Ge quantum dot arrays grown by ultrahigh vacuum molecular beam epitaxy on the Si(001) surface: nucleation, morphology and CMOS compatibility

Issues of morphology, nucleation and growth of Ge cluster arrays deposited by ultrahigh vacuum molecular beam epitaxy on the Si(001) surface are considered. Difference in nucleation of quantum dots during Ge deposition at low (<600 deg C) and high (>600 deg. C) temperatures is studied by high resolution scanning tunneling microscopy. The atomic models of growth of both species of Ge huts---pyramids and wedges---are proposed. The growth cycle of Ge QD arrays at low temperatures is explored. A problem of lowering of the array formation temperature is discussed with the focus on CMOS compatibility of the entire process; a special attention is paid upon approaches to reduction of treatment temperature during the Si(001) surface pre-growth cleaning, which is at once a key and the highest-temperature phase of the Ge/Si(001) quantum dot dense array formation process. The temperature of the Si clean surface preparation, the final high-temperature step of which is, as a rule, carried out directly in the MBE chamber just before the structure deposition, determines the compatibility of formation process of Ge-QD-array based devices with the CMOS manufacturing cycle. Silicon surface hydrogenation at the final stage of its wet chemical etching during the preliminary cleaning is proposed as a possible way of efficient reduction of the Si wafer pre-growth annealing temperature.Comment: 30 pages, 11 figure

Laser-induced nonsequential double ionization: kinematic constraints for the recollision-excitation-tunneling mechanism

We investigate the physical processes in which an electron, upon return to its parent ion, promotes a second electron to an excited state, from which it subsequently tunnels. Employing the strong-field approximation and saddle-point methods, we perform a detailed analysis of the dynamics of the two electrons, in terms of quantum orbits, and delimit constraints for their momentum components parallel to the laser-field polarization. The kinetic energy of the first electron, upon return, exhibits a cutoff slightly lower than $10U_p$, where $U_p$ is the ponderomotive energy, as in rescattered above-threshold ionization (ATI). The second electron leaves the excited state in a direct ATI-like process, with the maximal energy of $2U_p$. We also compute electron-momentum distributions, whose maxima agree with our estimates and with other methods.Comment: 13 pages, 4 figure

Adenovirus-mediated siRNA targeting Bcl-xL inhibits proliferation, reduces invasion and enhances radiosensitivity of human colorectal cancer cells

<p>Abstract</p> <p>Introduction</p> <p>Bcl-xL, an important member of anti-apoptotic Bcl-2 family, plays critical roles in tumor progression and development. Previously, we have reported that overexpression of Bcl-xL was correlated with prognosis of colorectal cancer (CRC) patients. The aim of this study was to investigate the association of Bcl-xL expression with invasion and radiosensitivity of human CRC cells.</p> <p>Methods</p> <p>RT-PCR and Western blot assays were performed to determine the expression of Bcl-xL mRNA and protein in CRC cells and normal human intestinal epithelial cell line. Then, adenovirus-mediated RNA interference technique was employed to inhibit the expression of Bcl-xL gene in CRC cells. The proliferation of CRC cells was analyzed by MTT and colony formation assay. The migration and invasion of CRC cells was determined by wound-healing and tranwell invasion assays. Additionally, the in vitro and in vivo radiosensitivity of CRC cells was determined by clonogenic cell survival assay and murine xnograft model, respectively.</p> <p>Results</p> <p>The levels of Bcl-xL mRNA and protein expression were significantly higher in human CRC cells than in normal human intestinal epithelial cell line. Ad/shBcl-xL could significantly reduce the expression of Bcl-xL protein in CRC cells. Also, we showed that adenovirus-mediated siRNA targeting Bcl-xL could significantly inhibit proliferation and colony formation of CRC cells. Ad/shBcl-xL could significantly suppress migration and invasion of CRC cells. Moreover, Ad/shBcl-xL could enhance in vitro and in vivo radiosensitivity of CRC cells by increasing caspase-dependent apoptosis.</p> <p>Conclusions</p> <p>Targeting Bcl-xL will be a promising strategy to inhibit the metastatic potential and reverse the radioresistance of human CRC.</p

Big Data Analytics in the Internet-Of-Things And Cyber-Physical Systems

Lv, Z.; Song, H.; Lloret, J.; Kim, D.; De Souza, J. (2019). Big Data Analytics in the Internet-Of-Things And Cyber-Physical Systems. IEEE Access. 7:18070-18075. https://doi.org/10.1109/ACCESS.2019.2895441S1807018075

Some Field Theoretic Issues Regarding the Chiral Magnetic Effect

In this paper, we shall address some field theoretic issues regarding the chiral magnetic effect. The general structure of the magnetic current consistent with the electromagnetic gauge invariance is obtained and the impact of the infrared divergence is examined. Some subtleties on the relation between the chiral magnetic effect and the axial anomaly are clarified through a careful examination of the infrared limit of the relevant thermal diagrams.Comment: 19 pages, 4 figures in Latex. Typos fixed, version accepted to be published in JHE

