Modeling Fretting Wear Resistance and Shakedown of Metallic Materials with Graded Nanostructured Surfaces.

In applications involving fretting wear damage, surfaces with high yield strength and wear resistance are required. In this study, the mechanical responses of materials with graded nanostructured surfaces during fretting sliding are investigated and compared to homogeneous materials through a systematic computational study. A three-dimensional finite element model is developed to characterize the fretting sliding characteristics and shakedown behavior with varying degrees of contact friction and gradient layer thicknesses. Results obtained using a representative model material (i.e., 304 stainless steel) demonstrate that metallic materials with a graded nanostructured surface could exhibit a more than 80% reduction in plastically deformed surface areas and volumes, resulting in superior fretting damage resistance in comparison to homogeneous coarse-grained metals. In particular, a graded nanostructured material can exhibit elastic or plastic shakedown, depending on the contact friction coefficient. Optimal fretting resistance can be achieved for the graded nanostructured material by decreasing the friction coefficient (e.g., from 0.6 to 0.4 in 304 stainless steel), resulting in an elastic shakedown behavior, where the plastically deformed volume and area exhibit zero increment in the accumulated plastic strain during further sliding. These findings in the graded nanostructured materials using 304 stainless steel as a model system can be further tailored for engineering optimal fretting damage resistance.

Advances in drying techniques for retention of antioxidants in agro produces.

Antioxidants are compounds that are essential for the human body which prevents cell from disease causing free radicals. Antioxidants are present in a wide range of fruits, vegetables, and spices. However, a considerable amount of antioxidants is lost during the post-harvest drying operation of agro produces for their shelf-life enhancement. Hence, retention of antioxidants becomes utmost importance in preserving the nutritional aspects of fruits and vegetables. Compared to conventional hot air drying, methods like freeze drying, vacuum drying, and dehumidified drying helps in the retention of antioxidants. However, the drawbacks prevalent in current drying practices, such as high-power consumption and high capital cost, could be eliminated by adopting novel drying mechanisms. This review focuses on various pretreatment methods like ultra-sonication, high pressure processing, pulsed electric field and ethanol treatment prior to drying operation helps in enhancing the drying efficiency with maximum retention of antioxidants. In addition, hybrid drying technologies such as microwave assisted drying, IR-radiated drying and electro-magnetic assisted drying methods also could significantly improve the retention of antioxidants.HIGHLIGHTSDrying is the most commonly adopted unit operation for enhancing the shelf life of perishable agro produces.However, drying is accompanied by loss of bioactive, color, texture, and sensory attributes.Compared to conventional drying techniques like hot air drying, methods like freeze drying, vacuum drying and dehumidified drying helps in the retention of antioxidants present in agro/food produces.Pretreatment methods like Ozonation, ultra-sonication, and UV radiation prior to drying are also found to improve the drying performance with good retention of antioxidants.Recent developments like microwave-assisted and IR-assisted drying methods perform well in the retention of antioxidants with less energy consumption.

Evaluation of age-based local anaesthetic dosing of bupivacaine for popliteal sciatic nerve block in children undergoing foot and ankle surgery: A prospective single arm interventional study.

Background and Aims: Recommendations on paediatric single-injection local anaesthetic (LA) dosing for peripheral nerve blocks (PNBs) are based on the children's weight and limited by weight-based toxicity concerns. In this study, we assessed the extent of circumferential spread and block characteristics following the injection of an age-based volume (age in years = LA volume) of 0.25% bupivacaine following popliteal sciatic nerve block (PSNB). Methods: Thirty children aged between 2 and 12 years with the American Society of Anesthesiologists (ASA) physical status I and II and undergoing foot and ankle surgical procedures were given single-injection ultrasound-guided subparaneural PSNB using 0.25% bupivacaine at age-based LA volume after the administration of anaesthesia. The circumferential pattern of LA spread (primary objective) was assessed along the nerve (both cephalad and caudal) using ultrasound from the point of administration and the block characteristics in terms of duration of sensory block. Results: The mean [standard deviation (SD)] cephalic circumferential LA spread distance was 2.52 (0.68) [95% confidence interval (CI): 2.27-2.76] cm. The mean (SD) caudal circumferential LA spread distance was 2.27 (0.48) [95% CI: 2.09-2.44] cm. The mean (SD) duration of the sensory block was 9.03 (0.97) [95% CI: 8.67-9.38] h. Conclusion: The age-based LA volume of bupivacaine for ultrasound-guided PSNB resulted in a longitudinal circumferential spread of around 4.7 cm (adding both cephalic and caudal spread) and provided adequate analgesia for nine postoperative hours.

