Mitigating Off-Policy Bias in Actor-Critic Methods with One-Step Q-learning: A Novel Correction Approach

Compared to on-policy counterparts, off-policy model-free deep reinforcement learning can improve data efficiency by repeatedly using the previously gathered data. However, off-policy learning becomes challenging when the discrepancy between the underlying distributions of the agent's policy and collected data increases. Although the well-studied importance sampling and off-policy policy gradient techniques were proposed to compensate for this discrepancy, they usually require a collection of long trajectories and induce additional problems such as vanishing/exploding gradients or discarding many useful experiences, which eventually increases the computational complexity. Moreover, their generalization to either continuous action domains or policies approximated by deterministic deep neural networks is strictly limited. To overcome these limitations, we introduce a novel policy similarity measure to mitigate the effects of such discrepancy in continuous control. Our method offers an adequate single-step off-policy correction that is applicable to deterministic policy networks. Theoretical and empirical studies demonstrate that it can achieve a "safe" off-policy learning and substantially improve the state-of-the-art by attaining higher returns in fewer steps than the competing methods through an effective schedule of the learning rate in Q-learning and policy optimization

Age structure of a population ofChalcides ocellatus(Forskal, 1775) (Sauria: Scincidae) in Mediterranean Anatolia

Cicek, Kerim/0000-0002-6753-0757WOS: 000544572500001We studied the age structure of a population of the Ocellated Skink,Chalcides ocellatusin Mediterranean Turkey using the skeletochronological method. We examined the cross sections of femoral diaphyseal of a total of 106 museum specimens including 53 adult females and 42 adult males. the snout-vent length was significantly correlated with age. the mean age was 6.0 years (3-10 year) for males and 5.8 years for females, but the difference was statistically not significant. Sexual maturity is reached after their third hibernation period. the lifespan was significantly shorter in southwestern Anatolia than in southern Anatolia (mean age 5.43 years vs. 6.50 years for both sexes combined; P<0.004). According to von Bertalanffy growth curves, the growth rates were lower in southwestern Anatolia than in southern Anatolia than

Serum cystatin C and neutrophil gelatinase-associated lipocalin in predicting the severity of coronary artery disease in diabetic patients

Objective: Cystatin C and neutrophil gelatinase-associated lipocalin (NGAL) are biomarkers of renal functions. We evaluated their roles in predicting the severity of coronary artery disease (CAD). Methods: Fifty-two consecutive type 2 diabetic patients (32 males, 65.7 +/- 8.6 years) who underwent coronary angiography (CAG) for stable CAD were included in this single-center, prospective, cross-sectional study. Patients with an estimated glomerular filtration rate <60mL/min/1.73m(2) and with a history of by-pass surgery and/or coronary stent implantation were excluded. The vessel score and Gensini score were calculated to assess the presence and severity of CAD. Mann-Whitney U test, Spearman test, and multiple linear regression analysis were used for the main statistical analyses. Results: Serum cystatin C levels were higher in patients with multivessel disease than in those with single vessel disease [1260 ng/mL (953-1640) vs. 977 ng/mL (599-1114), p=0.017]. According to the median Gensini score, the higher score group also had higher cystatin C levels than the lower score group [1114 ng/mL (948-1567) vs. 929 ng/mL (569-1156), p=0.009]. However, serum NGAL levels were similar between these subgroups. There was a positive correlation between cystatin C and Gensini score (r=0.334, p=0.016). Multiple linear regression analysis revealed serum cystatin C as an independent predictor of the Gensini score (beta=0.360, t=2.311, p=0.026). These results may aid in defining cystatin C as a surrogate marker of the extent of CAD in further clinical trials. Conclusion: Serum Cystatin C, but not NGAL levels, could predict the severity of CAD in diabetic patients

New records of the Anatolian Worm Lizard, Blanus strauchi (BEDRIAGA, 1884), from Turkey (Squamata: Amphisbaenia: Blanidae)

WOS: 000299766500001In this study, eight specimens of Blanus strauchi (BEDRIAGA, 1884) from two new localities in Turkey (Dutluca Village, Kemaliye, Erzincan and Burdur) were examined in terms of morphological characters and included in the subspecies B. s. aporus (WERNER, 1898). With the record of Dutluca Village, the distribution of the species was extended about 120 km northwards, whereas the record of Burdur is a new locality within its distributional range. An updated distribution map of B. strauchi in Turkey was provided.TUBITAKTurkiye Bilimsel ve Teknolojik Arastirma Kurumu (TUBITAK) [CAYDAK-105Y016]This study was partly financially supported by TUBITAK [CAYDAK-105Y016]. The authors are indebted to these institutions for granting financial support

