Direct Observation of Landau Level Resonance and Mass Generation in Dirac Semimetal Cd3As2 Thin Films

Three-dimensional topological Dirac semimetals have hitherto stimulated unprecedented research interests as a new class of quantum materials. Breaking certain types of symmetries has been proposed to enable the manipulation of Dirac fermions, and that was soon realized by external modulations such as magnetic fields. However, an intrinsic manipulation of Dirac states, which is more efficient and desirable, remains a significant challenge. Here, we report a systematic study of quasi-particle dynamics and band evolution in Cd₃As₂ thin films with controlled chromium (Cr) doping by both magneto-infrared spectroscopy and electrical transport. We observe the √B relation of inter-Landau-level resonance in Cd₃As₂, an important signature of ultrarelativistic massless state inaccessible in previous optical experiments. A crossover from quantum to quasi-classical behavior makes it possible to directly probe the mass of Dirac fermions. Importantly, Cr doping allows for a Dirac mass acquisition and topological phase transition enabling a desired dynamic control of Dirac fermions. Corroborating with the density-functional theory calculations, we show that the mass generation can be explained by the explicit C₄ rotation symmetry breaking and the resultant Dirac gap engineering through Cr substitution for Cd atoms. The manipulation of the system symmetry and Dirac mass in Cd₃As₂ thin films provides a tuning knob to explore the exotic states stemming from the parent phase of Dirac semimetals.

Distinguishing thermal lens effect from electronic third-order nonlinear self-phase modulation in liquid suspensions of 2D nanomaterials

The interaction of light with atomically thin nanomaterials has attracted enormous research interest in order to understand two-dimensional (2D) electron systems and develop novel opto-electronic devices. The observations of spatial self-phase modulation and the associated multiple diffraction ring patterns in liquid suspensions of 2D nanomaterials are believed to be excellent examples of strong laser interaction with 2D nanomaterials and this phenomenon has been attributed to their large electronic third-order susceptibilities. By performing a series of control experiments with liquid suspensions of graphene and graphene oxide flakes in different solvents at various temperatures under an increasing modulation frequency of laser illumination, we first show that the diffraction ring pattern has little dependence on the type of nanomaterial but strongly depends on the duration of laser illumination. A laser induced local refractive index change is then monitored by a weaker probe beam, resulting in the divergent diffraction of the probe beam that indicates a lower self-induced refractive index in the center of the pump laser beam than at its periphery: a clear signature of the thermal lens effect. Finally, we use computational fluid dynamics to simulate laser induced temperature and index changes of the suspensions. The evolution of diffraction rings is well correlated to the transient temperature distribution. Our understanding of complex laser interactions with nanomaterial suspensions and the associated thermal lens effect paves the way for further basic studies and fluid opto-electronic applications of 2D nanomaterials.

MiR-155 regulates oral squamous cell carcinoma Tca8113 cell proliferation, cycle, and apoptosis via regulating p27Kip1

OBJECTIVE

P27Kip1 is the one of the negative regulators of the cell cycle that plays an important role in regulating cell cycle and inhibiting cell proliferation by restraining cell in G1 phase. P27Kip1 downregulation maybe related to the occurrence of oral squamous cell carcinoma (OSCC). It was found that miR-155 significantly upregulated in OSCC tissue. Bioinformatics analysis revealed that miR-155 may bind with the 3'-UTR of p27Kip1. This study investigated the role of miR-155 in regulating p27Kip1 and affecting Tca8113 cell proliferation, cycle, and apoptosis.

PATIENTS AND METHODS

A total of 46 cases of OSCC patients received treatment in our hospital were enrolled to obtain tumor tissue. Another 25 normal oral mucosa samples were selected as control to detect the relationship between miR-155 and p27Kip1 expressions. Dual luciferase assay was adopted to confirm the targeted relationship between miR-155 and p27Kip1. Flow cytometry was applied to test cell apoptosis and cell cycle. CCK-8 assay was used to evaluate cell proliferation. Caspase-3 activity was detected by spectrophotometry.

