418 research outputs found
Heterogeneous condensation of the Lennard-Jones vapor onto a nanoscale seed particle
The heterogeneous condensation of a Lennard-Jones vapor onto a nanoscale seed
particle is studied using molecular dynamics simulations. Measuring the
nucleation rate and the height of the free energy barrier using the mean first
passage time method shows that the presence of a weakly interacting seed has
little effect on the work of forming very small cluster embryos but accelerates
the rate by lowering the barrier for larger clusters. We suggest that this
results from a competition between the energetic and entropic features of
cluster formation in the bulk and at the heterogeneity. As the interaction is
increased, the free energy of formation is reduced for all cluster sizes. We
also develop a simple phenomenological model of film formation on a small seed
that captures the general features of the nucleation process for small
heterogeneities. A comparison of our simulation results with the model shows
that heterogeneous classical nucleation theory provides a good estimate of the
critical size of the film but significantly over-estimates the size of the
barrier.Comment: 9 pages, 10 figures, In Print J. Chem. Phy
Desiccation and Cracking Behavior of Three Compacted Landfill Liner Soils
Tests were conducted to investigate desiccation cracking of three compacted liner soils obtained from local landfills in southeast Michigan. The soils had low plasticity with varying fines content. Large-scale samples of the soils were subjected to wetting and drying cycles. Surficial dimensions of cracks and suction in the soils were monitored. Surficial dimensions of cracks were quantified using the crack intensity factor (CIF), which is the ratio of the surface area of cracks to the total surface area of a soil. All of the soils were subjected to a compaction–dry cycle (i.e. soils were allowed to dry after compaction) and a subsequent wet–dry cycle. An additional sample of one of the soils was subjected to a compaction–dry cycle and three wet–dry cycles. The maximum CIF obtained in the tests was 7% and suctions exceeding 6000 kPa were recorded. It was observed that cracking was affected by the fines content of the soils. In general, high suctions, rapid increases in suctions, and high amount of cracking were observed in soils with high fines content, with less cracking observed in soil with low fines content. In addition, it was observed that cracking increased significantly due to addition of moisture to the soils. The CIF for wet–dry cycles were significantly greater than the CIF for compaction–dry cycles. Subsequent to moisture addition to the soils, critical suctions that caused a significant change in CIF during the drying cycles were wet–dry cycles, the amount of cracking did not change significantly after the second cycle
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Risk factors associated with post-traumatic stress symptoms following childbirth in Turkey
OBJECTIVE: this study examined factors associated with symptoms of post-traumatic stress (PTS) following childbirth in women with normal, low-risk pregnancies in Nigde, Turkey.
DESIGN: a prospective longitudinal design where women completed questionnaire measures at 20+ weeks' gestation and 6-8 weeks after birth.
SETTING: eligible pregnant women were recruited from nine family healthcare centres in Nigde between September 2013 and July 2014.
PARTICIPANTS: a total of 242 women completed questionnaires at both time points.
MEASURES: PTS symptoms were measured using the Impact of Event Scale-Revised (IES-R) 6-8 weeks after birth. Potential protective or risk factors of childbirth self-efficacy, fear of childbirth, adaptation to pregnancy/motherhood, and perceived social support were measured in pregnancy and after birth. Perceived support and control during birth was measured after birth. Demographic and obstetric information was collected in pregnancy using standard self-report questions.
FINDINGS: PTS symptoms were associated with being multiparous, having a planned pregnancy, poor psychological adaptation to pregnancy, higher outcome expectancy but lower efficacy expectancy during pregnancy, urinary catheterization during labour, less support and perceived control in birth, less satisfaction with hospital care, poor psychological adaptation to motherhood and increased fear of birth post partum. Regression analyses showed the strongest correlates of PTS symptoms were high outcome and low efficacy expectancies in pregnancy, urinary catheterization in labour, poor psychological adaptation to motherhood and increased fear of birth post partum. This model accounted for 29% of the variance in PTS symptoms.
CONCLUSIONS: this study suggests women in this province in Turkey report PTS symptoms after birth and this is associated with childbirth self-efficacy in pregnancy, birth factors, and poor adaptation to motherhood and increased fear of birth post partum.