Single Mutation in Shine-Dalgarno-Like Sequence Present in the Amino Terminal of Lactate Dehydrogenase of Plasmodium Effects the Production of an Eukaryotic Protein Expressed in a Prokaryotic System

One of the most important step in structure-based drug design studies is obtaining the protein in active form after cloning the target gene. In one of our previous study, it was determined that an internal Shine-Dalgarno-like sequence present just before the third methionine at N-terminus of wild type lactate dehydrogenase enzyme of Plasmodium falciparum prevent the translation of full length protein. Inspection of the same region in P. vivax LDH, which was overproduced as an active enzyme, indicated that the codon preference in the same region was slightly different than the codon preference of wild type PfLDH. In this study, 5'-GGAGGC-3' sequence of P. vivax that codes for two glycine residues just before the third methionine was exchanged to 5'-GGAGGA-3', by mimicking P. falciparum LDH, to prove the possible effects of having an internal SD-like sequence when expressing an eukaryotic protein in a prokaryotic system. Exchange was made by site-directed mutagenesis. Results indicated that having two glycine residues with an internal SD-like sequence (GGAGGA) just before the third methionine abolishes the enzyme activity due to the preference of the prokaryotic system used for the expression. This study emphasizes the awareness of use of a prokaryotic system to overproduce an eukaryotic protein

OSTEOPROTEGERIN PLASMA CONCENTRATIONS ARE CORRELATED WITH FORCED EXPIRATORY VOLUME AT 1 SECOND (FEV1) IN PATIENTS WITH CHRONIC OBSTRUCTIVE PULMONARY DISEASE

[No Abstract Available

Comparison of a novel antigen detection test with reverse transcription polymerase chain reaction assay for laboratory diagnosis of SARS-CoV-2 infection

Molecular diagnosis of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) by real-time reverse transcription polymerase chain reaction (RT-PCR) in respiratory specimens is considered the gold standard method. This method is highly sensitive and specific but it has some limitations such as being expensive and requiring special laboratory equipment and skilled personnel. RapidFor (TM) Antigen Rapid Test Kit is a commercially available Ag-RDT which is produced in Turkey and designed to detect the nucleocapsid antigen of SARS-CoV-2 in nasopharyngeal swab samples. The aim of this study was to evaluate the performance of this novel SARS-CoV-2 antigen detection considering the RT-PCR method as the gold standard. Four hundred forty-four nasopharyngeal swab samples which were collected from the patients who met clinical criteria of COVID-19 from ten centers in Turkey between September 2020 and February 2021 were included in the study. All the nasopharyngeal swab samples were tested for SARS-CoV-2 RNA using commercial RT-PCR kits (Bioeksen and A1 Lifesciences, Istanbul, Turkey) according to the manufacturer's instructions. Viral loads were assessed according to the cycle threshold (Ct) values. RapidFor (TM) SARS-CoV-2 antigen test (Vitrosens Biotechnology, Istanbul, Turkey) was used to investigate the presence of SARS-CoV-2 antigen in all samples following the manufacturer's instructions. Out of 444 nasopharyngeal swab samples tested, 346 (77.9%) were positive and 98 (22.1%) were negative for SARS-CoV-2 RNA by RTPCR. Overall sensitivity of the RapidFor (TM). Antigen Rapid Test Kit was 80.3% whereas specificity was found to be 87.8%. Positivity rate of rapid antigen test in samples with Ct values over 25 and below 30 was 82.7%, while it increased to 95.7% in samples 20 <= Ct < 25 and reached 100% in samples with Ct values below 20. RapidFor (TM) SARS-CoV-2 Ag test might be a good choice in the screening of symptomatic and asymptomatic patients and their contacts for taking isolation measures early, with advantages over RT-PCR as being rapid, easy and being applicable in every laboratory and even at point of care.Sevket Onur Taflan and Kagan Etka YorukSevket Onur Taflan and Kagan Etka Yoruk are co-founders of Vitrosens which provided RapidForT Ag tests for the study. No other financial support was provided by this company