Role of endoscopic ultrasound-guided tissue acquisition for the diagnosis of gastric wall thickening: a retrospective study with meta-analysis

Background

Tissue acquisition from a thickened gastric wall using biopsy forceps may not always lead to diagnosis, given the submucosal location of the pathology. Endoscopic ultrasound (EUS)-guided tissue acquisition (TA) may serve as a minimally invasive diagnostic tool in such cases. Hence, we aimed to assess the diagnostic outcome and safety of EUS-TA from thickened gastric walls.

Methods

Data from patients with gastric wall thickening undergoing EUS-TA at 5 tertiary care centers from August 2020 to August 2022 were retrospectively analyzed. These data were pooled with studies obtained from a comprehensive search of Medline, Embase and Scopus from January 2000 to November 2022 and a meta-analysis was performed. Pooled event rates were calculated using an inverse variance model.

Results

The search strategy yielded 13 studies that were combined with data from 30 patients from our centers; a total of 399 patients were included in the analysis. The pooled rate of sample adequacy was 94.1% (95% confidence interval [CI] 90.0-98.2), while the pooled rate of diagnostic accuracy was 91.3% (95%CI 87.0-95.5). The pooled sensitivity and specificity for diagnosing malignant lesions with EUS-TA from gastric wall thickening were 94.8% (95%CI 91.3-97.2) and 100% (95%CI 93.6-100), respectively. There were no reported adverse events in any of the studies.

Conclusions

EUS-TA offers a safe and accurate diagnostic modality for the etiological diagnosis of thickened gastric walls. Further research is required to identify the needle type and optimal technique for improving outcomes.

Obstructive Jaundice with skin involvement - An unusual presentation of Myeloid Sarcoma

Biliary obstruction secondary to malignancy is a common clinical problem. Rarely, biliary obstruction is due to leukemia, and obstructive jaundice in these patients usually presents late in the course of the disease. We present a rare case of a patient who presented with fever, jaundice, and pruritus with multiple nodular swellings in the left shoulder, left thigh, and lower back. Magnetic resonance cholangiopancreatography (MRCP) revealed periampullary mass lesion causing dilated common bile duct (CBD) and intrahepatic bile ducts; hence, endoscopic retrograde cholangiography with plastic stenting was done. Biopsy from the shoulder lesion revealed a mesenchymal tumor, and immunohistochemistry (IHC) confirmed the lesion as myeloid sarcoma. Myeloid sarcoma is an extramedullary tumor, a subtype of acute myeloid leukemia, and presentation as biliary lesions with multiple anatomical sites is very rare. The patient was started on chemotherapy after the normalization of bilirubin. The patient showed improvement of skin lesions and normalization of liver function test (LFT) after 3 weeks of chemotherapy.

A Prospective Study on the Clinical Significance of Infections in a Hospital Setting Among the Cirrhotic Patients and Their Outcomes

Aim and objectives The infection of microbial agents in cirrhosis has increased due to poor immunity, which increases morbidities and mortalities worldwide. The present study aimed to assess the incidence, the type of infections, the pattern of resistance, and the course of hospitalization among cirrhotic patients in the Eastern coastal region. Methodology The study was a descriptive cross-sectional study, and the current study was undertaken for 24 months at the Department of Gastroenterology and Hepatobiliary Sciences, IMS, and SUM. Hospital, Bhubaneswar. Consecutive cirrhotic patients admitted with bacterial infection were prospectively evaluated, and the infection patterns were accessed. The data were collected in a well-structured proforma designed by our study team. Results Out of the total 200 cases, a fraction of 72.5% of males outnumbered the females; the mean age of presentation was 59 ± 12 years. A fraction of 59% of cases had the habit of consuming alcohol which amounted to the predominant etiological factor for cirrhosis, followed by non-alcoholic steatohepatitis (NASH). Urinary tract infection (UTI) and spontaneous bacterial peritonitis (SBP) were more common types of infections in the healthcare-associated (HCA) group; however, pneumonia and skin and soft tissue infections (SSTI) were predominant types of infections in community-acquired (CA) group. The model for end-stage liver disease (MELD) scores were not significantly different amongst the three groups with infections at the time of Diagnosis infection and at the time of hospitalization. However, the MELD scores were substantially higher at the time of infection diagnosis than the MELD scores at the time of admission amongst the three groups with infection. Conclusion The present study showed that infections in cirrhosis were relatively common. Due to increasing resistance patterns, the judicious usage of antibiotics in cirrhosis could be the need of the hour.

Burkholderia cepacia causing liver and splenic abscess: Two case reports

Burkholderia cepacia infections are common among immunocompromised patients but multiple reports have shown that it can affect immunocompetent patients also. We are reporting two patients with multiple liver and splenic abscesses caused by Burkholderia cepacia. First case is a 54-year-old diabetic male presenting with fever, abdominal pain, bilateral lower limb weakness, and incontinence of urine. Second case is a 41-year-old male presenting with fever and confusion. Both had liver and splenic abscesses. Pus aspirated from the abscesses grew Burkholderia cepacia. Both responded to cotrimoxazole. Our case report emphasizes growing incidence of Burkholderia cepacia in immunocompetent patients.

Knowledge, Awareness and Prevalence of Hepatitis B Among Urban Slum Dwellers and Residents of Social Welfare Home: A Cross sectional Study From Eastern India

Background/aims

In view of limited data on the knowledge and awareness of hepatitis B virus (HBV) and the available preventive strategies at the community level, it was aimed to analyse the knowledge and awareness of HBV in the community.

Methods

A cross-sectional questionnaire-based survey was conducted among residents of an urban slum and a social welfare home in Bhubaneswar, Odisha, from October 2019 to April 2021. The prevalence of HBV infection was also measured by testing the serum positivity for hepatitis B surface antigen using rapid point-of-care test kits. The statistical analysis was done by using the software SPSS version 20.

Results

A total of 370 individuals (mean age 38.7 ± 14.9 years, males: 55.1%) were assessed. Although 18.1% (67) had good knowledge, only 16.7% (62) had good awareness about HBV. Approximately 14.8% (55) knew that a vaccine is available in the country for HBV, and 6.2% (23) identified themselves as being vaccinated. Educational status was a significant independent predictor of knowledge and awareness such that people with education level of matriculation and above had odds of 11.05 (95% confidence interval: 5.3-22.7) and 14.7 (95% confidence interval: 6.5-33.1) for having good knowledge and awareness regarding HBV, respectively. A total of 10 participants tested positive for hepatitis B surface antigen contributing to a point prevalence rate of 2.7%. The proportion of individuals with an education status of matriculation and above was higher in the slum area when compared with the welfare home (67% vs 33%; P < 0.001), the knowledge (71.6% vs 28.4%; P < 0.001) and so was the awareness (71% vs 29%; P < 0.001) about HBV as well.

Conclusion

The relatively low figures of knowledge and awareness identified in our study undermine the need for intensification of health education and promotion activities regarding the prevalence of hepatitis B infection on a large scale at the community level.

Unusual presentations of abdominal tuberculosis: A case series of clinical mysteries

Abdominal tuberculosis is one of the common extra pulmonary tuberculosis with diverse clinical manifestations. It has high disease burden in endemic countries like India leading to significant morbidity and mortality when left untreated. It is of vital importance to treat to prevent significant disease related mortality. We report 4 patients of abdominal tuberculosis who presented with atypical presentations. The aim of our case series is to know the uncommon presentations of a common disease.

