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Biomedical subjects

S Karaca

Publications and source records attributed to S Karaca.

At least 19 recordsLinked to original sources
PubMed2006

Acquired port-wine stain related to acoustic neuroma.

Port-wine stains are frequently seen congenital vascular malformations consisting of ectatic dermal capillaries. Acquired port-wine stain that develops later in life is an uncommon vascular lesion that is morphologically identical to a congenital port-wine stain. In the majority of acquired port-wine stains, the aetiology is unknown, but trauma is an important causative factor. Other proposed aetiologies include chronic sun exposure, hormonal changes, frostbite injury, obstruction of the peritoneovenous shunt, herpes zoster infection, and cerebral arteriovenous malformation. Here we report the first case of a patient who had an acquired port-wine stain related to a solid brain tumour.

Adult↗
PubMed2005

Production of granular activated carbon from waste Rosa canina sp. seeds and its adsorption characteristics for dye.

An activated carbon was developed from Rosa canina sp. seeds, characterized and used for the removal of methylene blue (basic dye) from aqueous solutions. Adsorption studies were carried out at 20 degrees C and various initial dye concentrations (20, 40, 60, 80, and 100 mg/L) for different times (15, 30, 60, and 120 min). The adsorption isotherm was obtained from data. The results indicate that the adsorption isotherm of methylene blue is typically S-shaped. The shape of isotherm is believed to reflect three distinct modes of adsorption. In region 1, the adsorption of methylene blue is carried out mainly by ion exchange. In region 2 by polarizations of pi-electrons established at cyclic parts of the previously adsorbed methylene blue molecules is occurred. However, it is not observed any change at the sign of the surface charge although zeta potential value is decreased with increase of amount adsorbed. In region 3, the slope of the isotherm is reduced, because adsorption now must overcome electrostatic repulsion between oncoming ions and the similarly charged solid. Adsorption in this fashion is usually complete when the surface is covered with a monolayer of methylene blue. To reveal the adsorptive characteristics of the produced active carbon, porosity and BET surface area measurements were made. Structural analysis was performed using SEM-EDS. The produced active carbon has the specific surface area of 799.2 m2 g-1 and the iodine number of 495 mg/g.

Adsorption↗
PubMed2005

The adsorption kinetics of the cationic dye, methylene blue, onto clay.

In this study, adsorption kinetics of a cationic dye, methylene blue, onto clay from aqueous solution with respect to the initial dye concentration, temperature, pH, mixing rate and sorbent dosage were investigated. In order to understand the adsorption mechanism in detail, zeta potentials and the conductivities of clay suspensions at various pH (1-11) and cation exchange capacity (CEC) were measured. Porosity and BET surface area of clay studied were determined. The results showed that the adsorption has been reached to equilibrium in 1 h. It was found that the amount adsorbed of methylene blue increases with decreasing temperature and also with increasing both sorbent dosage and increasing initial dye concentration. Adsorption capacity decreases with increasing pH, except for the natural pH (5.6) of clay suspensions. The adsorption kinetics of methylene blue has been studied in terms of pseudo-first-order, pseudo-second-order sorption and intraparticle diffusion processes thus comparing chemical sorption and diffusion sorption processes. It was found that the pseudo-second-order mechanism is predominant and the overall rate of the dye adsorption process appears to be controlled by the more than one-step.

Adsorption↗
PubMed2005

Adsorptive removal of phosphate from aqueous solutions using raw and calcinated dolomite.

This study explored the feasibility of utilizing raw and calcinated dolomite under CO2 atmosphere for phosphate removal in laboratory experiments. The experimental work emphasized the evaluation of phosphate adsorption characteristics of this adsorbent material. Studies were conducted to delineate the effect of contact time, initial phosphate concentration, temperature, pH, stirring speed, adsorbent dose and calcination temperature. Phosphate removal decreased with increasing temperature and slightly increased with increasing of pH. The observed decrease in the adsorption capacity with increase of the temperature from 20 to 40 and to 60 degrees C indicates that the low temperatures favor the phosphate removal by adsorption onto dolomite. Phosphate removal was seen to decrease with increasing calcination temperature due to the structural changes occurring in the structure and pore size distribution of dolomite samples during calcination. The experimental data obtained were applied to the Freundlich, Langmuir, BET, Halsey, Harkins-Jura, Smith and Henderson isotherm equations to test the fit of these equations to raw and calcinated dolomite samples. By considering the experimental results and adsorption models applied in this study, it can be concluded that adsorption of phosphate occurs predominantly through physical interactions, and the dolomite sample has a heteroporous structure. The large values of the constants for Henderson equation and the high value of y(m) obtained from BET equation indicate the microporous structure is more stable in raw and calcinated dolomite samples.

Adsorption↗
PubMed2005

Mucormycosis presenting with painful ophthalmoplegia.

