Role of C and B4C barrier layers in controlling diffusion propagation across the interface of Cr/Sc multilayers.

The optical performance of low-bilayer-thickness metallic multilayers (ML) can be improved significantly by limiting the intermixing of consecutive layers at the interfaces. Barrier layers are supposed to exhibit a decisive role in controlling diffusion across the interfaces. The element-specific grazing incidence extended X-ray absorption fine structure technique using synchrotron radiation has been used in conjunction with grazing incidence X-ray reflectivity and diffuse X-ray scattering measurements to study the impact of the two most common barrier layers, viz., C and B4C, at the interfaces of Cr/Sc MLs. The diffusion propagation is reduced by both the barrier layers; however, it is found that the improvement is more significant with the B4C barrier layer. It is seen that C forms an intermixed layer with Sc and leads to carbide formation at the interface, which then acts as shielding and prevents further interdiffusion, while B4C hardly penetrates into Sc and stops the overlap between Sc and Cr directly by wetting the corresponding interface. Thus, the above measurements reveal crucial and precise information regarding the elemental diffusion kinetics at the interfaces of Cr/Sc MLs in a non-destructive way, which is very important for technological applications of these MLs as X-ray optical devices.

Retrospective analysis and risk of progression of partial anterior cruciate ligament injuries in a young population.

BACKGROUND: The anterior cruciate ligament (ACL) is a common knee ligament injury. Partial ACL tears are common, and at least 10-27% of isolated ACL tears are diagnosed as partial tears. Patients with partial tears have high risk of progression of tears to complete tears, which may require surgical reconstruction. The risk factors associated with the progression to a complete tear are poorly understood. METHODS: The present case-control study assessed the incidence and risk factors for the progression of conservatively treated partial ACL tears to complete tears in 351 patients younger than 45 years. The diagnosis of partial ACL tears was based on clinical evaluation, side-to-side difference on Rolimeter, and magnetic resonance imaging. These patients were managed conservatively and followed up for a mean of 17.5 months or until the progression of the tear into a complete tear, requiring surgery. The patients in whom the tear progressed to complete tear (group P) were compared with those in whom the tear remained stable for a minimum of 18-month follow-up period (group S). RESULTS: Of the 351 partial ACL tear patients, 166 (47.3%) patients progressed to a complete tear at a mean duration of 17.5 months, whereas the tear in 185 (52.7%) patients remained stable and did not progress to a complete tear. Group P had mean international knee documentation committee (IKDC) scores and Tegner scores of 95.7 ± 3.7 and 7.6 ± 1.6, respectively, before the injury, and scores decreased to 52.4 ± 4.1 and 5.7 ± 2.2, respectively, at the 24-month follow-up. CONCLUSION: Partial ACL tear progressed to a complete tear in 47.3% of evaluated patients. The associated risk factors were age less than 35 years, rigorous physical activities, high ACL-Return to Sport after Injury score during early rehabilitation days, early return to activity, and pivoting contact sports.

Assessment of Mobilization Potential of Per- and Polyfluoroalkyl Substances for Soil Remediation.

This study investigated the mobilization of a wide range of per- and polyfluoroalkyl substances (PFASs) present in aqueous film-forming foams (AFFFs) in water-saturated soils through one-dimensional (1-D) column experiments with a view to assessing the feasibility of their remediation by soil desorption and washing. Results indicated that sorption/desorption of most of the shorter-carbon-chain PFASs (C ≤ 6) in soil reached greater than 99% rapidly─after approximately two pore volumes (PVs) and were well predicted by an equilibrium transport model, indicating that they will be readily removed by soil washing technologies. In contrast, the equilibrium model failed to predict the mobilization of longer-chain PFASs (C ≥ 7), indicating the presence of nonequilibrium sorption/desorption (confirmed by a flow interruption experiment). The actual time taken to attain 99% sorption/desorption was up to 5 times longer than predicted by the equilibrium model (e.g., ∼62 PVs versus ∼12 PVs predicted for perfluorooctane sulfonate (PFOS) in loamy sand). The increasing contribution of hydrophobic interactions over the electrostatic interactions is suggested as the main driving factor of the nonequilibrium processes. The inverse linear relationship (R2 = 0.6, p < 0.0001) between the nonequilibrium mass transfer rate coefficient and the Freundlich sorption coefficient could potentially be a useful means for preliminary evaluation of potential nonequilibrium sorption/desorption of PFASs in soils.

