On hydrogen bond correlations at high pressures

In situ high pressure neutron diffraction measured lengths of O H and H O pairs in hydrogen bonds in substances are shown to follow the correlation between them established from 0.1 MPa data on different chemical compounds. In particular, the conclusion by Nelmes et al that their high pressure data on ice VIII differ from it is not supported. For compounds in which the O H stretching frequencies red shift under pressure, it is shown that wherever structural data is available, they follow the stretching frequency versus H O (or O O) distance correlation. For compounds displaying blue shifts with pressure an analogy appears to exist with improper hydrogen bonds.Comment: 12 pages,4 figure

Seam performance of knitted fabrics based on seam strength and seam efficiency

The current study has been conducted on 100% cotton, polyester/cotton and cotton/lycra single jersey fabrics for investigation of seam performance in term of seam strength and seam efficiency. The influence of various parameters, viz. sewing needle size, sewing needle type and seam angle, on seam performance of these fabrics have been studied and analyzed. The response surface methodology is employed to investigate their effect on seam strength and seam efficiency by analysis of variance and regression equations. The test results reveal that cotton and cotton/lycra fabrics have lower seam strength as compared to polyester/cotton fabric. Also, with increase in seam angle and needle size, seam strength decreases. However, with sewing needle type, an increase in seam strength is observed for all the three fabrics. The cotton/lycra half plated fabric shows higher seam efficiency among all the three fabrics. It is noted that seam efficiency increases with seam angle and sewing needle type. It has been found that SES needle type (Small ball point) exhibits poor seam efficiency but an improvement in efficiency has been observed with SUK (Medium ball point) and SAN needle type (Conical point) for all three knitted fabrics

Seam grinning behavior of single jersey fabric

Influence of fibre, yarn count, loop length and fabric direction on seam grinning behavior of a single jersey fabric has been investigated. A 33 Box–Behnken design is employed to investigate the influence of various parameters on seam grinning behavior of single jersey fabric. The test results show that the seam grinning d5ecreases for the specimen having lycra filament but it is maximum for 100% cotton specimen. At higher value of loop length, seam grinning decreases in cotton and polyester/cotton fabrics but increases for polyester-lycra and cotton-lycra fabric samples. It had also been seen that seam grinning is higher in wale-wise and bias direction as compared to that in course-wise direction. Hence, seam grinning can be reduced by choosing appropriate values of yarn count, loop length for a particular kind of fibre. This study will be helpful for garment industrialist to minimise the seam grinning effect among knitted garments and to improve quality of producing seam

Effect of yarn count and loop length on needle penetration force and needle cut index in single jersey fabrics

The present study embodies the sewability of single jersey knitted fabric based on needle penetration force and needle cut index. Four types of single jersey fabric, viz. 100% cotton, polyester/cotton, polyester/lycra, and cotton/lycra, are taken for investigation. The materials are prepared on circular knitting machine by varying the yarn count and loop length. The influence of various parameters, viz. type of fibre, yarn count and loop length, on needle penetration force and needle cut index have been analyzed. In addition, the influence of seam direction on the needle cut index is also studied. A 3_level factorial design is employed to analyse the influence of there parameters. The statistical analysis shows that yarn count and loop length has a significant effect on needle penetration force and needle cut index. It has been observed that in all single jersey knitted fabrics, cotton-lycra and polyester-lycra half plated fabrics have higher value of needle penetration force than cotton and polyester/cotton.  The test results also show that for both coarser yarn and finer yarn count, longer loop length gives a lower value of needle penetration force. The needle cut index decreases with increase in the yarn count and loop length. Also it is observed that, the needle cut index is more in wale direction as compared to that in course direction. It is also concluded that cotton fabric samples are more susceptible to needle damages as compared to their counterparts.

Pressure effects on single wall carbon nanotube bundles

We report high pressure Raman studies on single wall carbon nanotube bundles under hydrostatic conditions using two different pressure transmitting media, alcohol mixture and pure water. The radial and tangential modes show a blue shift when SWNT bundle is immersed in the liquids at ambient pressures. The pressure dependence of the radial modes is the same in both liquids. However, the pressure derivatives dω/dP of the tangential modes are slightly higher for the water medium. Raman results are compared with studies under non-hydrostatic conditions and with recent high-pressure X-ray studies. It is seen that the mode frequencies of the recovered sample after pressure cycling from 26 GPa are downshifted by ~7-10 cm−1 as compared to the starting sample

Pressure-induced phase transformation and structural resilience of single-wall carbon nanotube bundles

