Smoothing tool design and performance during subaperture glass polishing.

During subaperture tool grinding and polishing, overlaps of the tool influence function can result in undesirable mid-spatial frequency (MSF) errors in the form of surface ripples, which are often corrected using a smoothing polishing step. In this study, flat multi-layer smoothing polishing tools are designed and tested to simultaneously (1) reduce or remove MSF errors, (2) minimize surface figure degradation, and (3) maximize the material removal rate. A time-dependent convergence model in which spatial material removal varies with a workpiece-tool height mismatch, combined with a finite element mechanical analysis to determine the interface contact pressure distribution, was developed to evaluate various smoothing tool designs as a function of tool material properties, thicknesses, pad textures, and displacements. An improvement in smoothing tool performance is achieved when the gap pressure constant, h¯ (which describes the inverse rate at which the pressure drops with a workpiece-tool height mismatch), is minimized for smaller spatial scale length surface features (namely, MSF errors) and maximized for large spatial scale length features (i.e., surface figure). Five specific smoothing tool designs were experimentally evaluated. A two-layer smoothing tool using a thin, grooved IC1000 polyurethane pad (with a high elastic modulus, E p a d =360M P a), thicker blue foam (with an intermediate modulus, E f o a m =5.3M P a) underlayer, and an optimized displacement (d t=1m m) provided the best overall performance (namely, high MSF error convergence, minimal surface figure degradation, and high material removal rate).

Understanding and reducing mid-spatial frequency ripples during hemispherical sub-aperture tool glass polishing.

During sub-aperture tool polishing of glass optics, mid-spatial surface ripples are generated because of material removal non-uniformities during tool linear translation (resulting in feed ripples) and tool pathway step overlaps (resulting in pitch ripples). A variety of tool influence function (TIF) spots, trenches, and patches were created to understand and minimize such ripples on fused silica workpieces after polishing with cerium oxide slurry using a rotating hemispherical pad-foam tool. The feed ripple amplitude can be decreased by reducing the non-uniformities in the pad texture and/or by minimizing a derived feed ripple metric (rf=Vmax0.5Vf/Rt) via adjustments in processing parameters. Pitch ripples can be minimized by reducing relative step distance to spot radius ratio (xs/at) and by achieving a flat bottom trench shape cross section or by reducing the material removal per pass. Using the combined methods, an overall ripple error of ∼1.2nm rms has been achieved.

Mechanisms influencing and prediction of tool influence function spots during hemispherical sub-aperture tool polishing on fused silica.

Sub-aperture tool polishing of precision optics requires a detailed understanding of the local material removal [tool influence function (TIF)] at the contact spot between the workpiece and tool to achieve high removal determinism and hence precision of the optic relative to the desired/design surface figure. In this study, the mechanisms influencing and the quantitative prediction of the removal rate and shape of TIF spots during polishing of fused silica glass with cerium oxide slurry using a rotating hemispherical pad-foam tool for a wide variety of process conditions (including tool properties, kinematics, and applied displacements) are investigated. The TIF volumetric removal rate can be estimated utilizing the average relative velocity and contact area using a simple analytical model. In addition, stability of the volumetric removal rate for fixed process conditions is shown to be greatly dependent on the pad preparation and amount of tool use (affecting both pad topography and slurry buildup), whose general behavior shows an increase in removal rate followed by stabilization with polishing time. The determination of the TIF removal shape is more complex. An extended version of the Preston removal model is developed to explain a comprehensive set of measured TIF removal shapes to within ∼22%. This model incorporates a number of phenomena impacting the TIF removal shape including: (a) temporal and spatial dependent relative velocity between the workpiece and tool; (b) an elastic mechanics based, as well as hydrodynamic, pressure distribution; (c) a spatially dependent friction coefficient possibly caused by both reduced slurry replenishment in low velocity regions and pad slurry islands (100 µm scale) and porosity (millimeter scale); and (d) a shear-based removal mechanism on the periphery of the contact spot.

Effect of workpiece curvature on the tool influence function during hemispherical sub-aperture tool glass polishing.