RESULTS

MiR-155 upregulated, while p27Kip1 declined in OSCC tissue compared with normal oral mucosa. Their expressions were related to TNM stage. MiR-155 targeted suppressed p27Kip1 expression. MiR-155 mimic and/or pEGFP-p27Kip1 transfection obviously declined p27Kip1 expression, blocked cell cycle in G1 phase, reduced cell proliferation, enhanced Caspase-3 activity, and increased cell apoptosis in Tca8113 cells.

CONCLUSIONS

MiR-155 increased, while p27Kip1 reduced in OSCC tissue. Inhibition of miR-155 upregulated p27Kip1 expression, blocked cell cycle in G1 phase, weakened cell proliferation, and induced cell apoptosis.

[Direct anterior approach versus posterolateral approach for total hip arthroplasty in the lateral decubitus position]

Objective: To compare the clinical efficacy of the direct anterior approach (DAA) and the posterolateral approach (PLA) for total hip arthroplasty (THA) in the lateral decubitus position. Methods: From July to December, 2014, 104 patients randomly divided into two equal groups of the DAA group and the PLA group underwent unilateral primary THA procedures.All procedures were performed by the same surgeon in the Department of Orthopaedics, the Affiliated Anhui Provincial Hospital of Anhui Medical University.General data, perioperative index, postoperative function and radiological evaluation were recorded and statistically analyzed. Results: The patients had an average follow-up of 14 (range, 10-16) months.No significant differences were detected with respect to the operation time, incision length, preoperative Hb concentration and transfusion rate between two groups (P> 0.05 for all comparisons). However, there were significant differences associated with the intraoperative bleeding, postoperative drainage and postoperative Hb concentration in the two groups(P<0.05 for all comparisons). The DAA group showed significant superior outcomes compared with the PLA group in the Harris hip scores [(83.6±7.1) vs (79.8±6.6), P<0.05], WOMAC[ (28.9±6.1) vs (36.1±6.9), P<0.001], and VAS pain scores[ (2.2±0.9) vs (2.9±1.1), P<0.05]at 1 month after surgery. No differences were seen between the study groups in the evaluation of radiography and the incidence of adverse event (P> 0.05 for all comparisons). Conclusions: Compared with the posterolateral approach, the present study shows the exciting results in patients underwent the DAA THA in the lateral decubitus position at early follow-up.The advantages of THA using the DAA include less operative trauma, alleviation of postoperative pain, and faster postoperative rehabilitation. It is a safe, reliable and effective surgery approach.

Grass Hosts Harbor More Diverse Isolates of Puccinia striiformis Than Cereal Crops

Puccinia striiformis causes stripe rust on cereal crops and many grass species. However, it is not clear whether the stripe rust populations on grasses are able to infect cereal crops and how closely they are related to each other. In this study, 103 isolates collected from wheat, barley, triticale, rye, and grasses in the United States were characterized by virulence tests and simple sequence repeat (SSR) markers. Of 69 pathotypes identified, 41 were virulent on some differentials of wheat only, 10 were virulent on some differentials of barley only, and 18 were virulent on some differentials of both wheat and barley. These pathotypes were clustered into three groups: group one containing isolates from wheat, triticale, rye, and grasses; group two isolates were from barley and grasses; and group three isolates were from grasses and wheat. SSR markers identified 44 multilocus genotypes (MLGs) and clustered them into three major molecular groups (MG) with MLGs in MG3 further classified into three subgroups. Isolates from cereal crops were present in one or more of the major or subgroups, but not all, whereas grass isolates were present in all of the major and subgroups. The results indicate that grasses harbor more diverse isolates of P. striiformis than the cereals.

Weak antilocalization in Cd3As2 thin films

Recently, it has been theoretically predicted that Cd3As2 is a three dimensional Dirac material, a new topological phase discovered after topological insulators, which exhibits a linear energy dispersion in the bulk with massless Dirac fermions. Here, we report on the low-temperature magnetoresistance measurements on a ~50 nm-thick Cd3As2 film. The weak antilocalization under perpendicular magnetic field is discussed based on the two-dimensional Hikami-Larkin-Nagaoka (HLN) theory. The electron-electron interaction is addressed as the source of the dephasing based on the temperature-dependent scaling behavior. The weak antilocalization can be also observed while the magnetic field is parallel to the electric field due to the strong interaction between the different conductance channels in this quasi-two-dimensional film.