Comparing the Leaching Behavior of Per- and Polyfluoroalkyl Substances from Contaminated Soils Using Static and Column Leaching Tests.

Soil contaminated with aqueous film-forming foams (AFFFs) containing per- and polyfluoroalkyl substances (PFASs) at firefighting training sites has become a major concern worldwide. To date, most studies have focused on assessing soil-water partitioning behavior of PFASs and the key factors that can affect their sorption, whereas PFASs leaching from contaminated soils have not yet been widely investigated. This study evaluated the leaching and desorption of a wide range of PFASs from twelve contaminated soils using the Australian Standard Leaching Procedure (ASLP), the U.S. EPA Multiple Extraction Procedure (MEP), and Leaching Environmental Assessment Framework (LEAF). All three leaching tests provided a similar assessment of PFAS leaching behavior. Leaching of PFASs from soils was related to C-chain lengths and their functional head groups. While short-chain (CF2 ≤ 6) PFASs were easily desorbed and leached, long-chain PFASs were more difficult to desorb. PFASs with a carboxylate head group were leached more readily and to a greater extent than those with a sulfonate or sulfonamide head group. Leaching of long-chain PFASs was pH-dependent where leaching increased at high pH, while leaching of short-chain PFASs was less sensitive to pH. Comparing different leaching tests showed that the results using the alkaline ASLP were similar to the cumulative MEP data and the former might be more practical for routine use than the MEP. No single soil property was adequately able to describe PFAS leaching from the soils. Overall, the PFAS chemical structure appeared to have a greater effect on PFAS leaching from soil than soil physicochemical properties.

On the universality of medical device regulations: the case of Benin.

BACKGROUND: Regulatory frameworks surrounding medical devices (MDs) and medical locations are of utter importance for safeguarding patients and users, and for granting a universal access to healthcare. Currently, as the main existing regulatory frameworks are drafted by high-income countries, they pretend to be general and applicable globally, but fail to understand particular contexts, specifically those in low-resource settings (LRSs), resulting, therefore, inapplicable. In particular, LRSs present a varied situation, with legal transplants of guidelines from their previous colonial regimes. This apparently theoretical issue, is, effectively, a tangible and rising matter of concern, given the ever-increasing number of MD patent applications per year, as well as the appearance of low- and middle-income countries (LMICs) on the MD market itself. This article will focus on the European Regulation on MDs 745/2017 and its applicability in LRSs, specifically presenting the case of Benin, a Sub-Saharan African country. METHODS: This work is based on a field study conducted in 2019 in Benin, which is particularly exemplar to show the complexity of the "legal transplantation" concept. A multidisciplinary approach, comprising the standard tools and methods of ethics, law, and biomedical engineering, was used to draft a heuristic hermeneutic framework, and to analyse related bioethical issues concerning Medical Device Regulations (MDRs) in LRSs, the role of Maintenance, and other sociological questions; as well as the rural population's perception on MDs and health technologies, and the role of ethics in the hospitals of LRSs. RESULTS: The definition of these themes helped approach the local perspective and define the research questions. Downstream of the analysis of the Medical Devices Regulations, the Maintenance and other bioethical issues in Benin, the heuristic hermeneutic framework was created to guide a shift in the paradigm of law and regulation making, so as to make them more contextualised and inclusive, globally. CONCLUSION: This article proposes a framework that will help policymakers take into account the particularism of each context, especially those of the most vulnerable countries, when drafting and issuing regulatory frameworks, promoting an ever-evolving model of universalism.

Does the immediate repair of Bankart lesion following first dislocation reduce the chances of recurrence after arthroscopic repair in soldiers?

