Characteristics, outcome, duration of hospitalization, and cycle threshold of patients with COVID-19 referred to four hospitals in Babol City: a multicenter retrospective observational study on the fourth, fifth, and sixth waves.

BACKGROUND: The aim of the present study was to compare the epidemiological patterns of severe acute respiratory syndrome coronavirus 2 (SARS-CoV2) infections, hospitalizations, deaths, and duration of hospitalization during the fourth, fifth and sixth epidemic waves of coronavirus disease 2019 (COVID-19) in Iran. METHODS: A multicenter retrospective observational study was conducted on hospitalized patients in four hospitals in the Babol district of northern Iran. The study periods were during the fourth, fifth, and sixth waves of the epidemic in Iran, (March 2021 to March 2022). A total of 13,312 patients with suspected COVID-19 were included. Patient demographics, medical history, length of hospital stay, and clinical outcomes were obtained from the hospital information system. Data on the cycle threshold (Ct) and SARS-CoV2 variant were collected for SARS-CoV2-positive cases. RESULTS: The highest number of hospitalized patients was reported during the fifth (Delta) wave (5231; 39.3%), while the lowest number of hospitalized patients was reported during the sixth (Omicron) wave (2143; 16.1%). In total, 6459 (48.5%) out of 13,312 hospitalized patients with suspected COVID-19 had a positive rRT-PCR result. The fifth (Delta) wave had the highest number of SARS-CoV2 rRT-PCR-positive hospitalized patients (3573, 55.3%), while the sixth (Omicron) wave had the lowest number (835, 12.9%). Moreover, 238 (3.7%) patients with laboratory-confirmed COVID-19 died. The hospital mortality rate was 6.8% in the fourth (Alpha) wave, which reduced to 2.7 and 3.5% in the fifth (Delta) and sixth (Omicron) waves, respectively (p < 0.001). CONCLUSIONS: This is the most comprehensive study evaluating the epidemiologic characteristics of laboratory-confirmed SARS-CoV2 cases in Iran during the Alpha, Delta, and Omicron waves. The highest number of SARS-CoV2-positive hospitalized patients was in the fifth wave of COVID-19 (dominance of the Delta variant), while the sixth wave (dominance of the Omicron variant) had the lowest number. Comorbidities were similar, and cardiovascular disease, diabetes, kidney disease, and hypertension were the main risk factors in all waves.

Cumulative Effects of Paraoxon and Leptin on Oxidative Damages in Rat Tissues: Prophylactic and Therapeutic Roles of N-Acetylcysteine.

Exposure to paraoxon (POX) and leptin (LP) could cause an imbalance between oxidants and antioxidants in an organism, which can be prevented by introduction of exogenous antioxidants such as N-acetylcysteine (NAC). The aim of this study was to evaluate synergic or additive effects of administration of exogenous LP plus POX on the antioxidant status, as well as the prophylactic and therapeutic roles of NAC in various rat tissues. Fifty-four male Wistar rats were divided into nine groups treated with different compounds: Control (no treatment), POX (0.7 mg/kg), NAC (160 mg/kg), LP (1 mg/kg), POX+LP, NAC-POX, POX-NAC, NAC-POX+LP, and POX+LP-NAC. In the last five groups, only the order of administered compounds differed. After 24 h, plasma and tissues were sampled and examined. The results showed that administration of POX plus LP significantly increased biochemical indices in plasma and antioxidant enzymes activities and decreased glutathione content in the liver, erythrocytes, brain, kidney, and heart. In addition, cholinesterase and paraoxonase 1 activities in the POX+LP-treated group were decreased and malondialdehyde level was increased in the liver, erythrocytes, and brain. However, administration of NAC rectified induced changes although not to the same extent. Our study suggests that POX or LP administration engage the oxidative stress system per se; however, their combination did not produce significantly greater effects. Moreover, both prophylactic and therapeutic treatments of rats with NAC supported the antioxidant defense against oxidative damage in tissues, most probably through both its free radical scavenging ability and maintaining intracellular GSH levels. It can therefore be suggested that NAC has particularly protective effects against POX or/and LP toxicity.

Plastic litter fate and contaminant transport within the urban environment, photodegradation, fragmentation, and heavy metal uptake from storm runoff.