On the Evolution of Nano-Structures at the Al-Cu Interface and the Influence of Annealing Temperature on the Interfacial Strength.

Molecular dynamics (MD) simulations are invoked to simulate the diffusion process and microstructural evolution at the solid-liquid, cast-rolled Al-Cu interfaces. K-Means clustering algorithm is used to identify the formation and composition of two types of nanostructural features in the Al-rich and Cu-rich regions of the interface (i.e., the intermetallic Al2Cu near the Al-rich interface and the intermetallic Al4Cu9 near the Cu-rich interface). MD simulations are also used to assess the effects of annealing temperature on the evolution of the compositionally graded microstructural features at the Al-Cu interfaces and to characterize the mechanical strength of the Al-Cu interfaces. It is found that the failure of the Al-Cu interface takes place at the Al-rich side of the interface (Al2Cu-Al) which is mechanically weaker than the Cu-rich side of the interface (Cu-Al4Cu9), which is also verified by the nanoindentation studies of the interfaces. Centrosymmetry parameter analyses and dislocation analyses are used to understand the microstructural features that influence deformation behavior leading to the failure of the Al-Cu interfaces. Increasing the annealing temperature reduces the stacking fault density at the Al-Cu interface, suppresses the generation of nanovoids which are precursors for the initiation of fracture at the Al-rich interface, and increases the strength of the interface.

Synthesis and characterization of a series of N,N'-substituted urea derivatives by using electrospray ionization tandem mass spectrometry: Differentiation of positional isomers.

RATIONALE: Characterization of N,N'-substituted ureas was found to be challenging by nuclear magnetic resonance (NMR) spectroscopy, particularly N-di- and tri-alkylated ureas because of the absence of adjacent protons. In the present study, electrospray ionization tandem mass spectrometry has been used to differentiate positional isomeric pairs and to characterize a series of N,N'-substituted ureas, as these compounds have significant importance for drug discovery. Additionally, urea is an essential functionality in several bioactive compounds as well as a variety of clinically approved therapies. METHODS: High-resolution electrospray ionization tandem mass spectrometry (ESI-HR-MS/MS) has been used to characterize a series of N,N'-substituted urea derivatives and differentiate two pairs of positional isomers. The data was acquired by Xcaliber application in positive ionization mode. RESULTS: ESI-HR-MS/MS spectra of [M + H]+ ions of the positional isomeric urea derivatives 8a and 8b show distinct fragmentation patterns. For example, the MS/MS spectrum of the [M + H]+ ion of isomer 8a displays the abundant fragment ion at m/z 285.1595, which was totally absent in isomer 8b. This would be plausibly formed by the cleavage of the C-N bond of the urea group with the elimination of the isocyanate moiety. In contrast, the MS/MS spectrum of the [M + H]+ ion of isomer 8b shows an intense ion at m/z 311.1389 which is completely absent in isomer 8a which would be formed by the cleavage of the C-N bond attached to the ring nitrogen. Similarly, another pair of positional isomers, 8c and 8d, have been clearly distinguished by their fragmentation behaviour. In addition, a series of N,N'-substituted urea derivatives were studied to investigate the impact of different substitution on the fragmentation behaviour. CONCLUSIONS: The present study demonstrates that ESI-HR-MS/MS can be used to differentiate pairs of N,N'-substituted urea positional isomers and characterize a series of derivatives. It was observed that a characteristic fragment ion was formed by the C-N bond cleavage with the elimination of an isocyanate moiety. The proposed mechanism of fragmentation was supported by the change in the fragmentation pathway upon alkylation of the NH. In order to generalize this fragmentation pattern, a series of N-alkylated ureas was synthesized and studied by MS/MS.

