bluuebunny/crossref_metadata_2025 huggingface dataset:
Audit on the role and efficacy of PET/CT in recurrent ovarian cancer settings in a tertiary care centre in India
Authors: Suhas K. R.
Published: February 2021

Ovarian cancers tend to recur in 15-70% cases. CA-125 - is a tumor marker used for monitoring therapeutic response, and in surveillance, for recurrent disease. However, it has a limited role as a persistent high level can signify either recurrence or persistence of residual tumor. Metastases from ovarian cancer primarily involve the peritoneum rather than parenchymal sites; thus, the presence of small-volume recurrence or metastatic deposits on the visceral surfaces poses a challenge for interpretation of CT and MR images. PET/CT utilizes its property of higher accumulation in malignant cells to provide both anatomic and functional information for diagnosing malignant tumors.

Objectives: The objectives of the study were to find the correlation between PET/CT findings and final histopathological diagnosis after a secondary cytoreductive surgery in suspected ovarian cancer recurrences.

Materials and Methods: PET/CT was done in cases with rising or above normal CA-125 and no radiological findings. These patients with abnormal PET/CT findings were taken up for a secondary cytoreductive surgery and histopathological proven were taken as the standard against which PET/CT positive findings was compared.

Results: The mean age in our group of patients with suspected recurrence was 53 years (Range 39-74 years). Of the 52 patients with suspected recurrence, 40 patietnts with a PET-CT scan with findings suggestive of an avid uptake underwent surgery. 22 patients had serous histology, 12 mucinous and 8 had clear cell carcinoma. Stage-wise distribution at the time of primary surgery is as follows stage I-3, stage II-7, stage III-26, stage IV-4. Of the 40 patients who underwent a second look surgery 32 had histopathologically confirmed recurrence. PET-CT detected a total of 86 lesions in the 40 patients who underwent surgery. Of these, 38 were in the lymph nodes 28 in para-aortic and 10 in pelvic, 32 were peritoneal lesions and 14 were pelvic, 2 were metastatic in the parenchyma of liver. Detection of the lesion on PET-CT was size dependant, of the 9 lesions were missed on PET-CT, 7 were less than 0.5 cm. The mean diameter of the lesions detected was 2.2 cm (range 0.3-6.2 cm). PET-CT accurately identified 62 of 70 histopathologically proven lesions. The overall lesion-based sensitivity of PET-CT is 88.6%, specificity 56.2%, Positive predictive value being 72.1%, negative predictive value of 69.2%. Accuracy of detecting lesions greater than 1 cm is 78.6% (44 of 56 lesions).

Conclusions: Corelation between PET/CT and histopathologicaldisease: k (cohen value) = 0.81 which suggests excellent correlation. For selected patients with ovarian cancer recurrence may benefit from a comprehensive radiographic imaging survey (PET-CT) at the time of even no or minimal CA-125 elevation in early detection and successful cytoreductive surgical resection and an increase in overall survival.
Role of human epididymis protein 4 for detection of ovarian carcinoma in adnexal masses: A pilot study
Authors: Bansal Nidhi , Suneja A. , Guleria K. , Vaid N. B. , Mishra K. , Bhatt S. , Mehndiratta M.
Published: February 2021

Introduction: HE4 is a novel tumour biomarker used for early diagnosis of ovarian cancer. This study evaluated the diagnostic accuracy of HE4 alone and in combination with CA125, risk of malignancy index (RMI), risk of malignancy algorithm (ROMA).

Methods: It was a cross sectional study conducted recruiting 88 women with adnexal masses who were planned for surgery. After baseline work up and ultrasound examination, serum samples were collected for estimation of CA 125 and HE4 levels. Serum HE4 levels were estimated using ELISA kit. RMI and ROMA score were calculated and diagnostic accuracy of HE4, CA 125, RMI, ROMA and their combination were compared. Cut off for HE4 and ROMA score were calculated using ROC curve.

Results: Of 88 subjects, 66 were analyzed with 19 malignant (including 5 LMP) and 47 benign cases. The median value of HE4 among malignant cases was found to be significantly higher than among the benign cases. PPV and NPV of HE4 at a cut off 130.8 pMol/ml was 85.7% and 77.9% respectively. Highest PPV (88.9%) with acceptable NPV (80.7%) was found with ROMA followed by HE4 (PPV 85.7%; NPV 77.97%), RMI (PPV 76.92%; NPV 83%) and CA125 (PPV 52%; NPV 80.85%).

Conclusion: HE4 levels were lower in Indian population both in malignant and benign tumours as compared to other studies. HE4 is a good discriminator and gives best accuracy when it is combined with CA125 in a logistic algorithm, ROMA.
Successful pregnancy outcome in recurrent ovarian cancer
Authors: Chaudhary Sushila
Published: February 2021

Incidences of ovarian cancer in pregnancy are increasing nowadays due to routine use of ultrasonography in first trimester and postponement of childbirth to an older age. Reported incidence of ovarian tumor in pregnancy is 1:1000 among them3.6% are malignant. We report a case of recurrent ovarian tumor with successful pregnancy outcome. She was a 26 yr old primi had ovarian cancer recurrence 2 year after primary surgery. In present pregnancy she was given chemotherapy with two doses of carboplatin, and had viable baby at 34 weeks of pregnancy. At present mother and baby are doing well and on regular follow-up at radiotherapy departments.
Preoperative and intraoperative assesment of myometrial invasion and histological grade in endometrial cancer: Role of MRI and frozen section
Authors: Ranade Rohit Raghunath
Published: February 2021

Introduction: The role of systematic lymphadenectomy in clinically early stage endometrial cancer is controversial. A number of factors can predict lymph node metastasis including myometrial invasion, tumor grade in endometrial cancers. The purpose of the present study is to evaluate the accuracy of preoperative MRI and intraoperative frozen section in determining the depth of myometrial invasion, cervical involvement, tumor size and lymph nodal status. We also studied the accuracy of preoperative endometrial biopsy and intraoperative frozen section in determining the grade of the tumor.