C-reactive protein/albumin and ferritin as predictive markers for severity and mortality in patients with acute pancreatitis

Introduction

Acute pancreatitis (AP) is a life-threatening gastrointestinal disease with high mortality and morbidity. However, scoring systems or prognostic indicators for assessing AP are cumbersome and expensive, and have not proved accurately to predict outcomes.

Aim

We conducted a study with the aim of evaluating the predictive accuracy of C-reactive protein (CRP)/albumin and ferritin regarding outcomes in patients with AP.

Material and methods

A prospective study was conducted in a tertiary care referral centre in Odisha from March 2020 to April 2021. A total of 116 consecutive patients of AP were enrolled in the study. CTSI, APACHE II, ferritin, and the CRP/albumin ratio were calculated.

Results

The mean age of patients was 40.63 ±5.49 years with a male predominance (73%). Alcohol was most common aetiology (46.6%), and the overall mortality was 18%. Mean ferritin and the CRP/albumin ratio were also significantly higher in severe AP as compared to moderately severe AP and mild AP (p < 0.001). The CRP/albumin ratio (AOR = 1.26, 95% CI: 1.02-1.56, p = 0.02) was found to be independent predictor of mortality in Cox regression multivariate analysis and had the highest AUC for predicting the severity of acute pancreatitis. Serum ferritin had higher AUC (0.89, 0.83-0.91, p < 0.001) for the development of necrosis in acute pancreatitis, but it failed to be proven as an independent predictor of mortality.

Conclusions

CRP/albumin is a simple, cheap, and easily available biomarker predicting the development of severe pancreatitis, and it was found to be an independent predictor of mortality in AP.

A pilot study on some critical immune elements in HBV infection: evidence of Alpha-1 Antitrypsin as an immunological biomarker

Aim

This study is an attempt to screen the key immune elements that participate during HBV infection and the related pathways that are modulated.

Background

The pathogenesis of Hepatitis B virus and the corresponding clinical manifestations in the host are primarily immune-mediated.

Methods

This study utilizes a PCR array to screen immune-related genes that are differentially expressed in the presence of the virus in HBV replicating HepG2.2.15 cells as compared to control HepG2 cells. The significantly up-regulated genes were subjected to bioinformatic analysis utilizing GSEA and STRING. Additionally, ELISA was used to corroborate the levels of Alpha 1 antitrypsin (AAT) from patients' sera.

Results

The expressions of 31% of the studied genes were significantly up-regulated (> 2-fold, p<0.05) in HepG2.2.15 cells compared to controls, and this included the SERPINA1, FN1, IL1R2, LBP, LY96, LYZ and PROC genes. When they were clustered based on biological processes, signaling pathways, and disease progression, the genes related to biotic stimulus, complement-coagulation cascades, and fibrosis, respectively, showed the highest (p<0.05) enrichment. Analysis of patients' sera by ELISA revealed that the serum AAT (SERPINA1) levels were significantly higher in asymptomatic carriers and in patients with chronic liver disease than in controls (p<0.05). Moreover, SERPINA1 levels were also positively correlated with the levels of serum ALT (r=0.4495, p<0.05) among HBV infected patients.

Conclusion

The current study highlights the key immune elements and pathways that are modulated during HBV infection and proposes the possible use of AAT as a non-invasive immunological biomarker to follow the progression of liver disease.

Tuberculosis is still the most Common Cause of Mediastinal and Intra-abdominal Lymphadenopathy by EUS-FNA in India

Background Lymph nodal tuberculosis is reported to occur in 4% to 7% of all tuberculosis, and mediastinal lymphadenopathy accounts for 10% of lymph nodal tuberculosis but the diagnosis still remains a challenge due to inaccessibility to these sites. There is a scarcity of recent data from India about the etiology of intra-abdominal and mediastinal lymphadenopathy despite being frequently detected in cross-sectional imaging.

Methods A retrospective study was conducted after reviewing hospital records over a period of 3 years from December 2017 to December 2020 who underwent endoscopic ultrasonography (EUS). A total of 126 patients with mediastinal and/or intra-abdominal lymphadenopathy detected by cross-sectional imaging were examined for clinical features, EUS, and histopathology records.

Results The mean age of patients was 53.12 ± 14.15 years. Seventy-one patients (56%) had intra-abdominal lymph nodes and 55 (44%) had mediastinal lymph nodes. The average number of needle passes was 2.35 ± 0.58 (range: 2–4). The majority of patients had tubercular etiology (53.2%) followed by metastatic (26.2%). Other etiologies were reactive (4.8%), lymphoma (4.8%), sarcoidosis (3.2%), and GIST (1.6%). No diagnosis could be ascertained in 6.3% of patients. The EUS features that favored tubercular etiology over metastatic were heterogeneous echotexture (72% vs. 30%), irregular shape (78% vs. 12%), indistinct borders (81% vs. 30%) and calcification (43% vs. 15%). Partial anechoic area and hyperechoic area were seen in 21% and 64% of tubercular patients, respectively. EUS only had sensitivity and specificity of 63% and 84%, respectively, and EUS FNA had a very high sensitivity and specificity of 93% and 100%, respectively.

Conclusion Tuberculosis is still the most common cause of lymph nodes. EUS FNA had a very high sensitivity and specificity of 93% and 100%, respectively, for the diagnosis of mediastinal and intra-abdominal lymphadenopathy.

Serotype and genotype diversity of dengue viruses circulating in India: a multi-centre retrospective study involving the Virus Research Diagnostic Laboratory Network in 2018

OBJECTIVES

A retrospective study was undertaken to investigate the circulating dengue virus (DENV) serotypes and genotypes in India in 2018.

METHODS

In total, 4963 samples referred to virus research diagnostic laboratories (n=21), the Indian Council of Medical Research-National Institute of Virology (ICMR-NIV) and ICMR-NIV field units (n=2) for diagnosis of dengue in 2018 were tested using a real-time reverse transcription polymerase chain reaction assay for the presence of DENV serotypes. Representative samples were sequenced for the envelope (E) gene.

RESULTS

Regional diversity was observed with regard to the dominant circulating serotypes. DENV-2 was found to be the most common serotype in many states. Thrombocytopenia, petechiae and malaise were associated with DENV-2 infection. Phylogenetic analyses of DENV E gene sequences revealed the circulation of genotypes I and V of DENV-1, two lineages of DENV-2 genotype IV, DENV-3 genotype III and DENV-4 genotype I.

CONCLUSIONS

This study found regional differences in the prevalence of circulating DENV serotypes in India, and provides baseline data for continuous molecular surveillance. Molecular surveillance may have implications for predicting large-scale outbreaks of dengue if regional shifts in the predominantly circulating serotypes and genotypes are detected during the early phase of the dengue season.