PURPOSE: The study attempted to compare the effects of immediate and delayed arthroscopic Bankart repair on the shoulder dislocation recurrence. METHODS: In total, 465 soldiers with first-time anterior shoulder dislocation were included in the study. Of the total, 285 soldiers underwent a quick arthroscopic Bankart repair procedure, whether 180 soldiers underwent a delayed repair procedure. The initial dislocation was traumatic in both groups and operated using the standard arthroscopic suture anchor repair technique. Patient's age, repair time since the first dislocation, number of dislocations before surgery, number of suture anchors used during the repair, duration of surgical procedure, duration from surgery to return to work, and recurrence of dislocation after surgery were recorded. Rowe score, Constant score, and American Shoulder and Elbow Surgeons score were used for clinical assessment. RESULTS: The operating time and recurrence rate were higher in the group subjected to delayed repair procedure than in the group subjected to immediate repair procedure. Repair timing was found to be crucial for a successful outcome. CONCLUSIONS: The findings suggest that Bankart repair must be performed immediately to minimize recurrence and other degenerative changes, which may require an additional surgical procedure for satisfactory repair. More studies are required to reach a definitive conclusion. LEVELS OF EVIDENCE: Level III.

First-Generation SARS-CoV-2 Vaccines: A Comparative Analysis between Vaccinated and Unvaccinated Hospitalized Patients Infected with SARS-CoV-2.

Background Severe acute respiratory syndrome corona virus-2 (SARS-CoV-2) variants, which have emerged due to several mutations in spike protein, have a potential to escape immune protection provided by the first-generation vaccines, thereby resulting in breakthrough infections. Objective To identify the socio-demographic factors, clinical features, and outcomes in both vaccinated and unvaccinated hospitalized patients infected with SARS-CoV-2. Method Socio-demographic details, clinical features, and the outcomes among fully vaccinated (double for Covishield/AstraZeneca and BBIBP-CorV and single for Janssen), partially vaccinated, and unvaccinated hospitalized patients with coronavirus disease of 2019 (COVID-19) were collected and analyzed using SPSS version 17. Result Among the hospitalized COVID-19 patients (n=299), 175 (58.5%) patients received a single-dose, 82 (27.4%) double-dose, and 124 (41.5%) did not receive any dose of the COVID-19 vaccines. The risk of SARS-CoV-2 infection when compared between vaccinated and unvaccinated patients was found to be associated among professional degree holders (23.4% versus 9.7%) (p<0.05), professional workers (43.4% vs. 25.0%) (p<0.05), hospitalization to general ward (76.6% vs. 72.6%) (p<0.05), and presence of multiple symptoms (> or equel 3) (86.8% vs. 75.0%) (p>0.05) and comorbidities (> or equal 2) (15.5% vs. 13.7%) (p>0.05). Despite such approximate incidences, the risk of in-hospital mortality among the vaccinated patients was reduced (0.6% vs. 3.2%) (p>0.05), when compared to the unvaccinated patients. The risk of in-hospital mortality was associated with the older age and the presence of multiple comorbidities including bronchial asthma, diabetes, and hypertension. Conclusion Full or partial vaccination against the SARS-CoV-2 variants of concerns might be effective in preventing in-hospital mortality among COVID-19 patients.

Interface modification of Cr/Ti multilayers with C barrier layer for enhanced reflectivity in the water window regime.

The influence of a carbon barrier layer to improve the reflectivity of Cr/Ti multilayers, intended to be used in the water window wavelength regime, is investigated. Specular grazing-incidence X-ray reflectivity results of Cr/Ti multilayers with 10 bilayers show that interface widths are reduced to ∼0.24 nm upon introduction of a ∼0.3 nm C barrier layer at each Cr-on-Ti interface. As the number of bilayers increases to 75, a multilayer with C barrier layers maintains almost the same interface widths with no cumulative increase in interface imperfections. Using such interface-engineered Cr/C/Ti multilayers, a remarkably high soft X-ray reflectivity of ∼31.6% is achieved at a wavelength of 2.77 nm and at a grazing angle of incidence of 16.2°, which is the highest reflectivity reported so far in the literature in this wavelength regime. Further investigation of the multilayers by diffused grazing-incidence X-ray reflectivity and grazing-incidence extended X-ray absorption fine-structure measurements using synchrotron radiation suggests that the improvement in interface microstructure can be attributed to significant suppression of inter-diffusion at Cr/Ti interfaces by the introduction of C barrier layers and also due to the smoothing effect of the C layer promoting two-dimensional growth of the multilayer.