A significant portion of urban litter is plastic which contaminates the environment and threatens ecological safety. The conversion of plastic litter into small fragments called microplastics (MPs) intensifies their critical risks by facilitating their transport and altering their physicochemical features. This study focuses on low density polyethylene (LDPE) and polyethylene terephthalate (PET) as the main components of urban litter. The photodegradation of LDPE and PET MPs due to the accelerated weathering experiments is investigated through surface chemistry and morphology analysis. The influence of MPs' photodegradation on their fragmentation behavior is evaluated through the innovative accelerated mechanical weathering experiments that simulated the abrasion of MPs with the road deposits. Furthermore, the role of MPs as the vehicles to transport the heavy metals from the urban environment to the water resources is evaluated by studying the kinetics of lead (Pb) uptake by new and weathered MPs in synthetic stormwater. The surface morphology investigation revealed the formation of crazes and the crack networks onto the MPs due to the weathering experiments. The surface chemistry analysis revealed the generation of several oxidized carbon surface functional groups onto the photodegraded MPs and their increased susceptibility to fragmentation due to the abrasion with the road deposits. The photodegradation increased the Pb accumulation onto the LDPE and PET MPs from 467 µg/m2 and 21 µg/m2 to 2290 µg/m2 and 725 µg/m2, after five days of metal exposure. The fundamental knowledge developed in this research provides a better conceptual understanding of the mechanisms controlling MPs persistence and contaminant transport within the urban environment, which is crucial to estimate their negative impacts on the ecosystem.

A Large Retrospective Study of Epidemiological Characteristics of COVID-19 Patients in the North of Iran: Association between SARS-CoV-2 RT-PCR Ct Values with Demographic Data.

Objectives: To avoid worsening from mild, moderate, and severe diseases and to reduce mortality, it is necessary to identify the subpopulation that is more vulnerable to the development of COVID-19 unfavorable consequences. This study aims to investigate the demographic information, prevalence rates of common comorbidities among negative and positive real-time reverse-transcriptase polymerase chain reaction (rRT-PCR) patients, and the association between SARS-CoV-2 cycle threshold (Ct) at hospital admission, demographic data, and outcomes of the patients in a large population in Northern Iran. Methods: This large retrospective cross-sectional study was performed from 7 March to 20 December 2020. Demographic data, including gender, age, underlying diseases, clinical outcomes, and Ct values, were obtained from 8,318 cases suspected of COVID-19, who were admitted to four teaching hospitals affiliated to Babol University of Medical Sciences (MUBABOL), in the north of Iran. Results: Since 7 March 2020, the data were collected from 8,318 cases suspected of COVID-19 (48.5% female and 51.5% male) with a mean age of 53 ± 25.3 years. Among 8,318 suspected COVID-19 patients, 3,250 (39.1%) had a positive rRT-PCR result; 1,632 (50.2%) patients were male and 335 (10.3%) patients died during their hospital stay. The distribution of positive rRT-PCR revealed that most patients (464 (75.7%)) had a Ct between 21 and 30 (Group B). Conclusion: Elderly patients, lower Ct, patients having at least one comorbidity, and male cases were significantly associated with increased risk for COVID-19-related mortality. Moreover, mortality was significantly higher in patients with diabetes, kidney disease, and respiratory disease.

The association between patellofemoral alignment and osteoarthritis in magnetic resonance imaging.

Objectives: Osteoarthritis (OA) is the most common joint disease in the world, becoming more prevalent with increasing age, and causes a significant burden on individuals and society. So far, several factors have been identified in association with OA of the knee joint. Age is the most crucial uncontrollable risk factor for OA. There are conflicting results regarding the relationship between patellofemoral joint orientation and OA. This study aims to elucidate the relationship between patellofemoral joint alignment and OA evidence. Material and methods: A total of 277 MRIs performed at Imam Reza Hospital during the first half of 2017 were included. Patients were divided into two groups, under 50 years old and over 50 years old. Femoral sulcus angle (SA) and depth (SD), lateral patellar displacement (LPD), tibial tubercle-trochlear groove (TTTG), lateral patellofemoral angle (LPFA), and Insall-Salvati index were measured in axial and sagittal images. The morphology of the patellofemoral articular cartilage was evaluated and the grade of joint damage was determined. P-value < 0.05 was considered as significant. Results: Significant correlations between SA (p-value = 0.01), SD (p-value < 0.001), Insall-Salvati index (p-value < 0.001), LPD (p-value = 0.02) values and OA in patients less than 50 years old were observed. A weak correlation was observed between SD and Insall-Salvati index values with increasing grade of articular cartilage damage (r = 0.21 and r = 0.21, respectively). Conclusions: Patellofemoral joint asymmetry in the younger people was significantly associated with joint cartilage damage and premature patellofemoral joint OA. Joint misalignment by stressing the articular cartilage causes joint cartilage changes that may be congenital or due to bone injuries such as trauma and surgery.