Materials and Methods: Medical records of 235 consecutive cases of clinically early stage endometrial cancer were reviewed retrospectively. A record of depth of myometrial invasion, tumor size, cervical involvement and presence of enlarged lymph nodes was made on a preoperative MRI. Similarly depth of myometrial invasion, tumor size, cervical involvement and grade of the tumor were recorded on an intraoperative frozen section. The grade of the tumor was also recorded on a preoperative endometrial biopsy. Standard statistical calculations were used.

Results: The sensitivity and specificity of MRI for myometrial invasion for the first 160 cases were 81.3 and 75%, respectively while that for frozen section were 80 and 96.2%, respectively. For tumor grade the sensitivity and specificity of preoperative endometrial biopsy were 60 and 95.6%, respectively while that of frozen section were 53.8 and 97.6%, respectively. For cervical involvement the sensitivity of MRI and frozen section was 62.5 and 98.4%, respectively. Updated results of the entire cohort of 235 cases will be presented at the conference if selected.

Conclusion: Although the sensitivity of both frozen section and MRI for predicting deep myometrial invasion was similar (80 vs 81.3%) but the specificity (96.2 vs 75%) and negative predictive value (92.7 vs 88.2%) of frozen section were superior to MRI. Both preoperative biopsy and intraoperative frozen section had low sensitivity (60 vs 53.8%) for detecting a high grade lesion.
To find the prevalence of female genital tract malignancies in a tertiary care hospital
Authors: Pandher Dilpreet K.
Published: February 2021

Genital tract and breast are two most common sites of malignancy in females. Out of the genital tract malignancies, carcinoma cervix is so far found to be the commonest followed by ovary and endometrium. In developed countries, carcinoma cervix incidence is comparatively quite low due to good regular screening of females. One year review of patients was done, who underwent definitive/debulking surgery for a diagnosed malignant pathology of the genital tract, in obstetrics and gynaecology department of Govt. medical College and Hospital, Chandigarh. Total 62 patients were operated, most common indication was carcinoma ovary, followed by endometrial cancer, cancer cervix and gestational trophoblastic neoplasia. 166 patients underwent biopsies for suspicious symptoms or the abnormal findings on examination and the patients with final malignancy report were either operated as described above and the inoperable cases were referred to oncotherapy department for further management.
A rare case of ovarian and endometrial adenocarcinoma metastasized from carcinoma of jejunum
Authors: Agrawal Sonam , Dahiya Pushpa
Published: February 2021

Introduction: Krukenberg tumor of ovary is a rare clinical entity and accounts for 1-2% of all ovarian tumor. Stomach is most common primary site but other organs can also serve as a primary site. Accurate diagnosis of krukenberg tumor requires thorough endoscopic and histopathological examination to exclude primary tumor.

Case Report: 32 years old female presented with AUB for 2 months and history of jejunum carcinoma which was an incidental finding on biopsy after a surgery for intestinal obstruction. Endometrial biopsy showed endometrial carcinoma of mucin secreting signet ring type. CECT showed bilateral adnexal masses. Staging laparotomy was planned but due to dense adhesion and bladder and bowel infiltration optimal debulking could not be done and tumor was removed as much as possible. Patient was reffered for chemotherapy.

Conclusion: Krukenberg tumor is uncommon metastatic signet ring cell adenocarcinoma of ovary with transcoelomic spread. It is essential to rule out other ovarian malignancy to avoid the misdiagnosis and management of krukenberg tumor.
To find the prevalence of female genital tract malignancies in a tertiary care hospital
Authors: Pandher Dilpreet K.
Published: February 2021

Genital tract and breast are two most common sites of malignancy in females. Out of the genital tract malignancies, carcinoma cervix is so far found to be the commonest followed by ovary and endometrium. In developed countries, carcinoma cervix incidence is comparatively quite low due to good regular screening of females. One year review of patients was done, who underwent definitive/debulking surgery for a diagnosed malignant pathology of the genital tract, in obstetrics and gynaecology department of Govt medical College and Hospital, Chandigarh. Total 62 patients were operated, most common indication was carcinoma ovary, followed by endometrial cancer, cancer cervix and gestational trophoblastic neoplasia. 166 patients underwent biopsies for suspicious symptoms or the abnormal findings on examination and the patients with final malignancy report were either operated as described above and the inoperable cases were referred to oncotherapy department for further management.
Changing trends in coagulation profile of 30 patients undergoing CRS with HIPEC in the peri-operative period
Authors: Pathak Soumi
Published: February 2021

Background: With advent of surgical advancements like HIPEC several unstudied pathophysiological aspects need to be evaluated. We studied the trends in coagulation profile in patients undergoing CRS with HIPEC in the peri-operative period, utilizing Thromboelastography (TEG) in comparison with standard coagulation tests. The utility of TEG as a guide for transfusion of blood products was also evaluated.