BL-02: a versatile X-ray scattering and diffraction beamline for engineering applications at Indus-2 synchrotron source.

A hard X-ray engineering applications beamline (BL-02) was commissioned recently and started operation in March 2019 at the Indian synchrotron source, Indus-2. This bending-magnet-based beamline is capable of operating in various beam modes, viz. white, pink and monochromatic beam. The beamline utilizes the X-ray diffraction technique in energy-dispersive and angle-dispersive modes to carry out experiments mainly focused on engineering problems, viz. stress measurement, texture measurement and determination of elastic constants in a variety of bulk as well as thin-film samples. An open-cradle six-circle diffractometer with ∼12 kg load capacity allows accommodation of a wide variety of engineering samples and qualifies the beamline as a unique facility at Indus-2. The high-resolution mode of this beamline is suitably designed so as to carry out line profile analysis for characterization of micro- and nano-structures. In the present article the beamline is described starting from the beamline design, layout, optics involved, various operational modes and experimental stations. Experiments executed to validate the beamline design parameters and to demonstrate the capabilities of the beamline are also described. The future facilities to be incorporated to enhance the capabilities of the beamline are also discussed.

Influences of Chemical Properties, Soil Properties, and Solution pH on Soil-Water Partitioning Coefficients of Per- and Polyfluoroalkyl Substances (PFASs).

The aim of this study was to assess the soil-water partitioning behavior of a wider range of per- and polyfluoroalkyl substances (PFASs) onto soils covering diverse soil properties. The PFASs studied include perfluoroalkyl carboxylates (PFCAs), perfluoroalkane sulfonates (PFSAs), fluorotelomer sulfonates (FTSs), nonionic perfluoroalkane sulfonamides (FASAs), cyclic PFAS (PFEtCHxS), per- and polyfluoroalkyl ether acids (GenX, ADONA, 9Cl-PF3ONS), and three aqueous film-forming foam (AFFF)-related zwitterionic PFASs (AmPr-FHxSA, TAmPr-FHxSA, 6:2 FTSA-PrB). Soil-water partitioning coefficients (log Kd values) of the PFASs ranged from less than zero to approximately three, were chain-length-dependent, and were significantly linearly related to molecular weight (MW) for PFASs with MW > 350 g/mol (R2 = 0.94, p < 0.0001). Across all soils, the Kd values of all short-chain PFASs (≤5 -CF2- moieties) were similar and varied less (<0.5 log units) compared to long-chain PFASs (>0.5 to 1.5  log units) and zwitterions AmPr- and TAmPr-FHxSA (∼1.5 to 2 log units). Multiple soil properties described sorption of PFASs better than any single property. The effects of soil properties on sorption were different for anionic, nonionic, and zwitterionic PFASs. Solution pH could change both PFAS speciation and soil chemistry affecting surface complexation and electrostatic processes. The Kd values of all PFASs increased when solution pH decreased from approximately eight to three. Short-chain PFASs were less sensitive to solution pH than long-chain PFASs. The results indicate the complex interactions of PFASs with soil surfaces and the need to consider both PFAS type and soil properties to describe mobility in the environment.

Spatial evaluation of prevalence, pattern and predictors of cervical cancer screening in India.

OBJECTIVE: To investigate the social determinants of cervical cancer screening and report the locations vulnerable to poor utilization of cervical cancer screening services. STUDY DESIGN: An ecological study with the data derived from fourth round of the National Family Health Survey conducted in India in the period 2015-2016. METHODS: The study focused on the percentage of women who have never undergone cervical cancer screening across 639 districts in India. Moran's I statistic was used to investigate the overall clustering of location. The Getis-Ord Gi* statistic was used for the detection of significant local clusters. Spatial error, spatial lag, spatial Durbin and spatial Durbin error models were compared, and the model with best fit was reported. ArcGIS, GeoDa and R software were used for the analysis. RESULTS: The existence of spatial autocorrelation (Moran's I = 0.61) necessitates the consideration of spatial component while studying the screening data. A significant clustering of districts with poor screening has been observed in the North-Central and North-Eastern regions of India. The geographic arrangement of the percentage of women who have undergone cervical cancer screening was associated with the percentage of women with poor wealth index (P < 0.001), not using a modern method of contraception (P < 0.001), residing in rural areas (P = 0.033) and never heard of sexually transmitted infection (P = 0.014). The range of percentage of women getting cervix screened for cancer was 0.5-68.4%, presenting the heterogeneity among the population elements. CONCLUSION: A higher risk of poor cervical cancer screening is observed in the districts where most of the women have poor wealth index, reside in urban area, have never heard of sexually transmitted infection and do not use a modern method of contraception.