Nonlamellar liquid crystals: a new paradigm for the delivery of small molecules and bio-macromolecules.

The aim of this article is to collate the recent developments in the field of drug delivery, medical therapeutics and diagnostics specifically involving the nonlamellar liquid crystalline (NLC) systems. This review highlights different NLC phases having cubic, hexagonal and sponge internal structures, and their application in the field of drug delivery, such as dose reduction, toxicity reduction and therapeutic efficacy enhancement either in the form of nanoparticles, colloidal dispersion or gels. In addition, application of NLC systems as vehicles for peptides, proteins and as a theranostic system in cancer and other disease conditions is also elaborated, which is a growing platform of interest. Overall, the present review gives us a complete outlook on applications of NLC systems in the field of medicine.

Morphometric analysis of tricuspid valve: An Indian perspective.

BACKGROUND: The morphometry of tricuspid valve complex is of clinical importance for cardiovascular surgeons and there is scarcity of such data in Indian literature. The study was conducted to record normal tricuspid valve measurements which would serve as baseline data for the Indian population. MATERIAL AND METHODS: The study was carried out on 100 formalin fixed hearts without any pathology from patients who had died of non-vascular causes and whose age ranged from 8 to 85 yrs. The hearts were grouped into three cohorts corresponding to age, 54 hearts aged between 8 to 40 yrs, 42 hearts aged between 41 to 64 yrs and 4 hearts aged 65 yrs and above. Dissection was performed according to standard autopsy techniques. The measurements were recorded using a flexible millimeter ruler and surgical suture material. The dimensions measured were the attachment lengths of anterior, posterior and septal leaflets. The circumference of the valve along with the frontal and sagittal dimensions was measured. Area of the valve expressed as a triangle and as an ellipse was calculated. RESULTS: The measurements obtained were assessed using SPSS software. Statistically significant increase in tricuspid valve measurements were observed with advancing age both in men and women. In younger hearts the tricuspid valve resembled a triangle and with advancing age the tricuspid valve became more elliptical in shape. CONCLUSION: We hope this study will serve as baseline data for the tricuspid valve measurements in the Indian population and it will be of clinical use for patients with various tricuspid valve abnormalities.

Differential expression of TLR-2 and TLR-4 in the epithelial cells in oral lichen planus.

OBJECTIVE: Oral lichen planus (OLP) is a chronic inflammatory condition of the mucosa mediated by a complex signalling network between the keratinocytes and the sub-epithelial lymphocytes. Since OLP occurs in constantly renewing epithelium continuously exposed to commensals, we hypothesised that the epithelial cell microflora interactions may mediate the persistent inflammation. By virtue of their ability to respond to most oral commensal microorganisms, the toll like receptor-2 (TLR-2) and TLR-4 are the most widely investigated receptors in oral diseases. The overall objective of this study was to investigate the role of TLR-2 and TLR-4 in OLP. DESIGN: Systemically healthy OLP and control subjects were recruited after obtaining the institutional review board approval. Expression of TLR-2 and TLR-4 proteins and transcripts in the tissue epithelium and in the epithelial cells isolated from saliva were determined by immunohistochemistry and quantitative real-time polymerase chain reaction respectively. RESULTS: The tissue epithelium and the salivary epithelial cells expressed reduced TLR-2 and increased TLR-4 proteins and transcripts in OLP. The salivary epithelial cells from OLP subjects secreted elevated IL-12. However, upon stimulation with bacterial lipopolysaccharide the epithelial cells from OLP exhibited a mixed Th1 (IL-12) and Th2 (IL-4) response. Presence of dexamethasone significantly reduced inflammatory cytokines in the in vitro stimulated cultures of salivary epithelial cells from OLP subjects. CONCLUSION: Collectively, our data support a critical role for the host-microbial interactions in the OLP pathogenesis. The potential use of exfoliated oral epithelial cells in saliva for functional analysis exponentially increases its value as biological specimen for clinical research.

