Biomedical subjects

N Guler

Publications and source records attributed to N Guler.

At least 19 recordsLinked to original sources

PubMed2006

Measurement of the N-->Delta(+)(1232) transition at high-momentum transfer by pi(0) electroproduction.

We report a new measurement of the exclusive electroproduction reaction gamma(*)p-->pi(0)p to explore the evolution from soft nonperturbative physics to hard processes via the Q(2) dependence of the magnetic (M(1+)), electric (E(1+)), and scalar (S(1+)) multipoles in the N-->Delta transition. 9000 differential cross section data points cover W from threshold to 1.4 GeV/c(2), 4pi center-of-mass solid angle, and Q(2) from 3 to 6 GeV(2)/c(2), the highest yet achieved. It is found that the magnetic form factor G(M)(*) decreases with Q(2) more steeply than the proton magnetic form factor, the ratio E(1+)/M(1+) is small and negative, indicating strong helicity nonconservation, and the ratio S(1+)/M(1+) is negative, while its magnitude increases with Q(2).

Journal Article↗

PubMed2006

Search for Theta++ pentaquarks in the exclusive reaction gammap-->K+K-p.

The reaction gammap --> pK+K- was studied at Jefferson Lab with photon energies from 1.8 to 3.8 GeV using a tagged photon beam. The goal was to search for a Theta++ pentaquark, a narrow, doubly charged baryon state having strangeness S=+1 and isospin I=1, in the pK+ invariant mass spectrum. No statistically significant evidence of a Theta++ was found. Upper limits on the total and differential cross section for the reaction gammap --> K-Theta++ were obtained in the mass range from 1.5 to 2.0 GeV/c2, with an upper limit for a narrow resonance with a mass M(Theta++) = 1.54 GeV/c2 of about 0.15 nb, 95% C.L.. This result places a stringent upper limit on the Theta++ width Gamma(Theta++) <0.1 MeV/c2.

Journal Article↗

PubMed2006

Measurement of deeply virtual compton scattering with a polarized-proton target.

The longitudinal target-spin asymmetry AUL for the exclusive electroproduction of high-energy photons was measured for the first time in ep-->e;'pgamma. The data have been accumulated at JLab with the CLAS spectrometer using 5.7 GeV electrons and a longitudinally polarized NH3 target. A significant azimuthal angular dependence was observed, resulting from the interference of the deeply virtual Compton scattering and Bethe-Heitler processes. The amplitude of the sinvarphi moment is 0.252+/-0.042stat+/-0.020sys. Theoretical calculations are in good agreement with the magnitude and the kinematic dependence of the target-spin asymmetry, which is sensitive to the generalized parton distributions H and H.

Journal Article↗

PubMed2006

Search for the Theta+ Pentaquark in the gammad--> DeltanK+ reaction measured with the CLAS spectrometer.

For the first time, the reaction gammad-->DeltanK+ has been analyzed in order to search for the exotic pentaquark baryon Theta+(1540). The data were taken at Jefferson Laboratory, using the Hall-B tagged-photon beam of energy between 0.8 and 3.6 GeV and the CEBAF Large Acceptance Spectrometer (CLAS). No statistically significant structures were observed in the nK+ invariant-mass distribution. The upper limit on the gammad-->DeltaTheta+ integrated cross section has been calculated and found to be between 5 and 25 nb, depending on the production model assumed. The upper limit on the differential cross section is also reported.

Journal Article↗

PubMed2006

Search for the Theta+ pentaquark in the reaction gammad --> pK-K+n.

A search for the Theta+ in the reaction gammad --> pK-K+n was completed using the CLAS detector at Jefferson Lab. A study of the same reaction, published earlier, reported the observation of a narrow Theta+ resonance. The present experiment, with more than 30 times the integrated luminosity of our earlier measurement, does not show any evidence for a narrow pentaquark resonance. The angle-integrated upper limit on Theta+ production in the mass range of 1.52-1.56 GeV/c2 for the gammad --> pK-Theta+ reaction is 0.3 nb (95% C.L.). This upper limit depends on assumptions made for the mass and angular distribution of Theta+ production. Using Lambda(1520) production as an empirical measure of rescattering in the deuteron, the cross section upper limit for the elementary gamman --> K-Theta+ reaction is estimated to be a factor of 10 higher, i.e., approximately 3 nb (95% C.L.).

