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J Rehácek

Publications and source records attributed to J Rehácek.

At least 19 recordsLinked to original sources
PubMed2006

Biased tomography schemes: an objective approach.

We report on an intrinsic relationship between the maximum-likelihood quantum-state estimation and the representation of the signal. A quantum analogy of the transfer function determines the space where the reconstruction should be done without the need for any ad hoc truncations of the Hilbert space. An illustration of this method is provided by a simple yet practically important tomography of an optical signal registered by realistic binary detectors.

Journal Article↗
PubMed2004

Triggered qutrits for quantum communication protocols.

A general protocol in quantum information and communication relies in the ability of producing, transmitting, and reconstructing, in general, qunits. In this Letter we show for the first time the experimental implementation of these three basic steps on a pure state in a three-dimensional space, by means of the orbital angular momentum of the photons. The reconstruction of the qutrit is performed with tomographic techniques and a maximum-likelihood estimation method. For the tomographic reconstruction we used more than 2400 different projections. In this way we also demonstrate that we can perform any transformation in the three-dimensional space.

Journal Article↗
PubMed2002

Invariant information and quantum state estimation.

The invariant information, introduced by C. Brukner and A. Zeilinger [Phys. Rev. Lett. 83, 3354 (1999)], is reconsidered from the point of view of quantum state estimation. We show that this quantity is directly related to the mean error of the standard reconstruction from the measurement of a complete set of mutually complementary observables. We give its generalization in terms of the Fisher information. Provided that the optimum reconstruction is adopted, the information loses its invariant character.

Journal Article↗
PubMed2000

Characterization of a new spotted fever group rickettsia detected in Ixodes ricinus (Acari: Ixodidae) collected in Slovakia.

Two previously undescribed rickettsiae were detected in Ixodes ricinus Ricketts by polymerase chain reaction. Ixodes ricinus Slovakia (IRS) 3 and IRS4 were identified in ticks collected in northeastern and southwestern Slovakia, respectively. Sequences of the 16S rRNA citrate synthase (gltA) and outer membrane protein rOmpA (ompA) encoding genes of both strains were nearly identical but were distinct from those of all other known rickettsiae. Phylogenetic relationships inferred from the comparison of these sequences with those of other members of the genus Rickettsia indicate that IRS3 and IRS4 constitute a new rickettsial genotype and form a separate cluster among the spotted fever group rickettsiae.

Animals↗
PubMed1998

Rickettsia slovaca sp. nov., a member of the spotted fever group rickettsiae.

The name Rickettsia slovaca sp. nov. (type strain is strain B) is proposed for a member of the spotted fever group (SFG) rickettsiae which was isolated from Dermacentor marginatus ticks in Slovakia in 1968, and was recently implicated in human febrile illness. This rickettsia can be phenotypically distinguished from other SFG rickettsiae by microimmunofluorescence serotyping, SDS-PAGE, Western blotting and mAbs. Genotypic differences between R. slovaca and the other SFG representatives can be demonstrated by PCR-RFLP analysis, pulsed-field gel electrophoresis and sequencing of 16S rRNA, gltA and ompA genes.

Animals↗
PubMed1996

[Q-fever--occurrence and significance of this disease in the Czech Republic and Slovak Republic].

The paper summarizes the most important knowledge of Q fever and its causative agent Coxiella burnetti since the first descriptions of nosologic unit and causative agent until now. With respect to disease occurrence, distribution and importance the attention is focused on the territory of the former Czechoslovakia, i.e. currently on the territories of the Czech Republic and Slovak Republic. Taking into account normal occurrence of C. burnetii in cows which is however shown in latent form only, taking into account that no cases of human clinical infections related to these latent infections in cattle have been reported at present either in the territory of the Czch Republic or of the Slovak Republic, and considering that the results of experimental infections in sheep by the autochthonous strain of C. burnetii did not reveal its virulence, it can be stated that the strains of C. burnetti currently circulating on cattle farms are little virulent or even avirulent. This decrease in virulence can be ascribed to repeated subcultures of C. burnetti strains in cattle populations excluding ticks from this circulation. Q fever prevention should currently include measures to avoid in the territories of the Czech and Slovak Republics uncontrolled imports of infected animals and/or contaminated raw materials from animal or plant sources to introduce foreign fully virulent strains that can cause clinical infections both in humans and in domestic animals.