We report here an in situ X-ray diffraction investigation of the structural changes in carbon single-wall nanotube bundles under quasihydrostatic pressures up to 13 GPa. In contrast with a recent study [Phys. Rev. Lett. 85, 1887 (2000)] our results show that the triangular lattice of the carbon nanotube bundles continues to persist up to ~10 GPa. The lattice is seen to relax just before the phase transformation that is observed at ~10 GPa. Further, our results display the reversibility of the two-dimensional lattice symmetry even after compression up to 13 GPa well beyond the 5 GPa value observed recently. These experimental results explicitly validate the predicted remarkable mechanical resilience of the nanotubes

Infrared transient-liquid-phase joining of SCS-6/{beta}21S titanium matrix composite

Fiber-reinforced titanium matrix composites (TMCs) are among the advanced materials being considered for use in the aerospace industry due to their light weight, high strength, and high modulus. A rapid infrared joining process has been developed for the joining of composites and advanced materials. Rapid infrared joining has been shown not to have many of the problems associated with conventional joining methods. Two models were utilized to predict the joint evolution and fiber reaction zone growth. TMC, 16-ply SCS-6/{beta}21S, has been successfully joined with total processing times of under 2 min utilizing the rapid infrared joining technique. The process utilizes a 50 C/sec ramping rate, 17-{micro}m Ti-15Cu-15Ni wt % filler material between the faying surfaces; a joining temperature of 1,100 C; and 120 sec of time to join the composite material. Joint shear strength testing of the rapid infrared joints at temperatures as high as 800 C has revealed no joint failures. Also, due to the rapid cooling of the process, no poststabilization of the matrix material is necessary to prevent the formation of a brittle omega phase during subsequent use of the TMC at intermediate temperatures, 270 to 430 C, for up to 20 h

An innovative approach to measure skill about artificial insemination in buffaloes

Data pertaining to 3 trainings on artificial insemination (AI) were analyzed and 44 farmers constituted as the study sample. The respondents selected for the study were those who had earlier exposure to AI as they were doing it in the field but needed further refinement of skills. To study skill development in AI, the process was broken into different steps, viz. estrus check, washing of buffaloes, thawing, loading, passage of AI gun and important precautions. Each step was assigned scores of 10, 10, 10, 40, 10 and 20, respectively, by seeking the response from 30 scientists working in the Institute and LUVAS (Lala Lajpat Rai University of Veterinary and Animal Sciences, Hisar). Scores were assigned to each step and summated to arrive at final score of a respondent based on their skill of each step. Thus, individual pre- and post-training scores attained by the respondents during these training programs were calculated. Mean pre-training score of respondents was 51.36 while their post-training score was 67.73 out of 100. Thus, scores of respondents were worked for the AI process- before and after the training program. The difference between the pre- and post-training scores of the respondents was 6.56 (z=6.56), which was significant. Thus, significant gain in skill of the respondents who had undergone this training was observed

Reversible Pressure-Induced Amorphization in Solid C70 : Raman and Photoluminescence Study

We have studied single crystals of $C_{70}$ by Raman scattering and photoluminescence in the pressure range from 0 to 31.1 GPa. The Raman spectrum at 31.1 GPa shows only a broad band similar to that of the amorphous carbon without any trace of the Raman lines of $C_{70}$. After releasing the pressure from 31.1 GPa, the Raman and the photoluminescence spectra of the recovered sample are that of the starting $C_{70}$ crystal. These results indicate that the $C_{70}$ molecules are stable upto 31.1 GPa and the amorphous carbon high pressure phase is reversible, in sharp contrast to the results on solid $C_{60}$. A qualitative explaination is suggested in terms of inter- versus intra-molecular interactions.Comment: To appear in Phys. Rev. Lett., 12 pages, RevTeX (preprint format), 3 figures available upon reques

Investigation of structure and hydrogen bonding of super-hydrous phase B (HT) under pressure using first principles density functional calculations

High pressure behaviour of superhydrous phase B(HT) of Mg10Si3O14(OH)4 (Shy B) is investigated with the help of density functional theory based first principles calculations. In addition to the lattice parameters and equation of state, we use these calculations to determine the positional parameters of atoms as a function of pressure. Our results show that the compression induced structural changes involve cooperative distortions in the full geometry of the hydrogen bonds. The bond bending mechanism proposed by Hofmeister et al [1999] for hydrogen bonds to relieve the heightened repulsion due to short H--H contacts is not found to be effective in Shy B. The calculated O-H bond contraction is consistent with the observed blue shift in the stretching frequency of the hydrogen bond. These results establish that one can use first principles calculations to obtain reliable insights into the pressure induced bonding changes of complex minerals.Comment: 16 pages, 4 figure