Spiral organization of quasi-periodic shrimp-shaped domains in a discrete predator-prey system.

In this paper, we report the discovery of some novel dynamical scenarios for quasi-periodic shrimp-shaped structures embedded within chaotic phases in bi-parameter space of a discrete predator-prey system. By constructing high-resolution, two-dimensional stability diagrams based on Lyapunov exponents, we observe the abundance of both periodic and quasi-periodic shrimp-shaped organized domains in a certain parameter space of the system. A comprehensive comparative analysis is conducted to elucidate the similarities and differences between these two types of shrimps. Our analysis reveals that, unlike periodic shrimp, quasi-periodic shrimp induces (i) torus bubbling transition to chaos and (ii) multistability with multi-tori, torus-chaotic, and multi-chaotic coexisting attractors, resulting from the crossing of its two inner antennae. The basin sets of the coexisting attractors are analyzed, and we observe the presence of intriguing basin boundaries. We also verify that, akin to periodic shrimp structures, quasi-periodic shrimps also maintain the three-times self-similarity scaling. Furthermore, we encounter the occurrence of spiral organization for the self-distribution of quasi-periodic shrimps within a large chaotic domain. We believe that these novel findings will significantly enhance our understanding of shrimp-shaped structures and the intricate dynamics exhibited by their distribution in chaotic regimes.

Multistability for nonlinear acoustic-gravity waves in a rotating atmosphere.

The multistable states of low-frequency, short-wavelength nonlinear acoustic-gravity waves propagating in a small slope with respect to the vertical ones are explored in a rotating atmosphere. The bifurcation patterns en route to irregular behaviors and the long-term dynamics of the low-order nonlinear model system are studied for varying air Prandtl number σ between 0.5 and 1. In contrast to non-rotation, the transition to the unsteady motion occurs both catastrophically and non-catastrophically due to the Earth's rotation. The connections between the Prandtl number and the slope parameter on the stabilities of the system are highlighted. The model system exhibits hysteresis-induced multistability with coexisting finite multi-periodic, periodic-chaotic attractors in certain parameter spaces depending on the initial conditions. Studies revealed that the rotation parameter instigates these heterogeneous coexisting attractors, resulting in the unpredictable dynamics. However, the relevance of this study is strongly restricted to a very small vertical wavelength, a small slope, and a weakly stratified atmosphere.

Cooperation delay induced chaos in an ecological system.

In the present paper, we investigate the impact of time delay during cooperative hunting in a predator-prey model. We consider that cooperative predators do not aggregate in a group instantly, but individuals use different stages and strategies such as tactile, visual, vocal cues, or a suitable combination of these to communicate with each other. We observe that delay in hunting cooperation has stabilizing as well as destabilizing effects in the system. Also, for an increase in the strength of the delay, the system dynamics switch multiple times and eventually become chaotic. We see that depending on the threshold of time delay, the system may restore its original state or may go far away from its original state and unable to recollect its memory. Furthermore, we explore the dynamics of the system in different bi-parameter spaces and observe that for a particular range of other parameter values, the system dynamics switch multiple times with an increase of delay in all the planes. Different kinds of multistability behaviors, the coexistence of multiple attractors, and interesting changes in the basins of attraction of the system are also observed. We infer that depending on the initial population size and the strength of cooperation delay, the populations can exhibit stable coexistence, oscillating coexistence, or extinction of the predator species.

Impact of iron chelators on growth and expression of iron-related genes of Cryptococcus species.