Neurochemical and neurobehavioral effects of low lead exposure on the developing brain.

Lead is found in small but appreciable quantities in air, soil drinking water and food. Exposure to such amounts of lead does not cause acute lead toxicity, but produces subtle effects, particularly in children. The CDC advocates "safe" or "acceptable" levels of blood lead up to 10 µg/dl, while OSHA declares blood lead levels up to 40 µg/dl as "safe" or "acceptable" in the occupationally exposed. The objective of the study was to see if blood levels considered "safe" can cause changes in the biogenic neurotransmitters in the developing brain which may cause neurobehavioral defects like hyperactivity and other cognitive disorders. Albino Wistar rats were divided into the control and lead-treated groups. The control group was given unleaded water, while the lead-treated group was fed with 50 ppm lead acetate in drinking water. On day 45 the animals were subjected to a passive avoidance test, their blood analysed for ZPP and lead. They were then sacrificed and the neurotransmitters-Norepinephrine (NE) and its metabolite-methoxyhydroxyphenylglycol (MHPG) estimated in the brain areas associated with learning and memory-the frontal cortex, hippocampus and the striatum by HPLC-ECD. Our results showed significant increases in blood lead, NE and MHPG, while ZPP increase was insignificant. The rats showed neurobehavioral abnormalities as assessed by the passive avoidance test. We concluded that low blood levels of lead cannot be considered "safe" or "acceptable" as it causes neurotransmitter alterations. Increased NE turnover is implicated in hyperactivity disorders such as ADHD and Tourette syndrome.

Three cases of lead toxicity associated with consumption of ayurvedic medicines.

Ayurveda is a traditional form of medicine used by majority of the Indians. Here we report three cases of lead toxicity, following intake of Ayurvedic medicines. Three patients presented with blood lead levels (BLLs) of 122.4, 115 and 42.8 µg/dl respectively at the time of hospitalization. The first case was chelated with D- penicillamine, the second with calcium disodium ethylene diamino tetra acetate (EDTA) and the third with environmental intervention and education. Associated Ayurvedic products were collected from patients and analyzed for metallic concentration. Cessation of Ayurvedic medication along with chelation, nutritional intervention and education, reduced the BLL to 27.4 µg/dl in the first case after 1 year, 21.1 µg/dl after 9 months in the second and 18.2 µg/dl after 6 months in the third case.

Radial neuropathy due to occupational lead exposure: Phenotypic and electrophysiological characteristics of five patients.

Lead is a ubiquitous and versatile metal that has been used by mankind for many years. It is a toxic heavy metal that ranks as one of the most important environmental poisons in the world. Research conducted in recent years has increased public health concern about the toxicity of lead at low doses and has supported a reappraisal of the levels of lead exposure that may be safely tolerated in the workplace. Neuropathy is one complication of lead poisoning. The aim of this study is to describe the phenotypic and electrophysiological profile in five male patients working in a battery factory who developed radial nerve neuropathy due to lead exposure. All patients had elevated blood lead levels that were in the toxic range. The concerned regulatory bodies should make it mandatory for workers to undergo regular health checkups to detect signs of lead poisoning and must ensure that workers are aware about the ill effects of exposure to this metal. Chelation therapy removes lead from the blood and soft tissues and chronic lead exposure often requires repeated courses of treatment.

Role of activated carbon fabric mask to prevent lead absorption--a short report.