Effect of reducing energy intake during the dry period on milk production, udder health, and body condition score of Jersey crossbred cows in the tropical lower Gangetic region.

To find out the effect of reducing energy intake during dry period on milk production, udder health, and body condition, the experiment was conducted on 14 Jersey crossbred cows during whole dry period and continued up to 120 days of lactation. Reduction in energy intake was done during far-off period for each dry cow of treatment group as compared to control group. Statistically analyzed data revealed that overall significantly (P < 0.01) lower DMI and WI were recorded in control than treatment group. Overall significantly (P < 0.01) higher total milk production was found in treatment than control group. Overall significantly (P < 0.01) lower milk SCC, MCMT, pH, and EC were found in treatment than control group. Nonsignificant difference in milk fat, SNF, total solid, total protein, and fat:protein ratio was found. Overall significantly (P < 0.01) better quality milk (MBRT) was found in treatment than control groups. BCS during dry period and at calving was significantly (P < 0.01) different between groups. Significantly (P < 0.01) higher plasma NEFA concentration was estimated in control than treatment groups in all stages. No significant difference was found for plasma concentrations of glucose, urea, and total protein. The coefficients of correlation indicated significant (P < 0.01) correlation among BCS, milk production, milk SCC, MCMT, pH, and EC. It can be concluded that reducing energy intake during far-off dry period can lead to achieve optimum BCS at calving. Suitable BCS at calving was beneficial to get higher milk production with improved quality, better maintenance of udder health and body condition of Jersey crossbred cows at tropical lower Gangetic region.

Depth-resolved compositional analysis of W/B4C multilayers using resonant soft X-ray reflectivity.

W/B4C multilayers (MLs) consisting of ten layer pairs with varying boron carbide layer thicknesses have been investigated. The ML structures were characterized using grazing-incidence hard X-ray reflectivity (GIXR), resonant soft X-ray reflectivity (RSXR), hard X-ray photoelectron spectroscopy (HAXPES) and X-ray absorption near-edge spectroscopy (XANES). Depth-resolved spectroscopic information on the boron carbide layer in W/B4C MLs was extracted with sub-nanometre resolution using reflectivity performed in the vicinity of the B K-edge. Interestingly, these results show that the composition of boron carbide films is strongly dependent on layer thicknesses. HAXPES measurements suggest that most of the boron is in the chemical state of B4C in the multilayer structures. XANES measurements suggest an increase in boron content and C-B-C bonding with increase in boron carbide layer thickness.

Drivers of land use/cover change and its impact on Pong Dam wetland.

Population growth, urbanization, and changing land use/cover practices are responsible for the loss of ecosystem services of wetlands around the world. The present study investigated wetland degradation that occurred in the Western Himalaya, Himachal Pradesh, India. The land use/cover change maps between 2001 and 2016 derived from remotely sensed imagery showed that the Pong Dam wetland is severely affected due to anthropogenic pressure posing risks of habitat destruction within its catchment area. The agriculture area increased by 159% and barren land decreased by 53% between 2001 and 2016. It indicates the rapid conversion of unused or scrub land for agriculture purpose in the area. The rate of sedimentation in the wetland is around 24.4 M.cum/year, and the survival age of the wetland is about 100 years. This rate is likely to increase in the near future due to large-scale unregulated development in the area. To reduce further destruction in this wetland, agricultural practices should be minimized in the area, and agroforestry practices should be encouraged to maintain the health and ecology of the wetland.

Topical propranolol for infantile haemangiomas: a systematic review.