INTRODUCTION: Iron chelator has previously demonstrated fungicidal effects. This study aimed to investigate the antifungal activity of the iron chelators deferoxamine (DFO) and deferasirox (DSX) against Cryptococcus. MATERIALS AND METHODS: Cryptococcus neoformans and Cryptococcus gattii were used to determine the minimal inhibitory concentrations (MICs) of DFO and DSX, and the fractional inhibitory concentration index (FICI) of DFO and DSX when combined with amphotericin B (AMB). Expression of cryptococcal CFT1, CFT2, and CIR1 genes was determined using real-time polymerase chain reaction (PCR). RESULTS: Neither DFO nor DSX alone showed antifungal activity against Cryptococcus strains. When combined with AMB, the MICs of DFO and DSX decreased from>200µg/mL to 6.25 or 12.5µg/mL. The MIC of AMB decreased one-fold dilution in most strains when combined with iron chelators. The FICI of DFO+AMB and DSX+AMB was 0.5 and 1, respectively. C. neoformans showed significant growth retardation when incubated with a combination of sub-MIC concentrations of AMB and DFO; whereas, C. gattii demonstrated lesser growth retardation in DFO+AMB. No cryptococcal growth retardation was observed when DSX was combined with AMB. When C. neoformans was grown in DFO, the CFT1, CFT2, and CIR1 proteins were expressed 1.7, 2.0, and 0.9 times, respectively. When C. neoformans was grown in DSX, the CFT1, CFT2, and CIR1 genes were expressed 0.5, 0.6, and 0.3 times, respectively. CONCLUSION: Synergistic antifungal activity of combination DFO and AMB was observed in Cryptococcus. Relatively increased CFT1 and CFT2 expression may be associated with the effect of DFO that inhibits the growth of fungi.

Organized structures of two bidirectionally coupled logistic maps.

We report some organized structures of two linearly coupled logistic maps with different harvesting. The coupled system exhibits chaos via period-bubbling and quasiperiodic routes for identical and weak coupling strength, in contrast to conventional period-doubling route for a simple logistic map. Studies reveal the existence of infinite families of periodic Arnold tongues and self-similar shrimp-shaped structures with period-adding sequences for periodic windows embedded in quasiperiodic and chaotic regions, respectively. Different Fibonacci-like sequences are formed leading to the Golden Mean. The shrimp-shaped structures maintain period 3-times self-similarity scaling. The quasiperiodicity route is the necessary condition for the occurrence of periodic Arnold tongues in this coupled system resulting in the appearance of shrimps in the chaotic region near the tongues. It is also revealed that the existence of shrimp implies the period-bubbling cascade but the reverse is not true. The bifurcation-induced hysteresis is born in a certain parameter range resulting in the birth of coexisting multiple attractors of different kinds. Basin sets of the coexisting attractors have either self-similar or intertwining fractal basin boundaries.

Collateral damage of using colistin in hospitalized patients on emergence of colistin-resistant Escherichia coli and Klebsiella pneumoniae colonization and infection.

Background: Colistin has been used for therapy of carbapenem-resistant Gram-negative infections in Thailand, especially carbapenem-resistant A. baumannii and P. aeruginosa, for more than 10 years. However, the prevalence of colistin-resistant A. baumannii or P. aeruginosa is still less than 5%. Colistin-resistant Enterobacteriaceae has been increasingly reported globally over the past few years and the use of colistin in food animals might be associated with an emergence of colistin resistance in Enterobacteriaceae. This study aimed to determine the effect of colistin exposure in hospitalized patients who received colistin on development of colistin-resistant (CoR) Escherichia coli (EC) or Klebsiella pneumoniae (KP) colonization and infection. Methods: A prospective observational study was performed in adult hospitalized patients at Siriraj Hospital who received colistin for treatment of infections during December 2016 and November 2017. The surveillance culture samples were collected from the stool and the site of infection of each patient who received colistin at the study enrollment, days 3 and 7 after the study enrollment, and once a week thereafter for determination of CoR EC and CoR KP. CoR EC and CoR KP were also tested for a presence of mcr-1 gene. Results: One hundred thirty-nine patients were included. Overall prevalence of CoR EC or CoR KP colonization was 47.5% among 139 subjects. Prevalence of CoR EC or CoR KP colonization was 17.3% of subjects at study enrollment, and 30.2% after study enrollment. Use of fluoroquinolones, aminoglycosides, and colistin was found to be significantly associated with CoR EC or CoR KP colonization. The mcr-1 gene was detected in 13.0% of CoR EC or CoR KP isolates, and in 27.3% of subjects with CoR EC or CoR KP colonization. CoR EC or CoR KP colonization persisted in 65.2% of the subjects at the end of the study. Five patients with CoR KP infections received combination antibiotics and they were alive at hospital discharge. Conclusions: Prevalence of CoR EC or CoR KP colonization in hospitalized patients receiving colistin was high and it was associated with the use of colistin. Therefore, patients who receive colistin are at risk of developing CoR EC or CoR KP colonization and infection.