Materials and Methods: It was a Prospective observational Cohort study which included 30 consecutive patients undergoing CRS with HIPEC at RGCI in 2015.

Methodology: Preoperatively standard coagulation tests were done as a baseline. Intra-operative arterial blood samples were collected for ABG, PT, APTT, and TEG at following time points: before starting of HIPEC, after completion of HIPEC and on 1 and 2 postoperative days. Statistical analysis was done using Chi-square test and unpaired t-test for categorical and continuous variables. Pearson’s correlation coefficient was calculated for analysing the correlation between the variables. P < 0.05 was considered statistically significant.

Results: A strong correlation was observed between PT & R values of TEG. Similar correlation was also observed between the α angle, MA of TEG and platelet count throughout the peri-operative period. Immediately post HIPEC, we observe value of APPT decreases while the other parameters of coagulation profile showed a rising trend. R value showed rising trend after CRS, a dip after HIPEC followed by a rising trend on first post operative day which normalizes only after second post operative day. It gives a mixed picture of both hypo and hyper coagulable state. α angle, MA rise immediately after HIPEC and continue to rise till the second postoperative day. There was no requirement of transfusion of blood and blood products as guided by the TEG findings and no clinical evidence of any bleeding or thromboembolic episode occurred.

Conclusion: To conclude, our study demonstrated TEG to be a useful and comprehensive tool to assess coagulopathy and accordingly guide blood product transfusion in patients undergoing CRS with HIPEC.
Unusual clinical presentation of chriocarcinoma in young patients – Neulological meatastasis
Authors: Yadav Sushma
Published: February 2021

Introduction: Choriocarcinoma is a malignant trophoblastic tumor, usually of placenta and characterized by ‘early hematogenous spread’ to lungs. Choriocarcinoma of placenta is preceded by – H. Mole (50%), spontaneous abortion (20%), ectopic pregnancy (2%) and normal term pregnancy (20%-30%). It is chemosensitive tumor and even in metastatic lesion cure rate is 90%-95%. Most common site of metastasis is lung and vagina, vulva, kidney, liver, ovaries, brain and intestine. If tumor is not diagnosed and managed timely, because of its vascularity, it bleeds profusely leading to death.

Cases: We encountered 2 rare cases, with age of 25 and 27 years respectively with choriocarcinoma with unusual clinical presentation. Both patients presented with neurological symptoms of brain metastasis and succumbed to death within a short span of time. In both cases histopathological report failed to detect chorio-carcinoma but b-HCG and radiological findings were suggestive of choriocarcinoma.

Conclusion: If b–HCG level are unusually high with radiological findings, the patients should be considered for chemotherapy even if HPE is inconclusive. Without chemotherapy chorio-carcinoma has a rapid progression and mortality which can be prevented by early suspicion and timely management.
R-VEIL in carcinoma vulva
Authors: Jain Vandana , Sekhon Rupinder , Giri Shveta , Rawal Sudhir
Published: February 2021

Background: Vulvar cancer accounts for about 3-5% of gynaecologic malignancies. Prognosis is strongly dependent on presence of inguinofemoral lymph node metastases. Effective management of regional lymph nodes is the most important factor in the curative management of early vulvar cancer. Despite careful dissection and maintaining vascularity of skin, surgical morbidity is seen in 50% cases. Video – endoscopic inguinofemoral lymphadenectomy was developed by Bishoff in 2003 by dissecting two cadaveric models and in one patient with stage T3N1M0 penile carcinoma. VEIL is an alternative to reduce the morbidity without compromising the oncologic outcomes. VEIL has continued to evolve into single site and robotic variants. R-VEIL is a minimally invasive procedure duplicating the standard open procedure with less morbidity.

Aims and Objectives: A video presentation to describe the technique of R-VEIL in vulvar cancer and discuss the advantages and outcome.

Conclusions: R – VEIL is an attractive minimally invasive technique to do inguinal block dissection in a single sitting in patients with vulvar carcinoma as the surgeon does not get tired as happens in VEIL technique. R-VEIL allows the removal of inguinal lymph nodes within the same limits as in open procedure and potentially reduces surgical morbidity. It is better accepted cosmetically and reduces hospital stay. Long term oncological results are not available. Randomized multi-institutional studies are required to prove its efficacy over open counterpart.
Dermoid cyst in an 82-year-old woman: Can be non malignant: Its management
Authors: Chithra Sravani , Manchanda Rahul , Kausar Hena , Jain Nidhi , lekhi Anshika
Published: February 2021

