diagnosis and treatment of hypertension in family practice exists in this region.S Afr Med J 1990; 78: 7-1

Health-related quality of life in a PD-First programme in South Africa

Groote Schuur Hospital in Cape Town, South Africa, offers a PD-First policy as a result of haemodialysis (HD) restrictions and resource limitations. This study aimed to compare health-related quality of life (HRQOL) between HD and peritoneal dialysis (PD) patients, given the lack of autonomy in modality choice and the socio-economic challenges. This single-centre, cross-sectional study was performed between July 2015 and December 2016. Demographic, socio-economic variables and perceptions of safety were collected. HRQOL was assessed using the Kidney Disease Quality of Life-Short Form (KDQOL-SFTM) version 1.3. All data were compared between the two dialysis modalities; 77 HD and 33 PD patients were included in the study and there were no significant differences in demographics. Median age was 42.5 years (IQR: 32.4–48.6) and 57.3% were female. HD patients had less pain (P = 0.036), better emotional well-being (P = 0.020) and a better energy/fatigue score (P = 0.015). Both cohorts experienced role-limitations due to physical health with PD being more affected overall (P = 0.05). The only significant symptom in the kidney domain was that PD patients experienced more shortness of breath (P < 0.001). Patients in both groups had very poor socio-economic circumstances, and safety within their communities was a major concern. The patients in our dialysis service have very challenging social circumstances. Those on PD scored worse in four HRQOL domains, possibly due to a lack of autonomy in dialysis modality choice and less frequent contact with dialysis staff. Additional psychological and social support needs to be instituted to help improve our patients’ well-being on PD