The influence of workpiece curvature on the tool influence function spot during polishing of fused silica glass with cerium oxide slurry, while using a rotating hemispherical pad-foam tool for a wide variety of process conditions (tool displacement, inclination angle, and rotation rate), has been investigated. (Workpiece curvature ranged from 500 mm radius concave to 43 mm radius convex.) The TIF spot decreases in diameter and increases in the peak removal rate on more convex workpieces. In contrast, the TIF spot increases both in diameter and peak removal rate on more concave workpieces. For the range of workpiece curvatures investigated, both the spot size and the peak removal rate changed significantly, as much as 2 times. An elastic sphere-sphere contact mechanics model, which utilizes both a modified displacement (that leads to a change in the applied load) as well as a mismatch factor (that influences the pressure distribution shape), has been developed. The model was validated using both offline load-displacement measurements and finite-element analysis simulations. The model quantitatively describes the measured change in the relative contact diameter and relative pressure distribution, as well as semiquantitively describes the change in the relative volumetric removal rate on a large variety of TIF spots. The change in the volumetric removal rate for convex workpieces is a result of the balance between a decreasing spot size (reducing removal) and an increasing peak pressure (increasing removal), which usually results in relatively small changes in volumetric removal. In the case of concave workpieces, the volumetric removal rate change is also governed by a similar balance, but the spot size increase contribution dominates, resulting in a significant increase in volumetric removal rate. Understanding these trends can enable methods to add greater determinism during the fabrication of freeform optics by adjusting polishing parameters (such as dwell time) while the tool translates along a workpiece surface with different local curvatures.

Sapphire advanced mitigation process: wet etch to expose sub-surface damage and increase laser damage resistance and mechanical strength.

A novel, to the best of our knowledge, method of wet chemical etching of sapphire workpieces (such as optics, wafers, windows, and cones), called the sapphire advanced mitigation process (or sapphire AMP), has been developed that exposes sub-surface mechanical damage created during the optical fabrication process and significantly enhances the surface laser damage resistance ($ \gt {2{\times}}$>2×) and mechanical strength (up to $\sim{2.6{\times}}$∼2.6×). Sapphire AMP involves first treating the workpiece with a mixture of sulfuric and phosphoric acid $([{\rm H_{2}{\rm SO_{4}}}]:[{\rm H_{3}{\rm PO_{4}}}]=1:3)$([H2SO4]:[H3PO4]=1:3) at 220°C, followed with phosphoric acid at 160°C, then with sodium hydroxide base (NaOH) and surfactant at 40°C, and finally with a high-pressure deionized water spray rinse. Sapphire AMP has been demonstrated on both A- and C-plane sapphire workpieces. The mechanism of this etch process involves the reaction of the sapphire $({\rm Al_{2}}{\rm O_{3}})$(Al2O3) surface with sulfuric acid $({\rm H_{2}}{\rm SO_{4}})$(H2SO4) forming aluminum sulfate $[{{\rm Al}_2}{({{\rm SO}_4})_3}]$[Al2(SO4)3], which has low solubility. The high phosphoric acid content in the first and second steps of sapphire AMP results in the efficient conversion of ${{\rm Al}_2}{({{\rm SO}_4})_3}$Al2(SO4)3 to aluminum phosphate $({\rm AlPO_{4}})$(AlPO4), which is very soluble, greatly reducing reaction product redeposition on the workpiece surface. Sapphire AMP is shown to expose sub-surface mechanical damage on the sapphire surface created during the grinding and polishing processes, whose etched morphology has either isotropic or anisotropic evolution depending on the nature of the initial surface damage. Sapphire AMP was also designed to remove the key known surface, laser absorbing precursors (namely, foreign chemical impurities, the fracture surface layer of preexisting sub-surface damage, and reaction product or foreign species redeposition or precipitation). Static and sliding indention induced surface microfractures on sapphire are shown after sapphire AMP to have a significant decrease in the fast photoluminescence intensity (a known metric for measuring the degree of laser damaging absorbing precursors). In addition, the onset of laser damage (at 351 nm 3 ns) on sapphire AMP treated workpieces was shown to increase in fluence from $\sim{4}$∼4 to $ \gt {9}.{5}\;{{\rm J/cm}^2}$>9.5J/cm2. Finally, biaxial ball-on-ring mechanical tests on sapphire disks showed an increase in the failure stress from 340 MPa (with pre-existing 28 µm flaws) to $\sim{900}\;{\rm MPa}$∼900MPa after sapphire AMP, which is attributed to the blunting of the surface microfractures.

