90 research outputs found
The Maximum Lifetime of the Quark-Gluon Plasma
The width of the deconfinement transition region is shown to
influence strongly the flow structure in the (Landau-) hydrodynamical expansion
of a quark-gluon plasma. For a sharp first order transition () the
mixed phase is rather long-lived, with a lifetime that has a maximum when the
initial energy density is at the phase boundary between mixed and pure
quark-gluon matter. For increasing , however, the lifetime decreases
rapidly. Hadronic matter, however, remains long-lived as a consequence of the
rapid change in the degrees of freedom in the transition region and the
corresponding ``softening'' of the equation of state.Comment: 22 pages, latex, 12 uuencoded figure
Hot Spots and Turbulent Initial Conditions of Quark-Gluon Plasmas in Nuclear Collisions
As a result of multiple mini-jet production, initial conditions of the QCD
plasma formed in ultrarelativistic nuclear collisions may be inhomogeneous,
with large fluctuations of the local energy density (hot spots), and turbulent,
with a chaotic initial transverse velocity field. Assuming rapid local
thermalization, the evolution of such plasmas is computed using longitudinal
boost-invariant 3+1-dimensional hydrodynamics. We compare the evolution in case
that the speed of sound in the plasma is constant to one resulting from an
equation of state involving a strong first order transition, with a minimum of
the velocity of sound as a function of energy density. We find that azimuthally
asymmetric fluctuations and correlations of the transverse energy flow can
develop in both cases due to the initial inhomogeneities. Hot spots also
enhance significantly high-transverse momenta direct photon yields. In the case
with a phase transition, the hadronization surface evolves into an unusual
foam-like structure. Also in that case, we find that hadronization is
considerably delayed relative to the ideal gas case, just as previous studies
have found for homogeneous initial conditions. The time-delay signature of a
rapid cross-over transition region in the QCD equation of state (as observable
via meson interferometry) is thus found to be remarkably robust to
uncertainties in the initial conditions in heavy-ion reactions.Comment: 28 pages, LaTeX, 20 figures, available as uucompressed file
(including LaTeX-file) ftp://nt1.phys.columbia.edu/pub/turb/turb2.uu
(username: ftp, password: complete email address
The Time-Delay Signature of Quark-Gluon-Plasma Formation in Relativistic Nuclear Collisions
The hydrodynamic expansion of quark-gluon plasmas with spherical and
longitudinally boost-invariant geometries is studied as a function of the
initial energy density. The sensitivity of the collective flow pattern to
uncertainties in the nuclear matter equation of state is explored. We
concentrate on the effect of a possible finite width, ,
of the transition region between quark-gluon plasma and hadronic phase.
Although slow deflagration solutions that act to stall the expansion do not
exist for , we find, nevertheless, that the equation of
state remains sufficiently soft in the transition region to delay the
propagation of ordinary rarefaction waves for a considerable time. We compute
the dependence of the pion-interferometry correlation function on ,
since this is the most promising observable for time-delayed expansion. The
signature of time delay, proposed by Pratt and Bertsch, is an enhancement of
the ratio of the inverse width of the pion correlation function in
out-direction to that in side-direction. One of our main results is that this
generic signature of quark-gluon plasma formation is rather robust to the
uncertainties in the width of the transition region. Furthermore, for
longitudinal boost-invariant geometries, the signal is likely to be maximized
around RHIC energies, AGeV.Comment: 27 pages, 18 figure
Evaluation of lymphatic vessel dilatations by anterior segment swept-source optical coherence tomography: Case report
Background: Conjunctival lymphangiectasia is a rare condition presumably caused by the obstruction of lymphatic channels or by an abnormal connection between conjunctival lymphatic and blood vessels. Diagnosis is based on clinical appearance and histology. We report a case of conjunctival lymphangiectasia in which anterior segment optical coherence tomography (OCT) was used to assist the diagnosis and the planning of the biopsy location. Case presentation: A 31-year-old woman was referred with repeated episodes of conjunctival "hemorrhages" and chemosis with extended recovery periods over the last months. Other symptoms were dryness, redness, burning sensation and itching. Photo documentation, anterior segment OCT, ultrasound, computer tomography (CT) and magnetic resonance imaging (MRI) of the brain were performed. MRI revealed dilated atypical Virchow-Robin space (VRS). Conjunctival biopsy was taken and the location of the biopsy was selected based on OCT findings. Based on the clinical appearance we suspected the case to be conjunctival lymphangiectasia or lymphangioma. Histology and immunhistochemistry confirmed the diagnosis of conjunctival lymphangiectasia. Conclusions: Anterior segment OCT is a non-invasive tool, useful in the evaluation of conjunctival lesions and planning surgery. © 2017 The Author(s)
Bilateral cystoid macular edema following docetaxel chemotherapy in a patient with retinitis pigmentosa: a case report.