Journal Article↗

PubMed2006

Measurement of two- and three-nucleon short-range correlation probabilities in nuclei.

The ratios of inclusive electron scattering cross sections of 4He, 12C, and 56Fe to 3He have been measured at 1 < xB <. At Q2 > 1.4 GeV2, the ratios exhibit two separate plateaus, at 1.5 < xB < 2 and at xB > 2.25. This pattern is predicted by models that include 2- and 3-nucleon short-range correlations (SRC). Relative to A = 3, the per-nucleon probabilities of 3-nucleon SRC are 2.3, 3.1, and 4.4 times larger for A = 4, 12, and 56. This is the first measurement of 3-nucleon SRC probabilities in nuclei.

Journal Article↗

PubMed2006

Eta' photoproduction on the proton for photon energies from 1.527 to 2.227 GeV.

Differential cross sections for the reaction gamma p --> eta' p have been measured with the CLAS spectrometer and a tagged photon beam with energies from 1.527 to 2.227 GeV. The results reported here possess much greater accuracy than previous measurements. Analyses of these data suggest for the first time the coupling of the eta'N channel to both the S11(1535) and P11(1710) resonances, known to couple strongly to the etaN channel in photoproduction on the proton, and the importance of J = 3/2 resonances in the process.

Journal Article↗

PubMed2006

Search for Theta+ (1540) Pentaquark in High-Statistics Measurement of gammap-->K0K+n at CLAS.

The exclusive reaction gammap-->K0K+n was studied in the photon energy range between 1.6 and 3.8 GeV searching for evidence of the exotic baryon Theta+ (1540)-->nK+. The decay to nK+requires the assignment of strangeness S=+1 to any observed resonance. Data were collected with the CLAS detector at the Thomas Jefferson National Accelerator Facility corresponding to an integrated luminosity of 70 pb-1. No evidence for the Theta+ pentaquark was found. Upper limits were set on the production cross section as function of center-of-mass angle and nK+ mass. The 95% C.L. upper limit on the total cross section for a narrow resonance at 1540 MeV was found to be 0.8 nb.

Journal Article↗

PubMed2006

The relation between plasminogen activator inhibitor activity and disease activation in acute myeloblastic leukaemia patients.

Coagulation and fibrinolytic abnormalities are common in patients with acute myeloblastic leukaemia (AML) like other forms of leukaemias. In this study, we investigated if total plasminogen activator inhibitor (PAI) activity, which is believed to increase in initial diagnosis and relapse in AML patients could be accepted as a relapse criterion or not. Total of 34 AML patients and 18 healthy volunteers were included in this study. The patients' diagnosis were based on clinical criteria as well as morphological, cytochemical, immunuphenotypic examinations of peripheral blood and bone marrow specimens. Total PAI activity was measured with Dade Behring Bericrom PAI reagent in BCS system. Total PAI activity was higher than 3.5 U/ml in 11 AML patients while it was normal (0.3-3.5 U/ml) in control group (P < 0.01). There was no significant difference in total PAI activity between AML subgroups (P > 0.05). We found significant difference in total PAI activity between patients who have active disease and remission. In conclusion, the total PAI activity could be accepted as a relapse and an initial diagnosis criterion of AML patients during follow up.

Adult↗

PubMed2006

Rising trend of asthma prevalence among Turkish schoolchildren (ISAAC phases I and III).

BACKGROUND: Asthma is a common chronic illness in childhood. The aim of the study was to examine time trends in the prevalence of asthma using the ISAAC questionnaire in 6- to 12-year-old schoolchildren in Istanbul and factors affecting asthma prevalence. METHODS: Two cross-sectional surveys were performed, 9 years apart (1995 and 2004) using the ISAAC protocol. The survey conducted in 1995 was repeated in 2004 using the same questionnaire in the same age group, in the same schools in the same season. The 2500 questionnaires were distributed to the children to be completed by their parents at home. RESULTS: A total of 2387 children (response rate 95.5%) in the 2004 study and 2216 children (response rate 94.3%) in 1995 were included in the final analysis. The overall lifetime prevalence of wheeze increased from 15.1% to 25.3%; prevalence odds ratio (POR) = 1.91, 95% confidence interval (95% CI) = 1.64-2.21, and P < 0.001. The overall 12-month prevalence of wheeze increased from 8.2% to 11.3%; POR = 1.43, 95% CI = 1.18-1.75, and P < 0.001. The prevalence of asthma increased significantly from 9.8% to 17.8%; POR = 1.99, 95% CI = 1.67-2.36, and P < 0.001. In both 1995 and 2004, family history of asthma, eczema diagnosed by a physician, food allergy diagnosed by a physician, frequent otitis, frequent sinusitis were associated significantly with high risk for asthma. CONCLUSIONS: In the 9-year period from 1995 to 2004, the prevalence of asthma symptoms has increased in 6- to 12-year-old schoolchildren in Istanbul. Risk factors affecting asthma prevalence remained unchanged during the 9-year period.