IMPLICATIONS FOR PRACTICE: maternity care services in Turkey need to recognise the potential impact of birth experiences on women's mental health and adaptation after birth. The importance of self-efficacy in pregnancy suggests antenatal education or support may protect women against developing post partum PTS, but this needs to be examined further
Role of the compaction energy level on the small strain stiffness of a silty sand soil subjected to wetting and drying
The dynamic properties of a soil are routinely quantified to describe its engineering behaviour under repeated loading. While the results of previous research studies indicate that the effect of changes in suction on the dynamic response is significant, only limited research has been engaged in the assessment of post-compacted changes in suction induced by cycles of wetting and drying. In this paper, aspects related to the dynamic properties with special reference to small strain shear modulus behaviour at different compaction energy levels are described and outlined. Particular emphasis is placed on the hysteric behaviour observed (i.e. amplitude of the hysteresis loop) and its dependence on the imparted compaction energy. The results not only confirm the importance of the recent suction ratio (or CSR) in governing the mechanical response at small strain, but they also indicate that higher compaction energy levels induce smaller hysteresis loops
Pattern and Outcome of Chest Injuries at Bugando Medical Centre in Northwestern Tanzania.
Chest injuries constitute a continuing challenge to the trauma or general surgeon practicing in developing countries. This study was conducted to outline the etiological spectrum, injury patterns and short term outcome of these injuries in our setting. This was a prospective study involving chest injury patients admitted to Bugando Medical Centre over a six-month period from November 2009 to April 2010 inclusive. A total of 150 chest injury patients were studied. Males outnumbered females by a ratio of 3.8:1. Their ages ranged from 1 to 80 years (mean = 32.17 years). The majority of patients (72.7%) sustained blunt injuries. Road traffic crush was the most common cause of injuries affecting 50.7% of patients. Chest wall wounds, hemothorax and rib fractures were the most common type of injuries accounting for 30.0%, 21.3% and 20.7% respectively. Associated injuries were noted in 56.0% of patients and head/neck (33.3%) and musculoskeletal regions (26.7%) were commonly affected. The majority of patients (55.3%) were treated successfully with non-operative approach. Underwater seal drainage was performed in 39 patients (19.3%). One patient (0.7%) underwent thoracotomy due to hemopericardium. Thirty nine patients (26.0%) had complications of which wound sepsis (14.7%) and complications of long bone fractures (12.0%) were the most common complications. The mean LOS was 13.17 days and mortality rate was 3.3%. Using multivariate logistic regression analysis, associated injuries, the type of injury, trauma scores (ISS, RTS and PTS) were found to be significant predictors of the LOS (P < 0.001), whereas mortality was significantly associated with pre-morbid illness, associated injuries, trauma scores (ISS, RTS and PTS), the need for ICU admission and the presence of complications (P < 0.001). Chest injuries resulting from RTCs remain a major public health problem in this part of Tanzania. Urgent preventive measures targeting at reducing the occurrence of RTCs is necessary to reduce the incidence of chest injuries in this region
CacheZoom: How SGX Amplifies The Power of Cache Attacks
In modern computing environments, hardware resources are commonly shared, and
parallel computation is widely used. Parallel tasks can cause privacy and
security problems if proper isolation is not enforced. Intel proposed SGX to
create a trusted execution environment within the processor. SGX relies on the
hardware, and claims runtime protection even if the OS and other software
components are malicious. However, SGX disregards side-channel attacks. We
introduce a powerful cache side-channel attack that provides system adversaries
a high resolution channel. Our attack tool named CacheZoom is able to virtually
track all memory accesses of SGX enclaves with high spatial and temporal
precision. As proof of concept, we demonstrate AES key recovery attacks on
commonly used implementations including those that were believed to be
resistant in previous scenarios. Our results show that SGX cannot protect
critical data sensitive computations, and efficient AES key recovery is
possible in a practical environment. In contrast to previous works which
require hundreds of measurements, this is the first cache side-channel attack
on a real system that can recover AES keys with a minimal number of
measurements. We can successfully recover AES keys from T-Table based
implementations with as few as ten measurements.Comment: Accepted at Conference on Cryptographic Hardware and Embedded Systems
(CHES '17
Sex estimation in a Turkish population using Purkait’s triangle: a virtual approach by 3-dimensional computed tomography (3D-CT)
Sex estimation is considered one of the first steps in the forensic identification process.
Morphological and morphometrical differences between males and females have been
used as means for morphoscopic and metric methods on both cranial and postcranial
skeletal elements. When dry skeletal elements are not available, virtual data can be used
as a substitute. The present research explores 3-dimensional (3D) scans from a Turkish
population to test a sex estimation method developed by Purkait (2005). Overall, 296
individuals were used in this study (158 males and 138 females). Purkait’s triangle
parameters were measured on computed tomography (CT) scans obtained from both
right and left femora of each patient at the Bakirkoy Dr. Sadi Konuk Training Research
Hospital (Istanbul, Turkey). Intra- and inter-observer errors were assessed for all variables
through technical error of measurements analysis. Bilateral asymmetry and sex differences
were evaluated using parametric and non-parametric statistical approaches. Univariate
and multivariate discriminant function analyses were then conducted. Observer errors
demonstrated an overall agreement within and between experts, as indicated by technical
error of measurement (TEM) results. No bilateral asymmetries were reported, and all
parameters demonstrated a statistically significant difference between males and females.