Animals↗
PubMed1996

[Contamination in areas of Slovakia with strains of Coxiella burnetii imported from abroad].

Following the upsurge of Q fever epidemic in the village Jedl'ové Kostol'any, Nitra district, Slovakia, in April 1993, the possibility of the penetration of coxiellae into free nature was investigated for the next two years. Micromammals and their ectoparasites, primarily ticks, were employed as indicators of the presence of the infection in nature. The infestation of mammals and their ectoparasites was followed in J. Kostol'any on the farm where the goats were housed as well as in its close proximity. The infestation of ticks with coxiellae was further followed in four localities of the Rimavská Sobota district, where the goats after the eradication of Q fever outbreak in J. Kostol'any were transferred for breeding. The presence of coxiellae was not proved in these investigated localities. It is suggested that the pathogenicity of imported C. burnetii strains through Bulgarian goats was decreased under local environmental conditions including the ability to circulate freely in nature or these strains found inconvenient conditions for maintaining their viability.

Animals↗
PubMed1995

Prevalence of ticks infected with Francisella tularensis in natural foci of tularemia in western Slovakia.

The prevalence of ticks infected with F. tularensis was followed during a systematic surveillance in endemic area of tularemia in western Slovakia over the years 1984-93. Ticks were collected from vegetation in localities of Podunajské Biskupice, in the vicinity of the capital of Slovakia, Bratislava, near the river Danube. In total 6033 ticks, mostly adults of Dermacentor reticulatus and Ixodes ricinus (4994 and 1004, respectively) and 35 nymphs of Haemaphysalis concinna, were examined for the presence of F. tularensis. Out of 4542 starving ticks, 34 F. tularensis strains were isolated predominantly from D. reticulatus (30), and to a smaller extent also from I. ricinus (3) and H. concinna (1). Natural infection with F. tularensis was further proved from 1491 adults of D. reticulatus fed on laboratory animals, rabbits and white mice, together in 27 cases. From that, 21 times it was by positive isolation either from suspensions of partly or fully engorged ticks and their feaces, or from spleens of animals dead after the feeding of ticks. In addition, solely the development of antibodies against the agent was confirmed in 6 rabbit hosts. The presence of F. tularensis in all the above mentioned tick species and namely the relatively high and permanent infestation of D. reticulatus adults, ranging between 0.5-2% during the followed time period, demonstrated the maintenance of active natural focus of tularemia in the area under study. The present paper also emphasizes the epidemiologic consequence of various species of ticks in endemic foci of tularemia and the aspect of possible ways of transmission of the agent to humans.

Adult↗
PubMed1995

Prevalence of Lyme borrelia in ticks in Bratislava, Slovak Republic.

A total of 2857 unfed Ixodes ricinus adult ticks were collected in 2-3 week intervals in 1991 in Bratislava to survey their prevalence with spirochaetes. Five hundred twenty eight, i.e. 17.8% harboured borreliae as detected by dark field microscopy. The infection rates of examined ticks varied from 15.3 to 21.8% in females and from 14.5 to 16.9% in males. The infestation of ticks was related to the season of their collection, the highest being in summer months. At this time the highest number of spirochaetes per tick was seen, too. Tick infestation with spirochaetes in March and April 1991/92 and 1992/93 at 13 and 9.3% respectively, indicated borreliae do hibernate in these arthropods. The strain isolated from two females collected in October 1992 was determined by PCR typing as Borrelia garinii. Out of 371 patients suspected in Dérer's Hospital, Bratislava, from Lyme disease, 81 (21.8%) had antibodies to B. burgdorferi. This demonstrates the presence of Lyme disease in Bratislava with Ixodes ricinus ticks being probably a vector of that spirochaetosis.