Factors Predicting Cardiac Dysfunction in Patients with Liver Cirrhosis

BACKGROUND Left ventricular diastolic dysfunction (LVDD) is the earliest cardiac dysfunction noted in patients with liver cirrhosis, which increases the morbidity and mortality in such patients. There are sparse studies from India evaluating the predictive factors of LVDD in patients with cirrhosis. Hence we undertook this prospective study with an aim to evaluate the factors predicting the development of LVDD in liver cirrhosis. METHODS 104 patients with cirrhosis were enrolled in this prospective study. A detailed cardiac evaluation was done by 2 D echocardiography with tissue Doppler imaging by an experienced senior cardiologist. The severity of liver disease was defined by Model For End-Stage Liver Disease (MELD) and Child-Pugh score. RESULTS The prevalence of LVDD was 46% in our study. Multivariate logistic regression analysis revealed that serum albumin, MELD score, and presence of ascites (OR = 0.1, 95%CI 0.03-0.3, p < 0.001; Or = 1.12, 95%CI 1.03-1.22, p < 0.001; OR = 4.19, 95%CI 1.38-12.65, p < 0.01, respectively) were independent predictors of LVDD in patients with cirrhosis. Diastolic dysfunction was unrelated to age, sex, and etiology of cirrhosis. The patients with cirrhosis and LVDD had significantly higher child Pugh score, MELD score, and lower serum albumin than patients without LVDD. The echocardiographic parameters like E/e' ratio, Deceleration time (DT), and Left atrial volume index (LAVI) were significantly different in cirrhotic patients with higher MELD and child Pugh score than lower. CONCLUSION The present study showed a significant correlation of diastolic dysfunction with the severity of the liver disease. Low serum albumin, high MELD score, and presence of ascites significantly predict the development of LVDD in patients with cirrhosis.

Predictors of early mortality among patients with acute-on-chronic liver failure

Background and Aim

Acute-on-chronic liver failure (ACLF) is a transpiring entity, which possesses high short-term/early mortality (28 days). Several mortality predictors have been studied, but none were proved reliable. Serum ferritin, an acute phase reactant and marker of hepatic necro-inflammation, is found to predict mortality in multiple liver diseases. We aimed to evaluate the role of serum ferritin and other clinical features, biochemical parameters and conventional scoring systems in predicting early mortality among ACLF.

Methods

A prospective cohort study was done from October 2017 to March 2019 at a tertiary care (non-transplant) center in eastern India. A total of consecutive 50 ACLF patients diagnosed, based on Asia Pacific Association for the Study of liver disease definition, were investigated for ferritin and other laboratory parameters on day-0, day-7, and followed up for 28 days.

Results

Although the majority did not have organ failure (ACLF grade 0) according to European Association for Study of Liver-chronic liver failure sequential organ failure assessment criteria, early mortality was high (56%). On undergoing univariate analysis, multiple variables (ascites, HE, creatinine, total leucocyte count (TLC), bilirubin, albumin) predicted mortality. However, on multivariate analysis, only total bilirubin independently predicted. None of the scores on day-0 were predictive, while model for end-stage liver disease [area under the receiver operating characteristics (AUROC)-0.703, 95% confidence interval [CI]: 0.535-0.859] and Child-Turcotte-Pugh (AUROC-0.697, 95% CI: 0.550-0.855) on day-7 did.

Conclusion

ACLF is a dynamic process; day-7 assessment with above predictors, to be considered a milestone for prognostication and opting treatment modalities. Serum ferritin does not predict early mortality in ACLF.

SPINK1 Mutation in Idiopathic Chronic Pancreatitis: How Pertinent Is It in Coastal Eastern India?

Background and aim Idiopathic chronic pancreatitis (ICP) is said to be present when no identifiable etiology can be identified. Robust evidence suggested that the serine protease inhibitor nucleus Kazol type 1 (SPINK1) N34S mutation was frequently associated with ICP. As there is a paucity of data on genetic studies in ICP cases from the coastal eastern region of India, we performed this study with an aim to evaluate the SPINK1 genetic mutations and other associated clinical correlates in ICP cases. Material and methods Consecutive ICP cases attending the department of gastroenterology, Institute of Medical Sciences (IMS) and SUM Hospital, were enrolled and evaluated for the pertinent clinical history and undergone detailed biochemical and radiological evaluations. Two ml of venous blood in ethylenediaminetetraacetic acid (EDTA) vials were collected from each case and subjected to a polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) test for genetic analysis. Result In this study, the mean age of the cases at the time of the first consultation with us and the age of the first clinical presentation were 34.52±6.44 and 28.73±5.52 years, respectively. Males outnumbered females (Male:Female - 2.12:1). Out of the total of 200 cases, 50% had no SPINK1 mutation, whereas 40% and 10% cases had SPINK1 N34S heterozygous and homozygous mutations, respectively. The mean age of clinical presentation, severe abdominal pain, exocrine and endocrine insufficiency, and parenchymal atrophy were significantly more common in mutants as compared to non-mutants (p-value <0.05). Conclusion In our region, 50% of ICP cases had the SPINK1 N34S mutation. The SPINK1 mutants had a relatively more severe variety of pancreatitis as compared to non-mutants.

Irritable Bowel Syndrome and the Menstrual Cycle

Introduction: Irritable bowel syndrome (IBS) is a common gastrointestinal (GI) disorder. Female patients with bowel disease commonly report worsening of symptoms in the menstrual cycle. However, there is a paucity of data regarding IBS presentations' variation during different phases of the menstrual cycle. The current study aimed to evaluate the same in female IBS patients.

Materials and Methods: Consecutive premenopausal female patients with the diagnosis of IBS attending the outdoor (OPD) of Department of Gastroenterology and Gynaecology; IMS and SUM Hospital, Bhubaneswar, Odisha from June 2019 to December 2019 were included in the study and evaluated by a set of questionnaires regarding various presentations during all the three phases of the menstrual cycle.

Results: Consecutive 102 cases with the diagnosis of IBS were included in the study and evaluated. The mean age of presentation was in mid-30s. Most of the subjects suffered from IBS mixed (IBS-M) type. More patients significantly suffered from constipation (27.27%) during the luteal phase of their menstrual cycles than the menstrual period of their cycles (p - 0.009). More than 50% of all the cases suffered from abdominal bloating during all phases of the menstrual cycle, which was quite disturbing and affected the quality of life. These IBS patients were more symptomatic with more significant limitation of daily activities, suffered from low quality of life, and obtained physician consultation during the menstrual phase as compared to other cycle stages.

Conclusion: Premenopausal female patients with IBS become much more symptomatic during the menstrual phase of the cycle than other stages of the cycle.

Effect of Exercise on NAFLD and Its Risk Factors: Comparison of Moderate versus Low Intensity Exercise

Background and Aims: Lifestyle (exercise and dietary) modification is the mainstay of treatment for non-alcoholic fatty liver disease (NAFLD). However, there is paucity of data on effect of intensity of exercise in management of NAFLD, and we aimed to study the effect of variable intensities of exercise on NAFLD. Methods: The study was performed in the Department of Gastroenterology of the SCB Medical College, Cuttack and the Biju Patnaik State Police Academy, Bhubaneswar. The subjects were police trainees [18 in a moderate intensity exercise group (MIG) and 19 in a low intensity exercise group (LIG)] recruited for a 6-month physical training course (261.8 Kcalorie, 3.6 metabolic equivalent in MIG and 153.6 Kcalorie, 2.1 metabolic equivalent in LIG). NAFLD was diagnosed by ultrasonography, with exclusion of all secondary causes of steatosis. All participants were evaluated by anthropometry (weight, height, body mass index (BMI), waist circumference), assessed for blood pressure and biochemical parameters (blood glucose, liver function test, lipid profile, serum insulin), and subjected to transabdominal ultrasonography before and after 6 months of physical training, and the results were compared. Results: Both the groups had similar BMI, fasting plasma glucose, AST, gamma-glutamyl transpeptidase, insulin, and homeostatic model assessment-insulin resistance (known as HOMA-IR) (p>0.05). However, subjects in the LIG were older and had lower alanine transaminase, higher triglycerides and lower high-density lipoproteins than MIG subjects. There was a significant reduction in BMI (27.0±2.1 to 26.8±2.0; p=0.001), fasting blood glucose (106.7±21.6 to 85.8±19.0; p<0.001), serum triglycerides (167.5±56.7 to 124.6±63.5; p=0.017), total cholesterol (216.8±29.2 to 196.7±26.6; p=0.037), low-density lipoprotein cholesterol (134.6±21.4 to 130.5±21.9; p=0.010), serum aspartate transaminase (39.3±32.2 to 30.9±11.4; p<0.001), serum alanine transaminase (56.6±28.7 to 33.0±11.3; p<0.001) and HOMA-IR (2.63±2.66 to 1.70±2.59; p<0.001) in the MIG. However, changes in these parameters in the LIG were non-significant. Hepatic steatosis regressed in 66.7% of the NAFLD subjects in the MIG but in only 26.3% of the LIG NAFLD subjects (p=0.030). Conclusions: Moderate rather than low intensity physical activity causes significant improvement in BMI, serum triglycerides, cholesterol, serum transaminases and HOMA-IR, and regression of ultrasonographic fatty change in liver among NAFLD subjects.