Long-distance dispersal suppresses introgression of local alleles during range expansions.

During range expansions, even low levels of interbreeding can lead to massive introgression of local alleles into an invader's genome. Nonetheless, this pattern is not always observed in human populations. For instance, European Americans in North America are barely introgressed by Amerindian genes in spite of known contact and admixture. With coalescent spatially explicit simulations, we examined the impact of long-distance dispersal (LDD) events on introgression of local alleles into the invading population using a set of different demographic scenarios applicable to a diverse range of natural populations and species. More specifically, we consider two distinct LDD models: one where LDD events originate in the range core and targets only the expansion front and a second one where LDD events can occur from any area to any other. We find that LDD generally prevents introgression, but that LDD events specifically targeting the expansion front are most efficient in suppressing introgression. This is likely due to the fact that LDD allows for the presence of a larger number of invader alleles at the wave front, where effective population size is thus increased and local introgressed alleles are rapidly outnumbered. We postulate that the documented settlement of pioneers directly on the wave front in North America has contributed to low levels of Amerindian admixture observed in European Americans and that this phenomenon may well explain the lack of introgression after a range expansion in natural populations without the need to evoke other mechanisms such as natural selection.

Swim-up of tammar wallaby (Macropus eugenii) spermatozoa in Biggers, Whitter and Whittingham (BWW) medium: maximisation of sperm motility, minimisation of impairment of sperm metabolism and induction of sperm hyperactivation.

A variety of media were compared for their ability to sustain the motility of tammar wallaby spermatozoa over an 8-h period following swim-up from coagulated semen. The study demonstrated that a modified Tyrode's solution, Biggers, Whitter and Whittingham medium (BWW) was significantly better than any of the other assessed media in supporting wallaby sperm motility. After 8h of incubation in BWW, motility was maintained at 79.3±9.3%, with 77.0±10.4% rapid and 65.7±8.7% progressively motile spermatozoa. By contrast, motility was <10% at the same 8-h time point in all of the other media assessed. After 2h of incubation in BWW, tammar spermatozoa consumed more oxygen than their counterparts in PBS (52.0±2.7 vs 75.0±6.6µL per 108 spermatozoa per 2h; P<0.001). Motility was not enhanced in any of these media by the addition of 5mM N-acetyl-D-glucosamine, the major energy substrate in wallaby semen. However, addition of dibutyryl cAMP and pentoxifylline in BWW resulted in the extremely rapid induction of hyperactivated motility in the entire sperm population. This burst of hyperactivated motility was entirely dependent on calcium in BWW and significantly inhibited by calmidazolium, a calmodulin inhibitor. A set of computer-assisted sperm analysis parameters were identified that permitted the accurate quantification of hyperactivation rates in this species. This is the first comparative analysis of media for harvesting and incubating marsupial spermatozoa and the first record of hyperactivated motility in any marsupial species.

Acute Kidney Injury is More Common in Acute Haemorrhagic Stroke in Mymensingh Medical College Hospital.

Acute kidney injury (AKI) is a common complication after acute stroke and is an independent predictor of both early and long-term mortality after acute stroke. Acute kidney injury is associated with increased mortality in haemorrhagic stroke patients. This cross sectional observational study was conducted in Nephrology, Neuromedicine and Medicine department of Mymensingh Medical College & Hospital, Mymensingh from July 2012 to June 2014. A total of 240 patients with newly detected acute stroke confirmed by CT scan of brain were included in this study. According to this study, 15.42% of acute stroke patients developed AKI. Among the patients with haemorrhagic stroke 21.87% developed AKI while only 13.07% patients with ischaemic stroke developed AKI. So, early diagnosis and management of AKI in patients with acute stroke especially in haemorrhagic stroke is very important to reduce the morbidity and mortality of these patients.