Pre-transplant cytomegalovirus (CMV) serostatus remains the most important determinant of CMV reactivation after allogeneic hematopoietic stem cell transplantation in the era of surveillance and preemptive therapy.

Between January 2001 and June 2008, 315 adult patients (median age 43 years, range 16-65) including 203 males and 112 females undergoing hematopoietic stem cell transplantation (HSCT) had serial monitoring for cytomegalovirus (CMV) followed by initiation of preemptive therapy. The majority (62.1%) had a conventional myeloablative transplant with 116 (36.9%) having a reduced-intensity conditioning (RIC) transplant, using either matched sibling/family (63.3%) or unrelated donors (36.7%). Graft source was peripheral blood stem cells in 257 (81.5%), bone marrow in 41 (13.1%), and cord blood in 16 (5.4%). T-cell depletion with anti-thymocyte globulin or alemtuzumab was used in 35%. Based upon CMV serostatus, patients were classified into low risk (donor [D]-/recipient [R]-), intermediate risk (D+/R-), or high risk (D-/R+ or D+/R+). Serial weekly monitoring for CMV viremia was performed using a qualitative polymerase chain reaction (PCR) and when positive, quantification was done using either pp65 antigen or a quantitative PCR. CMV reactivation was seen in 123 patients (39.1%) at a median of 50 days post HSCT (range 22-1978). CMV serostatus was the most important risk factor with incidence of 53% in the high-risk group (53.3%) compared with 10.2% in the intermediate risk and 0% in the low-risk group (P<0.0001). Other significant risk factors identified included use of alemtuzumab during conditioning (P=0.03), RIC transplants (P=0.06), and the presence of acute graft-versus-host disease (GVHD) (P<0.0001). On a multivariate analysis, CMV serostatus, RIC transplants, and acute GVHD remained independent predictors of CMV reactivation. All were treated with antiviral therapy with responses seen in 109 (88.6%). Sixteen patients (13%) developed CMV disease at a median of 59 days post HSCT (range 26 days-46 months), 8 of whom died. At a median follow up of 43 months (range 6-93), 166 patients (52.6%) are alive with a significantly higher survival among patients without CMV reactivation (57.2%) as compared with patients with CMV reactivation (45.5%; P=0.049). CMV reactivation and disease remains a major problem in high-risk patients undergoing allogeneic HSCT. Novel prophylactic measures such as immunotherapy and drug prophylaxis need to be considered in this specific group of patients.

Solitary calvarial metastases: an unusual presentation of thoracic neuroblastoma.

A primary thoracic origin occurs only in 20% of neuroblastomas, and their classical presentation is mediastinal or cord compression. Skeletal metastases of neuroblastomas are characteristically multiple, and calvarial deposits usually show simultaneous involvement of orbit. Solitary metastases in neuroblastoma, is an unusual entity and its presentation as a large calvarial mass, especially from a thoracic primary, is rare. Furthermore, calvarial metastases are relatively uncommon in children compared to adults. We discuss the clinical, radiographic, CT features, and differential diagnosis of a large calvarial mass with sunray spiculation in a child, which was due to a solitary metastases from an occult thoracic neuroblastoma. The possibility of neuroblastoma presenting in this unique fashion and the importance of considering a chemosensitive tumor such as neuroblastoma in the differential diagnosis of a solitary calvarial mass in a child is highlighted by our report.