Dermoid cyst of ovary is the second most common type of ovarian germ cell tumor which constitutes 30 to 40% among ovarian tumors. It occurs mostly in women of reproductive age group between 20 and 40 years and very rarely in postmenopausal women. Postmenopause has its own set of symptoms and risks. One such risk is the possibility of malignancy of ovarian cyst with an incidence of 0.5 to 2%. We present an unusual and rare case of an 82 year old woman, who presented with complaints of pain abdomen and constipation for one year duration. Colonoscopy revealed diverticulitis. Despite being treated for diverticulitis, her symptoms persisted. CT was done which showed a right ovarian mass. Diagnostic laparoscopy was done and pus seen in the abdominal cavity was collected, bowel was distended, and dermoid cyst of ovary of 12 × 10 cm size which had undergone torsion three and a half times. Detorsion of ovary with right oophorectomy was done. Histopathology confirmed features of dermoid cyst with torsional changes in the wall and focal gangrene with no evidence of malignancy. Dermoid cyst occurs very rarely in postmenopausal women and treatment of choice is oophorectomy. Authors with this case highlight the proper management of ovarian dermoid cyst in symptomatic postmenopausal women.
Aggressive Therapy for Acute Pulmonary Embolism: Systemic Thrombolysis and Catheter-Directed Approaches
Authors: Todoran Thomas M. , Petkovich Bradley
Published: February 2021

Venous thromboembolism (VTE) is the third most common cause of cardiovascular disease after myocardial infarction and stroke. Population-based studies estimate that up to 94,000 new cases of pulmonary embolism (PE) occur in the United States annually with an increasing incidence with age. Mortality from PE is the greatest in the first 24 hours, with a decreased survival extending out 3 months. Thus, acute PE is a potentially fatal illness if not recognized and treated in a timely manner. Contemporary management includes systemic anticoagulation, thrombolysis, catheter-based procedures, and surgical embolectomy. This article reviews current clinical evidence and societal guidelines for the use of systemic and catheter-directed thrombolysis for treatment of acute PE.
Anticoagulation Prescription and Outcomes in Relation to Renal Function in Patients with Atrial Fibrillation: Results from GLORIA-AF
Authors: van der Wall Sake J. , Teutsch Christine , Dubner Sergio J. , Diener Hans-Christoph , Halperin Jonathan L. , Ma Chang Sheng , Rothman Kenneth J. , Paquette Miney , Zint Kristina , França Lionel Riou , Lu Shihai , Lip Gregory Y. H. , Huisman Menno V. ,   on behalf of the GLORIA-AF Investigators
Published: February 2021

Objective Anticoagulation management in patients with atrial fibrillation (AF) and impaired renal function is challenging. This study aimed to evaluate anticoagulation prescription patterns in relation to renal function and to describe 2-year clinical outcomes among dabigatran users.

Methods Global Registry on Long-Term Oral Antithrombotic Treatment in Patients with Atrial Fibrillation (GLORIA-AF) is an international, prospective, and observational study program involving patients with newly diagnosed AF at risk for stroke. Prescription patterns were assessed by creatinine clearance (CrCl) at enrollment. Dabigatran users were followed for 2 years. Clinical outcomes were standardized for stroke and bleeding risk, based on CHA2DS2-VASc and HAS-BLED scores, with missing values imputed.

Results Baseline CrCl values were available for 12,056 of 15,308 eligible patients (79%). With declining renal function, prescriptions increased for vitamin K antagonists (VKAs) and decreased for dabigatran (30–47% and 34–12%, respectively). The prescription of other non-vitamin K antagonists remained similar across CrCl groups (14–19%). In 4,873 dabigatran users, standardized stroke rates were low across all CrCl groups; 0.58/100 patient-years (95% confidence interval [CI]: 0.30–0.90) in CrCl ≥80 mL/min, 0.85 (95% CI: 0.48–1.21) in CrCl 50 to 79 mL/min, and 0.33 (95% CI: 0.06–1.11) in CrCl 30 to 49 mL/min. Similarly, major bleeding rates were low and numerically increased with declining renal function (0.68/100 patient-years, 95% CI: 0.39–1.03; 0.92, 95% CI: 0.58–1.32; and 1.26, 95% CI: 0.66–1.97, respectively).

Conclusion In patients with AF, VKA prescriptions increased and dabigatran prescriptions decreased with declining renal function. Rates of stroke and major bleeding in dabigatran patients remained low across the categories of renal impairment.
Do Millennials share similar perceptions of brand experience? A clusterization based on brand experience and other brand-related constructs: the case of Netflix
Authors: Amoroso Sara , Pattuglia Simonetta , Khan Imran
Published: February 2021

This study aims to explore, in the case of the Over-The-Top (OTT) sector, Millennials’ perceptions of brand experience in relation to the well-established brand Netflix. In particular, the work addresses a clusterization of Millennials on the basis of their experience with the brand. The study first explores the theoretical background, highlighting current perspectives on Over-The-Top industry and on brand experience as a strategic process for creating holistic customer value, achieving differentiation and sustainable competitive advantage. Second, it offers a quantitative study (using a survey) and highlights the principal results related to the brand. Moreover, this work will attempt to use cluster analysis methodology exploiting brand experience validated scale and other related brand and behavioural constructs to cluster consumers. Both academics and marketing managers should focus on approaches able to deliver strong and memorable brand experiences. A positive and durable brand experience is related to other important consequences for consumer action and behaviour, such as the willingness to place brand trust, consumer loyalty towards the brand, an enduring consumer-brand relationship, repurchase intentions, and lastly, the long-term life of the brand
The impact of artificial intelligence along the insurance value chain and on the insurability of risks
Authors: Eling Martin , Nuessle Davide , Staubli Julian
Published: February 2021