Fatty changes associated with N-Nitrosodiethylamine (DEN) induced hepatocellular carcinoma: a role of sonic hedgehog signaling pathway

Backgrounds and Aims: Hepatocellular Carcinoma (HCC) is the leading cause of cancer-related mortality across the world. Non-viral etiological factors including obesity and metabolic syndrome have now become prevalent cause of hepatocellular carcinoma. Sonic Hedgehog (SHH) pathway is activated in hepatocellular carcinoma but its role in regulation of lipogenic molecules during the hepatocarcinogenesis is not known. The aim of present study is to explore the role of SHH pathway in fatty changes associated with hepatocarcinogenesis at different stages and to further correlate the expression of SHH with lipogenic pathways.

Results: Our results demonstrated significant increase in lipidosis and fibrosis in DEN+CCl4 treated animals. It was simultaneously associated with the enhanced expression level of SHH, E2F1, adiponectin, and lipogenic molecules in DEN+CCl4 treated animals. These results were also corroborated with the similar findings in higher stage patients’ biospecimens.

Methods: N-Nitrosodiethylamine (DEN) and Carbon TetraChloride (CCl4) induced hepatocellular acrcinoma model in male Wistar rats were established to study the expression level of SHH pathway and associated fatty changes during different stages of hepatocarcinogenesis. The expression levels of SHH, E2F1, and lipogenic molecules were checked at different stages of hepatocellular carcinoma. These results were further compared with biospecimens of hepatocellular carcinoma patients of different stages.

Conclusions: Our results revealed an unknown aspect of SHH pathway in hepatocarcinogenesis via its control over lipogenesis. It gives insight into the lipogenic properties of DEN+CCl4 induced rodent hepatocarcinogenesis model and how SHH pathway operate to arbitrate this response.

Direct conversion of carbon nanofibers and nanotubes into diamond nanofibers and the subsequent growth of large-sized diamonds

We report a pulsed laser annealing method to convert carbon fibers and nanotubes into diamond fibers at ambient temperature and pressure in air. The conversion of carbon nanofibers and nanotubes into diamond nanofibers involves melting in a super undercooled state using nanosecond laser pulses, and quenching rapidly to convert into phase-pure diamond. The conversion process occurs at ambient temperature and pressure, and can be carried out in air. The structure of diamond fibers has been confirmed by selected-area electron diffraction in transmission electron microscopy, electron-back-scatter-diffraction in high-resolution scanning electron microscopy, all showing characteristic diffraction lines for the diamond structure. The bonding characteristics were determined by Raman spectroscopy with a strong peak near 1332 cm-1, and high-resolution electron-energy-loss spectroscopy in transmission electron microscopy with a characteristic peak at 292 eV for σ* for sp3 bonding and the absence of π* for sp2 bonding. The Raman peak at 1332 cm-1 downshifts to 1321 cm-1 for diamond nanofibers due to the phonon confinement in nanodiamonds. These laser-treated carbon fibers with diamond seeds are used to grow larger diamond crystallites further by using standard hot-filament chemical vapor deposition (HFCVD). We compare these results with those obtained without laser treating the carbon fibers. The details of diamond conversion and HFCVD growth are presented in this paper.

INASL Position Statements on Prevention, Diagnosis and Management of Hepatitis B Virus Infection in India: The Andaman Statements

Hepatitis B Virus (HBV) infection is one of the major causes of morbidity, mortality and healthcare expenditure in India. There are no Indian consensus guidelines on prevention, diagnosis and management of HBV infection. The Indian National Association for Study of the Liver (INASL) set up a taskforce on HBV in 2016, with a mandate to develop consensus guidelines for diagnosis and management of HBV infection, relevant to disease patterns and clinical practices in India. The taskforce first identified contentious issues on various aspects of HBV management, which were allotted to individual members of the taskforce who reviewed them in detail. A 2-day round table discussion was held on 11th and 12th February 2017 at Port Blair, Andaman & Nicobar Islands, to discuss, debate, and finalize the consensus statements. The members of the taskforce reviewed and discussed the existing literature threadbare at this meeting and formulated the 'INASL position statements' on each of the issues. The evidence and recommendations in these guidelines have been graded according to the Grading of Recommendations Assessment Development and Evaluation (GRADE) system with minor modifications. The strength of recommendations (strong: 1, weak: 2) thus reflects the quality (grade) of underlying evidence (A, B, C, D). We present here the INASL position statements on prevention, diagnosis and management of HBV in India.

Simple Anthropometric Indices are Useful for Predicting Non-alcoholic Fatty Liver Disease [NAFLD] in Asian Indians

BACKGROUND AND AIMS

With the rising prevalence of obesity and metabolic syndrome, nonalcoholic fatty liver disease (NAFLD) has become the most common liver disorder in both developed and developing nations. Several studies on NAFLD have described waist circumference, a surrogate marker of visceral fat accumulation and waist height ratio as a better screening tool for NAFLD and metabolic syndrome than body mass index (BMI). We conducted this study to assess simple abdominal obesity indices as a predictor of NAFLD and determine the appropriate cut-off levels with reference to NAFLD.

METHODS

1000 subjects with NAFLD detected ultrasonographically and 360 controls attending a Gastroenterology Clinic at Cuttack, Odisha were included in the study and subjected to detailed anthropometric measurements. The abdominal anthropometric cut offs were determined using ROC analysis. Statistical analysis was performed by using SPSS software version 16.

RESULTS

All receiver operating curve (ROC) curves of waist circumference, waist-height ratio and BMI were significantly above the diagonal line. There were no significant differences in the area under the curve values among these abdominal obesity indices in each gender. The appropriate cut-off point of waist circumference in screening for NAFLD was 89 cm for men and 84 cm for women and the optimal cut-off point of waist-height ratio was 0.53 for men and 0.57 for women and the cut-off point of waist to hip ratio was 0.94 for men and 0.87 for women with very good sensitivity and specificity.

CONCLUSIONS

The simple anthropometric parameters, such as BMI, waist circumference, waist-hip ratio and waist-height ratio are useful for predicting NAFLD in Indian adults. The anthropometry cut offs would be very useful in setting target points of life style modification and weight reduction. Besides, our study also clearly demonstrated that a simple assessment of BMI is as efficacious as other anthropometry parameters in predicting NAFLD.