BACKGROUND: Docetaxel is a chemotherapeutic agent of the taxane class of drugs for the treatment of breast cancer. We present a female patient who noted decreased vision after docetaxel treatment. CASE PRESENTATION: A 45-year-old female patient received docetaxel treatment after resection of a breast carcinoma. Funduscopy and optical coherence tomography (OCT) showed cystoid macular edema on both eyes. Dilated funduscopy also showed bone spicule-like pigmented deposits, typical for retinitis pigmentosa. Besides the fundus appearance restricted peripheral vision and scotopic electroretinogram confirmed the diagnosis of retinitis pigmentosa. Chemotherapy was discontinued following a consulation with the oncologist of the patient. After five weeks, visual acuity improved significantly along with decrease of retinal thickness measured by OCT. CONCLUSION: Docetaxel may cause ocular adverse effects such as cystoid macular edema. Ophthalmological examination is warranted for patients with visual complaints during docetaxel chemotherapy
A Two-Gene Balance Regulates Salmonella Typhimurium Tolerance in the Nematode Caenorhabditis elegans
Lysozymes are antimicrobial enzymes that perform a critical role in resisting infection in a wide-range of eukaryotes. However, using the nematode Caenorhabditis elegans as a model host we now demonstrate that deletion of the protist type lysozyme LYS-7 renders animals susceptible to killing by the fatal fungal human pathogen Cryptococcus neoformans, but, remarkably, enhances tolerance to the enteric bacteria Salmonella Typhimurium. This trade-off in immunological susceptibility in C. elegans is further mediated by the reciprocal activity of lys-7 and the tyrosine kinase abl-1. Together this implies a greater complexity in C. elegans innate immune function than previously thought
Impact of safety-related dose reductions or discontinuations on sustained virologic response in HCV-infected patients: Results from the GUARD-C Cohort
BACKGROUND:
Despite the introduction of direct-acting antiviral agents for chronic hepatitis C virus (HCV) infection, peginterferon alfa/ribavirin remains relevant in many resource-constrained settings. The non-randomized GUARD-C cohort investigated baseline predictors of safety-related dose reductions or discontinuations (sr-RD) and their impact on sustained virologic response (SVR) in patients receiving peginterferon alfa/ribavirin in routine practice.
METHODS:
A total of 3181 HCV-mono-infected treatment-naive patients were assigned to 24 or 48 weeks of peginterferon alfa/ribavirin by their physician. Patients were categorized by time-to-first sr-RD (Week 4/12). Detailed analyses of the impact of sr-RD on SVR24 (HCV RNA <50 IU/mL) were conducted in 951 Caucasian, noncirrhotic genotype (G)1 patients assigned to peginterferon alfa-2a/ribavirin for 48 weeks. The probability of SVR24 was identified by a baseline scoring system (range: 0-9 points) on which scores of 5 to 9 and <5 represent high and low probability of SVR24, respectively.
RESULTS:
SVR24 rates were 46.1% (754/1634), 77.1% (279/362), 68.0% (514/756), and 51.3% (203/396), respectively, in G1, 2, 3, and 4 patients. Overall, 16.9% and 21.8% patients experienced 651 sr-RD for peginterferon alfa and ribavirin, respectively. Among Caucasian noncirrhotic G1 patients: female sex, lower body mass index, pre-existing cardiovascular/pulmonary disease, and low hematological indices were prognostic factors of sr-RD; SVR24 was lower in patients with 651 vs. no sr-RD by Week 4 (37.9% vs. 54.4%; P = 0.0046) and Week 12 (41.7% vs. 55.3%; P = 0.0016); sr-RD by Week 4/12 significantly reduced SVR24 in patients with scores <5 but not 655.
CONCLUSIONS:
In conclusion, sr-RD to peginterferon alfa-2a/ribavirin significantly impacts on SVR24 rates in treatment-naive G1 noncirrhotic Caucasian patients. Baseline characteristics can help select patients with a high probability of SVR24 and a low probability of sr-RD with peginterferon alfa-2a/ribavirin
Drosophila melanogaster as an Animal Model for the Study of Pseudomonas aeruginosa Biofilm Infections In Vivo
Pseudomonas aeruginosa is an opportunistic pathogen capable of causing both acute and chronic infections in susceptible hosts. Chronic P. aeruginosa infections are thought to be caused by bacterial biofilms. Biofilms are highly structured, multicellular, microbial communities encased in an extracellular matrix that enable long-term survival in the host. The aim of this research was to develop an animal model that would allow an in vivo study of P. aeruginosa biofilm infections in a Drosophila melanogaster host. At 24 h post oral infection of Drosophila, P. aeruginosa biofilms localized to and were visualized in dissected Drosophila crops. These biofilms had a characteristic aggregate structure and an extracellular matrix composed of DNA and exopolysaccharide. P. aeruginosa cells recovered from in vivo grown biofilms had increased antibiotic resistance relative to planktonically grown cells. In vivo, biofilm formation was dependent on expression of the pel exopolysaccharide genes, as a pelB::lux mutant failed to form biofilms. The pelB::lux mutant was significantly more virulent than PAO1, while a hyperbiofilm strain (PAZHI3) demonstrated significantly less virulence than PAO1, as indicated by survival of infected flies at day 14 postinfection. Biofilm formation, by strains PAO1 and PAZHI3, in the crop was associated with induction of diptericin, cecropin A1 and drosomycin antimicrobial peptide gene expression 24 h postinfection. In contrast, infection with the non-biofilm forming strain pelB::lux resulted in decreased AMP gene expression in the fly. In summary, these results provide novel insights into host-pathogen interactions during P. aeruginosa oral infection of Drosophila and highlight the use of Drosophila as an infection model that permits the study of P. aeruginosa biofilms in vivo
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