Based on a data set of 91 papers and 22 industry studies, we analyse the impact of artificial intelligence on the insurance sector using Porter’s (1985) value chain and Berliner’s (1982) insurability criteria. Additionally, we present future research directions, from both the academic and practitioner points of view. The results illustrate that both cost efficiencies and new revenue streams can be realised, as the insurance business model will shift from loss compensation to loss prediction and prevention. Moreover, we identify two possible developments with respect to the insurability of risks. The first is that the application of artificial intelligence by insurance companies might allow for a more accurate prediction of loss probabilities, thus reducing one of the industry’s most inherent problems, namely asymmetric information. The second development is that artificial intelligence might change the risk landscape significantly by transforming some risks from low-severity/high-frequency to high-severity/low-frequency. This requires insurance companies to rethink traditional insurance coverage and design adequate insurance products.
Numerical simulation study on operation characteristics of PEMFC in low temperature environment
Authors: Yang Penghui , Wang Yongqing , Jin Zunlong
Published: February 2021

When the proton exchange membrane fuel cell is used as a power source device to operate in a low temperature environment, the cell will have a series of problems such as difficulty in starting due to the overall low temperature, reduced output performance, and reduced life. External heating agent heating is one of the important methods to solve the above problems. In this paper, based on the most commonly used rectangular DC channel fuel cell model, a numerical simulation method is used to analyze the effect of different temperature heating agents on the continuous output performance of the cell at an ambient temperature of 253.15 K. By analyzing the cell polarization curve, temperature, material distribution, and current density under four operating conditions, it was found that the addition of an external heating agent helps to improve the output performance of the cell in a low-temperature environment. Among them, the optimization effect is most obvious when the temperature of the heating agent is 313.15 K in the studied temperature range.
Hot-electron photocurrent detection of near-infrared light based on ZnO
Authors: Hou Y. , Liang H. , Tang A. , Du X. , Mei Z.
Published: February 2021

We demonstrate an unconventional near-infrared photodetector fabricated from a ZnO chip with a metallic subwavelength grating structure as a contact and optical window, which harvests hot electrons generated by plasmonic resonances introduced by incident light. The grating structure has a strong selection of the polarization of incident light, meaning that the detector is naturally polarization-sensitive. In our device, the polarization extinction ratio is as high as 64:1, much higher than that relying on crystal orientations. Since the photoresponse is introduced by plasmonic resonance, a narrow photoresponse spectrum with a linewidth of 32.1 nm at 1.201 μm is obtained. By simply changing the grating period, the spectral position can be tailored freely within the near-infrared region, i.e., wavelength-selective. Such a spectral response is not likely to be realized with conventional semiconductor photodetectors, which depend on the band edge absorption. We propose a modified Fowler's model, which well explains the line shape of photoresponse spectra of such devices.
The electron–phonon coupling coefficient for high-temperature superconductors
Authors: Chauhan Radhika , Indu B. D.
Published: February 2021

The expression for the electron–phonon coupling coefficient (gk) is obtained by solving a six order polynomial equation obtained via the quantum dynamical many-body theory of the electron and phonon Green’s function for high-temperature superconductors (HTSs). The developed equation depends on the temperature; electron, phonon, and pairon frequencies; and distribution functions. The YBa2Cu3O7−δ cuprate superconductor has been used for the purpose of analysis and is found to be in agreement with the fact that gk decreases with the increase in temperature above 0 K. The distinct behavior obtained via dispersion for gk in different directions, [100] and [010], marked the anisotropy of electron–phonon coupling in HTSs. The derived expression for gk is further used for the evaluation of the superconducting gap via the Bardeen–Cooper–Schrieffer and the McMillan gap equation and both superconducting gap equations approach the Tc value for YBa2Cu3O7−δ, and the obtained reduced gap ratio [2Δ(0)/kBTc] is found to be in the limit of the reduced gap ratio of HTSs.
A critical evaluation of Ag- and Ti-hyperdoped Si for Si-based infrared light detection
Authors: Lim S. Q. , Akey A. J. , Napolitani E. , Chow P. K. , Warrender J. M. , Williams J. S.
Published: February 2021

Following recent successful demonstrations of enhanced infrared absorption in Au-hyperdoped Si, there has been strong interest in fabricating other metal-hyperdoped Si systems as a highly attractive approach for Si-based infrared photodetection. In this work, we address the somewhat contentious issue in the literature as to whether it is possible, using ion implantation and nanosecond pulsed-laser melting, to achieve hyperdoping of Si with Ag and Ti at concentrations exceeding that required to form an intermediate impurity band within the Si bandgap (NIB∼6×1019cm−3). A wide range of characterization techniques were used to investigate these material systems, especially the quality of liquid-phase epitaxy, impurity concentration distribution both in depth and laterally, and impurity lattice location. Our results indicate that the high concentrations of opto-electrically active Ag or Ti in monocrystalline Si required to form an impurity band are not achieved. In particular, the usual behavior during rapid solidification is for near-complete surface segregation of the impurity, or for it to be trapped within a highly defective subsurface layer due to filamentary breakdown. Although our measurements showed that the maximum concentration of impurities outside metal-rich filaments is comparable to NIB for both Ag and Ti, there is no preferential Ag or Ti lattice location after pulsed-laser melting anywhere in the material. Thus, the concentration of opto-electrically active Ag and Ti that can be homogeneously incorporated into Si is expected to be well below NIB, leaving Au as the only viable impurity to date for achieving the required level of hyperdoping in Si.
Highly efficient charge-to-spin conversion from in situ Bi2Se3/Fe heterostructures
Authors: Zhu Dapeng , Wang Yi , Shi Shuyuan , Teo Kie-Leong , Wu Yihong , Yang Hyunsoo
Published: February 2021