Infantile haemangiomas are the most common tumour of infancy. Whilst the majority are left untreated to involute spontaneously, residual skin changes commonly occur, particularly in superficial haemangiomas. The current first-line treatment for problematic lesions is oral propranolol; however due to the risk of systemic adverse effects, the use of off-label topical preparations has recently been investigated. Our systematic review was conducted in accordance with PRISMA guidelines. Four databases were searched to identify original articles evaluating the use of topical propranolol as the primary therapy for infantile haemangiomas. Twelve articles with a total of 597 patients and 632 haemangiomas were included. Three topical propranolol preparations were used, creams, ointments and gels and were all prepared by local pharmaceutical laboratories. The concentration of propranolol ranged from 0.5% to 5%. Treatment duration ranged from two weeks to 16.5 months. Overall, 90% of lesions improved following the initiation of topical propranolol. A good or excellent response, defined as a reduction in the size of at least 50%, was seen in 59% of lesions. Earlier initiation of treatment (less than 3 months of age) was associated with improved outcomes. No systemic adverse effects were reported. Minor local reactions were seen in 1.3% of patients. Topical propranolol is safer than oral propranolol, though may be less effective. Topical propranolol may be more suitable for patients with small, superficial haemangiomas at risk of cosmetic sequelae, where the cosmetic or symptomatic impact does not warrant oral propranolol treatment.

Association analysis of novel polymorphisms in 2', 5'-oligoadenylate synthetase gene with reproductive traits in indigenous and cross-bred cattle of Indian Origin.

2', 5'-Oligoadenylate synthetases (OAS) are important components of an interferon-mediated antiviral pathway. No polymorphisms in exonic regions of bovine OAS1 gene have been identified and associated with reproduction traits. The objective of the study was to detect and evaluate the effects of mutations in exonic region of bovine OAS1 gene with reproduction traits in cattle. DNA samples collected from 250 individual cows of two Indian dairy breeds (Sahiwal and Frieswal) of cattle were used in the study. The genetic variants of the OAS1 gene were identified with polymerase chain reaction-single-strand conformation polymorphism (PCR-SSCP) and sequence analysis using seven set of primer pairs. The PCR-SSCP analysis revealed polymorphism in the fragments comprising of exon 2, exon 5 and first fragment of exon 6 while the fragments of exons 1, 3, 4 and second fragment of exon 6 were monomorphic in Sahiwal and Frieswal cattle. The mutations in the amplified region comprising of exon 2 were found to have significant association with age at first breeding and calving, service period, dry period and pregnancy rate. Significant associations were found between SNPs in the exon 5 and service and dry periods of the animal, whereas the genetic variants in the first fragment of the exon 6 showed significant association with age at first breeding and calving. To our knowledge, this study demonstrated for the first time that the polymorphisms in OAS1 gene were associated with reproductive traits and it can be chosen as a candidate gene for improvement of reproductive performance of cattle.

Does time of surgery and complication have any correlation in the management of hip fracture in elderly and can early surgery affect the outcome?

OBJECTIVE: Hip fractures in the elderly are usually associated with a high rate of morbidity and mortality and affect quality of life. On review of published data, the current guidelines in the literature indicate that early surgery should be performed within 24 h of injury because it is associated with better functional outcomes and lower rates of perioperative complications and mortality. The aim of this study was to evaluate whether any correlation exists between early surgical intervention and functional outcomes. METHODS: In a retrospective study, we analyzed the records between January 2010 and December 2016 and 550 elderly patients between the age group of 65-95 were included. RESULTS: The results of early surgery were promising, 451 (82%) patients did not have any complication, 42 (7.6%) has developed bed sore, 23 (4%) developed a hospital-acquired infection, 13 (2.3%) developed wound infection, 08 (1.4%) developed DVT, 04 (0.7%) developed implant failure, and 09 (01%) died of some or other complications. CONCLUSION: Still, there is conflicting evidence in the published data that early surgery would improve mortality and function. However, early surgery definitively improves outcome and reduces morbidity, bed sores, infection, and the length of hospital stay could be improved by reducing the waiting time of hip surgery following fracture. We concluded that it is beneficial to the elderly patients to receive surgical treatment as early as possible.

Physiochemical properties of greatly enhanced photoluminescence of aqueous dispersible upconversion CaF2:Yb/Er nanoparticles.