Mucormycosis is a rare fungal infection that can involve the sino-orbito-cerebral region. Sino-orbito-cerebral mucormycosis is most common in patients who are immunocompromised or have diabetes mellitus, severe malnutrition or burns. This condition can be fatal if it is not diagnosed early and treated aggressively. This article presents 4 cases of mucormycosis, including 2 with orbital apex syndrome, 1 with cavernous sinus syndrome, and 1 with multiple cranial nerve involvement. All of the patients were presented with painful ophthalmoplegia. The predisposing factors for mucormycosis included diabetes mellitus (three patients) and chronic leukemia (one patient). In all cases, mucormycosis was diagnosed by examining endoscopic sinus drainage material and was treated with surgical debridement and amphotericin B. Two patients with central nervous system involvement died. The others have survived, but still exhibiting various neurologic abnormalities after aggressive treatment. Patients with mucormycosis rarely present with orbital apex syndrome. The possibility of mucormycosis should be investigated in any patient with painful ophthalmoplegia, and prompt otorhinolaryngologic examination is recommended to ensure rapid diagnosis and treatment.

Aged↗
PubMed2004

Kinetic modeling of liquid-phase adsorption of phosphate on dolomite.

The adsorption of phosphate from aqueous solution on dolomite was investigated at 20 and 40 degrees C in terms of pseudo-second-order mechanism for chemical adsorption as well as an intraparticle diffusion mechanism process. Adsorption was changed with increased contact time, initial phosphate concentration, temperature, solution pH. A pseudo-second-order model and intraparticle diffusion model have been developed to predict the rate constants of adsorption and equilibrium capacities. The activation energy of adsorption can be evaluated using the pseudo-second-order rate constants. The adsorption of phosphate onto dolomite are an exothermically activated process. A relatively low activation energy and a model highly fitting to intraparticle diffusion suggest that the adsorption of phosphate by dolomite may involve not only physical but also chemisorption. This was likely due to its combined control of chemisorption and intraparticle diffusion. However, for phosphate/dolomite system chemical reaction is important and significant in the rate-controlling step, and for the adsorption of phosphate onto dolomite the pseudo-second-order chemical reaction kinetics provides the best correlation of the experimental data.

Adsorption↗
PubMed2004

Determination of adsorptive properties of clay/water system: methylene blue sorption.

In this study, adsorption of methylene blue onto clay was investigated. The effect of adsorption time and temperature on the adsorption process was studied. To reveal the adsorptive characteristics of the clay studied, porosity and BET surface area measurements were made. It was observed that the adsorption capacity decreases with increasing temperature, and adsorption equilibrium was attained within 1 h. It was found that the data fit well to Langmuir, Halsey, Henderson, and Harkins-Jura models but experimental data deviate significantly from BET and Freundlich models at especially high concentrations. Furthermore, isosteric adsorption enthalpy and entropy are calculated as -7.99 kJ mol(-1) and 25.41 JK(-1)mol(-1), respectively.

Journal Article↗
PubMed2002

Voice analysis and videolaryngostroboscopy in patients with Parkinson's disease.

Parkinson's disease (PD) is clinically characterized by a resting tremor, bradykinesia, cogwheel phenomenon, rigidity, disorder of postural reflexes and especially changes in voice and speech. We studied 30 PD patients who were treated with dopamine and 20 normal subjects as the control group. The parameters of vocal fold edges, glottal closure, vertical levels of cords, amplitude of vibration, mucosal wave, vibratory behavior, phase symmetry, ventricular folds and movements, periodicity, arytenoids and thick mucous were evaluated by videolaryngostroboscopy. The Unified Parkinson's Disease Rating Scale was applied to the patient group. The voices of the patients were evaluated by the Dr.Speech-4 and Spectra-PRO computer programs. Maximum phonation time, fundamental frequency, amplitude and the harmonic-to-noise ratio were recorded and compared with those of the control group. The abnormal videolaryngostroboscopic findings were more frequent in the PD group (70% versus 45%; P<0.05). Voice analysis showed significant differences in the parameters such as maximum phonation time, maximum fundamental frequency, the frequency range and the harmonic-to-noise ratio. We thought that these methods and parameters yielded sufficient information for diagnosis and follow-up of vocal function in patients with PD.

Female↗
PubMed2001

Assessment of the effectiveness of postmenopausal tibolone therapy on neural functions by measuring visual evoked potentials: a placebo-controlled study.