Topological insulators (TIs) show bright prospects in exerting spin–orbit torques (SOTs) and inducing magnetization switching in the adjacent ferromagnetic (FM) layer. However, a variation of the SOT efficiency values may be attributed to the ex situ deposition of the FM layer or the complex capping/decapping processes of the protection layer. We have employed an in situ fabrication of Bi2Se3/Fe heterostructures and investigated the SOT efficiency by spin torque ferromagnetic resonance. An enhanced SOT efficiency and large effective spin mixing conductance have been obtained especially below 100 K as compared with ex situ methods. The enhancement of the SOT efficiency is attributed to a much thinner interfacial layer (0.96 nm) in the in situ case and thus the enhanced interface spin transparency. Our results reveal the crucial role of interface engineering in exploring highly efficient TI-based spintronic devices.
Pressure-tailored synthesis of confined linear carbon chains
Authors: Li Xuan , Zhang Yifan , Wu Yangliu , Shi Lei
Published: February 2021

High-temperature annealing of carbon nanotubes in both vacuum and in inert gas has been approved to yield linear carbon chains (LCCs) inside the carbon nanotubes. How the environmental pressure utilized for the annealing affects the formation of the LCCs is not studied yet, although it is an important factor to be considered, since the gas molecules could move back and forth inside the carbon nanotubes to prevent the formation of the LCCs. In this paper, the LCCs were synthesized by controlling the pressure during the annealing, and we found that the yield of the LCCs can be indeed tuned by the pressure. Chemical reaction kinetic analysis reveals that the lower the pressure, the smaller the activation energy, which then explains that it is easier to enable the synthesis of the LCCs in better vacuum. In addition, we found that the applied pressures at 10−3 and 101 Pa result in similar yields of the LCCs, suggesting that low vacuum is good enough for the synthesis, which would practically benefit the future large-scale synthesis and applications of the LCCs.
Core level photoelectron spectroscopy of heterogeneous reactions at liquid–vapor interfaces: Current status, challenges, and prospects
Authors: Dupuy Rémi , Richter Clemens , Winter Bernd , Meijer Gerard , Schlögl Robert , Bluhm Hendrik
Published: February 2021

Liquid–vapor interfaces, particularly those between aqueous solutions and air, drive numerous important chemical and physical processes in the atmosphere and in the environment. X-ray photoelectron spectroscopy is an excellent method for the investigation of these interfaces due to its surface sensitivity, elemental and chemical specificity, and the possibility to obtain information on the depth distribution of solute and solvent species in the interfacial region. In this Perspective, we review the progress that was made in this field over the past decades and discuss the challenges that need to be overcome for investigations of heterogeneous reactions at liquid–vapor interfaces under close-to-realistic environmental conditions. We close with an outlook on where some of the most exciting and promising developments might lie in this field.
Reactivity of Ni–Al nanocomposites prepared by mechanical activation: A molecular dynamics study
Authors: Fourmont A. , Politano O. , Le Gallet S. , Desgranges C. , Baras F.
Published: February 2021

High energy ball milling of metallic powders leads to high reactivity in the milled mixture. The reaction is often faster and starts at a lower temperature. However, the mechanisms responsible for this high reactivity are not yet completely understood. The aim of this study is to evaluate one of the possible activating factors of this heightened reactivity: nano-scale mixing of the reagents. Molecular dynamics was used to analyze the role of an amorphous Ni–Al mixing layer, mimicking the powder microstructure after milling, between two Ni layers. The impact of temperature and stoichiometry was investigated in relation to the formation of the B2-NiAl intermetallic compound. At low temperatures, pre-mixing does not seem to slow down the diffusion of Ni atoms in an amorphous Al region. Homogeneous nucleation was observed in this peculiar milled microstructure. These two phenomena explain why the nano-scale mixing observed experimentally after high energy milling is indeed an activating factor in the reactivity of metallic systems such as Ni–Al.
The vacuum boundary problem for the spherically symmetric compressible Euler equations with positive density and unbounded entropy
Authors: Rickard Calum
Published: February 2021

Global stability of the spherically symmetric nonisentropic compressible Euler equations with positive density around global-in-time background affine solutions is shown in the presence of free vacuum boundaries. Vacuum is achieved despite a non-vanishing density by considering a negatively unbounded entropy, and we use a novel weighted energy method, whereby the exponential of the entropy will act as a changing weight to handle the degeneracy of the vacuum boundary. Spherical symmetry introduces a coordinate singularity near the origin for which we adopt a method developed for the Euler–Poisson system [Y. Guo et al., Arch. Ration. Mech. Anal. 239, 431–552 (2021)] to our problem.
Simulation of decelerating streamers in inhomogeneous atmosphere with implications for runaway electron generation
Authors: Starikovskiy A. Yu. , Aleksandrov N. L. , Shneider M. N.
Published: February 2021