Combination of pioglitazone and clomiphene citrate versus clomiphene citrate alone for infertile women with the polycystic ovarian syndrome.

BACKGROUND: Anovulation is one of the common causes of infertility. Polycystic ovary syndrome (PCOS) is the most common disorder with chronic Anovulation. To the best of our knowledge, insulin resistance relates significantly to PCOS. Therefore administration of insulin-sensitizing drugs such as pioglitazone can be used for ovulation stimulation in PCO patients. METHODS: After obtaining approval from the Ethics Committee of Mashhad University of Medical Sciences, 61 patients with PCOS were enrolled in the study based on inclusion/ exclusion criteria. Patients were divided into two groups. The first group received 30 mg (mg) of pioglitazone daily from the second day of the menstrual period. The second one received a placebo. 150 mg clomiphene citrate was administered from the third to the seventh day of the menstrual cycle. Vaginal sonography was performed in all women, and in cases with the mature follicle, intrauterine insemination was conducted after human chorionic gonadotropin injection. Ovary stimulation and pregnancy rate were compared between groups. RESULTS: There were no differences between groups regard to demographic characteristics and infertility type. Body mass index was higher in the pioglitazone group (28.3 ± 3.8 versus 26.2 ± 3.5, P value = 0.047). The size of the follicle was not significantly different between groups (2.2 ± 1.4 versus 1.3 ± 1.1, P value = 0.742). pregnancy rate [4 (12.9%) versus 4 (13.3%), P value = 1] had no differences between groups. CONCLUSION: Although the number of follicles was higher in the pioglitazone group, our study showed no differences in ovary stimulation and pregnancy rate.

Electron-Hole Asymmetry of Surface States in Topological Insulator Sb2Te3 Thin Films Revealed by Magneto-Infrared Spectroscopy.

When surface states (SSs) form in topological insulators (TIs), they inherit the properties of bulk bands, including the electron-hole (e-h) asymmetry but with much more profound impacts. Here via combining magneto-infrared spectroscopy with theoretical analysis, we show that e-h asymmetry significantly modifies the SS electronic structures when interplaying with the quantum confinement effect. Compared with the case without e-h asymmetry, the SSs now bear not only a band asymmetry, such as that in the bulk, but also a shift of the Dirac point relative to the bulk bands and a reduction of the hybridization gap of up to 70%. Our results signify the importance of e-h asymmetry in the band engineering of TIs in the thin-film limit.

Clinical Trial Assessment of Intermittent and Continuous Infusion Dose of N-Acetylcysteine on Redox Status of the Body in Patients with Sepsis Admitted to the ICU.

PURPOSE: Conflicting results exist regarding the efficacy of N-acetyl cysteine (NAC) in sepsis treatment. A pivotal factor affecting the therapeutic potency of NAC in sepsis is timing and dosing of its infusion. We aimed to assess the effect of NAC on redox status of patients with sepsis and to compare its efficacy in intermittent and continuous infusion with the objective of developing the infusion regimen and optimizing the timing. MATERIALS AND METHODS: A prospective, randomized clinical trial was designed to compare the antioxidative effect of NAC in intermittent infusion group (IV: 25 mg/kg bolus and then 25 mg/kg/8 hours 3 times) and continuous infusion group (IV: 25 mg/kg bolus and then 75 mg/kg over 24 hours) in 60 critically ill patients with sepsis (20 patients in each group). Blood samples were collected immediately before and after intervention for total antioxidant capacity (TAC) and malondialdehyde (MDA) assessment. RESULTS: N-acetyl cysteine considerably increased TAC levels in both intermittent (0.68 ± 0.60; P value = .036) and continuous (0.69 ± 0.64; P value = .015) infusion groups when compared to placebo (0.61 ± 0.10); however, the difference in TAC levels between the intermittent and the continuous infusion did not reach statistical significance (P value = .942). Likewise, NAC treatment decreased MDA levels in both intermittent (19.45 ± 4.18; P value = 0.001) and continuous (22.47 ± 6.68; P value = .002) infusion groups when compared to placebo (31.76 ± 11.06), while the difference in MDA levels between the intermittent and the continuous infusion did not reach statistical significance (P value = .481). CONCLUSION: Our data confirmed the antioxidative effect of NAC treatment in patients with sepsis, with no significant difference in intermittent and continuous infusion.