Rotavirus is Predominent Enteropathogen in Acute Childhood Diarrhea in Mymensingh.

The study was carried out from July 2011 to June 2012 in the Department of Microbiology, Mymensingh Medical College. A total of 200 clinically diagnosed diarrheal paediatrics patients were included in this study. Stool specimens were examined by standard laboratory methods for identification of enteropathogens. Diarrheagenic Escherichia coli strains were detected by Multiplex PCR following standard methods and Rotavirus genome was detected by Polyacrylamide Gel Electrophoresis (PAGE). Rotavirus was the most common enteropathogen detected in 69(34.5%) cases, followed by Diarrheagenic Escherichia coli (DEC) and Campylobacter species in 34(17.0%) and 23(11.5%) cases respectively. Rotavirus detection rate was high in upto 1 year age group which was 51(25.5%).

Genetic consequences of habitat fragmentation during a range expansion.

We investigate the effect of habitat fragmentation on the genetic diversity of a species experiencing a range expansion. These two evolutionary processes have not been studied yet, at the same time, owing to the difficulties of deriving analytic results for non-equilibrium models. Here we provide a description of their interaction by using extensive spatial and temporal coalescent simulations and we suggest guidelines for a proper genetic sampling to detect fragmentation. To model habitat fragmentation, we simulated a two-dimensional lattice of demes partitioned into groups (patches) by adding barriers to dispersal. After letting a population expand on this grid, we sampled lineages from the lattice at several scales and studied their coalescent history. We find that in order to detect fragmentation, one needs to extensively sample at a local level rather than at a landscape level. This is because the gene genealogy of a scattered sample is less sensitive to the presence of genetic barriers. Considering the effect of temporal changes of fragmentation intensities, we find that at least 10, but often >100, generations are needed to affect local genetic diversity and population structure. This result explains why recent habitat fragmentation does not always lead to detectable signatures in the genetic structure of populations. Finally, as expected, long-distance dispersal increases local genetic diversity and decreases levels of population differentiation, efficiently counteracting the effects of fragmentation.

Use of modified blood agar plate for identification of pathogenic campylobacter species at Mymensingh Medical College .

This cross sectional study was carried out from July 2011 to June 2012 in the Department of Microbiology, Mymensingh Medical College to diagnose etiology of diarrhea caused by Campylobacter species. A total of 200 clinically diagnosed diarrheal pediatric patients were included in this study. Among the 200 stool specimens evaluated, 23(11.5%) samples were positive for Campylobacter species, isolation rate was 15(65.2%) in upto 1 year age group and 08(34.7%) in more than 1 year age group. Among 23 positive cases, 20(86.95%) were C. jejuni and 03(13.05%) were C. coli. The prevalence of Campylobacter infection found in the present study was higher below 1 year age group and was very much close to other countries of this Sub continent.

Multiplex polymerase chain reaction for detection of Campylobacter from stool specimen.

This was a study to prospectively evaluate the sensitivity and specificity of multiplex polymerase chain reaction (PCR) to identify Campylobacter. Multiplex polymerase chain reaction (PCR) based on cadF, hipO & asp gene for Campylobacter genus, C. jejuni & C. coli were tested for detection of Campylobacter jejuni & C. coli in naturally infected faecal samples of human. All the samples were subjected to the cultural isolation of organism and biochemical characterization. The samples resulted in the amplification of a DNA fragment of size 400 bp, 500 bp &735 bp in PCR assay. Two hundred faecal samples comprising diarrheal stools, 23(11.5%) could be detected by isolation whereas 24(12.0%) were found positive by PCR. All culture positive cases were positive by PCR and among 01 culture negative case, were positive by PCR. PCR was found to be more sensitive for Campylobacter detection in faecal samples 12.0% as relative to culture isolation which could detect the organism in 11.5% samples. Sensitivity and specificity of PCR were 100% and 99.4% respectively taking Culture as gold standard. The results depicted the superior efficacy of PCR for rapid screening of samples owing to its high sensitivity, specificity and automation potential.

Campylobacteriosis - an overview.

