Characterization of Saturn's bow shock: magnetic field observations of quasi-perpendicular shocks

Collisionless shocks vary drastically from terrestrial to astrophysical regimes resulting in radically different characteristics. This poses two complexities. First, separating the influences of these parameters on physical mechanisms such as energy dissipation. Second, correlating observations of shock waves over a wide range of each parameter, enough to span across different regimes. Investigating the latter has been restricted since the majority of studies on shocks at exotic regimes (such as supernova remnants) have been achieved either remotely or via simulations, but rarely by means of in situ observations. Here we present the parameter space of MA bow shock crossings from 2004 to 2014 as observed by the Cassini spacecraft. We find that Saturn's bow shock exhibits characteristics akin to both terrestrial and astrophysical regimes (MA of order 100), which is principally controlled by the upstream magnetic field strength. Moreover, we determined the θBn of each crossing to show that Saturn's (dayside) bow shock is predominantly quasi-perpendicular by virtue of the Parker spiral at 10 AU. Our results suggest a strong dependence on MA in controlling the onset of physical mechanisms in collisionless shocks, particularly nontime stationarity and variability. We anticipate that our comprehensive assessment will yield deeper insight into high MA collisionless shocks and provide a broader scope for understanding the structures and mechanisms of collisionless shocks

The genetic and molecular basis of bacterial invasion of epithelial cells - a review

In this review, two of the most important virulence factors of bacterial invasion of epithelial cells (adhesion and invasion) were studied from the genetic and molecular point of view. Other virulence factors are; attachment to host cells multiplication within the host, interference with host defense systems, and damage to the host. These are the determinants of microbial pathogenicity. Animal cells in tissue cultures (in-vitro) were used to study adherence and invasive properties of pathogenic bacteria. Invasion of epithelial cells was demonstrated to be triggered by invasion plasmid antigens B, C, and D ( IpaB, IpaC and IpaD ) which is accomplished by intracellular spread gene icsA. The invasion of epithelial cells by some individual species of bacteria were also reviewed.Yersinia enterocolitica invasiveness was shown to be mediated by inv gene product, invasin. Salmonella typhi was found to have four invasion loci; inv A-D, but H genes are contained in 33kb DNA fragment. Enteropathogenic E. coli (EPEC) achieve invasion by assembly of highly organized cytoskeletal structures in the epithelial cells just beneath the adherent bacteria, while Shigella flexneri was found to harbor large plasmid which encodes or regulates some functions required for epithelial cells penetration. Generally, virulence factors in bacteria may be encoded on chromosomal DNA, bacteriophage DNA, and plasmids or transposons. Key words: Genetics, Molecular, Epithelial cells, Invasion, Pathogenicity and Virulenc

Profiles of Diabetic Ketoacidosis in Multiethnic Diabetic Population of Malaysia

Purpose: To outline first-time patient profiles of diabetic ketoacidosis (DKA) in the absence of reported incidence and mortality rates of DKA in Malaysian diabetic population.Methods: A retrospective cross-sectional study was designed and all medical records of patients with a discharge note of DKA were reviewed. Admissions from January 2009 to December 2011 were included. Data were analyzed in terms of socio-demographic variables in order to provide incidence and mortality rates. Medical history, as well as physical and biochemical characteristics were analyzed to report epidemiology of DKA patients.Results: Out of a total of 207 admissions for DKA, 132 were selected for the present study. Female (62.9 %), Malay ethnic (47.0 %) and the elderly (45.1 years and above) contributed most to DKA episodes. Type 2 diabetes mellitus (51.1 %) patients were prone to develop DKA. Most patients experienced mild to moderate episode of DKA by the time they sought medical attention. Although, there was no significant relationship between chronic co-morbidity and occurrence of DKA, hypertension (54.5 %), dyslipidemia (43.0 %) and cardiac disorders (35.6 %) were, however, the most frequently observed co-morbidities. Non-adherence (43.2 %), sepsis (31.9 %) and respiratory tract infection (12.2 %) were the most encountered precipitating factors for DKA episode. Mortality rate was as high as 17.6 %.Conclusion: With a higher incidence and mortality rate of DKA in Malaysia, the patterns observed in this study seem to be different from those of developed nations. Further extended studies need to be undertaken to elaborate regional and national patterns of DKA.Keywords: Incidence, Mortality, Diabetic ketoacidosis, Diabetes, Hypertension, Cardiac disorders, Dyslipidemia, Comorbidit

Whistler mode waves upstream of Saturn

Whistler mode waves are generated within and can propagate upstream of collisionless shocks. They are known to play a role in electron thermodynamics/acceleration and, under certain conditions, are markedly observed as wave trains preceding the shock ramp. In this paper, we take advantage of Cassini's presence at ~10 AU to explore the importance of whistler mode waves in a parameter regime typically characterized by higher Mach number (median of ~14) shocks, as well as a significantly different interplanetary magnetic field structure, compared to near Earth. We identify electromagnetic precursors preceding a small subset of bow shock crossings with properties which are consistent with whistler mode waves. We find these monochromatic, low-frequency, and circularly polarized waves to have a typical frequency range of 0.2–0.4 Hz in the spacecraft frame. This is due to the lower ion and electron cyclotron frequencies near Saturn, between which whistler waves can develop. The waves are also observed as predominantly right handed in the spacecraft frame, the opposite sense to what is typically observed near Earth. This is attributed to the weaker Doppler shift, owing to the large angle between the solar wind velocity and magnetic field vectors at 10 AU. Our results on the low occurrence of whistler waves upstream of Saturn also underpin the predominantly supercritical bow shock of Saturn

