Biomedical subjects

M J Krieger

Publications and source records attributed to M J Krieger.

10 recordsLinked to original sources

PubMed2000

Ant-like task allocation and recruitment in cooperative robots.

One of the greatest challenges in robotics is to create machines that are able to interact with unpredictable environments in real time. A possible solution may be to use swarms of robots behaving in a self-organized manner, similar to workers in an ant colony. Efficient mechanisms of division of labour, in particular series-parallel operation and transfer of information among group members, are key components of the tremendous ecological success of ants. Here we show that the general principles regulating division of labour in ant colonies indeed allow the design of flexible, robust and effective robotic systems. Groups of robots using ant-inspired algorithms of decentralized control techniques foraged more efficiently and maintained higher levels of group energy than single robots. But the benefits of group living decreased in larger groups, most probably because of interference during foraging. Intriguingly, a similar relationship between group size and efficiency has been documented in social insects. Moreover, when food items were clustered, groups where robots could recruit other robots in an ant-like manner were more efficient than groups without information transfer, suggesting that group dynamics of swarms of robots may follow rules similar to those governing social insects.

Algorithms↗

PubMed2000

Mating frequency and genetic structure of the Argentine ant Linepithema humile.

The nest and population genetic structures of the Argentine ant, Linepithema humile were investigated using eight microsatellite loci. Genotypes of the sperm from spermathecae of 87 queens were consistent with all queens being singly inseminated. The probability of a double mating remaining undetected was low (0.012) suggesting that no queens or only a very low proportion mate multiply. The relatedness between the queens and their mates was negative (R = -0.164 +/- 0.044) and significantly different to zero (P = 0.020). However, the high negative relatedness value was caused by a significant allele frequency difference between the sexes at a single locus (Lhum-28). When this locus was removed from the analyses, the relatedness was not significantly different from zero (R = 0.013 +/- 0.050, P = 0.812). Analysis of 10 nests revealed that the genetic differentiation among nests was weak (FST = 0.003) and not distinguishable from zero (P = 0.468). Similarly, the overall relatedness among nestmate females was not significantly different from zero (R = 0.007 +/- 0.018, P = 0.706). These results are consistent with the lack of distinct nest boundaries and the large number of queens per nest in the population studied. Although mating takes place inside the nest, the inbreeding coefficient was close to zero (F = 0.007 +/- 0.025, P = 0.786). Overall, these data indicate substantial local gene flow mediated by movement of reproductives among colonies.

Animals↗

PubMed1999

Assessing genetic structure with multiple classes of molecular markers: a case study involving the introduced fire ant Solenopsis invicta.

We used 30 genetic markers of 6 different classes to describe hierarchical genetic structure in introduced populations of the fire ant Solenopsis invicta. These included four classes of presumably neutral nuclear loci (allozymes, codominant random amplified polymorphic DNAs (RAPDs), microsatellites, and dominant RAPDs), a class comprising two linked protein-coding nuclear loci under selection, and a marker of the mitochondrial DNA (mtDNA). Patterns of structure revealed by F statistics and exact tests of differentiation were highly concordant among the four classes of neutral nuclear markers, although the microsatellites were the most effective markers for detecting structure. The results from the mtDNA complemented those from the neutral nuclear markers by revealing that strong limitations to female-mediated gene flow were the cause of the local structure registered by the nuclear markers. The pattern of structure inferred from the selected nuclear loci was markedly different from the patterns derived from the other sets of markers but was predictable on the basis of the presumed mode of selection acting on these loci. In general, the results for all six classes of markers can be explained by known features of the social and reproductive biology of fire ants. Thus, the results from these diverse sets of markers, combined with detailed natural history data, provide an unusually complete picture of how the fundamental evolutionary forces of gene flow, drift, and selection govern the distribution of genetic variation within and between fire ant populations.

Animals↗

PubMed1997

Hierarchical analysis of genetic structure in native fire ant populations: results from three classes of molecular markers.

We describe genetic structure at various scales in native populations of the fire ant Solenopsis invicta using two classes of nuclear markers, allozymes and microsatellites, and markers of the mitochondrial genome. Strong structure was found at the nest level in both the monogyne (single queen) and polygyne (multiple queen) social forms using allozymes. Weak but significant microgeographic structure was detected above the nest level in polygyne populations but not in monogyne populations using both classes of nuclear markers. Pronounced mitochondrial DNA (mtDNA) differentiation was evident also at this level in the polygyne form only. These microgeographic patterns are expected because polygyny in ants is associated with restricted local gene flow due mainly to limited vagility of queens. Weak but significant nuclear differentiation was detected between sympatric social forms, and strong mtDNA differentiation also was found at this level. Thus, queens of each form seem unable to establish themselves in nests of the alternate type, and some degree of assortative mating by form may exist as well. Strong differentiation was found between the two study regions using all three sets of markers. Phylogeographic analyses of the mtDNA suggest that recent limitations on gene flow rather than longstanding barriers to dispersal are responsible for this large-scale structure.