Animals↗
PubMed1994

Immunochemical and antigenic characterization of Coxiella burnetii strains isolated in Europe and Mongolia.

SDS-PAGE, immunoblotting and serological methods such as microimmunofluorescence (MIF) test and ELISA were used to compare protein and lipopolysaccharide (LPS) profiles and antigenicity of 12 Coxiella burnetii strains isolated mostly from ticks in Europe and Mongolia with three reference C. burnetii strains originating from USA, namely Nine Mile from tick, Priscilla from goat placenta and S from human heart valve. Among strains from Europe and Mongolia, no significant differences in protein and LPS profiles were observed, irrespective of their origin, i.e. the country and source of isolation. The LPS profiles of these strains appeared to be more related to those of Nine Mile strain associated with acute Q fever, than to those of strains S and Priscilla associated with chronic Q fever. In immunoblots all strains isolated from Slovakia and Poland reacted more expressively with rabbit serum against Nine Mile than with serum against Priscilla strain. In the MIF test and ELISA there were no substantial differences in antibody-binding capacity between the reference and newly isolated C. burnetii strains, except for strain Priscilla reacting with homologous serum in lower antigenic concentration than other strains under study. However, in the MIF test much higher antigenic concentrations of each C. burnetii strain was required to detect antibodies in the Priscilla serum than in the Nine Mile, Luga and S sera.

Animals↗
PubMed1994

Isolation of Coxiella burnetii and of an unknown rickettsial organism from Ixodes ricinus ticks collected in Austria.

Two strains of Coxiella burnetii and two strains of an unidentified rickettsial organism were isolated for the first time from Ixodes ricinus ticks collected in the Alpine region of Tirol, Austria. The C. burnetii strains belong to the group of agents causing acute forms of Q fever. The other two strains of isolated rickettsial agent share some antigenic epitopes with C. burnetii and R. prowazekii but they differ from them by their high sensitivity to freezing and refreezing and by poor multiplication in yolk sacs of chick embryos. There is at present no evidence that these organisms cause human illness and no ecological information is available. We suggest they may be some new species of rickettsiae or rickettsia-like organisms.

Animals↗
PubMed1994

Use of partially engorged female ticks as laboratory animals in microbiological research.

Partially engorged female ticks were used as laboratory animals in microbiological research. The ticks, which were inoculated intracoelomally, became a convenient substrate for the detection of viruses, rickettsiae and protozoal parasites. This research concerned the isolation of newly recovered micro-organisms, the study of development, structure and distribution of microbial agents in ticks, and the study of their interaction with other pathogens or symbionts during mixed infection in a tick body. The isolation and maintenance of Rickettsiella phytoseiuli, the organism not of tick-borne origin, was achieved. For use in Central Europe the tick Dermacentor reticulatus is recommended for the above investigations.

Animals↗
PubMed1993

Transmission of antibodies to Chlamydia psittaci and Coxiella burnetii through eggs and "crop milk" in pigeons.

Young semi-domesticated pigeons captured or hatched from eggs gathered in Bratislava during 1989-1991 were examined for complement fixing antibodies to Chlamydia psittaci and agglutinating antibodies to Coxiella burnetii. Antibodies to Ch. psittaci were present in 76% of birds younger than 24 h, in 47.7% between 1 and 10 days of age and in 12% of nestlings over 10 days old. Antibodies to Ch. psittaci were also detected in "crop milk" of 4.1% of 1 to 10 day old birds and in 4.5% of specimens older than 10 days. Antibodies to C. burnetii were not found in juvenile birds under 24 h old, but antibodies against this agent were present in 16.4% birds between 1 and 10 days old and in 18% over 10 days old. Antibodies to C. burnetii were also detected in "crop milk" collected from crops of 2% of the young birds between 1 and 10 days.