Leech Infestation Presenting as Severe Rectal Bleeding

Leech or Hirudinea is a major parasite in rural India. Normally, the leech attacks the skin and exposed areas. An 18‑year‑old child presented with bleeding per rectum for 1 day along with giddiness. A history revealed that while the boy was working in a field, had acrawling sensation in the perianal area. After admission, the patient was resuscitated with crystalloids and a limited colonoscopy revealed a rectal ulcer with a leech head attached to its base. The hooklets were removed using foreign body removal forceps and injection Adrenaline at 1:10,000 dilutions was injected in 1 ml aliquots into four quadrant to achieve hemostasis. There was no postprocedure complication. Leech infestation can present with exsanguinating acute severe lower gastrointestinal bleed.

Anti-hepatitis B virus (HBV) response of imiquimod based toll like receptor 7 ligand in hbv-positive human hepatocelluar carcinoma cell line

Background

Toll like receptors (TLRs) play an important role in innate immunity and various studies suggest that TLRs play a crucial role in pathogenesis of hepatitis B virus (HBV) infection. The present study aims in looking into the status of crucial host and viral gene expression on inciting TLR7.

Methods

The transcription of TLR7 pathway signaling molecules and HBV DNA viral load were quantified by Real Time-PCR after stimulation of TLR7 with its imiquimod based ligand, R837. Cell cycle analysis was performed using flow-cytometry. Expression of TLR7 and chief cell cycle regulator governing G1/S transition, p53 was also seen in liver biopsysss samples of CHB patients. HBV induced alteration in histone modifications in HepG2 cells and its restoration on TLR7 activation was determined using western blot.

Results

The TLR7 expression remains downregulated in HepG2.2.15 cells and in liver biopsy samples from CHB patients. Interestingly HBV DNA viral load showed an inverse relationship with the TLR7 expression in the biopsy samples. We also evaluated the anti-viral activity of R837, an agonist of TLR7. It was observed that there was a suppression of HBV replication and viral protein production upon TLR7 stimulation. R837 triggers the anti-viral action probably through the Jun N-terminal Kinase (JNK) pathway. We also observed a downregulation of histone H3K9Me3 repression mark upon R837 treatment in HBV replicating HepG2.2.15 cells, mimicking that of un-infected HepG2 cells. Additionally, the G1/S cell cycle arrest introduced by HBV in HepG2.2.15 cells was released upon ligand treatment.

Conclusion

The study thus holds a close insight into the changes in hepatocyte micro-environment on TLR7 stimulation in HBV infection.

Electronic supplementary material

The online version of this article (doi:10.1186/s12879-017-2189-z) contains supplementary material, which is available to authorized users.

Anti-viral role of toll like receptor 4 in hepatitis B virus infection: An in vitro study

AIM

Toll like receptors plays a significant anti-viral role in different infections. The aim of this study was to look into the role of toll like receptor 4 (TLR4) in hepatitis B virus (HBV) infection.

METHODS

Real time PCR was used to analyze the transcription of TLR4 signaling molecules, cell cycle regulators and HBV DNA viral load after triggering the HepG2.2.15 cells with TLR4 specific ligand. Nuclear factor (NF)-κB translocation on TLR4 activation was analyzed using microscopic techniques. Protein and cell cycle analysis was done using Western Blot and FACS respectively.

RESULTS

The present study shows that TLR4 activation represses HBV infection. As a result of HBV suppression, there are several changes in host factors which include partial release in G1/S cell cycle arrest and changes in host epigenetic marks. Finally, it was observed that anti-viral action of TLR4 takes place through the NF-κB pathway.

CONCLUSION

The study shows that TLR4 activation in HBV infection brings about changes in hepatocyte microenvironment and can be used for developing a promising therapeutic target in future.

A 10-year-old child presenting with syndromic paucity of bile ducts (Alagille syndrome): a case report

Background

Alagille syndrome, a rare genetic disorder with autosomal dominant transmission, manifests with five major features: paucity of interlobular bile ducts, characteristic facies, posterior embryotoxon, vertebral defects, and peripheral pulmonary stenosis. Globally, only 500 cases have so far been reported, with only five cases reported in the Indian subcontinent. Rarely, Alagille syndrome also presents with skin manifestations and early-onset chronic liver disease, which was found in our case. We believe that we report what could be the first case of Alagille syndrome presenting with café au lait spots, as no such published case report could be found in the literature.

Case presentation

We report an unusual case of childhood cholestatic jaundice with neonatal onset of jaundice. A 10-year-old boy from the Indian subcontinent presented with obstructive jaundice from early infancy. He also had recurrent fractures of his upper limb bones, intermittent bleeding from his nose, productive cough, decreased night vision, hyperpigmented spots over his skin, and progressive enlargement of his abdomen. Histological examination of a liver biopsy specimen revealed a paucity of bile ducts and changes suggestive of chronic liver disease. Our patient was diagnosed with Alagille syndrome and managed conservatively but died 1 year after the final diagnosis.

Conclusions

This particular syndromic form of paucity of bile duct disorder has been rarely reported in the Indian literature so far. Our case is notable because the child had café au lait spots and very early onset of chronic liver disease, which is quite rare in Alagille syndrome. We believe this to be the first case report on Alagille syndrome manifesting with café au lait syndrome and such early onset of chronic liver disease.

Socioeconomic impact of alcohol in patients with alcoholic liver disease in eastern India

AIM

The aim of this study is to estimate the socioeconomic impact of alcohol use on patients with alcoholic liver disease (ALD) and their families.

METHODS

The demographic and socioeconomic data were collected from hospitalized ALD patients and attendants using a self designed non validated questionnaire and analyzed.

RESULTS

Study subjects included 100 consecutive ALD patients (all males). Sixty percent were between 30 and 50 years. Most were married (96 %), literate (63 %), either businessmen (37 %) or employed (30 %) and belonged to middle socioeconomic class. Ninety percent started alcohol use before age 30 years and half during teenage. Mean alcohol intake was 190 mL/day (mean duration 23 years); 60 % consumed alcohol daily. Concomitant tobacco abuse was noted in 79 %. Average expenditure on alcohol was Rs 3800/month. Average hospitalizations for ALD related problems was 2.6 times/year with average expenditure of INR 30,000 (~440 US$) during each hospitalization. For treatment expenses, 86 % of patients borrowed money from friends/relatives, 36 % used saving deposits, and 4 % sold personal belongings. Eleven percent lost their job, and 7 % sold immovable property. In 43 % of cases, children were deprived of education. Besides, 52 % had disturbed social and family life, 34 % abused their spouse, 20 % suffered accidents, and 37 % indulged in physical violence.

CONCLUSION

Majority of ALD patients and their families had disturbed social and family life and incurred severe financial loss arising of alcohol use.

Biochemical Profile of Nonalcoholic Fatty Liver Disease Patients in Eastern India with Histopathological Correlation

Aminotransferase assay is often used as a screening test as well as an endpoint for resolution of disease in nonalcoholic fatty liver disease (NAFLD). Aim of the study was to evaluate the relationship of transaminase level with metabolic variables and histology in NAFLD. Single center observational study was conducted in a gastroenterology clinic at Cuttack in coastal Odisha. Subjects were consecutive patients presenting with functional bowel disease and undergoing abdominal sonography. All participants were evaluated for the presence of metabolic syndrome (MS), insulin resistance, liver function test and lipid profile. Various parameters were compared between NAFLD subjects and controls. 53.5 % of NAFLD had normal serum transaminases, whereas 20.8 % of healthy controls had transaminitis. NAFLD patients had significantly higher BMI, fasting plasma glucose, serum transaminases, serum triglycerides, serum insulin and homeostatic model assessment (HOMA) IR than controls. NAFLD patients who had transaminitis had significantly higher incidence of MS and higher mean HOMA IR than those without. There was no significant difference in histopathological features between NAFLD with and without transaminitis. To conclude, over half of NAFLD subjects do not have transaminitis while transaminitis is present in a fifth of healthy people without fatty liver. Hence serum transaminase should not be used as screening test for NAFLD. NAFLD patients with transaminitis had a higher incidence of MS and insulin resistance than those without. However, there was no significant difference in histopathological features between these two groups.