Crystal phase morphological structure and optical properties of the as-prepared upconversion CaF2:Yb/Er(core) and sequential coating of an inert crystalline material and silica layers surrounding the seed core-nanoparticles (NPs) were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), selected area electron diffraction (SAED), optical absorption, FTIR spectroscopy and upconversion photoluminescence spectroscopy. Owing to the unique properties of CaF2 host matrix, we realized their practical applications in biomedical science to improve the upconversion luminescence property and aqueous dispersibility. The surface coating on the seed core particles will significantly influence the structural, optical band gap energy and upconversion luminescence properties. These NPs were well-dispersed in aqueous and non-aqueous solvents to form clear colloidal solutions. The colloidal solutions of three samples show a characteristic optical absorption band in UV/Visible region. As a result, optical band gap gradually decreases after sequential growth of the inert shell and amorphous silica due to an increase in the crystalline size. Comparative upconversion luminescence analysis showed that after inert shell growth, the upconversion intensity was greatly improved, and such an improvement was found to arise from efficient suppression of surface-related deactivation from the core nanocrystals. Interestingly, growth of an inert (CaF2) shell over the seed core NPs shows intense upconversion emission lines under 980 nm NIR laser excitation, highlighting their promising applications, such as multi-analyte biolabels, staining, displays and other photonic based technological applications.

Multifunctional role of dysprosium in HfO2: stabilization of the high temperature cubic phase, and magnetic and photoluminescence properties.

Hafnium oxide (HfO2) can exist in different crystalline structures such as monoclinic at room temperature, tetragonal at 1700 °C and cubic at 2600 °C. In the present study, nanocrystalline powders of HfO2 synthesized by a Pechini type sol-gel technique show a monoclinic phase, P21/c, at room temperature. By incorporating Dy into the HfO2 lattice, the intensity of all diffraction peaks corresponding to P21/c decreases and at a concentration of 11 at% of Dy, the monoclinic phase transforms completely to the cubic phase, Fm3[combining macron]m, showing a mixed phase of monoclinic and cubic at intermediate concentrations (5-9 at%) of Dy. For the first time, we have stabilized the high temperature cubic phase of HfO2 at room temperature by incorporating Dy. Selected area electron diffraction patterns confirm the monoclinic and the cubic phase as observed from the X-ray diffraction patterns. A mechanism for stabilization of the high temperature cubic phase in Hf1-xDyxO2 has been analyzed based on the substitution of dysprosium for hafnium ions and the formation of oxygen vacancies. While ferromagnetic ordering at room temperature observed in HfO2 nanoparticles is quenched after incorporating 1 at% of Dy, photoluminescence (PL) studies demonstrate excellent emissions in the blue and yellow region after exciting with UV light of wavelength 352 nm. Combining excitation and emission profiles, we have proposed a tentative energy band diagram illustrating the energetic processes taking place in Hf1-xDyxO2.

Influence of Shell Formation on Morphological Structure, Optical and Emission Intensity on Aqueous Dispersible NaYF4:Ce/Tb Nanoparticles.

A highly water-dispersible NaYF4:Ce/Tb (core), NaYF4:Ce/Tb@NaYF4(core/shell) and NaYF4:Ce/Tb@NaYF4@SiO2 (core/shell/SiO2) nanoparticles (NPs) were synthesized via a general synthesis approach. The growth of an inert NaYF4 and silica shell (~14 nm) around the core-NPs resulted in an increase of the average size of the nanopaticles as well as broadening of their size distribution. The optical band-gap energy slightly decreases after shell formation due to the increase the crystalline size. To optimize the influence of shell formation a comparative analysis of photoluminescence properties (excitation, emission, and luminescence decay time) of the core, core/shell, and core/shell/SiO2 NPs were measured. The emission intensity was significantly enhanced after inert shell formation around the surface of the core NPs. The Commission International de l'Eclairage chromaticity coordinates of the emission spectrum of core, core/shell, core/shell/SiO2 NPs lie closest to the standard green color emission at 545 nm. By quantitative spectroscopic measurements of surface-modified core-NPs, it was suggested that encapsulation with inert and silica layers was found to be effective in retaining both luminescence intensity and dispersibility in aqueous environment. Considering the high aqueous dispersion and enhanced luminescence efficiency of the core-NPs make them an ideal luminescent material for luminescence bioimaging and optical biosensors.