The dynamics of positive and negative streamers is numerically simulated in atmospheric pressure air in the range of parameters corresponding to the streamer deceleration and termination in the middle of the discharge gap. A detailed comparison with experiments in air at constant and variable density demonstrates good agreement between the 2D simulation results and the observations. It is shown that positive and negative streamers behave in radically different ways when decelerating and stopping. When the head potential drops, the negative streamer transits to the mode in which the propagation is due to the forward electron drift. In this case, the radius of the ionization wave front increases, whereas the electric field at the streamer head decreases further and the streamer stops. Its head diameter continues to increase due to the slow drift of free electrons in the residual under-breakdown field. On the contrary, the only advancement mechanism for a positive streamer with a decreasing head potential is a decrease in the effective radius of the ionization wave, leading to a local increase in the electric field. This mechanism makes it possible to compensate for the reduction in the efficiency of gas photoionization at small head diameters. A qualitative 1D model is suggested to describe streamer deceleration and stopping for different discharge polarities. Estimates show that, during positive streamer stopping, the local electric field at the streamer head can exceed the threshold corresponding to the transition of electrons to the runaway mode when the head potential (relative to the surrounding space) decreases to ∼1.2 kV in atmospheric pressure air. In this case, pulsed generation of a beam of runaway electrons directed into the channel of a stopping positive streamer can occur. The energy of the formed pulsed electron beam depends on the intensity of photoionization in front of the streamer head. This energy can vary from 700 V (when increasing the photoionization rate by a factor of 10 with respect to the value in atmospheric pressure air) to 2.6 kV (when decreasing the photoionization rate by a factor of 1000). It is possible that this behavior of decelerating positive streamers can explain the observed bursts of x-ray radiation during the streamer propagation in long air gaps.
Beaconless PAT and adaptive beam control using variable focus lens for free-space optical communication systems
Authors: Mai Vuong V. , Kim Hoon
Published: February 2021

Free-space optical communications (FSOCs) have recently emerged as a promising solution for various communication scenarios. However, the pointing, acquisition, and tracking (PAT) is a technically challenging issue, especially in airborne FSOC systems. In this paper, we present an adaptive beam control technique combined with beaconless PAT using a variable focus lens. By using the lens whose focal length can be tuned electrically, we facilitate the coarse PAT by enlarging the beam size and also mitigate the adverse effects of pointing errors by adjusting the beam divergence angle adaptively to the link conditions. The major benefit of the proposed scheme is that the beam control can be implemented in a simple and compact manner, without relying on mechanical movements. We carry out a proof-of-concept experimental demonstration of the proposed scheme for a 10-Gb/s free-space optical link over 104 m. The demonstration shows that the probability of PAT success can be improved considerably by using the proposed scheme. It also shows that the proposed scheme could result in a system loss reduction of 6.4 dB and improve the tolerance to pointing errors up to 500 μrad for a target bit-error ratio of 10−3. The response time of the lens is measured to be <211 ms. We confirm experimentally that the receiver size and the amount of pointing error determine the optimum beam size at the receiver.
Boron dangling bonds in a monolayer of hexagonal boron nitride
Authors: Turiansky Mark E. , Van de Walle Chris G.
Published: February 2021

Boron dangling bonds have been proposed as the likely source of the 2-eV single-photon emission observed in hexagonal boron nitride (h-BN). Here, we examine the effect of dimensionality on this defect by studying its properties in a single monolayer. Based on first-principles calculations, we find that the qualitative features of the boron dangling bond are similar to those in bulk h-BN, with only minor shifts to the energetics and optical properties. We discuss the importance of correctly handling the compensating background charge for the properties of charged defects in reduced dimensions. Our results highlight the potential for harnessing single-photon emitters in a monolayer of h-BN for applications in quantum information science.
On the role of hydrogen-bond exchanges in the spectral diffusion of water
Authors: Piskulich Zeke A. , Laage Damien , Thompson Ward H.
Published: February 2021

The dynamics of a vibrational frequency in a condensed phase environment, i.e., the spectral diffusion, has attracted considerable interest over the last two decades. A significant impetus has been the development of two-dimensional infrared (2D-IR) photon-echo spectroscopy that represents a direct experimental probe of spectral diffusion, as measured by the frequency–frequency time correlation function (FFCF). In isotopically dilute water, which is perhaps the most thoroughly studied system, the standard interpretation of the longest timescale observed in the FFCF is that it is associated with hydrogen-bond exchange dynamics. Here, we investigate this connection by detailed analysis of both the spectral diffusion timescales and their associated activation energies. The latter are obtained from the recently developed fluctuation theory for the dynamics approach. The results show that the longest timescale of spectral diffusion obtained by the typical analysis used cannot be directly associated with hydrogen-bond exchanges. The hydrogen-bond exchange time does appear in the decay of the water FFCF, but only as an additional, small-amplitude (<3%) timescale. The dominant contribution to the long-time spectral diffusion dynamics is considerably shorter than the hydrogen-bond exchange time and exhibits a significantly smaller activation energy. It thus arises from hydrogen-bond rearrangements, which occur in between successful hydrogen-bond partner exchanges, and particularly from hydrogen bonds that transiently break before returning to the same acceptor.
Creating wounds in cell monolayers using micro-jets
Authors: Soitu Cristian , Panea Mirela , Castrejón-Pita Alfonso A. , Cook Peter R. , Walsh Edmond J.
Published: February 2021