Modification of properties of yttria stabilized zirconia epitaxial thin films by excimer laser annealing

This study focuses on the ultrafast improvement of surface wettability, electrical, and room temperature magnetic characteristics of cubic zirconia single crystalline thin films after laser annealing. The point defects generated by the laser treatment are envisaged to play a critical role in altering the above properties. Yttria stabilized zirconia (YSZ) thin films were epitaxially grown on Si(100) substrates by pulsed laser deposition technique and subsequently annealed by a KrF excimer laser beam (τ = 25 ns) using low-energy laser pulses. An atomically sharp interface, parallel to the film free surface, between laser annealed layer and the pristine region was observed. The single crystalline nature of thin films was preserved following the laser treatment. The laser-solid interaction with YSZ led to the introduction of point defects, i.e., oxygen vacancies, resulting in a strained structure which, in turn, resulted in the formation of a tetragonal-like zirconia. With the increase of number of laser pulses the laser treated films got highly disordered due to the high concentration of the point defects, while maintaining their crystalline nature. Although the surface of the pristine sample showed weak hydrophilic characteristics (contact angle ∼ 73°), the laser annealed samples exhibited significantly improved hydrophilic characteristics. It was found that there is an optimum number of laser pulses where the maximum hydrophilicity (contact angle ∼ 22°) is obtained. The carrier concentration in the sample with the highest hydrophilicity was determined to be higher by about 5 orders of magnitude compared to the pristine sample. This sample possessed the lowest electrical resistivity. The laser annealed YSZ epilayers showed a superior room-temperature ferromagnetic behavior, compared to the pristine samples. A 2-fold enhancement in the magnetization of the samples was observed following the laser treatment which is a clear demonstration of the key role of defects and their transient distribution throughout the lattice. All these observations were correlated with the formation of point defects due to the photon interaction with YSZ and absorption of energy of the KrF laser photons to produce defects.

CRYSTAL STRUCTURE AND DEFECTS IN NITROGEN-DEFICIENT GaN

We have studied crystal structure and associated defects in GaN films grown on sapphire under nitrogen-deficient conditions by metalorganic chemical vapor deposition (MOCVD) and pulsed laser deposition (PLD). The structural quality of the PLD films grown at 750 °C was comparable with those grown by MOCVD at 1050 °C having threading dislocations density of about 1010 cm−2 at a film thickness 150-200 nm. Microstructure of the PLD films grown at temperatures above 780°C was found to be similar to that of nitrogen-deficient MOCVD films indicating the loss of nitrogen due to thermal decomposition of the nitride layers. Nitrogen-deficient MOCVD and PLD films exhibit polycrystalline structure with a mixture of cubic zinc-blende and wurtzite hexagonal GaN grains retaining tetragonal bonding across the boundaries and hence the epitaxial orientations and polarity. Renucleation of the wurtzite phase at different {111} planes of cubic GaN results in a rough and faceted surface of the film. Most of the stoichiometric films displayed (0001) Ga-face polarity, but the renucleated inclined wurtzite grains grew in the opposite N-face polarity. The major defects related to the cubic structural metastability are stacking faults and microtwins which being nuclei of the metastable cubic phase have an extremely low energy. We elucidate that the cubic phase is more stable under the nitrogen deficiency and, therefore, can exist without decomposition at higher nitrogen vacancy concentrations in the material.

Nanosecond laser switching of surface wettability and epitaxial integration of c-axis ZnO thin films with Si(111) substrates

We have achieved integration of polar ZnO[0001] epitaxial thin films with Si(111) substrates where cubic yttria-stabilized zirconia (c-YSZ) was used as a template on a Si(111) substrate. Using XRD (θ-2θ and φ scans) and HRTEM techniques, the epitaxial relationship between the ZnO and the c-YSZ layers was shown to be [0001]ZnO || [111]YSZ and [21¯1¯0]ZnO || [1¯01](c-YSZ), where the [21¯1¯0] direction lies in the (0001) plane, and the [1¯01] direction lies in the (111) plane. Similar studies on the c-YSZ/Si interface revealed epitaxy as (111)YSZ || (111)Si and in-plane (110)YSZ || (110)Si. HRTEM micrographs revealed atomically sharp and crystallographically continuous interfaces. The ZnO epilayers were subsequently laser annealed by a single pulse of a nanosecond excimer KrF laser. It was shown that the hydrophobic behavior of the pristine sample became hydrophilic after laser treatment. XPS was employed to study the effect of laser treatment on surface stoichiometry of the ZnO epilayers. The results revealed the formation of oxygen vacancies, which are envisaged to control the observed hydrophilic behavior. Our AFM studies showed surface smoothing due to the coupling of the high energy laser beam with the surface. The importance of integration of c-axis ZnO with Si(111) substrates is emphasized using the paradigm of domain matching epitaxy on the c-YSZ[111] buffer platform along with their out-of-plane orientation, which leads to improvement of the performance of the solid-state devices. The observed ultrafast response and switching in photochemical characteristics provide new opportunities for application of ZnO in smart catalysts, sensors, membranes, DNA self-assembly and multifunctional devices.

Interface magnetism in epitaxial BiFeO3-La0.7Sr0.3MnO3 heterostructures integrated on Si(100)

We report on the heteroepitaxial growth of ferroelectric (FE)-antiferromagnetic (AFM) BiFeO3 (BFO) on ferromagnetic La0.7Sr0.3MnO3 (LSMO), integrated on Si(100) using pulsed laser deposition via the domain matching epitaxy paradigm. The BFO/LSMO films were epitaxially grown on Si(100) by introducing epitaxial layers of SrTiO3/MgO/TiN. X-ray diffraction, scanning electron microscopy, high-resolution transmission electron microscopy, X-ray photo absorption spectroscopy, and atomic force microscopy were employed to fully characterize the samples. Furthermore, we have investigated the magnetic behavior of this five layer heterostructure, in which a d(5) system (Fe(3+)) manifested in FE-AFM BFO is epitaxially conjoined at the interface to a multivalent transition metal ion such as Mn(3+)/Mn(4+) in LSMO. The temperature- and magnetic field-dependent magnetization measurements reveal an unexpected enhancement in magnetic moment and improved magnetic hysteresis squareness originating from the BFO/LSMO interface. We observe a stronger temperature dependence of HEB when the polarity of field cooling is negative as compared to positive field cooling. We believe such an enhancement in magnetic moment and magnetic coupling is likely directly related to an electronic orbital reconstruction at the interface and complex interplay between orbital and spin degrees of freedom, similar to what has previously been reported in the literature. Future work will involve the linearly polarized X-ray absorption measurements to prove this hypothesis. This work represents a starting step toward the realization of magneto-electronic devices integrated with Si(100).