Animals↗
PubMed1993

Studies of the prevalence of Coxiella burnetii, the agent of Q fever, in the foothills of the southern Bavarian Forest, Germany.

In studies carried out in 1991 in the foothills of the southern part of the Bavarian Forest, in the district of Freyung/Grafenau, ticks and small mammals were collected and examined for the presence of Coxiella (C.) burnetii and sera of small mammals and cattle investigated for antibodies against this rickettsia. A total of 1716 imagines and nymphs of Ixodes ricinus were collected by flagging and 892 larvae and nymphs of the same tick species removed from small mammals. In addition to 1095 serum samples from cattle, 326 specimens of nine species of small terrestrian mammals were examined. Neither in ticks nor in rodents, C. burnetii was detected, however, in 17 of 21 localities, seropositive cattle were found. Altogether, 12% of all 1095 heads of cattle tested were seropositive for C. burnetii antibodies. These serological results indicated a wide dissemination of C. burnetii in cattle of the region investigated, but there was no indication of a natural focus. As in other areas of Europe, an independent natural cycle of the agent involving cattle only is assumed to occur in this region.

Animals↗
PubMed1993

Rickettsiae and their ecology in the Alpine region.

Two rickettsioses are known to be distributed in the Alpine Region, the ubiquitous Q fever and the so called tick-bite fever (fever boutonneuse) which is due to Rickettsia conorii. The latter is only temporarily seen and brought in via dogs by the dog tick Rhipicephalus sanguineus from Italy and southern France. Further, the presence of two apathogenic rickettsiae, R. slovaca (in Austria, Switzerland, Germany) and R. helvetica (Switzerland) has been determined. The present paper will discuss ecology, reservoirs, vectors, and abiotic and biotic environmental factors of these microorganisms. Finally, future perspectives of rickettsial research in the Alpine Region will be stated with respect to the epidemiology.

Animals↗
PubMed1993

The prevalence of small terrestrial mammals infected with tick-borne encephalitis virus and leptospirae in the foothills of the southern Bavarian forest, Germany.

In the district of Grafenau/Freyung (Bavaria, Germany), 266 specimens of small terrestrial mammals of 8 species were captured using live traps. From these mammals, Apodemus flavicollis (42.1%) and Clethrionomys glareolus (39.5%) were prevalent. All animals were tested for neutralizing antibodies to tick-borne encephalitis (TBE) virus and agglutinating antibodies to leptospirae. Seropositivity against TBE virus was 14.0% and against leptospirae 7.9%, respectively. Seropositivity to leptospirae appeared to be primarily to Leptospira grippotyphosa, less to Australis and occasionally to Javanica serovars. Only one A. flavicollis specimen was positive to both pathogens tested. The parasitocoenosis of trapped micromammals with ectoparasites consisted of 69.5% from ticks (mainly Ixodes ricinus, less from I. trianguliceps), 16.1% of mites (primarily Laelaps agilis) and 14.3% of fleas (mostly Ctenophthalmus agyrtes).

Animals↗
PubMed1993

[The ecology index, an epidemiologic marker of foci of Lyme borreliosis].

The ecological index (EI) as defined by Schulze et al. was determined in three localities of western Slovakia (Malacky, Podunajské Biskupice, Olichov) using the following criteria: suitability of the habitats for the occurrence of Ixodes ricinus ticks and their number, accessibility of habitat for men (I. phase); furthermore the abundance and infection rate of ticks (II. phase). A scoring procedure (point values of 1-5 for each parameter) was used to evaluate the EI of three localities studied. Based on obtained values it is suggested to differentiate foci as those with a definite (Malacky), potential (Podunajské Biskupice, Olichov), minimal and unprobable risk of transmission. The EI is considered a helpful method for assessing areas of risk for the transmission of Lyme borreliosis, indicating also the necessity of appropriate preventive measures.

Animals↗