An attempt was made to study the usefulness of activated carbon fabric (ACF) mask to prevent lead absorption. Indigenous ACF masks were provided to eight workers involved in the manufacture of batteries. Their blood lead levels were determined before and after using these masks. There was a substantial decrease in blood lead level after using the mask among those who were under treatment for high blood lead levels. Three workers who were not under treatment for lead also showed a decrease in blood lead level, after using this ACF mask, suggesting the usefulness of ACF in preventing further exposure. Such a study has not been reported anywhere in the available literature and similar such studies with more number of masks is necessary to evaluate its effectiveness.

Screening of school children for blood lead levels and attempts to reduce them by nonpharmacological means in a coastal city of India.

CONTEXT: Lead is a major health hazard, especially in children. Impact of lead poisoning on our society is not known. Effectiveness of environmental interventions in reducing blood lead levels is not exactly known, though the Center for Disease Control and Prevention strongly advocates use of such means. AIMS: We aimed at screening school children for blood lead levels (BLLs) and reducing the BLLs of children with preliminary BLL> 20 microg/dL by environmental intervention and intensive education. MATERIALS AND METHODS: To assess the extent of lead poisoning, a screening of 106 children was done, which showed that children belonging to a particular government primary school had higher BLLs. A second screening program of 87 children conducted in that school showed that only 19% had BLL < 10 microg/dL; whereas 44% had BLL between 10 and 20 microg/dL, and 37% had BLL> 20 microg/dL. Thirty-eight children having BLL> 20 microg/dL were selected from the two screening programs. After removing all potential sources of lead from their environment and educating them about the ways to prevent exposure to lead, follow-up of their BLLs was carried out at an interval of 6 months for a period of 1 year. STATISTICAL ANALYSIS: Values of the different follow-up studies were compared using repeated-measure ANOVA. RESULTS: Our results showed that there was a significant (P < 0.0001) reduction in the BLLs in the first and second follow-up studies. CONCLUSIONS: The study is a proof of the concept that a decline in the BLLs can be achieved by intense education and avoiding the potential environmental sources of lead.

Lead toxicity as a result of herbal medication.

Awareness about the toxic effects of non-essential metals is still lacking in developing countries. Lead is one among them, which ranks second in the Agency for Toxic Substances and Disease Registry' s top 20 lists of toxic metals. Some of the herbal medicines prepared from certain roots and leaves are known to contain this toxic metal at alarming levels. We have a case of a person who suffered from the toxic effects of lead such as vomiting and colicky abdominal pain after consuming a herbal remedy for Jaundice treatment. This went unrecognized initially because of the presence of multiple problems like Malaria and Renal calculi. Lead poisoning as causative factor for anemia, vomiting and colic were confirmed only when blood lead concentration was estimated. A combination of chelation therapy and nutritional supplementation was found to be useful in reducing the body lead burden.

Genetic susceptibility to lead poisoning-A case report.

Lead poisoning is well documented in persons occupationally exposed to lead. What is less known is, that even in persons working in lead based industries, the effect of lead and the appearance of signs and symptoms of lead poisoning is genetically determined. Three genes related to lead metabolism, exhibiting polymorphism have already been demonstrated-δALA-dehydratase, Vitamin D receptor gene and Hemochromatosis gene. These alleles determine the susceptibility of the individuals to lead. We present here a case of a lead acid battery worker, who presented without any signs and symptoms of lead poisoning except for a very high level of blood lead (82.8µg/dl and 47.5µg/dl 9 months later).

Clinical manifestations of lead workers of Mangalore, India.

OBJECTIVE: To correlate blood lead levels and clinical manifestations. PARTICIPANTS: Battery workers and painters (occupationally exposed to lead in and around Mangalore, India) and occupationally unexposed controls. MAIN OUTCOME MEASURES: We measured the blood lead levels by anodic stripping voltammetry, and a clinical examination was carried out on all participants. RESULTS: There was a statistically significant difference between the lead-exposed group and controls with respect to clinical manifestations. The prominent findings among the lead-exposed group were fatigue, abdominal colic, abdominal discomfort, backache, muscular exhaustability, myalgia and paresthesia, at a blood lead level ranging from 0.4 to 116.6 microg/dL. CONCLUSIONS: Such a study on battery workers and painters has not been reported in India. Several attempts have been made over the years to relate blood lead levels to adverse health effects. It was not possible to determine a precise blood lead level below which symptoms never occur or a blood lead level at which symptoms are always reported.