Asthma↗

PubMed2006

Atopy patch testing in children with asthma and rhinitis symptoms allergic to house dust mite.

The atopy patch test (APT) is generally used to assess immunoglobulin E (IgE) mediated sensitization to allergens in patients with atopic dermatitis, but its diagnostic role in children with respiratory allergy is still controversial. The aim of the study was to evaluate APT with house dust mite (HDM) in children with asthma and rhinitis symptoms allergic to HDM and its relevance to skin prick test (SPT) diameters and specific IgE levels. The study population consisted of 33 children, aged 8-16 yr (median: 12 yr) with asthma and 30 children with allergic rhinitis in the same age range (median: 11 yr). All patients had positive SPT results and high serum specific IgE levels for Dermatophagoides pteronyssinus APT was performed on back skin of all patients with 200 index of reactivity (IR)/ml of D. pteronyssinus allergen extracts in petrolatum (Stallerpatch) and evaluated at 72 h. Of 63 patients, 16 (25%) showed a positive patch test result. APT with HDM showed 30% (10/33) positivity among the patients with asthma and 20% (6/30) positivity among the patients with allergic rhinitis. APT presented no significant correlation with age, SPT diameter, serum total and specific IgE levels for D. pteronyssinus, nasal provocation test or pulmonary function test results. Patch testing with HDM may partly identify mite sensitive children with respiratory allergy. Positive APT results may imply that delayed hypersensitivity reactions play a role in children with asthma and rhinitis allergic to HDM.

Adolescent↗

PubMed2005

Beam-helicity asymmetries in double-charged-pion photoproduction on the proton.

Beam-helicity asymmetries for the two-pion-photoproduction reaction gammap-->ppi(+)pi(-) have been studied for the first time in the resonance region for center-of-mass energies between 1.35 and 2.30 GeV. The experiment was performed at Jefferson Lab with the CEBAF Large Acceptance Spectrometer using circularly polarized tagged photons incident on an unpolarized hydrogen target. Beam-helicity-dependent angular distributions of the final-state particles were measured. The large cross-section asymmetries exhibit strong sensitivity to the kinematics and dynamics of the reaction. The data are compared with the results of various phenomenological model calculations, and show that these models currently do not provide an adequate description for the behavior of this new observable.

Journal Article↗

PubMed2005

Expression of Fas and Fas-ligand and analysis of argyrophilic nucleolar organizer regions in squamous cell carcinoma: relationships with tumor stage and grade, and apoptosis.

The aim of this study was to investigate whether levels of Fas and Fas-ligand (Fas-L) expression in oral and oropharyngeal squamous cell carcinomas (SCCs) are associated with tumor stage and grade, and to assess whether parameters related to argyrophilic nucleolar organizer regions (AgNORs) correlate with apoptosis in SCC cells and adjacent normal epithelium. Fifty-two specimens taken from the tumoral and neighboring normal tissues of 26 patients with oral and oropharyngeal SCC were analyzed for Fas/Fas-L expression, and 24 specimens from 12 patients for AgNOR parameters. Seventeen (65%) of the tumors were Fas and/or Fas-L-positive (by immunohistochemistry). A significant positive correlation was found between Fas/Fas-L expression and clinical tumor stage (P<0.01). Mean AgNOR number per nucleus, AgNOR size and the percentage area of each nucleus occupied by AgNORs (percent of nuclear area) were significantly increased in the SCC cells (4.49+/-1.28, 4.48+/-1.42, 5.56+/-1.22, respectively) when compared with the control neighboring squamous epithelial cells (2.58+/-0.61, 1.64+/-0.59 and 4.35+/-0.62%, respectively) (P<0.01). A significant positive correlation was found between the AgNOR parameters and Fas/Fas-L expression as apoptotic markers in the tumoral cells of SCC (P<0.05). There was also a significant positive correlation between the AgNOR parameters and the grading of tumors (P<0.05). In conclusion, AgNOR count was a strong proliferation marker in patients with SCC, and Fas and Fas-L staining was useful in tumor grading.