Many wound-healing assays are used in cell biology and biomedicine; they are often labor intensive and/or require specialized and costly equipment. We describe a contactless method to create wounds with any imaginable 2D pattern in cell monolayers using the micro-jets of either media or an immiscible and biocompatible fluorocarbon (i.e., FC40). We also combine this with another method that allows automation and multiplexing using standard Petri dishes. A dish is filled with a thin film of media overlaid with FC40, and the two liquids are reshaped into an array of microchambers within minutes. Each chamber in such a grid is isolated from others by the fluid walls of FC40. Cells are now added, allowed to grow into a monolayer, and wounds are created using the microjets; then, healing is monitored by microscopy. As arrays of chambers can be made using media and Petri dishes familiar to biologists, and as dishes fit seamlessly into their incubators, microscopes, and workflows, we anticipate that this assay will find wide application in wound healing.
Wide range temperature-dependent (80–630 K) study of Hall effect and the Seebeck coefficient of
β
-Ga2O3 single crystals
Authors: Kumar Ashish , Singh Saurabh , Tak Bhera Ram , Patel Ashutosh , Asokan K. , Kanjilal D.
Published: February 2021

Investigation of the Seebeck coefficient in ultra-wide bandgap materials presents a challenge in measurements; nevertheless, it is essential for understanding fundamental transport mechanisms involved in electrical and thermal conduction. β-Ga2O3 is a strategic material for high-power optoelectronic applications. The present work reports the Seebeck coefficient measurement for single crystal Sn-doped β-Ga2O3 in a wide temperature range (80–630 K). The non-monotonic trend with large magnitude and a negative sign in the entire temperature range shows that electrons are dominant carriers. The structural and Raman characterization confirms the single-phase and the presence of low-, mid-, and high-frequency phonon modes, respectively. The temperature-dependent (90–350 K) Hall effect measurement was carried out as a supplementary study. Hall mobility showed that μ ∝ T1.12 for T < 135 K and μ ∝ T−0.70 for T > 220 K. Activation energies from the Seebeck coefficient and conductivity analysis revealed the presence of interband conduction due to impurity defects. The room temperature Seebeck coefficient, power factor, and thermal conductivity were found to be 68.57 ± 1.27 μV/K, 0.15 ± 0.04 μW/K2 cm, and 14.2 ± 0.6 W/mK, respectively. The value of the figure of merit for β-Ga2O3 was found to be ∼ 0.01 (300 K).
Structural properties of Fe49Ni49Ti2 alloy deformed by high pressure torsion
Authors: Ulyanov Maxim , Taskaev Sergey , Shevyrtalov Sergey , Medvedskaya Polina , Gunderov Dmitriy
Published: February 2021

Tetrataenite (L10-FeNi) is a promising candidate for use as a permanent magnet free of rare-earth elements because of its favorable properties such as high magnetic anisotropy and coercivity. We report on structural properties of Fe49Ni49Ti2 alloy after severe plastic deformation (SPD) by high pressure torsion (HPT) technique. The main magnetic and structural characteristics of bulk and HPT materials were determined. As a result of plastic deformation, all samples were obtained with high concentration of defects and stressed state. Low-temperature annealing was used to accelerate the kinetics of phase formation and the possible appearance of nuclei of a stable chemically ordered L10 phase of tetrataenite. Our research shows that it is premature to talk about the formation of even a small amount of phase L10. Additional research needs to be done.
Few and far apart: integrative taxonomy of Australian species of Gladiobela and Pagodibela (Conoidea : Raphitomidae) reveals patterns of wide distributions and low abundance
Authors: Hallan Anders , Criscione Francesco , Fedosov Alexander , Puillandre Nicolas
Published: February 2021

The deep-sea malacofauna of temperate Australia remains comparatively poorly known. However, a recent influx of DNA-suitable material obtained from a series of deep-sea cruises has facilitated integrative taxonomic study on the Conoidea (Caenogastropoda:Neogastropoda). Building on a recent molecular phylogeny of the conoidean family Raphitomidae, this study focussed on the genera Gladiobela and Pagodibela (both Criscione, Hallan, Puillandre & Fedosov, 2020). We subjected a representative mtDNA cox1 dataset of deep-sea raphitomids to ABGD, which recognised 14 primary species hypotheses (PSHs), 9 of which were converted to secondary species hypotheses (SSHs). Following the additional examination of the shell and hypodermic radula features, as well as consideration of bathymetric and geographic data, seven of these SSHs were recognised as new to science and given full species rank. Subsequently, systematic descriptions are provided herein. Of these, five are attributed to Gladiobela (three of which are endemic to Australia and two more widely distributed) and two are placed in Pagodibela (one endemic to southern Australia and one widespread in the Pacific). The rarity of many ‘turrids’ reported in previous studies is confirmed herein, as particularly indicated by highly disjunct geographic records for two taxa. Additionally, several of the studied taxa exhibit wide Indo-Pacific distributions, suggesting that wide geographic ranges in deep-sea ‘turrids’ may be more common than previously assumed. Finally, impediments to deep-sea ‘turrid’ taxonomy in light of such comparative rarity and unexpectedly wide distributions are discussed.