Studies on the age dependent changes in serum adenosine deaminase activity and its changes in hepatitis.

Serum Adenosine deaminase (ADA) activity in normal healthy control subjects increases upto 30 years, remains steady between 31-60 years of age and shows a steep increase in the age group of 61-70 years. This was compared with serum aspartate transaminase (AST) and alanine transaminase (ALT) activity which also showed a gradual increase upto 40 years of age and decreased thereafter. The activities of serum ADA, AST and ALT increased in patients with hepatitis of all age groups compared to their respective controls. The degree of increase in the activities of the above enzymes in hepatitis, decreased with age. The present study also shows that while studying serum ADA activity in hepatitis for diagnostic purposes, the value obtained in a particular age group should be compared with normal range of values for the respective age group only.

Portable lead analyzer to locate source of lead.

OBJECTIVE: To investigate the sources of lead in the environment in children with elevated blood, with the help of a Field Portable X-Ray Fluorescence Analyzer. METHODS: One hundred and seven school children were chosen for this study on a random basis, from Mangalore and Karnataka. Their blood lead was analyzed. Of the cases analyzed, 10 students whose blood lead level was more than 40 microg/dl were investigated using a field portable X-Ray Fluorescence Analyzer. This is the first time such a device has been available for this purpose in India. RESULTS: The 'likely' source of lead exposure could be determined in eight cases which was from the immediate environment of the children like 'lead-based' paint on surfaces in the house, on playground and other exterior equipment; lead storage batteries, contaminated dust and soil and other lead-containing substances. CONCLUSION: The use of an X-Ray Fluorescence Analyser appeared to be useful in determining the source of lead.

Faecal fat content in healthy adults by the 'acid steatocrit method'.

Malabsorption syndromes causing steatorrhoea are quite common in India. Estimation of faecal fat is an important non-invasive investigation, which provides vital information regarding the occurrence of malabsorption. The aim of this study was to estimate the fat excretion per day in stools of apparently healthy adults on an unrestricted diet in random spot stool samples using the Acid Steatocrit Method, which provides an alternate, simpler and yet reliable method of stool fat estimation. Several studies have proved the correlation of the acid steatocrit method with the conventional methods. In India, however, there has been no published data regarding the normal levels of fat in the stools, by the acid steatocrit method. We follow the normal range values, as set by the United States and the European countries, not having a range for the Indian population. Hence, we took up a preliminary study, to estimate stool fat in a section of normal and healthy Indian population. The result obtained after screening 600 healthy and normal adults, showed the mean of stool fat to be 8.72 gms/24 hours, which is much higher than that, defined by Western literature (7 gms/24 hours). This can be accounted for, by the cultural and ethnic variations in dietary and food habits. Further studies are required in the same direction, involving larger population groups, and in different malabsorptive conditions.

Estimation of reference values in liver function test in health plan individuals of an urban south Indian population.

Reference intervals in clinical chemistry are commonly based on results of measurements in reference western population or are taken from the western literature. Reference Values are thought to aid physicians to interpret results of measurements and, should be representative of a defined group of individuals. This group should be as similar as possible to the patients under investigation. The reference population in this, study has been recruited from the individuals attending the Health Plan Clinic who fulfill the defined inclusion and exclusion criteria as well as defined partition criteria. The samples were sorted based on the decision by the physician. The emerging group of individuals was considered as a reference population for the hospital patients and the results of measurements in this study was evaluated statistically, to stress on the urgent need to establish the in-house reference values. The reference limits are defined as the central 95 percentile of the population after eliminating the outliers. The lower, reference limit is the 2.5 percentile while the upper reference limit constituted the 97.5 percentile for the population.