Non-Ablative Fractional 1,540-nm Er:Glass Laser in the Treatment of Atrophic Cutaneous Leishmaniasis Scars.

OBJECTIVES: To evaluate the efficacy of nonablative fractional 1,540 nm laser to treat the atrophic scars caused by the cutaneous leishmaniasis (CL). METHODS: This clinical trial with a pre- and a posttreatment measurement was conducted on patients with atrophic CL scars. The lesions were treated with nonablative fractional 1,540 nm laser. We evaluated the patients initially and then monthly, before each treatment session. The final follow-up was done 6 months after the end of study for all patients. Patient assessment was performed by two physicians using the modified Manchester Scar Scale (MSS) as well as the interpretation of captured digital photographs. Moreover, the patients performed a self-assessment by filling in a researcher-made questionnaire. The data were statistically analyzed by SPSS software. P < 0.05 was considered statistically significant. RESULTS: Thirty patients with 37 skin lesions participated in the study. The pairwise comparison demonstrated a statistically significant difference between the modified MSS parameters (P < 0.05); however, no significant difference was observed between the modified MSS of the third and fourth (P = 0.82) as well as fourth and fifth (P = 0.636) sessions. The lesions improvement was significant based on the physician's evaluation (P < 0.001). Furthermore, patients' level of satisfaction was significantly increased in all six follow-ups (P < 0.001). No persistent complication was found. CONCLUSIONS: Nonablative fractional 1,540 nm laser is an effective and safe therapeutic choice for atrophic CL, even in darker skins. Lasers Surg. Med. © 2019 Wiley Periodicals, Inc.

Psoralen and narrowband UVB combination provides higher efficacy in treating vitiligo compared with narrowband UVB alone: A randomised clinical trial.

BACKGROUND/OBJECTIVES: Side effects of current treatments and the need for a safe treatment with higher efficiency necessitate seeking new treatment options for vitiligo. Few studies have investigated the combination of psoralen with narrowband ultraviolet B (NBUVB). In this study, we compared the efficacy and safety of psoralen and NBUVB combination (P-NBUVB) with NBUVB alone in treatment of vitiligo. METHODS: This randomised clinical trial was carried out during 2015-2017 in dermatology clinics of Ghaem and Imam Reza hospitals, Mashhad, Iran on 40 vitiligo patients with 5-60% body involvement. The patients were randomly divided into two groups of NBUVB alone and P-NBUVB. Both groups underwent 60 phototherapy sessions (three sessions per week), and the repigmentation rate was measured using vitiligo area severity index (VASI) score. SPSS v. 16 software and appropriate statistical tests were used to analyse the data. P < 0.05 was considered statistically significant. RESULTS: The mean age of patients was 33.9 ± 11.3 years. Twenty patients (50%) were females. The P-NBUVB group showed greater VASI improvement in lower extremities (P = 0.003) and overall (P = 0.026) compared with NBUVB group. Moreover, the treatment response appeared sooner in P-NUVB group. CONCLUSION: Based on our results, we can conclude that adding psoralen to NBUVB phototherapy can result in increased efficacy. However, more studies are needed to evaluate the long-term effects and side effects of this treatment.

Ferromagnetic Anomalous Hall Effect in Cr-Doped Bi2Se3 Thin Films via Surface-State Engineering.