Persistently high glucose levels in young children with type 1 diabetes

OBJECTIVES

The aim of the study was to characterize glucose levels and variability in young children with type 1 diabetes (T1D).

METHODS

A total of 144 children of 4-10 yr old diagnosed with T1D prior to age 8 were recruited at five DirecNet centers. Participants used a continuous glucose monitor (CGM) every 3 months during an 18-month study. Among the 144 participants, 135 (mean age 7.0 yr, 47% female) had a minimum of 48 h of CGM data at more than five of seven visits and were included in analyses. CGM metrics for different times of day were analyzed.

RESULTS

Mean hemoglobin A1c (HbA1c) at the beginning and end of the study was 7.9% (63 mmol/mol). Fifty percent of participants had glucose levels >180 mg/dL (10.0 mmol/L) for >12 h/d and >250 mg/dL (13.9 mmol/L) for >6 h/d. Median time <70 mg/dL (3.9 mmol/L) was 66 min/d and <60 mg/dL (3.3 mmol/L) was 39 min/d. Mean amplitude of glycemic excursions (MAGE) was lowest overnight (00:00-06:00 hours). The percent of CGM values 71-180 mg/dL (3.9-10.0 mmol/L) and the overall mean glucose correlated with HbA1c at all visits. There were no differences in CGM mean glucose or coefficient of variation between the age groups of 4 and <6, 6 and <8, and 8 and <10.

CONCLUSIONS

Suboptimal glycemic control is common in young children with T1D as reflected by glucose levels in the hyperglycemic range for much of the day. New approaches to reduce postprandial glycemic excursions and increase time in the normal range for glucose in young children with T1D are critically needed. Glycemic targets in this age range should be revisited.

Home Use of an Artificial Beta Cell in Type 1 Diabetes

BACKGROUND

The feasibility, safety, and efficacy of prolonged use of an artificial beta cell (closed-loop insulin-delivery system) in the home setting have not been established.

METHODS

In two multicenter, crossover, randomized, controlled studies conducted under free-living home conditions, we compared closed-loop insulin delivery with sensor-augmented pump therapy in 58 patients with type 1 diabetes. The closed-loop system was used day and night by 33 adults and overnight by 25 children and adolescents. Participants used the closed-loop system for a 12-week period and sensor-augmented pump therapy (control) for a similar period. The primary end point was the proportion of time that the glucose level was between 70 mg and 180 mg per deciliter for adults and between 70 mg and 145 mg per deciliter for children and adolescents.

RESULTS

Among adults, the proportion of time that the glucose level was in the target range was 11.0 percentage points (95% confidence interval [CI], 8.1 to 13.8) greater with the use of the closed-loop system day and night than with control therapy (P<0.001). The mean glucose level was lower during the closed-loop phase than during the control phase (difference, -11 mg per deciliter; 95% CI, -17 to -6; P<0.001), as were the area under the curve for the period when the glucose level was less than 63 mg per deciliter (39% lower; 95% CI, 24 to 51; P<0.001) and the mean glycated hemoglobin level (difference, -0.3%; 95% CI, -0.5 to -0.1; P=0.002). Among children and adolescents, the proportion of time with the nighttime glucose level in the target range was higher during the closed-loop phase than during the control phase (by 24.7 percentage points; 95% CI, 20.6 to 28.7; P<0.001), and the mean nighttime glucose level was lower (difference, -29 mg per deciliter; 95% CI, -39 to -20; P<0.001). The area under the curve for the period in which the day-and-night glucose levels were less than 63 mg per deciliter was lower by 42% (95% CI, 4 to 65; P=0.03). Three severe hypoglycemic episodes occurred during the closed-loop phase when the closed-loop system was not in use.

CONCLUSIONS

Among patients with type 1 diabetes, 12-week use of a closed-loop system, as compared with sensor-augmented pump therapy, improved glucose control, reduced hypoglycemia, and, in adults, resulted in a lower glycated hemoglobin level. (Funded by the JDRF and others; AP@home04 and APCam08 ClinicalTrials.gov numbers, NCT01961622 and NCT01778348.).