Reward-to-risk ratios in Turkish financial markets

This paper investigates how reward-to-risk ratios compare among various government debt security (GDS) indices and sector indices in the Istanbul Stock Exchange. Risk is measured by either standard deviation or nonparametric and parametric value at risk. We find that the GDS indices have higher reward-to-risk ratios compared to the sector indices. GDS indices with longer maturities have lower reward-to-risk ratios and this reduction is especially pronounced when the ratios take downside risk into account. The reward-to-risk rankings for the sector indices are similar for each measure and the results are robust to currency conversion

Risk-adjusted performances of world equity indices

This paper investigates whether equity indices of 24 emerging and 28 developed markets compensate their investors equally after taking risk into account. We place special emphasis on downside risk by calculating both nonparametric and parametric value at risk. We find that when all 52 markets are ranked based on their alternative reward-to-risk ratios, almost all of the countries in the top quartile are emerging markets whereas almost all of the countries in the bottom quartile are developed markets. These results are supported by the finding that pooled means of the reward-to-risk ratios are significantly higher for emerging markets compared to those of developed markets. Focusing on the period after the initiation of the recent financial crisis reveals that, although both developed and emerging markets suffered in terms of generating higher returns per unit risk, emerging markets continued to outperform developed markets and the outperformance became more pronounced

Reward-to-risk ratios in Turkish financial markets (Türkiye finans piyasalarında getiri-risk rasyoları)

This paper investigates how reward-to-risk ratios compare among various government debt security (GDS) indices and sector indices in the Istanbul Stock Exchange. Risk is measured by either standard deviation or nonparametric and parametric value at risk. We find that the GDS indices have higher reward-to-risk ratios compared to the sector indices. GDS indices with longer maturities have lower reward-to-risk ratios and this reduction is especially pronounced when the ratios take downside risk into account. The reward-to-risk rankings for the sector indices are similar for each measure and the results are robust to currency conversion

Implied volatility spreads and expected market returns

This article investigates the intertemporal relation between volatility spreads and expected returns on the aggregate stock market. We provide evidence for a significantly negative link between volatility spreads and expected returns at the daily and weekly frequencies. We argue that this link is driven by the information flow from option markets to stock markets. The documented relation is significantly stronger for the periods during which (i) S&P 500 constituent firms announce their earnings; (ii) cash flow and discount rate news are large in magnitude; and (iii) consumer sentiment index takes extreme values. The intertemporal relation remains strongly negative after controlling for conditional volatility, variance risk premium, and macroeconomic variables. Moreover, a trading strategy based on the intertemporal relation with volatility spreads has higher portfolio returns compared to a passive strategy of investing in the S&P 500 index, after transaction costs are taken into account

Betahistin dihidroklorür kullanımı pozisyonel nistagmusu etkiler mi?

Aim: In this study, we aimed to investigate the effect of betahistine dihydrochloride (BD) use on positional nystagmus as an objective criterion for the diagnosis of benign paroxysmal positional vertigo (BPPV). Methods: The retrospective study included 59 patients (15 males, 44 females) who were aged between 18 and 80 years and referred with suspected BPPV to the otorhinolaryngology clinic of the Istanbul Training and Research Hospital. Only patients who had no central pathology on oculomotor tests were included. Of the patients included, those not using BD were classified as Group I and those using BD medication (24 mg/day) within the last 48 hours as Group II. The positional nystagmus latency, duration, and slow-phase velocity (SPV) values were compared using videonystagmography. Results: There was no significant difference between the two groups in terms of oculomotor gains (p>0.05). While there was no difference between the two groups in terms of positional nystagmus latency and SPV values, nystagmus duration was found to be significantly longer in Group II. Conclusion: Although the BD use appears to prolong the duration of nystagmus in BPPV, it does not affect the other parameters of nystagmus, including SPV, and the prolonged duration is still within normal limits. Positional nystagmus can be investigated in patients with a history of suspected BPPV and BD prescription.Amaç: Bu çalışmada betahistin dihidroklorür (BD) kullanımının benign paroksismal pozisyonel vertigo (BPPV) tanısında objektif kriter olan pozisyonel nistagmus üzerine etkisini incelemek amaçlanmıştır. Yöntem: Retrospektif çalışmamız yaşları 18–80 yıl aralığında değişen ve BPPV şüphesiyle İstanbul Eğitim ve Araştırma Hastanesi’nin kulak–burun–boğaz polikliniğine yönlendirilen 59 (15 erkek, 44 kadın) hasta içerdi. Çalışmaya yalnızca okülomotor testlerde santral patoloji görülmeyen hastalar dahil edildi. Dahil edilen hastalardan BD kullanmayanlar Grup I, son 48 saat içinde BD grubu ilaç (24 mg/gün) kullananlar ise Grup II olarak tasnif edildi. Pozisyonel nistagmus latans, süre ve yavaş faz hızı (YFH) değerleri videonistagmografi kullanılarak karşılaştırıldı. Bulgular: İki grup arasında okülomotor kazançlar bakımından anlamlı bir fark bulunmadı (p>0,05). Yine iki grup arasında pozisyonel nistagmus latans ve YFH değerleri açısından fark saptanmazken nistagmus süresi Grup II’de anlamlı olarak daha uzun bulundu. Sonuç: BD kullanımı BPPV’de pozisyonel nistagmus süresini uzatıyor gibi görünse de YFH dahil diğer nistagmus parametrelerini etkilememektedir ve süredeki uzama halen normal sınırlar içindedir. BPPV şüphesi ve BD reçeteleme öyküsü olan hastalarda pozisyonel nistagmus araştırılabilir