The anomalous Hall effect (AHE) is a nonlinear Hall effect appearing in magnetic conductors, boosted by internal magnetism beyond what is expected from the ordinary Hall effect. With the recent discovery of the quantized version of the AHE, the quantum anomalous Hall effect (QAHE), in Cr- or V-doped topological insulator (TI) (Sb,Bi)2Te3 thin films, the AHE in magnetic TIs has been attracting significant interest. However, one of the puzzles in this system has been that while Cr- or V-doped (Sb,Bi)2Te3 and V-doped Bi2Se3 exhibit AHE, Cr-doped Bi2Se3 has failed to exhibit even ferromagnetic AHE, the expected predecessor to the QAHE, though it is the first material predicted to exhibit the QAHE. Here, we have successfully implemented ferromagnetic AHE in Cr-doped Bi2Se3 thin films by utilizing a surface state engineering scheme. Surprisingly, the observed ferromagnetic AHE in the Cr-doped Bi2Se3 thin films exhibited only a positive slope regardless of the carrier type. We show that this sign problem can be explained by the intrinsic Berry curvature of the system as calculated from a tight-binding model combined with a first-principles method.

Engineering Topological Superlattices and Phase Diagrams.

The search for new topological materials and states of matter is presently at the forefront of quantum materials research. One powerful approach to novel topological phases beyond the thermodynamic space is to combine different topological/functional materials into a single materials platform in the form of superlattices. However, despite some previous efforts there has been a significant gap between theories and experiments in this direction. Here, we provide the first detailed set of experimentally verifiable phase diagrams of topological superlattices composed of archetypal topological insulator, Bi2Se3, and normal insulator, In2Se3, by combining molecular-level materials control, low-temperature magnetotransport measurements, and field theoretical calculations. We show how the electronic properties of topological superlattices evolve with unit-layer thicknesses and utilize the weak antilocalization effect as a tool to gain quantitative insights into the evolution of conducting channels within each set of heterostructures. This orchestrated study opens the door to the possibility of creating a variety of artificial-topological-phases by combining topological materials with various other functional building blocks such as superconductors and magnetic materials.

Risk factors of the efficacy of hepatitis B vaccine in health-care workers.

BACKGROUND: Conventional hepatitis B virus vaccination fails to achieve efficient protection in about 5%-10% of the world population. Different factors influence the immunogenicity of hepatitis B vaccine. This study aimed to evaluate these factors in health-care workers. MATERIALS AND METHODS: This was a descriptive study which was implemented among 140 of medical and dental staff working as health-care workers who were low responder after vaccination entered the study. RESULTS: Age (>40 years), weight (body mass index >25), immunodeficiency diseases, (primary immune deficiency and immunosuppressant drugs), diabetes mellitus, and smoking were the important factors. CONCLUSION: In the high-risk group of hepatitis B disease, the risk factors of immunogenicity must be evaluated at vaccination and check titers of antibody after vaccination.

Epidemiology of lung cancer in northeast of Iran: A 25-year study of 939 patients.

Background: Lung cancer (LC) is a global public health priority. In this study, the epidemiology and current trends of primary LCs were investigated in northeast of Iran. Methods: Demographic and pathologic records of primary LCs during 1985-2012 in Mashhad (capital of northeast of Iran) were reviewed. Data were obtained from archives of the largest referral oncologic hospital and the only private outpatient radiation-oncologic clinic in the region. To investigate trends, study duration was classified into 3 periods: 1985-1995, 1995-2005, and 2005-2012. Patients were placed in one of these 3 groups, based on the date of their pathologic diagnosis. Data were analyzed by SPSS 16 software. T test, chi-squared, and ANOVA tests were used for data analysis, and statistical significant level was set at < 0.05. Results: Among 939 cases with pathologic diagnosis of primary LC, male-to-female ratio was 2.36. Mean±SD age at diagnosis was 61.47±12.01 years in males and 58.45±12.75 in females (p=0.001). Squamous cell carcinoma (SCC) was the most frequent pathologic subtype. Mean age at diagnosis and rate of smokers were unchanged during the study (p= 0.978 and 0.153, respectively). Relative frequency of leading pathologic subtypes changed in 3 intervals (p<0.001): it was increasing in adenocarcinoma and large cell carcinoma and decreasing in SCC and small cell lung cancer (SCLC). There were statistically significant differences in the mean age at diagnosis (p<0.001), rate of smokers (p<0.001), and male-to-female ratio (p=0.011) between leading pathologic subtypes. Conclusion: Similar to universal picture, rate of adenocarcinoma in northeast of Iran was rising during recent decades, especially among younger patients, women, and nonsmokers. These trends are indicative of changes in exposures and smoking habits and reveal the need for regional studies in these contexts.

