15 research outputs found
Quantum phase transitions and thermodynamic properties in highly anisotropic magnets
The systems exhibiting quantum phase transitions (QPT) are investigated
within the Ising model in the transverse field and Heisenberg model with
easy-plane single-site anisotropy. Near QPT a correspondence between parameters
of these models and of quantum phi^4 model is established. A scaling analysis
is performed for the ground-state properties. The influence of the external
longitudinal magnetic field on the ground-state properties is investigated, and
the corresponding magnetic susceptibility is calculated. Finite-temperature
properties are considered with the use of the scaling analysis for the
effective classical model proposed by Sachdev. Analytical results for the
ordering temperature and temperature dependences of the magnetization and
energy gap are obtained in the case of a small ground-state moment. The forms
of dependences of observable quantities on the bare splitting (or magnetic
field) and renormalized splitting turn out to be different. A comparison with
numerical calculations and experimental data on systems demonstrating magnetic
and structural transitions (e.g., into singlet state) is performed.Comment: 46 pages, RevTeX, 6 figure
Assessment of lower urinary tract function in children before and after Swenson's 'pull through' for Hirschsprung's disease
Aims: Long-term sequelae in children with Hirschsprung's disease (HD)
are usually related to abnormalities in defecation. However, some of
these patients also suffer from voiding dysfunction. The aim of this
study is to assess and define the effects of Swenson's 'pull through'
procedure in patients with HD on lower urinary tract function by means
of urodynamic studies (UDS) performed before and after surgery.
Materials and Methods: Six patients with Hirschsprung's disease
underwent UDS before and after the definitive procedure. Parameters
observed were maximum cystometric capacity, compliance, unstable
detrusor contraction (UDCS), leak point pressure, residual volume, end
filling pressure, volume at Pdet < 20 cm H 2 O and volume at Pdet
< 30 cm H 2 O. Results: On UDS evaluation, one patient (16.6%)
showed a small-capacity bladder and one patient (16.6%) showed a
large-capacity bladder with occasional uninhibited detrusor contraction
(UDCS) preoperatively. All the children had good compliant bladders.
Postoperatively, one child was clinically symptomatic and showed
hyporeflexic large-capacity bladder without any UDCS, one patient
showed a small-capacity bladder with UDCS. Conclusions: In
Hirschsprung's disease, neurovesical dysfunction may exist
preoperatively and though the incidence of postoperative changes in
neurovesical function may appear high, a larger study is required for
statistical validation. Children who present with urinary problems
after surgery should be assessed urodynamically
Optimal life stage for radiation sterilization of Anopheles males and their fitness for release.
Mating by male Anopheles mosquitoes (Diptera: Culicidae) was evaluated in the laboratory to assess fitness effects of radio-sterilization applied during different life stages of the malaria vectors An. stephensi Liston and An. gambiae Giles sensu stricto. After reproductive sterilization by gamma-irradiation (120 Gy), equal proportions of sterile and fertile (unirradiated) male adults were released into cages with virgin females and allowed to compete for matings. Radio-sterilization was applied when the males were pupae aged 0-7 h or 24-32 h, or adults aged <24 h or 24-55 h. After being radio-sterilized in the adult stage, males of both species competed effectively with unirradiated males, whereas those sterilized in the pupal stage obtained significantly fewer matings than unirradiated males from the same cohort. There was no evidence of females obtaining multiple inseminations. These findings emphasize the need to radio-sterilize males as adults in order to minimize the fitness cost. Such males may be intended for sterile insect technique population suppression or for trial releases of transgenic anophelines
Barley starch
This thesis examined barley amylopectin structure and looked for correlations between the structure and physical properties of starch. The structure of amylopectin and gelatinisation and retrogradation of starch were studied in 10 different barley cultivars/breeding lines with differing genetic background.
Amylopectin is built up of thousands of chains of glucose monomers, organised into clusters. The detailed fine structure of amylopectin was studied by isolating clusters of amylopectin and their building blocks, which are the tightly branched units building up the clusters. Barley cultivars/breeding lines possessing the amo1 mutation had fewer long chains of DPâ„38 in amylopectin and more large building blocks. The structure of building blocks was rather conserved between the different barley cultivars/breeding lines studied and was categorized into different size groups. These different building blocks were shown to be randomly distributed in the amylopectin molecule. The C-chains in amylopectin can be of any length and are a category of chains different from the B-chains. The backbone in amylopectin consists of a special type of B-chains which, when cleaved by α-amylase, become chains of a similar type to C-chains.
Gelatinisation and retrogradation (recrystallisation of gelatinised starch) of barley starch was studied by differential scanning calorimetry. The amo1 mutation resulted in a broader gelatinisation temperature range and a higher enthalpy of retrogradation. Other structural features were also found to influence the physical properties of starch. Small clusters and denser structure of the building blocks resulted in higher gelatinisation temperature. Fast retrogradation was observed in barley which had amylopectin with shorter chains and many large building blocks consisting of many chains.
Amylopectin structure was also studied in developing barley kernels. Three barley cultivars/breeding lines were grown in a phytotron and kernels were harvested at 9, 12 and 24 days after flowering. The results showed that amylopectin synthesized at later stages of development had a more tightly branched structure. Expression of the enzymes involved in starch biosynthesis is also known to change during endosperm development