OBJECTIVE: To assess the effect of hormone replacement therapy on neural transmission in postmenopausal women using tibolone by a non-invasive, objective way. STUDY DESIGN: In a randomised, 3 cycle, placebo-controlled study, neurovisual transmission in optic pathways were evaluated by measuring visual evoked potentials (VEP). After neuroophtalmologic examination, eligible subjects were randomised into two groups. Treatment group (n=38) were given tibolone 2.5mg daily continuously for 3 months and control group (n=20) were treated with placebo. A baseline VEP measurement before the treatment and then at the end of first, second and third month were obtained by the EMG-evoked system in the Department of Neurology, University of Celal Bayar, Manisa, Turkey. RESULTS: Data from 31 women from treatment group and 16 from control group were available for evaluation. The mean P(100) latency values, which indicate the transition time period between the optic stimuli and electrical change recorded on the occipital area by the skin electrodes, have showed a significant decrease for the study group (from 100.39+/-0.58 to 97.90+/-0.65 ms, P<0.01) at the end of the first month of treatment according to the baseline values. This difference between two groups has remained constant during the study period. CONCLUSION: The change in latency measurements of VEP, reflecting the functional status in optic pathways from retina to occipital cortex were significantly different in the treatment group than in that of control. We concluded that a facilitating effect of tibolone was observed on neurovisual transmission.

Anabolic Agents↗
PubMed2001

Total intravenous anesthesia versus single breath technique and anesthesia maintenance with sevoflurane for bariatric operations.

BACKGROUND: The choice of anesthetic technique for general anesthesia in morbidly obese patients remains controversial. We aimed to compare blood gases, recovery and hemodynamic parameters using TIVA and sevoflurane anesthesia in bariatric surgery. METHODS: The study was performed with permission of the ethics committee. We studied 40 morbidly obese patients allocated to 2 groups. The total i.v. anesthesia (TIVA) group was named Group T, and the sevoflurane group was named Group S. In Group T, anesthesia induction was achieved with propofol. In Group S, anesthesia induction was achieved by sevoflurane with single breath technique, with maintenance provided with 1-2% volume sevoflurane. Student t, Chi square and ANOVA tests were used for data analysis; p-value < 0.05 was considered statistically significant. RESULTS: There was no significant difference between the 2 groups in demographic data, blood gas values and recovery characteristic. Hemodynamic values were significantly lower in Group T than Group S, during and after the operative period. CONCLUSION: While sevoflurane induction and maintenance is a suitable anesthetic modality for obese patients, TIVA can be applied easily in those patients possessing no extra risk factors other than morbid obesity.

Adult↗
PubMed2000

Do we need new indications for ECMO in neonates pretreated with high-frequency ventilation and/or inhaled nitric oxide?

OBJECTIVE: High-frequency ventilation (HFV) and/or inhaled nitric oxide (iNO) has reduced ECMO in neonates. But, frequently, improvement with HFV/iNO is temporary and only prolongs lung injury without preventing ECMO. We tried to identify a threshold oxygenation index (OI) that predicts temporary or persistent improvement with HFV/iNO in neonatal ECMO candidates as early as possible. DESIGN: Cohort study of all neonates with OI > 40 during intermittent positive pressure ventilation between 1992 and 1997. The first treatment was HFV; at an OI > 40 during HFV, iNO was added; at an OI > 40 during HFV+iNO, ECMO was initiated. Temporary improvement was defined as secondary need for ECMO or fatal chronic lung disease without ECMO. SETTING: University hospital level III neonatal intensive care unit. MAIN RESULTS: Ten of the 34 neonates studied rapidly required ECMO despite HFV/iNO. Eleven neonates temporarily improved for 1-10 days before the OI was again > 40. Nine received ECMO, two were denied ECMO after mechanical ventilation > 14 days and died of chronic lung disease. Thirteen neonates persistently improved with HFV/iNO without ECMO. The OI before, at 24 h or 48 h of HFV/iNO did not predict temporary or persistent improvement. However, after 72 h of HFV/iNO, neonates with persistent improvement had lower OIs than those with temporary improvement [median OI 16 (4-24) vs 31 (20-40); P = 0.0004]. In all neonates with an OI > or = 25 after 72 h, HFV/iNO eventually failed (positive predictive value 100%, sensitivity 91 %, specificity 100%, positive likelihood ratio 91). CONCLUSION: For neonates pretreated with HFV/iNO, an OI > 40 is an inadequate ECMO indication. Based on our data we hypothesize that an OI > or = 25 after 72 h of HFV/ iNO is a better ECMO indication that avoids prolonged barotrauma.

Administration, Inhalation↗
PubMed1995

Tracheal rupture during transhiatal esophagectomy and anaesthetic problems. A case report.

Tracheal rupture is a rare but potentially serious complication of transhiatal esophagectomy (THE). In this situation, ventilation of the patient can be extremely difficult, even impossible, due to excessive gas leakage from tracheal tear. In this case report, we present such a patient in whom emergency thoracotomy and patching of the trachea were performed in order to maintain ventilation and oxygenation.

Aged↗