Animals↗

PubMed1984

Major traumatic and septic genital injuries.

Major injuries to the testicles, penis, and genital skin from trauma and infection were seen in 62 patients over a 6-year period (1977 to 1983). Urethral injuries were excluded. In the past blunt testicle injuries were infrequently diagnosed and surgically ignored because of large surrounding hematomas. With the use of real-time ultrasound, 17 of 18 cases of testicle rupture were correctly diagnosed preoperatively. Surgical repair resulted in testicle salvage in 16 patients. Penetrating testicle injuries resulted in a high orchiectomy rate secondary to the infrequently described but recognized entity of self-emasculation in transsexuals. Penile rupture from blunt injuries (8) was successfully repaired and complete function was recovered. Penetrating penile injuries (4) were extensive and involved the urethra in two cases; full function returned after reconstruction. Major skin loss of the penis and/or scrotum (19) occurred from necrotizing fasciitis, burns, avulsion and penetrating injuries. Early debridement, bowel and urinary diversion followed by penile skin grafting, thigh pouches to protect testicles, and scrotal reconstruction resulted in acceptable cosmetic and functional results in all cases of major skin loss.

Debridement↗

PubMed1982

Self-performed bilateral orchiectomy in transsexuals.

This paper reviews three cases of self-performed bilateral orchiectomy seen within a 2-year period at San Francisco General Hospital. All three cases were male to female transsexuals. The patients were not considered psychotic by the psychiatric consultant, although two patients admitted to past suicide attempts and psychiatric treatment. The patients' histories and treatment are reviewed and suggestions for diagnosis, management, and treatment planning are offered.

Adult↗

PubMed1981

The importance of cultural factors in a brief reactive psychosis.

This paper reviews the case of a time-limited or brief reactive psychosis in a Thai immigrant. Although the patient claimed to have left behind his Thai culture, his previous Buddhist background proved extremely stressful when confronted with a family mortuary ritual. The importance of understanding and working with a patient's previous cultural and religious beliefs is discussed.

Acculturation↗

PubMed1980

Problems in the psychotherapy of children with histories of incest.

Therapists must be cognizant of the meaning of the patients' presentation and the extreme need for therapeutic safety. The therapists must be keenly aware of the deprivation issues for these patients and not be seduced by the sexual "red herring." At the same time, the therapist must be careful that his own discomfort does not make him run away from the sexual material. Thus the therapist must strike a difficult balance between the two. The therapist must avoid allying with the child solely as a victim, an alliance which would hinder an understanding of the child's motivation and subsequent guilt, and thus foster further difficulties. The therapist must work through his own outrage that a child has been molested so that he may avoid blame seeking. By attending to these issues, the individual psychotherapist will pass the patients' "test" and take the first step in helping patients and their families in forming a therapeutic working alliance.

Adolescent↗

PubMed1976

Schizophrenic behavior as a function of role expectation.

The hypothesis that the behavior of schizophrenic patients is determined in part by role expectation was investigated. The Holtzman Inkblot Technique and a word association task were administered to the same patients under two conditions: (1) Ss were led to believe that the interviewer was unaware of their patient status and expected them to behave in a normal manner; and (2) Ss were informed that the interviewer was interested in their behavior as mental patients. The results indicated that there was less evidence of pathology on the Holtzman when Ss were told that the interviewer expected them to behave in a normal manner. More specifically, there was less Pathognomonic Verbalization and more Form Appropriateness in the normal expectation condition. The findings are consistent with current views as to the pathogenic effects of labeling and institutionalization.

Adult↗

PubMedDate not supplied

Estimation of the proportion of triploids in populations with diploid and triploid individuals.

Populations with diploid and triploid individuals co-occur in various plant and animal species, but detecting their relative frequencies is problematic. Microsatellite markers can be used to detect triploids that have three distinct alleles at a given locus, but cannot identify triploids that are partially or fully homozygous (i.e., possessing two or three copies of the same allele). Detection of partially homozygous triploids is sometimes possible with allozymes if no dosage compensation occurs. However, the inference of triploidy from uneven band intensities is not always reliable, making it difficult to estimate the actual proportion of triploids in a population. We present an iterative mathematical procedure for estimating the overall proportion of triploids from allozyme and microsatellite data. This method also estimates corrected allele frequencies by accounting for potentially hidden cases of homozygosity occurring in triploid individuals with multiple copies of an allele.

Alleles↗