Simulations of the infrared, Raman, and 2D-IR photon echo spectra of water in nanoscale silica pores

Vibrational spectroscopy is frequently used to characterize nanoconfined liquids and probe the effect of the confining framework on the liquid structure and dynamics relative to the corresponding bulk fluid. However, it is still unclear what molecular-level information can be obtained from such measurements. In this paper, we address this question by using molecular dynamics (MD) simulations to reproduce the linear infrared (IR), Raman, and two-dimensional IR (2D-IR) photon echo spectra for water confined within hydrophilic (hydroxyl-terminated) silica mesopores. To simplify the spectra the OH stretching region of isotopically dilute HOD in D2O is considered. An empirical mapping approach is used to obtain the OH vibrational frequencies, transition dipoles, and transition polarizabilities from the MD simulations. The simulated linear IR and Raman spectra are in good general agreement with measured spectra of water in mesoporous silica reported in the literature. The key effect of confinement on the water spectrum is a vibrational blueshift for OH groups that are closest to the pore interface. The blueshift can be attributed to the weaker hydrogen bonds (H-bonds) formed between the OH groups and silica oxygen acceptors. Non-Condon effects greatly diminish the contribution of these OH moieties to the linear IR spectrum, but these weaker H-bonds are readily apparent in the Raman spectrum. The 2D-IR spectra have not yet been measured and thus the present results represent a prediction. The simulated spectra indicates that it should be possible to probe the slower spectral diffusion of confined water compared to the bulk liquid by analysis of the 2D-IR spectra

Aqueous electrolytes confined within functionalized silica nanopores

Molecular dynamics simulations have been carried out to investigate structural and dynamical characteristics of NaCl aqueous solutions confined within silica nanopores in contact with a “bulk-like” reservoir. Two types of pores, with diameters intermediate between 20 Å and 37.5 Å, were investigated: The first one corresponded to hydrophobic cavities, in which the prevailing wall-solution interactions were of the Lennard-Jones type. In addition, we also examined the behavior of solutions trapped within hydrophilic cavities, in which a set of unsaturated O-sites at the wall were transformed in polar silanol Si–OH groups. In all cases, the overall concentrations of the trapped electrolytes exhibited important reductions that, in the case of the narrowest pores, attained 50% of the bulk value. Local concentrations within the pores also showed important fluctuations. In hydrophobic cavities, the close vicinity of the pore wall was coated exclusively by the solvent, whereas in hydrophilic pores, selective adsorption of Na+ ions was also observed. Mass and charge transport were also investigated. Individual diffusion coefficients did not present large codifications from what is perceived in the bulk; contrasting, the electrical conductivity exhibited important reductions. The qualitative differences are rationalized in terms of simple geometrical considerations.Peer ReviewedPostprint (published version

Origins of the non-exponential reorientation dynamics of nanoconfined water

This is the published version. Copyright 2014 American Institute of PhysicsThe dynamics of water are dramatically modified upon confinement in nanoscale hydrophilic silica pores. In particular, the OH reorientation dynamics of the interfacial water are non-exponential and dramatically slowed relative to the bulk liquid. A detailed analysis of molecular dynamics simulations is carried out to elucidate the microscopic origins of this behavior. The results are analyzed in the context of the extended jump model for water that describes the reorientation as a combination of hydrogen-bond exchanges, or jumps, and rotation of intact hydrogen bonds, with the former representing the dominant contribution. Within this model, the roles of surface and dynamical heterogeneities are considered by spatially resolving the hydrogen-bond jump dynamics into individual sites on the silica pore surface. For each site the dynamics is nearly mono-exponential, indicating that dynamical heterogeneity is at most a minor influence, while the distribution of these individual site jump times is broad. The non-exponential dynamics can also not be attributed to enthalpic contributions to the barriers to hydrogen-bond exchanges. Two entropic effects related to the surface roughness are found to explain the retarded and diverse dynamics: those associated with the approach of a new hydrogen-bond acceptor and with the breaking of the initial hydrogen-bond

Results of domestic migration on juvenile delinquency in Adana, Turkey

PubMedID: 28601041Objective The aim of this study is to determine the effect of migration on children in the juvenile justice system. The study takes into account whether these children arrived in the city via migration or not, the types of crimes against property and persons committed by the children brought before the Juvenile Courts, and the types, frequency, and durations of punishments and precautionary decisions they received. In addition, the study examines the children's ability to realize the meaning and consequences of their crimes and to lead their future behaviors effectively. Method Data gathered from children between 3 and 18 years of age who appeared before the 1, 2, and 3 numbered Juvenile Courts of Adana Courthouse after January 2004 on charges of committing a crime, and/or children who were sent to or who applied to the Provincial Directorate for National Education based on the decision of the Court has been evaluated retrospectively. Results Six hundred and eighty children were studied. Of these, 602 (88.5%) were male and 78 (11.5) were female. The average age of the child at the time of the commitment of the crime was 13 years and 8 months ± 2.18 years. It has been observed that there are statistically meaningful differences for children involved in delinquency between cases whether they come via migration or regardless of migration and types of crimes committed (p = 0.004). When cities faced with migration from other places and types of crime committed by children are compared, it has been observed that there are meaningful differences between the types of crimes committed by non-migrant versus migrant children (p = 0.012). Conclusions It is important to state the reasons for delinquency and to obtain data to prevent future delinquency and to put forward regional and local recommendations within the scope of the data. © 2017 Elsevier Ltd and Faculty of Forensic and Legal Medicin