Sonographic diagnosis of Ascaris-induced cholecystitis and pancreatitis in a child.

We describe the sonographic diagnosis of Ascaris-induced acute cholecystitis and pancreatitis in a 2-year-old girl. Abdominal sonography revealed a grossly distended gallbladder with a thick (0.5-cm) wall. The common bile duct was dilated to 0.6 cm without sludge or calculi. The pancreas was hypoechoic, with an enlarged, 3.3-cm pancreatic head. Sonography showed dilatation of the small- and large-bowel loops, with multiple roundworms in duodenal and colonic loops. Sonography has an important role not only in the diagnosis of this uncommon condition but also in the documentation of its unusual etiologic agent.

Lipoprotein(a), atherosclerosis, and apolipoprotein(a) gene polymorphism.

High plasma lipoprotein(a) [Lp(a)] levels have been implicated as an independent risk factor for coronary artery disease in Caucasians, Chinese, Africans, and Indians. Apo(a) that evolved from a duplicated plasminogen gene during recent primate evolution is responsible for the concentration of Lp(a) in the artery wall leading to atherosclerosis, by virtue of its ability to bind to the extracellular matrix and its role in stimulating the proliferation and migration of human smooth muscle cells. Several types of polymorphisms, size as well as sequence changes both in the coding and regulatory sequences, have been reported to influence the variability of Lp(a) concentration. Apo(a) exhibits genetic size polymorphism varying between 300 and 800 kDa that could be attributed to the number of k-4 VNTR (variable number of transcribed kringle-4 repeats). An inverse relationship between Lp(a) level and apo(a) allele sizes is a general trend in all ethnic populations although apo(a) allele size distribution could be significantly variable in ethnic types. A negative correlation between the number of pentanucleotide TTTTA(n) repeat (PNR) sequences in the regulatory region of the apo(a) gene and Lp(a) level has also been observed in Caucasians and Indians, but not in African Americans. However, a significant linkage disequilibrium was noted between the PNR number and k-4 VNTR. In order to correlate the role of apo(a) gene polymorphisms to apo(a) gene regulation, we have proposed that liver-specific transcriptional activators and repressors might contribute to the differential expression of apo(a) gene, in an individual-specific manner.

Simultaneous mutations (A/G(-418) and C/T(-384)) in the apo(a) promoter of individuals with low Lp(a) levels.

High plasma levels of Lp(a), a low-density lipoprotein particle with an attached apo(a), are associated with the development of atherosclerosis. We present two simultaneous mutations in the apo(a) promoter (A/G(-418) and C/T(-384)) in healthy Indians with a low Lp(a) level (<5 mg/dl). No such mutations were detected in coronary artery disease positive individuals with very high Lp(a) levels (>200 mg/dl). The mutations described here might be useful in understanding the transcriptional regulation of the apo(a) gene.

Paraoxonase gene polymorphism and coronary artery disease in Indian subjects.

The human serum HDL-linked paraoxonase enzyme limits the LDL peroxidation by preventing transformation of LDL into biologically active atherogenic particles. Paraoxonase serum activity varies among individuals due to an Gln/Arg polymorphism with low (A phenotype) and high activity (B phenotype). The present study correlates the paraoxonase enzyme activity and the paraoxonase gene polymorphism among 200 Indians with or without coronary artery disease (CAD). We analyzed the PON enzyme activity and have identified A and B phenotypes by Alwl restriction mapping. In 120 CAD patients, the genotypes A and B constituted 75 and 25%, where as in 80 control subjects, the genotypes A and B constituted 25 and 17%, respectively. The frequency of AB genotype is higher in CAD subjects with or without diabetes, than in controls. Arg allele frequency was higher (0.45) in CAD subjects than in controls (0.17). The conventional risk factors and the family history of CAD did not affect the genotype frequency distribution among Indians. In conclusion, paraoxonase polymorphism may have been involved in the predisposition to CAD through a mechanism other than lipid oxidation.