Dioctadecyldimethylammonium bromide (DODAB), a potential candidate for applications in drug transport or DNA transfection, forms bilayer in aqueous media exhibiting a rich phase behavior. Here, we report the detailed dynamical features of DODAB bilayer in their different phases (coagel, gel and fluid) as studied by neutron scattering techniques. Elastic intensity scans show dynamical transitions at 327 K in the heating and at 311 K and 299 K during cooling cycle. These results are consistent with calorimetric studies, identified as coagel-fluid phase transition during heating, and fluid-gel and gel-coagel phase transitions during cooling. Quasielastic Neutron Scattering (QENS) data analysis showed presence of only localized internal motion in the coagel phase. However, in the gel and fluid phases, two distinct motions appear, namely lateral motion of the DODAB monomers and a faster localized internal motion of the monomers. The lateral motion of the DODAB molecule is described by a continuous diffusion model and is found to be about an order of magnitude slower in the gel phase than in the fluid phase. To gain molecular insights, molecular dynamics simulations of DODAB bilayer have also been carried out and the results are found to be in agreement with the experiment.
Over the last couple of decades, deep eutectic solvents (DESs) have emerged as novel alternatives to ionic liquids that are extensively used in synthesis of innovative materials, metal processing, catalysis, etc. However, their usage is limited, primarily because of the large viscosity and poor conductivity. Therefore, an understanding of the molecular origin of these properties is essential to improve their industrial applicability. Here, we present the report of the nanoscopic diffusion mechanism of acetamide in a DES synthesized with lithium perchlorate as studied using neutron scattering and molecular dynamics (MD) simulation techniques. Although, the acetamide based DES (ADES) has remarkably lower freezing point compared to pure acetamide, the molecular mobility is found to be enormously restricted in the former. MD simulation indicates a diffusion model with two distinct processes, corresponding to, long range jump diffusion and localised diffusion within a restricted volume. This model is validated by analysis of neutron scattering data in both molten acetamide and ADES. The long range diffusion process of acetamide is slower by a factor of three in ADES in comparison with molten acetamide. MD simulation reveals that the long range diffusion in ADES is restricted mainly due to the formation of hydrogen bond mediated complexes between the ionic species of the salt and acetamide molecules. Hence, the origin of higher viscosity observed in ADES can be attributed to the complexation. The complex formation also explains the inhibition of the crystallisation process while cooling and thereby results in depression of the freezing point of ADES.
Despite well-known side effects, nonsteroidal anti-inflammatory drugs (NSAIDs) are one of the most prescribed drugs worldwide for their anti-inflammatory and antipyretic properties. Here, we report the effects of two NSAIDs, aspirin and indomethacin, on the thermotropic phase behavior and the dynamics of a dioctadecyldimethylammonium bromide (DODAB) lipid bilayer as studied using neutron scattering techniques. Elastic fixed window scans showed that the addition of aspirin and indomethacin affects the phase behavior of a DODAB bilayer in both heating and cooling cycles. Upon heating, there is a change in the coagel- to fluid-phase transition temperature from 327 K for pure DODAB bilayer to 321 and 323 K in the presence of aspirin and indomethacin, respectively. More strikingly, upon cooling, the addition of NSAIDs suppresses the formation of the intermediate gel phase observed in pure DODAB. The suppression of the gel phase on addition of the NSAIDs evidences the synchronous ordering of a lipid headgroup and chain. Analysis of quasi-elastic neutron scattering data showed that only localized internal motion exists in the coagel phase, whereas both internal and lateral motions exist in the fluid phase. The internal motion is described by a fractional uniaxial rotational diffusion model in the coagel phase and by a localized translation diffusion model in the fluid phase. In the coagel phase, the rotational diffusion coefficient of DODAB is found to be almost twice for the addition of the drugs, whereas the mobility fraction did not change for indomethacin but becomes twice for aspirin. In the fluid phase, the lateral motion, described well by a continuous diffusion model, is found to be slower by about ∼30% for indomethacin but almost no change for aspirin. For the internal motion, addition of aspirin leads to enhancement of the internal motion, whereas indomethacin did not show significant effect. This study shows that the effect of different NSAIDs on the dynamics of the lipid membrane is not the same; hence, one must consider these NSAIDs individually while studying their action mechanism on the cell membrane.
1. The results of thirty-nine operations for correction of drop-foot in thirty-three patients with leprosy are discussed. 2. The procedure used was circumtibial, subcutaneous, two-tailed, tendon-to-tendon transfer of the tibialis posterior to extensor hallucis longus and to extensor digitorum longus and peroneus tertius. The motor slips were inserted into the recipient tendons on the dorsum of the foot. 3. Analysis of the results showed some correlation between the angle of active dorsiflexion and the range ofactive movement ofthe ankle. The angle ofdorsiflexion seemed to determine the range of movement. 4. When contracture of the tendo calcaneus was present, simultaneous lengthening improved the angle of dorsiflexion more than the range of active movement. 5. The causes of failure were sepsis, failure of re-education and unrecognised tightness of the tendo calcaneus. 6. The advantages of the present procedure are mentioned.
As handwriting is influenced by physiology, training, and other behavioral factors, a study of the handwriting of twins can shed light on the individuality of handwriting. This paper describes the methodology and results of such a study where handwriting samples of twins were compared by an automatic handwriting verification system. The results complement that of a previous study where a diverse population was used. The present study involves samples of 206 pairs of twins, where each sample consisted of a page of handwriting. The verification task was to determine whether two half-page documents (where the original samples were divided into upper and lower halves) were written by the same individual. For twins there were 1236 verification cases-including 824 tests where the textual content of writing was different, and 412 tests where it was the same. An additional set of 1648 test cases were obtained from handwriting samples of nontwins (general population). To make the handwriting comparison, the system computed macro features (overall pictorial attributes), micro features (characteristics of individual letters), and style features (characteristics of whole-word shapes and letter pairs). Four testing scenarios were evaluated: twins and nontwins writing the same text and writing different texts. Results of the verification tests show that the handwriting of twins is less discriminable than that of nontwins: an overall error rate of 12.91% for twins and 3.7% for nontwins. Error rates with identical twins were higher than with fraternal twins. Error rates in all cases can be arbitrarily reduced by rejecting (not making a decision on) borderline cases. A level of confidence in the results obtained is given by the fact that system error rates are comparable to that of humans (lower than that of lay persons and higher than that of questioned document examiners [QDEs]).KEYWORDS: forensic science, questioned document examination, handwriting processing, document analysis, writer verification, twins studyThe distinctiveness of each person's handwriting has long been intuitively observed. Methods have been developed for a human expertise of handwriting matching over many decades (1-5). Yet there is a need for studies in the quantitative assessment of the discriminative power of handwriting particularly for the acceptance by the courts of evidence provided by questioned document examiners (QDE). In a previous study of handwriting individuality (6), we reported on the discriminability of handwriting of a diverse population from across the United States. The present paper reports on a complementary study of the discriminatory power of handwriting when the population consists of a cohort group consisting of twins. Both the previous study and the current study are based on automated methods for handwriting comparison. The current study uses algorithms that are updated with respect to the types of handwriting features that are computed.The necessity of studying cohort groups such as twins has been considered to be i...
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