Risk prediction of major haemorrhage with surgical treatment of live cesarean scar pregnancies

Objective: To evaluate the association between demographic and ultrasound variables and major intra-operative blood loss during surgical transcervical evacuation of live caesarean scar pregnancies. Study Design: This was a retrospective cohort study conducted in a tertiary referral center between 2008 and 2019. We included all women diagnosed with a live caesarean scar ectopic pregnancy who chose to have surgical management in the study center. A preoperative ultrasound was performed in each patient. All women underwent transcervical suction curettage under ultrasound guidance. Our primary outcome was the rate of postoperative blood transfusion. The secondary outcomes were estimated intra-operative blood loss (ml), rate of retained products of conception, need for repeat surgery, need for uterine artery embolization and hysterectomy rate. Descriptive statistics were used to describe the variables. Univariate and multivariable logistic regression models were constructed using the relevant covariates to identify the significant predictors for severe blood loss. Results: During the study period, 80 women were diagnosed with a live caesarean scar pregnancy, of whom 62 (78%) opted for surgical management at our center. The median crown-rump length was 9.3 mm (range 1.4–85.7). Median blood loss at the time of surgery was 100 ml (range, 10–2300), and six women (10%; 95%CI 3.6–20) required blood transfusion. Crown-rump length and presence of placental lacunae were significant predictive factors for the need for blood transfusion and blood loss > 500 ml at univariate analysis (p < .01); on multivariate analysis, only crown-rump length was a significant predictor for need for blood transfusion (OR = 1.072; 95% CI 1.02–1.11). Blood transfusion was required in 6/18 (33%) cases with the crown-rump length ≥ 23 mm (≥9+0 weeks of gestation), but in none of 44 women presenting with a crown-rump length < 23 mm (p < .01). Conclusion: The risk of severe intraoperative bleeding and need for blood transfusion during or after surgical evacuation of live caesarean scar pregnancies increases with gestational age and is higher in the presence of placental lacunae. One third of women presenting at ≥ 9 weeks of gestation required blood transfusion and their treatment should be ideally arranged in specialized tertiary centers

Development of the utero-placental circulation in cesarean scar pregnancies: A case-control study

BACKGROUND: Cesarean scar pregnancies (CSP) are at high risk of pregnancy complications including placenta previa with antepartum hemorrhage, placenta accreta spectrum (PAS) and uterine rupture. OBJECTIVE: To evaluate the development of the utero-placental circulation in the first half of pregnancy in ongoing CSP and compare it to pregnancies implanted in the lower uterine segment above a prior cesarean section scar with no evidence of PAS at delivery. MATERIAL AND METHODS: This was a retrospective case-control study conducted in two tertiary referral centers. The study group included 27 women diagnosed with a live caesarean scar pregnancy in the first trimester of pregnancy who elected to conservative management. The control group included 27 women diagnosed with a low-lying/placenta previa at 19-22 weeks of gestation who had a first and an early second trimester ultrasound examinations. In both groups, the first ultrasound examination was carried out at 6-10 weeks to establish pregnancy location, viability and to confirm the gestational age. The utero-placental and intra-placental vasculatures were examined using color Doppler imaging (CDI) and described semi quantitatively using CDI score 1-4. The remaining myometrial thickness (RMT) was recorded in the study group whereas in the controls the ultrasound features of prior cesarean scar were noted including the presence of a niche. Both CSP and controls had also ultrasound examinations at 11-14 and 19-22 weeks of gestation. RESULTS: The mean CDI vascularity score at the 6-10 weeks ultrasound examination was significantly (P <.001) higher in the CSP group than in the controls. The high vascularity scores 3 and 4 were recorded in 20/27 (74%) cases of the CSP group. There was no vascularity score of 4 and only 3/27 (11%) controls had vascularity score of 3. In 15/27 (55.6%) CSPs the RMT was < 2 mm. At the 11-14 weeks ultrasound examination, there was no significant difference between the groups for the number of cases with increased subplacental vascularity but 12 CSPs (44%) presented with one or more placental lacunae whereas there was no case with lacunae in the controls. In the 18 CSP that progressed into the third trimester, ten were diagnosed with placenta previa creta at birth, including 4 creta and 6 increta. At the 19-22 weeks ultrasound examination, eight of the ten PAS presented with subplacental hypervascularity out of which, six showed also placental lacunae. CONCLUSION: The vascular changes in the utero-placental and intervillous circulations in CSPs are due to the loss of the normal uterine structure in the scar area and the development of placental tissue in proximity of large diameter arteries of the outer uterine wall. The intensity of these vascular changes, development of PAS and risk of uterine rupture depend on the RMT of the cesarean scar defect at the start of pregnancy. A better understanding of the pathophysiology of the utero-placental vascular changes associated with CSP should help in identifying those cases that may develop major complications and thus contribute to counselling women about the risks associated with different management strategies