Defect mediated photocatalytic decomposition of 4-chlorophenol on epitaxial rutile thin films under visible and UV illumination

We show that pure rutile TiO(2) can be photo-responsive even under low energy visible light after annealing in vacuum where we envisage that the point defects, i.e. oxygen vacancies and titanium interstitials, serve an important role. In this study, single crystal rutile films were grown by the pulsed laser deposition technique and then vacuum annealed under different oxygen pressures to introduce defects into their lattices. 4-chlorophenol was selected as a model material and decomposed by the annealed TiO(2) films where the maximum photocatalytic reaction rate constants were determined as 0.0107 and 0.0072 min(-1) under UV and visible illumination. Epitaxial growth along the [200] direction was confirmed by φ-scan and 2θ-scan XRD and the epitaxial relationship between the rutile film and the c-sapphire substrate was explained as (100)[010](R) [parallel] (0001)[12[combining overline]10](S). The formation of atomically sharp interfaces and the epitaxial growth were ascertained by annular dark-field STEM imaging. Based on the XPS, UV-vis and PL spectroscopy results, it was found that the defect concentration increased after annealing under lower pressures, e.g. 5 × 10(-6) Torr. In contrast, more perfect crystals were obtained when the films were annealed under high oxygen pressures, namely 5 × 10(1) Torr. The morphology of the films was also investigated by employing an AFM technique. It was observed that increase of the annealing pressure results in the formation of larger grains. It was also found that the electrical resistivity of the rutile films strongly increased by about three orders of magnitude when the annealing pressure increased from 5 × 10(-4) to 5 × 10(1) Torr.

Defects in room-temperature ferromagnetic Cu-doped ZnO films probed by x-ray absorption spectroscopy

We report a comprehensive study of the defects in room-temperature ferromagnetic (RTFM) Cu-doped ZnO thin films using x-ray absorption spectroscopy. The films are doped with 2 at.% Cu, and are prepared by reactive magnetron sputtering (RMS) and pulsed laser deposition (PLD), respectively. The results reveal unambiguously that atomic point defects exist in these RTFM thin films. The valence states of the Cu ions in both films are 2(+). In the film prepared by PLD, the oxygen vacancies (V(O)) form around both Zn ions and Cu ions in the hexagonal wurtzite structure. Upon annealing of the film in O(2), the V(O) population reduces and so does the RTFM. In the film prepared by RMS, the V(O)s around Cu ions are not detected, and the V(O) population around Zn ions is also smaller than in the PLD-prepared film. However, zinc vacancies (V(Zn)) are evidenced. Given the low doping level of spin-carrying Cu ions, these results provide strong support for defect-mediated ferromagnetism in Cu-doped ZnO thin films.

The Inverse Hall-Petch Effect—Fact or Artifact?

This paper critically reviews the data in the literature which gives softening—the inverse Hall-Petch effect—at the finest nanoscale grain sizes. The difficulties with obtaining artifactfree samples of nanocrystalline materials will be discussed along with the problems of measurement of the average grain size distribution. Computer simulations which predict the inverse Hall-Petch effect are also noted as well as the models which have been proposed for the effect. It is concluded that while only a few of the experiments which have reported the inverse Hall-Petch effect are free from obvious or possible artifacts, these few along with the predictions of computer simulations suggest it is real. However, it seems that it should only be observed for grain sizes less than about 10 nm.

Electrical Transport Dissipation Effects in Epitaxial Y1ba2cu3o7.X Thin Films

The electrical transport properties of a series of Y1Ba2Cu307.x thin films deposited onto single crystal substrates by thermal coevaporation and laser ablation were investigated. For fully epitaxial, c‐oriented films on (001) substrate surfaces, the critical current density Jc showed large high‐field enhancements for the film aligned with H parallel to the copper‐oxygen planes. With H||c, a precipitous decay of Jc with increasing field is described by thermally activated flux motion. Films on (110) SrTiO3 substrates were comprised of finely‐divided arrays of grains having [110], and <103>‐type orientations, and exhibited granular behavior. For these “triaxial” films, the transport dissipation was also thermally activated but with much smaller energy barriers.

Pulsed Laser Deposition of High Tc Superconducting Thin Films: Deposition Physics and in-Situ Processing

The pulsed laser evaporation (PLE) technique for deposition of thin films is characterized by a number of unique properties. Based on the experimental characteristics, a theoretical model is developed which considers the formation and anisotropic three dimensional expansion of the laser generated plasma. This model explains most of the experimental features observed in PLE. We have also employed the PLE technique for in-situ fabrication of YBa2Cu3O7 superconducting thin films on different substrates in the temperature range of 500–650°C. At temperatures below 600–C, a biased interposing ring between the substrate and the target was found to significantly improve the superconducting properties. The minimum ion channeling yields were between 3-3.5 % for films deposited on (100) SrTiO3 and (100) LaA1O3 substrates. The films exhibit very high critical current densities (Jc) with maximum values exceeding 6.5 x 106 amps/cm2 for silver doped YBa2Cu3O7 films on (100) LaA1O3 substrates, and the Jc also varies anisotropically with the magnetic field.

In-Situ Preparation and Characterization of Superconducting Thin Films and Related Materials by Mocvd for the Development of Three Terminal Switching Devices

Metalorganic chemical vapor deposition (MOCVD) has the potential of emerging as a major technique for the fabrication of high temperature superconductor devices. In this paper, we present preliminary results of in-situ deposition of Y-Ba-Cu-0 thin films (Tc = 79K) by rapid isothermal processing assisted MOCVD on BaF2/silicon substrates.

Laser Assisted Techniques for Diamond and Diamondlike Thin Films

We have deposited diamond-shaped particles using a non equilibrium process of laser ablation from a solid graphite target in a hydrogen discharge. The nucleation on the heated silicon surface occurs in small regions of ∼ 0.1 to 0.5 mm covering a small fraction of the surface. The faceting of the crystals observed are mainly octahedral [111] faces. The results of using an eximer laser to ablate a graphite target are described. SEM micrographs show octahedral faceting. Micro Raman spectroscopy on the crystalline features exhibit two bands at 1348 and at ∼ 1600 cm−1. The peak position and large FWHM suggests the existence of disordered sp3 bonding or short range order existing in the film. Another possibility is the existence of a stress state in the crystal due to the non equilibrium nature and the high rate of growth of the crystals. We have also irradiated HFCVD grown diamond film with a XeCl UV- eximer laser. The results indicated that sp2 bonded graphitic and amorphous component are selectively ablated, enhancing the sp3 hybrid bonds in the film.

Laser-Target Interactions and its Effect on Surface Morphology of Laser Deposited thin films

The laser-target interactions during pulsed laser evaporation (PLE) of materials have been investigated in detail. Sub-surface temperatures have been calculated to be higher than the surface temperatures during planar surface evaporation of the target material. While the evaporating surface is being cooled due to the latent heat of vaporization, sub-surface superheating occurs due to the finite absorption depth of the laser beam. Detailed computer simulations have been carried out to understand the evaporation characteristics of different targets (Si, YBa2Cu3O7 ) as a function of laser and target variables. For silicon targets irradiated with 25 nanosecond laser pulses (energy density of 10J/cm2, absorption coefficient of 105 cm−1), the sub-surface temperatures were found to be more than 2000°C above the surface evaporation temperatures. The sub-surface superheating increased with increasing energy density and absorption depth. This internal superheating effects may lead to volume evaporation of the target where a solid material in form of particles may be ejected from the target surface. Based on the above understanding, parameters required to reduce the particle density in PLE films are predicted.