Do the Age of Implantation, the Widths of Internal Acoustic Canal and Bony Cochlear Nerve Canal Affect the Auditory Performance of Primary School Children with Bilateral Cochlear Implants?

Objective:To reveal the correlation between implantation age, the internal acoustic canal (IAC) width, bony cochlear nerve canal (BCNC) width, and auditory performance in primary school children with bilateral cochlear implantation (CI).Methods:Preoperative IAC and BCNC widths of 57 pre-lingually deaf children aged 7–11 years who had previously undergone bilateral CI in our institution were reviewed and cut-off values were calculated. Twenty-four patients who had additional problems and could not attend school and those who refused to participate in the study were excluded. The remaining 33 were invited to the hospital, and their speech perception tests, and language development scores were analyzed (16 of 33 patients had been operated on before the age of 24 months).Results:The cut-off values calculated from the 114 ears of 57 patients were 3.86 mm for IAC width and 1.56 mm for BCNC width. The auditory performances of the 33 patients after CI were not significantly different in the narrow and normal width groups. However, speech perception test results, and language development scores of patients implanted before the age of 24 months were significantly higher.Conclusion:There are some studies showing that children with bilateral sensorineural hearing loss have narrower IAC and BCNC widths. However, we concluded that the widths of the IAC and the bone cochlear nerve canal did not affect auditory performance. We found that implantation age is the single most important determinant of speech-language development after CI

Giant Ovarian Tumor Presenting as an Incarcerated Umbilical Hernia: A Case Report

We report a rare case of a giant ovarian tumor presenting as an incarcerated umbilical hernia. A 61-yr-old woman was admitted to the hospital with severe abdominal pain, an umbilical mass, nausea and vomiting. On examination, a large, irreducible umbilical hernia was found. The woman underwent an urgent operation for a possible strangulated hernia. A large, multilocular tumor was found. The tumor was excised, and a total abdominal hysterectomy and bilateral salphingo-oophorectomy were performed. The woman was discharged 6 days after her admission. This is the first report of incarcerated umbilical hernia containing a giant ovarian tumor within the sac

Role of Fine-Needle Aspiration Biopsy in the Management of Salivary Gland Masses

Objective:Fine-needle aspiration biopsy (FNAB) is widely used in the management of salivary gland masses. Its main advantage is its ability to differentiate benign from malignant disease. In this study, we aimed to evaluate the diagnostic ability of FNAB in salivary gland masses.Methods:The records of patients who had undergone FNAB before parotidectomy or submandibular gland excision between 2005 and 2013 were retrospectively analyzed. FNAB results were classified as negative, positive, suspicious for malignancy, and non-diagnostic. Preoperative FNAB results were compared with definitive histopathological results. The sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and accuracy of FNAB results were calculated.Results:A total of 285 patients were enrolled. Among them, 230 (80.7%) had parotid gland and 55 (19.3%) had submandibular gland masses. Following a definitive histopathological examination, the most common benign tumor was pleomorphic adenoma (52.6%), whereas malignant tumors were mucoepidermoid carcinoma (2%) and squamous cell carcinoma (2%). The sensitivity, specificity, PPV, NPV and accuracy of FNAB results were 76.9%, 95.4%, 75%, 95.9%, and 92.6%, respectively. The rate of a suspicious cytology was 5.2% (15 patients) and that of a non-diagnostic cytology was 8.8% (25 patients).Conclusion:FNAB is a safe and simple diagnostic tool for the diagnosis of salivary gland masses and has a relatively high sensitivity and specificity. It may provide valuable information for patient counselling and surgical planning. The major drawbacks include a lower sensitivity than specificity and a relatively high rate of non-diagnostic results

An Angiomatous Antrochoanal Polyp with Epistaxis and Bony Destruction

Angiomatous polyps are rare sinonasal masses and may present with intense epistaxis. Angiomatous antrochoanal polyps are rare variants of antrochoanal polyps, and their diagnosis and management requires more detailed evaluation in respect to classical antrochoanal polyps. In both antrochoanal polyps and angiomatous polyps, bone destruction is an exceptional finding. The signs of bone destruction and epistaxis suggest additional pathologies including inverted papilloma, lobular capillary haemangioma and carcinoma as differential diagnoses. In this case, total excision of a left-sided angiomatous antrochoanal polyp with bone destruction was managed with nasal endoscopic approach. Troublesome intraoperative bleeding was avoided with effective additional measures