Campylobacteriosis is a collective term, used for infectious, emerging foodborne disease caused by Campylobacter species comprising Gram negative, curved, and microaerophilic pathogens. The true incidence of human campylobacteriosis is unknown for most countries of the world including Bangladesh. But campylobacteriosis is not uncommon in our country. Due to its increasing incidence in many countries of the world, it is an important issue now a day. Animals such as birds are the main sources of infection. Farm animals such as cattle, poultry are commonly infected from such sources and raw milk, undercooked or poorly handled meat becomes contaminated. Transmission of campylobacteriosis to human occurs through consumption of infected, unpasteurized animal milk and milk products, undercooked poultry and through contaminated drinking water. Contact with contaminated poultry, livestock or household pets, especially puppies, can also cause disease. Due to variability of clinical features and limited availability of laboratory facilities, the disease remains largely under-reported. Early and specific diagnosis is important to ensure a favourable outcome regarding this food borne disease. Antibiotic treatment is controversial, and has only a benefit on the duration of symptoms. Campylobacter infections can be prevented by some simple hygienic food handling practices.

Culture of pathogenic campylobacter species at Mymensingh Medical College.

Childhood diarrhea represents a major public health problem in developing countries, where campylobacteriosis is widespread and causes significant morbidity and mortality in infants and children. Despite the increasing importance of campylobacteriosis, most developing countries and even many developed countries do not have surveillance systems to measure the health and economic burden of human campylobacteriosis, nor detect trends in outbreaks. The present study was carried out to diagnose etiology of diarrhea caused by Campylobacter species. A total of 150 clinically diagnosed diarrheal pediatric patients were included in this study, of which 98(65.3%) were male and 52(34.6%) female from the Department of Pediatrics, Mymensingh Medical College Hospital, Mymensingh, Bangladesh from July 2011 to April 2012. Stool specimens were collected from each of the cases. The specimens were cultured in appropriate media and Campylobacters were isolated and identified by recommended tests. Among 150 cases, 17(11.3%) were culture positive for Campylobacter species, of which 15(88.2%) were C. jejuni and 02(11.7%) were C. coli. Of the cases, below 1 year of age group were 106(70.6%) cases showing 12(70.5%) positive for Campylobacters and 44(29.33%) cases were above 1 year of age group showing 05(29.41%) positive. The prevalence of Campylobacter infection found in the present study was higher below 1 year age group and was very much close to other countries of this subcontinent.

Safety, Feasibility and Efficacy of Lokomat® and Armeo®Spring Training in Deconditioned Paediatric, Adolescent and Young Adult Cancer Patients.

BACKGROUND: Rehabilitation robotics is a field of study which aims to understand and augment rehabilitation through the use of robotics devices. OBJECTIVE: This proof of concept study aimed to test the safety (no. adverse events, incidence of infection), feasibility (program demand, adherence, participant satisfaction) and efficacy (Peak Oxygen uptake (VO2peak), 6-min walk test, gait speeds, Canadian Occupational Performance Measure, quality of life) of Lokomat® and Armeo®Spring training in children and adolescents and young adults (AYAs) during or soon after cancer treatment. METHOD: This was a 6-week single arm pre-post study. Cancer patients with significant musculoskeletal, neurological, gait and/or upper limb deficiency aged 5 to 25 years were recruited. The rehabilitation program included access to two robotic orthoses: the Lokomat® and/or Armeo®Spring. Robotic devices utilised real-time biofeedback and computer games to engage and guide participants through a repetitive functional range of movement aimed at improving functional deficiencies. Progressive increases in exercise intensity and duration were encouraged. RESULTS: Twentey-eight participants were approached for study; twenty-one consented. Seventy-six percent completed the six-week intervention with an overall adherence of 83%. The mean participant satisfaction score was 8.8/10. Forty-nine adverse events were recorded throughout the course of the study, forty-five grade 1, three grade 2 and one grade 3. No adverse events led to withdrawal from the study. Preliminary efficacy results indicate large beneficial effects on VO2peak (r = 0.63), 10 m comfortable pace walk (r = 0.51) and maximal pace walk (r = 0.60), 6-min walk test (r = 0.60), maximal back and leg strength (r = 0.71), trunk flexibility (r = 0.60), The European Organization for the Research and Treatment of Cancer Quality of Life Questionnaire (EORTC QLQ C30) (r = 0.61), Functional Assessment of Chronic Illness Therapy-Fatigue (FACIT F) r = 0.53 and the Canadian Occupational Performance Measure, satisfaction (r = 0.88) and performance scores (r = 0.83), and moderate beneficial effects on Leisure Score Index (LSI) (r = 0.30). CONCLUSION: Our results suggest that Lokomat® and Armeo®Spring training is safe and feasible for use in children and AYAs who are currently undergoing or have recently completed cancer therapy. A larger controlled trial investigating the efficacy of robotics rehabilitation in this cohort is warranted.