Fourteen discriminant models were generated by applying single and combined parameters,
producing a total correct sex classification ranging from 78.4% to 92.6%. In addition, over
67% of the total sample was accurately classified, with 95% or greater posterior probabilities.
Our study demonstrates the feasibility of 3D sex estimation using Purkait’s triangle on
a Turkish population, with accuracy rates comparable to those reported in other
populations. This is the first attempt to apply this method on virtual data and although
further validation and standardisation are recommended for its application on dry bone,
this research constitutes a significant contribution to the development of population-specific
standards when only virtual data are available
Respiratory syncytial virus-associated mortality among young infants in Karachi, Pakistan: A prospective postmortem surveillance study
Background: Respiratory syncytial virus (RSV) is an important cause of infant morbidity and mortality and a potential target for maternal immunization strategies. However, data on the role of RSV in young infant deaths in developing countries are limited.Methods: We conducted a community-based mortality surveillance from August 2018-March 2020 for infants ≤6 months in Karachi, Pakistan. We tested (reverse transcription-polymerase chain reaction) nasopharyngeal swabs from deceased infants for presence of RSV. We performed verbal autopsies and calculated odds of RSV-associated mortality with 95% CIs and used multivariable logistic regression to evaluate associations.Results: We collected 490 nasopharyngeal specimens from 1280 eligible infant deaths. There were 377/490 (76.9%) live births and 14/377 (3.7%; 95% CI: 1.8-5.6) were RSV positive. Most deaths occurred in neonates (254/377; 67.4%), males (226/377; 59.9%), and respiratory illnesses (206/377; 54.6%). Postneonatal age (10/14, 71.4%; OR: 5.5; 95% CI: 1.7-18.0), respiratory symptoms (12/14, 85.7%; OR: 5.2; 1.2-23.7), and high RSV season (9/14, 64.3%; OR: 4.4; 1.4-13.3) were associated with RSV mortality. In multivariable logistic regression analysis, respiratory symptoms (OR: 6.6; 95% CI: 1.3-32.5), RSV seasonality (6.1; 1.8-20.4), and age (9.2; 2.6-33.1) were significant predictors of RSV-associated mortality.Conclusions: RSV has a significant mortality burden in early infancy in Karachi, Pakistan. Age, RSV seasonality, and respiratory symptoms were significant predictors of RSV-associated mortality. Our findings have implications for clinical management of young infants with cold-like symptoms, policy development, and research regarding maternal immunization against RSV during pregnancy, in resource-constrained, low-income, and vaccine-hesitant populations
Use of polyethylene glycol coatings for optical fibre humidity sensing
Humidity induced change in the refractive index and thickness of the polyethylene glycol (PEG) coatings are in situ investigated for a range from 10 to 95%, using an optical waveguide spectroscopic technique. It is experimentally demonstrated that, upon humidity change, the optical and swelling characteristics of the PEG coatings can be employed to build a plastic fibre optic humidity sensor. The sensing mechanism is based on the humidity induced change in the refractive index of the PEG film, which is directly coated onto a polished segment of a plastic optical fibre with dip-coating method. It is observed that PEG, which is a highly hydrophilic material, shows no monotonic linear response to humidity but gives different characteristics for various ranges of humidity levels both in index of refraction and in thickness. It undergoes a physical phase change from a semi-crystal line structure to a gel one at around 80% relative humidity. At this phase change point, a drastic decrease occurs in the index of refraction as well as a drastic increase in the swelling of the PEG film. In addition, PEG coatings are hydrogenated in a vacuum chamber. It is observed that the hydrogen has a preventing effect on the humidity induced phase change in PEG coatings. Finally, the possibility of using PEG coatings in construction of a real plastic fibre optic humidity sensor is discussed. (C) 2008 The Optical Society of Japan
Right-invariant Sobolev metrics of fractional order on the diffeomorphism group of the circle
In this paper, we study the geodesic flow of a right-invariant metric induced
by a general Fourier multiplier on the diffeomorphism group of the circle and
on some of its homogeneous spaces. This study covers in particular
right-invariant metrics induced by Sobolev norms of fractional order. We show
that, under a certain condition on the symbol of the inertia operator (which is
satisfied for the fractional Sobolev norm for ), the
corresponding initial value problem is well-posed in the smooth category and
that the Riemannian exponential map is a smooth local diffeomorphism.
Paradigmatic examples of our general setting cover, besides all traditional
Euler equations induced by a local inertia operator, the Constantin-Lax-Majda
equation, and the Euler-Weil-Petersson equation.Comment: 40 pages. Corrected typos and improved redactio
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