Salvage therapy with Sodium chlorosum (formerly DAC N-055) for cases of refractory lupoid cutaneous leishmaniasis: results from a compassionate use study with 0.09% Sodium chlorosum in amphiphilic basic cream.

BACKGROUND: Lupoid cutaneous leishmaniasis (LCL) is known as a rare but serious complication of anthroponotic cutaneous leishmaniasis (ACL) resistant to conventional treatments. Sodium chlorosum, a pro-oxidative preparation of pharmaceutical sodium chlorite (NaClO2), has been successfully used for the treatment of Old World cutaneous leishmaniasis lesions (OWCL) and of some LCL cases in Afghanistan. This clinical trial study aimed to evaluate the effect of a last resort therapy with topical 0.09% sodium chlorosum on LCL in Iran. METHODS: Twenty Iranian patients (12 women and 8 men) with LCL refractory to treatment were included in this salvage study. A magistral preparation of sodium chlorosum (10 mM NaClO2 in amphiphilic basic cream) was applied twice daily to the lesions for 6 weeks and continued up to 12 weeks in patients who showed a clinical response within the first 6 weeks. Responders were followed up for a maximum of 1 year. Lesions were photographed during weekly visits. Disappearance of erythema and indurated lesions were rated as complete clinical response. RESULTS: Patients with a mean age of 28.6 (±24.3) and with an ACL proven lesion history of 3.8 (±1.4) years were treated for an average of 7.9 (±1.8) weeks. At the end of the treatment period (12th week), a complete response was observed in 9 of 20 patients (45%). During the one-year follow-up period, LCL lesions recurred in 4 of these 9 patients (with one patient showing only a tiny lesion) and one case lost to follow up whereas the other four remained completely lesion-free. Mild temporary side-effects such as erythema and itching were seen in 4 of 20 patients (20%). CONCLUSIONS: Topical sodium chlorosum showed promising therapeutic results and can be considered as safe, painless, and relatively effective treatment for LCL, an ethical prerequisite for a two-armed controlled trial. TRIAL REGISTRATION: This study was registered in Iranian registry of clinical trials on 2019-02-02 with registration number IRCT20190114042356N1.

Sentinel Node Biopsy in Urothelial Carcinoma of the Bladder: Systematic Review and Meta-Analysis.

OBJECTIVES: To determine the application of sentinel node biopsy in urothelial carcinoma of the bladder, we performed a systematic review and meta-analysis. METHODS: Pooled false negative rate and detection rate were presented using Meta-Disc (version 1.4), and comprehensive meta-analysis (version 2). Publication bias and heterogeneity were assessed using funnel plot, Cochrane Q test, and I2 index. RESULTS: The pooled detection rate was 91% (95% CI 87-93%) and pooled sensitivity was 79% (95% CI 0.69-0.86%). When the neoadjuvant chemotherapy group of patients was omitted, the pooled sensitivity changed to 82% (95% CI 74-88%), and the Cochrane Q and I2 statistics were 15.44 and 48.2%, respectively. The pooled sensitivity of studies that included > 50% of pT 3 or 4 patients was 70% (59-80), by omitting studies that enrolled > 50% of patients at pT stage of 3 or 4, the pooled sensitivity increased to 93% (81-98). CONCLUSIONS: Although the studies on SN biopsy of muscle invasive bladder cancer patients resulted in a high detection rate and sensitivity, further validated multicenter trials with larger sample size are essential to confirm the reliability and accuracy of this approach and obtain a standardized method. We showed that pT1 or pT2 bladder cancer patients with clinically negative lymph nodes are the most appropriated group for sentinel lymph node mapping.

Solution to the Hole-Doping Problem and Tunable Quantum Hall Effect in Bi2Se3 Thin Films.

Bi2Se3, one of the most widely studied topological insulators (TIs), is naturally electron-doped due to n-type native defects. However, many years of efforts to achieve p-type Bi2Se3 thin films have failed so far. Here, we provide a solution to this long-standing problem, showing that the main culprit has been the high density of interfacial defects. By suppressing these defects through an interfacial engineering scheme, we have successfully implemented p-type Bi2Se3 thin films down to the thinnest topological regime. On this platform, we present the first tunable quantum Hall effect (QHE) study in Bi2Se3 thin films and reveal not only significantly asymmetric QHE signatures across the Dirac point but also the presence of competing anomalous states near the zeroth Landau level. The availability of doping tunable Bi2Se3 thin films will now make it possible to implement various topological quantum devices, previously inaccessible.