Supporting career choices in dentistry.

The Cork University Dental School & Hospital, University College Cork, introduced an innovative programme in April 2011, which provided prospective dental students with an opportunity to participate in a one-day experiential workshop. The aim of the workshop was to provide students with an overview of the dental undergraduate programmes. Feedback on the workshop was exceptionally positive, and prospective students would recommend the workshop to a fellow student, as it helped to inform their decision about choosing dentistry as a first option.

Process evaluation and challenges in collecting data from an after-school sports and literacy program in a diverse, low-income community.

BACKGROUND: To understand how programs succeed we must evaluate them. The purpose of this paper was to examine the intervention and evaluation processes and identify areas of success and challenges in delivering and evaluating the Reflective Educational Approach to Character and Health (REACH) after-school program in a low SES community. METHODS: Sixty-six fifth and sixth graders from two schools participated. Data were collected at the intervention and control schools at four time points over the year. Data collected at baseline (Aug/Sep 2016), and Time 4 (May, 2017) were used for the analysis. Reach and fidelity to the intervention were assessed along with information on the process of data collection for variables of interest (e.g., accelerometer-measured physical activity level, FITNESSGRAM tests, vertical jump, and literacy). Missing data were imputed and a 2(School) by 2(Time) mixed factorial ANOVA was performed to examine the efficacy of the intervention. RESULTS: There were no significant time by school interactions for any of the outcomes assessed. There were several challenges in evaluating the program such as low compliance to wearing the accelerometer, lack of effort during literacy tests, peers affecting effort on physical tests, and missing data. CONCLUSIONS: We posit that research implementation be re-examined in community-based research that is conducted with students at the elementary level in low-income communities. Future research should engage with youth in the data collection process to make it a meaningful experience for them and to possibly reduce attrition from the program.

A statistical evaluation of models for the initial settlement of the american continent emphasizes the importance of gene flow with Asia.

Although there is agreement in that the Bering Strait was the entry point for the initial colonization of the American continent, there is considerable uncertainty regarding the timing and pattern of human migration from Asia to America. In order to perform a statistical assessment of the relative probability of alternative migration scenarios and to estimate key demographic parameters associated with them, we used an approximate Bayesian computation framework to analyze a data set of 401 autosomal microsatellite loci typed in 29 native American populations. A major finding is that a single, discrete, wave of colonization is highly inconsistent with observed levels of genetic diversity. A scenario with two discrete migration waves is also not supported by the data. The current genetic diversity of Amerindian populations is best explained by a third model involving recurrent gene flow between Asia and America, after initial colonization. We estimate that this colonization involved about 100 individuals and occurred some 13,000 years ago, in agreement with well-established archeological data.

Live attenuated, multiply deleted simian immunodeficiency virus causes AIDS in infant and adult macaques.

A substantial risk in using live attenuated, multiply deleted viruses as vaccines against AIDS is their potential to induce AIDS. A mutant of the simian immunodeficiency virus (SIV) with large deletions in nef and vpr and in the negative regulatory element induced AIDS in six of eight infant macaques vaccinated orally or intravenously. Early signs of immune dysfunction were seen in the remaining two offspring. Prolonged follow-up of sixteen vaccinated adult macaques also showed resurgence of chronic viremia in four animals: two of these developed early signs of disease and one died of AIDS. We conclude that this multiply deleted SIV is pathogenic and that human AIDS vaccines built on similar prototypes may cause AIDS.