47 research outputs found
A geometric approach to time evolution operators of Lie quantum systems
Lie systems in Quantum Mechanics are studied from a geometric point of view.
In particular, we develop methods to obtain time evolution operators of
time-dependent Schrodinger equations of Lie type and we show how these methods
explain certain ad hoc methods used in previous papers in order to obtain exact
solutions. Finally, several instances of time-dependent quadratic Hamiltonian
are solved.Comment: Accepted for publication in the International Journal of Theoretical
Physic
Relativistic wave equations for interacting massive particles with arbitrary half-intreger spins
New formulation of relativistic wave equations (RWE) for massive particles
with arbitrary half-integer spins s interacting with external electromagnetic
fields are proposed. They are based on wave functions which are irreducible
tensors of rank n=s-\frac12$) antisymmetric w.r.t. n pairs of indices,
whose components are bispinors. The form of RWE is straightforward and free of
inconsistencies associated with the other approaches to equations describing
interacting higher spin particles
Small-scale solar magnetic fields
As we resolve ever smaller structures in the solar atmosphere, it has become
clear that magnetism is an important component of those small structures.
Small-scale magnetism holds the key to many poorly understood facets of solar
magnetism on all scales, such as the existence of a local dynamo, chromospheric
heating, and flux emergence, to name a few. Here, we review our knowledge of
small-scale photospheric fields, with particular emphasis on quiet-sun field,
and discuss the implications of several results obtained recently using new
instruments, as well as future prospects in this field of research.Comment: 43 pages, 18 figure
Microbiological quality of shrimp imported from South-East Asia
Van de rauwe garnalen (15 monsters) varieerden de aerobe kiemgetallen van < 10-3 tot 10-6, de Enterobacteriaceae kiemgetallen van < 10 tot 10-2 en de S.aureus kiemgetallen van < 10 tot 10-3. In 4 monsters werd E.coli aangetoond, in een monster Salmonella en in een ander monster NAG-Vibrio. Van de niet-doorstraalde gepelde gekookte garnalen (54 monsters) varieerden de aerobe kiemgetallen van < 10-3 tot 10-7, de Enterobacteriaceae kiemgetallen van < 10 tot 10-2 en de S.aureus kiemgetallen van < 10 tot 10-4. In 11 monsters werd E.coli aangetoond, in 3 monsters Salmonella en in 1 monster NAG-Vibrio. In doorstraalde gepelde gekookte garnalen (7 monsters) waren de aerobe kiemgetallen steeds < 10-5 en de Enterobacteriaceae en S.aureus kiemgetallen < 10. De aanwezigheid van Shigella op gepelde gekookte garnalen afkomstig uit Zuid-Oost Azie blijft een potentieel risico voor de volksgezondheid.Abstract not availableHI
The effect of irradiation on spoilage organisms and shelf-life of bami and nasi goreng
Het doorstralen met 2,5 kGy resulteerde zowel met bami goreng als met nasi goreng in een reductie van het aeroob kiemgetal met 5 logeenheden. De Gram-negatieve flora nam sterker af dan de Gram-positieve. De overlevende flora bestond vooral uit Gram-positieve coccen. Tijdens bewaren bij 7 graden C nam het aeroob kiemgetal van doorstraalde nasi goreng niet, en van doorstraalde bami goreng slechts zeer langzaam toe. Er wordt geconcludeerd dat doorstraling leidt tot een verlenging van de houdbaarheid van bami en nasi.Abstract not availableHI
<i>Listeria monocytogenes</i>: heat resistance and behaviour during storage of milk and whey and making of Dutch types of cheese
The heat resistance of Listeria monocytogenes suspended in milk was determined with a plate pasteurizer and glass capillary tubes. The reduction of the, number of Listeria obtained by the plate pasteurizer was ,,;5 log 10 units at 64.0 °C for 10 s and 6-7 log 10 units at 67.0 °C for 10 s. The heat resistance of freely suspended and phagocyted Listeria was investigated with glass capillary tubes. The surviving Listeria were determined with and without resuscitation at 4 °C. Using the resuscitation method it appeared that phagocytosis did increase the heat resistance of one of the two tested Listeria strains by factor 2. With the resuscitation method up to 30 times more Listeria could be recovered than without resuscitation. The estimated decimal reduction times for the most heat-resistant strain was about 17 sat 64.0 °C and 8 sat 66.0 °C. Incubation tests of L. monocytogenes in raw and HTST-pasteurized milk (15 s 72 °C) at 4 and 7 °C showed some injury of Listeria during the first 1-2 days. Thereafter growth commenced. In intensively pasteurized milk (30 min 98 °C) Listeria was not injured. Gouda and Maasdam types of cheese were made from Listeria-contaminated milk. During the manufacture Listeria was concentrated in the curd by factor 10, and a limited growth occurred. During 6 weeks of ripening at 13 °C the number of Listeria was almost constant
Treatment of negative dysphotopsia with supplementary implantation of a sulcus-fixated intraocular lens
PURPOSE: Our aim was to evaluate the resolution of negative dysphotopsia supplementary implantation of a sulcus-fixated intraocular lens (IOL). This was a retrospective case series. Patients with severe negative were treated with supplementary implantation of the Rayner Sulcoflex (653 L) IOL. Primary outcome measurements were subjectively reported of dysphotopsia, best corrected distance visual acuity (CDVA), iris-IOL anterior chamber depth (ACD) and volume (ACV), angle opening distance trabecular-iris space area at 500 and 750 mum. RESULTS: A Rayner was implanted in seven patients (nine eyes) with negative dysphotopsias. resolved completely in six eyes, partially in one eye and remained two eyes. We did not find any significant changes in CDVA. Angle opening distance, ACD, ACV and iris-IOL distance reduced significantly after IOL implantation. CONCLUSIONS: Supplementary implantation of a Sulcoflex successfully treat negative dysphotopsia. The decrease in anterior dimensions in combination with the displacement of light rays by the edges of a Sulcoflex IOL may contribute to the resolution of symptoms
<i>Listeria monocytogenes</i>: heat resistance and behaviour during storage of milk and whey and making of Dutch types of cheese
The heat resistance of Listeria monocytogenes suspended in milk was determined with a plate pasteurizer and glass capillary tubes. The reduction of the, number of Listeria obtained by the plate pasteurizer was ,,;5 log 10 units at 64.0 °C for 10 s and 6-7 log 10 units at 67.0 °C for 10 s. The heat resistance of freely suspended and phagocyted Listeria was investigated with glass capillary tubes. The surviving Listeria were determined with and without resuscitation at 4 °C. Using the resuscitation method it appeared that phagocytosis did increase the heat resistance of one of the two tested Listeria strains by factor 2. With the resuscitation method up to 30 times more Listeria could be recovered than without resuscitation. The estimated decimal reduction times for the most heat-resistant strain was about 17 sat 64.0 °C and 8 sat 66.0 °C. Incubation tests of L. monocytogenes in raw and HTST-pasteurized milk (15 s 72 °C) at 4 and 7 °C showed some injury of Listeria during the first 1-2 days. Thereafter growth commenced. In intensively pasteurized milk (30 min 98 °C) Listeria was not injured. Gouda and Maasdam types of cheese were made from Listeria-contaminated milk. During the manufacture Listeria was concentrated in the curd by factor 10, and a limited growth occurred. During 6 weeks of ripening at 13 °C the number of Listeria was almost constant