Pleural Tuberculosis and its Treatment Outcomes

Purpose: To evaluate the incidence, treatment and clinical outcomes of tuberculosis pleuritis at a hospital in the state of Penang, Malaysia.Methods: A retrospective study was conducted in Hospital of Penang, Malaysia. Patient records were reviewed retrospectively to identify patients with confirmed diagnosis of tuberculous pleuritis from January 2006 to December 2008. Chest x-ray (CXR) and pleural biopsy were carried out on all patients. Directly observed therapy (DOT) was given to all patients. Data were analyzed using SPSS version 16.Results: Of 1548 tuberculosis cases, 80 (5.2 %) patients had tuberculous pleuritis. The mean age of the patients was 35.4 ± 12.87 years, with a male to female ratio of 3.4:1. Ethnically, a plurality (n = 30, 37.7 %) of cases among tuberculosis pleuritis patients were Chinese, followed by Malay (31.2 %). Out of the 80 patients with tuberculous pleuritis, 10 (12.5 %) also had diabetes mellitus, and 8 (10.0 %) HIV/AIDS. Fever, cough, chest pain and shortness of breathing were the most frequently reported symptoms. Treatment success rate was 1.558 times higher among TB group than pleuritis TB group (Odds ratio, 95 % CI, 1.06 – 2.59, p = 0.025).Conclusion: The incidence of TB pleuritis was gender- and race-related, with DM and HIV the most commonly reported risk factors. Treatment success rate was higher among pulmonary TB group than in those with TB pleuritis (extra pulmonary TB).Keywords: Tuberculosis, Pleuritis, HIV/AIDS, Biopsy, Pulmonary

An in situ Comparison of Electron Acceleration at Collisionless Shocks under Differing Upstream Magnetic Field Orientations

A leading explanation for the origin of Galactic cosmic rays is acceleration at high-Mach number shock waves in the collisionless plasma surrounding young supernova remnants. Evidence for this is provided by multi-wavelength non-thermal emission thought to be associated with ultrarelativistic electrons at these shocks. However, the dependence of the electron acceleration process on the orientation of the upstream magnetic field with respect to the local normal to the shock front (quasi-parallel/quasi-perpendicular) is debated. Cassini spacecraft observations at Saturn's bow shock have revealed examples of electron acceleration under quasi-perpendicular conditions, and the first in situ evidence of electron acceleration at a quasi-parallel shock. Here we use Cassini data to make the first comparison between energy spectra of locally accelerated electrons under these differing upstream magnetic field regimes. We present data taken during a quasi-perpendicular shock crossing on 2008 March 8 and during a quasi-parallel shock crossing on 2007 February 3, highlighting that both were associated with electron acceleration to at least MeV energies. The magnetic signature of the quasi-perpendicular crossing has a relatively sharp upstream–downstream transition, and energetic electrons were detected close to the transition and immediately downstream. The magnetic transition at the quasi-parallel crossing is less clear, energetic electrons were encountered upstream and downstream, and the electron energy spectrum is harder above ~100 keV. We discuss whether the acceleration is consistent with diffusive shock acceleration theory in each case, and suggest that the quasi-parallel spectral break is due to an energy-dependent interaction between the electrons and short, large-amplitude magnetic structures

Improving the Modelling of Robot Bunker with Camera

This study proposed an improvement on the model of robot bunker with camera. This is designed in order that robot is difficult to steal. The previous model is equipped with a security system. However, the system is not equipped with a camera so that when theft occurs, the action cannot be recorded. This study used 16 rules, because of the addition of variable pixels produced by the camera. The simulation is carried out as many as 30 (thirty) possible conditions of actions taken by the people on the robot with Matlab Fuzzy Toolbox. In the result of the simulations, the test results can change from safe conditions to alert or dangerous conditions. This is caused by changes in the number of pixels. The pixel value increases when someone tries to take a robot from the robot bunker. Thus the proposed model is more sensitive in detecting changes that occur around the robot bunker. Therefore this model can be applied in securing/protecting robot from theft

A Single Deformed Bow Shock for Titan-Saturn System

During periods of high solar wind pressure, Saturn’s bow shock is pushed inside Titan’s orbit exposing the moon and its ionosphere to the solar wind. The Cassini spacecraft’s T96 encounter with Titan occurred during such a period and showed evidence for shocks associated with Saturn and Titan. It also revealed the presence of two foreshocks: one prior to the closest approach (foreshock 1) and one after (foreshock 2). Using electromagnetic hybrid (kinetic ions and fluid electrons) simulations and Cassini observations,we showthat the origin of foreshock 1 is tied to the formation of a single deformed bow shock for the Titan-Saturn system. We also report the observations of a structure in foreshock 1 with properties consistent with those of spontaneous hot flow anomalies formed in the simulations and previously observed at Earth, Venus, and Mars. The results of hybrid simulations also show the generation of oblique fast magnetosonic waves upstream of the outbound Titan bow shock in agreement with the observations of large-amplitude magnetosonic pulsations in foreshock 2. We also discuss the implications of a single deformed bow shock for new particle acceleration mechanisms and also Saturn’s magnetopause and magnetosphere

Insight into potential mechanisms of hypobaric hypoxia–induced learning and memory deficit – Lessons from rat studies

Impairment of memory is one of the most frequently reported symptoms during sudden hypoxia exposure in human. Cortical atrophy has been linked to the impaired memory function and is suggested to occur with chronic high-altitude exposure. However, the precise molecular mechanism(s) of hypoxia-induced memory impairment remains an enigma. In this work, we review hypoxia-induced learning and memory deficit in human and rat studies. Based on data from rat studies using different protocols of continuous hypoxia, we try to elicit potential mechanisms of hypobaric hypoxia–induced memory deficit