Control over Electron-Phonon Interaction by Dirac Plasmon Engineering in the Bi2Se3 Topological Insulator.

Understanding the mutual interaction between electronic excitations and lattice vibrations is key for understanding electronic transport and optoelectronic phenomena. Dynamic manipulation of such interaction is elusive because it requires varying the material composition on the atomic level. In turn, recent studies on topological insulators (TIs) have revealed the coexistence of a strong phonon resonance and topologically protected Dirac plasmon, both in the terahertz (THz) frequency range. Here, using these intrinsic characteristics of TIs, we demonstrate a new methodology for controlling electron-phonon interaction by lithographically engineered Dirac surface plasmons in the Bi2Se3 TI. Through a series of time-domain and time-resolved ultrafast THz measurements, we show that, when the Dirac plasmon energy is less than the TI phonon energy, the electron-phonon coupling is trivial, exhibiting phonon broadening associated with Landau damping. In contrast, when the Dirac plasmon energy exceeds that of the phonon resonance, we observe suppressed electron-phonon interaction leading to unexpected phonon stiffening. Time-dependent analysis of the Dirac plasmon behavior, phonon broadening, and phonon stiffening reveals a transition between the distinct dynamics corresponding to the two regimes as the Dirac plasmon resonance moves across the TI phonon resonance, which demonstrates the capability of Dirac plasmon control. Our results suggest that the engineering of Dirac plasmons provides a new alternative for controlling the dynamic interaction between Dirac carriers and phonons.

Modulatory effects of vitamin C on biochemical and oxidative changes induced by acute exposure to diazinon in rat various tissues: Prophylactic and therapeutic roles.

Diazinon (DZN) as an organophosphate pesticide may cause oxidative stress in different tissues. Antioxidants increase tissue protection from oxidative stress. The aim of the present study was to investigate prophylactic and therapeutic effects of vitamin C against oxidative stress caused by DZN in various tissues of male Wistar rats. Thirty rats were divided into five groups: control group received corn oil as DZN solvent, DZN group received 100 mg/kg of DZN, C group received 200 mg/kg of vitamin C, C-DZN and DZN-C groups received vitamin C before and after DZN injection. Plasma and various tissues were prepared and evaluated for measurement of the biochemical parameters and oxidative stress biomarkers. Results showed that acute administration of DZN significantly increased superoxide dismutase and glutathione-S-transferase activities and malondialdehyde level in all tissues, catalase (CAT) activity in liver, kidney and heart and some plasma biochemical indices, while it decreased cholinesterase and lactate dehydrogenase activities and glutathione content in all tissues. CAT activity in erythrocytes, brain and spleen was decreased in DZN-exposed rats compared with the control group. Administration of vitamins C in both prophylactic and therapeutic groups ameliorated in these parameters, although all these tests in tissues did not return to the normal level. These data suggest that oxidative stress is an essential mechanism involved in DZN-induced adversity effect, as evidenced by the altered activity of antioxidant enzymes, depleted GSH content and the enhanced membrane lipid peroxidation. Both the prophylactic and therapeutic treatments of rats to vitamin C have beneficial effects against oxidative stress and cholinergic hyperactivity induced by DZN in tissues especially in the brain tissue through free radical scavenging.

Infrared Spectroscopy of the Topological Surface States of Bi_{2}Se_{3} by Use of the Berreman Effect.

The Berreman effect (BE) allows one to study the electrodynamics of ultrathin conducting films at the surface of dielectrics by use of grazing-angle infrared spectroscopy and polarized radiation. Here, we first apply the BE to the two-dimensional electron system (2DES) at the interface between a high-purity film of the topological insulator Bi_{2}Se_{3} and its sapphire substrate. We determine for the 2DES a charge density n_{s}=(8±1)×10^{12} cm^{-2}, a thickness d=0.6±0.2 nm, and a mobility µ^{IR}=290±30 cm^{2}/V s. Within errors, all of these parameters result in being independent of temperature between 300 and 10 K. These findings consistently indicate that the 2DES is formed by topological surface states, whose infrared response is then directly observed here.