Bochdalek hernia in adulthood: A review and an autopsy case report

PubMedID: 8064271Bochdalek hernia is rare in adulthood with fewer than 100 cases having been reported in the world literature. We present a delayed case of Bochdalek hernia in an adult leading to sudden death, first diagnosed at medicolegal autopsy

Sudden death due to a colloid cyst of the third ventricle: Report of three cases with a special sign at autopsy

PubMedID: 19446972Colloid cysts of the third ventricle are rare benign cysts but they may be potentially life-threatening. Three cases of sudden death resulting from colloid cysts of the third ventricle are presented. The first and second cases were treated for migraine headaches. In the first case, the patient was a 24-year-old woman who presented to the hospital with a severe headache and was sent back home after medical treatment. Six hours later, she was found dead in her bed. The second case was a 21-year-old woman who experienced a severe headache, dizziness and vomiting 1 day prior to her death. She was transported to the hospital, where she was pronounced dead upon arrival. The third case was a 25-year-old man who experienced headaches and vomiting and was diagnosed with and medically treated for sinusitis. He lost consciousness and was taken to hospital, where he was pronounced dead on arrival. During the autopsy of all three cases, there was a grey transillumination area observed that occurred due to the stretching of tissue at the base of brain between the corpus mamillare and chiasma opticum. Dissection of the brain revealed a colloid cyst of the third ventricle. To avoid such fatal complications, prompt diagnosis using CT or MRI is essential in patients who have a long-standing history of intermittent headaches. During the autopsy of the sudden deaths of people with medical antecedents of headaches, if a grey color is observed between the chiasma opticum and the corpus mamillare in the base of the brain, a colloid cyst should be considered and this region should be dissected and examined carefully. © 2009 Elsevier Ireland Ltd. All rights reserved

Growing skull fractures (craniocerebral erosion)

WOS: 000165245900006PubMed ID: 11086738The incidence of growing skull fractures ranges from less than 0.05% to 1.6%. We reviewed 22 growing skull fracture patients retrospectively. There were 15 boys and seven girls ranging in age from newborn to 6 years (mean: 12.4 months) at the time of injury. Falling was the most frequent cause of injury. In total, 17 patients presented with a scalp mass. The scalp was sunken over the bone defect in three patients. Other symptoms and signs were seizure in five patients, hemiparesis in four, recurrent meningitis in one, and pulsatile exophtalmus in one. The most common location was the parietal region. The extent of dural defect was always greater than that of bony defect, except in one case that had been previously shunted for hydrocephalus. In another patient with a growing fracture in the posterior cranial fossa, the dural edges could not be exposed, although a wide craniotomy was performed. Therefore, a cystoperitoneal shunt was inserted. Gliotic tissue was present in all the patients. Cyst or cystic lesions were observed in only nine patients, duraplasty was performed in 21, 16 were neurologically intact, and six had minor deficits. All patients under the age of 3 years with a diastatic skull fracture should be closely followed up. A sustaining diastatic fracture and brain herniation through the skull defect shown on CT or MRI imply a growing skull fracture

BOCHDALEK HERNIA IN ADULTHOOD - A REVIEW AND AN AUTOPSY CASE-REPORT

WOS: A1994NY09600026PubMed ID: 8064271Bochdalek hernia is rare in adulthood with fewer than 100 cases having been reported in the world literature. We present a delayed case of Bochdalek hernia in an adult leading to sudden death, first diagnosed at medicolegal autopsy

Accidental hanging deaths in children in Konya, Turkey between 1998 and 2007

PubMedID: 20202070In general, hanging cases are the result of suicide, and accidental and homicidal hanging cases are rarely seen. This study retrospectively investigated 4571 death examinations and autopsies that were performed at The Konya Branch of the Forensic Medicine Council (Turkey) between 1998 and 2007; hanging was involved in 201 (6.5%) of the cases. There were a total of 13 accidental hanging cases, where 12 of these involved children. In seven of the cases, the accidental hanging involved a scarf that wraps around swing-like cradles and is intended to prevent infants from falling down. It was concluded that accidental hanging deaths can be reduced by replacing swing-like cradles with cribs that are designed for children, removing ropes in and around the house, and preventing children from reaching and/or playing with rope-like objects. © 2010 American Academy of Forensic Sciences