Characterization of Ion Implanted Silicon by Spectroscopic Ellipsometry and Cross Section Transmission Electron Microscopy

This paper deals with the application of spectroscopic ellipsometry (SE) and cross-section transmission electron microscopy (XTEM), to the characterization of damaged surface layers in ion implanted Si single crystal. Si samples of 2–6Ω·cm resistivity and <100> orientation were implanted with 28Si+ ions in the dose range of 1.0 × 1016–1.5 × 1016 ions/cm2 using ion energies of 100 and 200 keV. Ion current densities were varied from 6 to 200 μA/cm2. Depth profiles of the implanted samples were evaluated from the spectroscopic ellipsometry data. These calculated profiles were compared with the TEM micrographs of the cross sections of the samples. Excellent agreement is obtained between the two characterization techniques. The characteristics of the depth profiles of the samples, as established by the two techniques, is shown to be the result of annealing occuring during implantation.

Pulsed Laser Melting of Amorphous Silicon: Time-Resolved and Post-Irradiation Studies

Measurements of the time of the onset of melting of self-implantation amorphized (a) Si, during an incident laser pulse, have been combined with modified melting model calculations and measurements of surface melt duration to demonstrate that the thermal conductivity, Ka, of a-Si is very low (≃0.02 W/cm-K). Ka is also shown to be the dominant parameter determining the dynamical response of ionimplanted Si to pulsed laser radiation; the latent heat and melting temperature of a-Si are relatively unimportant. Cross-sectional transmission electron micrographs on implantation-amorphized Si layers of several different thicknesses show that for energy densities less than the threshold value for complete annealing there are usually two distinct regions in the re-solidified a-Si, consisting of fine-grained and large-grained polycrystalline Si, respectively. The presence of the fine-grained poly-Si suggests that bulk nucleation occurs directly from the highly undercooled liquid phase. Thermal melting model calculations suggest that the nucleation temperature, Tn is ≃1200°C.

Modeling of Thermal Stresses in Composite Diamond Coatings and Mechanisms of Improvement of Adhesion

Thermal stress influences adhesion of many coatings applied on tool substrates. Management of thermal stresses is important for improvement of coatings and tool life. We have shown that stresses can be controlled by developing a composite layer of diamond with carbides and nitrides such as TiC or TiN. We have modeled the thermal stresses in these composite diamond coatings using finite element analysis. The composite diamond coatings consist of a discontinuous layer of diamond with an embedded layer of TiC or TiN, and a top layer of continuous diamond. For comparison, a single layer of diamond coating has also been used. The thermal stresses in these coatings on WC(Co) and Si3N4 tool substrates were calculated. Results show that the thermal stresses at the interface between the coatings and the substrate are relaxed after introducing the composite layers. This stress relaxation is responsible for the improvement of the adhesion of composite coatings.

Low Temperature Laser Physical Vapor Deposition of Multilayered Thin Films

We have investigated the formation of various multilayer thin films by the laser physical vapor deposition technique. A multi stage target holder was constructed to perform all process steps in-situ; target/substrate cleaning, deposition, and annealing. The laser physical vapor deposition technique offers many advantages over conventional physical vapor techniques, such as, lower substrate temperature, microstructural control, and very low contamination levels. Film thickness can be controlled from near atomic to micron dimensions. A layer-by-layer (two dimensional) growth can be achieved, resulting in nonequilibrium structures. The films were analyzed using cross-section and high resolution transmission electron microscopy (TEM). The significant reduction in substrate temperature for the formation of high quality multilayer and epitaxial films opens up many new areas of applications requiring reduced thermal-budget processing.

Growth of High Quality Single Crystal ZnO Films on Sapphire by Pulsed Laser Ablation

The structural and optical characterizations of single crystal zinc oxide films on sapphire have been performed. The ZnO films were deposited by pulsed laser deposition in an oxygen environment. These films were annealed in oxygen for further improvement in the oxygen stoichiometry. Both as-deposited and oxygen annealed films were high quality single crystal as characterized by X-ray diffraction and transmission electron microscopy. The defect density, comprised mainly of dislocations and stacking faults, was low as compared to high quality films of III-nitrides deposited on sapphire. Under these growth conditions, the ZnO films grow two dimensionally on sapphire as opposed to GaN which grows three dimensionally. The band edge photoluminescence was found to be dominant, and an order of magnitude higher in the annealed films. Transmission measurements and the electrical resistivity of the annealed films also show the films were of high quality after annealing. It is envisaged that these improvements in the quality of the ZnO films occur as a result of reduction of oxygen vacancies and the density of point defects.

Epitaxial Growth of Magnetic Nickel Nanodots by Pulsed Laser Deposition

Epitaxial nickel magnetic nanodots were obtained by pulsed laser deposition (PLD) technique on Si (100) substrate using epitaxial TiN film as the template. Characterization methods include: high-resolution transmission electron microscopy (HRTEM), scanning transmission electron microscopy (STEM) Z-contrast imaging, selected area electron diffraction (SAD), and X-ray diffraction (XRD) techniques. The results showed that as long as no coalescence between neighboring dots occurred, the dots are all single crystal. The predominant orientation relationship observed is Ni (100) // TiN (100) // Si (100), the so-called “cube-on-cube” orientation relationship. Other rotational orientation relationships, where the nickel crystal rotates an angle with respect to TiN (011) directions, were also observed. The dots are in faceted island shapes, bounded by (111) and (001) facets. The actual size of dots varies from a few nanometers to tens of nanometers, depending on the deposition time and temperature. The shape of a certain dot was found to be closely related to its epitaxial orientation. Effects of deposition temperature and template crystalline quality were studied. It was found that deposition temperature in a certain range does not have much influence on the epitaxial orientation of dots, while the crystalline quality of titanium nitride (the underlying template) is primarily responsible for the orientation variation. At the optimum condition, samples with a large fraction of cube-on-cube orientated nickel dots could be obtained in a rather wide temperature range (up to 250 °C), as evidenced by the strong reflections from both SAD and XRD. Samples containing more than one layer of nickel and titanium nitride matrix were also studied. The results showed that the degree of orientation perfection could be greatly improved by decreasing the size of dots.

Growth Of ZnO/MgZnO Superlattice On Sapphire

The optical and structural properties of ZnO/ MgZnO superlattices were investigated by transmission electron microscope, transmission measurement and photoluminescence. The uncoupled wells ranged in thickness from ∼30 Å to 75 Å. Modulation of the Mg content was observed in Z-contrast TEM indicating the alloy composition was periodic. The density of stacking faults in the superlattice was extremely high, however the photoluminescence in the narrowest well case was blue shifted, and substantially brighter than comparable bulk layers of ZnO and MgZnO indicating that the emission was enhanced. Excitonic features were observed in the optical absorption spectra and also revealed that diffusion of Mg from the barrier layers into the well was occurring.

Optical and Structural Characteristics Of Gold Nanocrystallites Embedded in a Dielectric Matrix

We have fabricated Gold (Au) crystallites in amorphous alumina matrix by pulsed laser deposition. The characterization of these multilayer sequences was performed by high resolution transmission electron microscopy (HRTEM) and optical transmission measurements. TEM studies revealed the morphology and the microstructure of these composites. The optical transmission spectra showed characteristic surface plasma resonance of Au particles confined by the host dielectric matrix. These resonances fall in the visible spectral range. The importance of pulsed laser deposition in fabricating these composite films is discussed.