Adult↗

PubMed2005

Gastrointestinal involvement in POEMS syndrome: a novel clinical manifestation.

POEMS syndrome (polyneuropathy, organomegaly, endocrinopathy, monoclonal gammopathy, and skin changes) is characterised by a rare multisystem disorder of unknown pathogenesis. Although its pathophysiology is not well understood, overexpression of proinflammatory cytokines has been implicated. Gastrointestinal system disorders have not been reported among the components of the syndrome. A case is reported of POEMS syndrome with gastrointestinal involvement shown by gastrointestinal endoscopy.

Adult↗

PubMed2004

Proton source size measurements in the eA-->e'ppX reaction.

Two-proton correlations at small relative momentum q were studied in the eA(3He,4He,C,Fe)-->e(')ppX reaction at E(0)=4.46 GeV using the CLAS detector at Jefferson Lab. The enhancement of the correlation function at small q was found to be in accordance with theoretical expectations. Sizes of the emission region were extracted, and proved to be dependent on A and on the proton momentum. The size of the two-proton emission region for He was measured in eA reactions for the first time.

Journal Article↗

PubMed2004

Synchronous squamous cell carcinoma of the stomach, the lung and the skin.

BACKGROUND: The incidence of multiple primary cancers is reported to be 0.3-4.3%. CASE REPORT: A 70-year-old man was admitted to the hospital because of fatigue, weight loss, epigastric pain with melena. A biopsy taken from a tumoral lesion in the gastric corpus revealed squamous cell carcinoma. A nodular lesion was also detected on the nasal columella and biopsy from this lesion also showed squamous cell carcinoma. Computed tomography performed as a part of metastatic work-up revealed a lesion in the left pulmonary lower lobe. Bronchoscopic biopsy from this lesion also demonstrated squamous cell carcinoma. RESULTS: We report a case with synchronous squamous cell carcinoma of the lung, skin and stomach and discuss the multiple synchronous occurrence of carcinoma with the same histopathology in different sites with a review of the literature.

Aged↗

PubMed2004

Myasthenic crisis following cisplatin chemotherapy in a patient with malignant thymoma.

Malignant thymomas are associated with numerous autoimmune disorders including myasthenia gravis. Myastenia gravis is characterized by antibodies against the acetylcholine receptors located on the neuromuscular junction of the skeletal muscle. We present a case with malignant thymoma who developed myasthenia crisis while he was treated with cisplatin chemotherapy.

Antineoplastic Agents↗

PubMed2003

[Efficacy and safety of the TAIS coronary stent implantation: nine month multicenter study].

AIM: Assessment of clinical and angiographic results of a balloon-expandable steel matrix stent TAIS in patients with atherosclerosis of the coronary arteries with no history of previous interventions in the course of an open non-randomized multicenter trial. MATERIAL AND METHODS: The TAIS stent was implanted in 187 patients into 199 stenoses. 47% patients had clinical manifestations of unstable angina pectoris. 29% cases were complicated. The length of the stenoses reached 11.3 +/- 5.4 mm, 22% stenoses were prolonged. RESULTS: This coronary stenting was effective in 100% cases, neither acute nor subacute thromboses were seen. Myocardial infarction without occlusion of the stent developed in 3 patients. The incidence of cardial complications (death, angina, restenosis, repeated revascularization) in 6 month follow-up was 11.8%. An angiographic control in 6 months was made in 184 patients (194 stenoses). The vascular diameter loss index was 0.40 +/- 0.21, a restenosis level--10.7%. A logistic regression analysis has revealed significant correlations between the length of the stent and a target vascular diameter with subsequent restenosis. Repeated revascularization was performed in all the patients with stent restenosis. After control angiography cardiac complications developed in 13.9% patients. Nine month follow-up registered cardiac complications in 17.6% cases. CONCLUSION: The TAIS stent was found effective in prevention of thrombosis and restenosis in patients with a relatively high risk of intervention.

Adult↗