Changes In Diffraction Pattern Research Articles

Why Muscle is an Efficient Shock Absorber

Skeletal muscles power body movement by converting free energy of ATP hydrolysis into mechanical work. During the landing phase of running or jumping some activated skeletal muscles are subjected to stretch. Upon stretch they absorb body energy quickly and effectively thus protecting joints and bones from impact damage. This is achieved because during lengthening, skeletal muscle bears higher force and has higher instantaneous stiffness than during isometric contraction, and yet consumes very little ATP. We wish to understand how the actomyosin molecules change their structure and interaction to implement these physiologically useful mechanical and thermodynamical properties. We monitored changes in the low angle x-ray diffraction pattern of rabbit skeletal muscle fibers during ramp stretch compared to those during isometric contraction at physiological temperature using synchrotron radiation. The intensities of the off-meridional layer lines and fine interference structure of the meridional M3 myosin x-ray reflection were resolved. Mechanical and structural data show that upon stretch the fraction of actin-bound myosin heads is higher than during isometric contraction. On the other hand, the intensities of the actin layer lines are lower than during isometric contraction. Taken together, these results suggest that during stretch, a significant fraction of actin-bound heads is bound non-stereo-specifically, i.e. they are disordered azimuthally although stiff axially. As the strong or stereo-specific myosin binding to actin is necessary for actin activation of the myosin ATPase, this finding explains the low metabolic cost of energy absorption by muscle during the landing phase of locomotion.

Electrochemical Cycling and Lithium Insertion in Nanostructured FeF3 Cathodes

The cycle lives for cathodes of nanocrystalline iron trifluoride (FeF3) were measured in rechargeable lithium batteries at different depths of discharge. When the discharge was limited to less than one Li+ ion per FeF3, both the cycle life and energy efficiency were considerably greater than when converting FeF3 into Fe and LiF in deep discharge. An in situ X-ray diffractometry (XRD) study of the FeF3 cathode during its initial discharge to LiFeF3 showed a continuous change of the FeF3 diffraction pattern, indicating Li+ insertion into the rhombohedral FeF3 causing distortion of its lattice parameters. Electrochemical cycling is most reversible when this mechanism occurs in the absence of other changes in the crystal structure.

New in-situ neutron diffraction cell for electrode materials

A novel neutron diffraction cell has been constructed to allow in-situ studies of the structural changes in materials of relevance to battery applications during charge/discharge cycling. The new design is based on the coin cell geometry, but has larger dimensions compared to typical commercial batteries in order to maximize the amount of electrode material and thus, collect diffraction data of good statistical quality within the shortest possible time. An important aspect of the design is its modular nature, allowing flexibility in both the materials studied and the battery configuration. This paper reports electrochemical tests using a Nickel-metal-hydride battery (Ni-MH), which show that the cell is able to deliver 90% of its theoretical capacity when using deuterated components. Neutron diffraction studies performed on the Polaris diffractometer using nickel metal and a hydrogen-absorbing alloy (MH) clearly show observable changes in the neutron diffraction patterns as a function of the discharge state. Due to the high quality of the diffraction patterns collected in-situ (i.e. good peak-to-background ratio), phase analysis and peak indexing can be performed successfully using data collected in around 30 min. In addition to this, structural parameters for the β-phase (charged) MH electrode obtained by Rietveld refinement are presented.

Films from resistant starch-pectin dispersions intended for colonic drug delivery

Free films were obtained by the solvent casting method from retrograded starch-pectin dispersions at different polymer proportions and concentrations with and without plasticizer. Film forming dispersions were characterized according to their hardness, birefringence and rheological properties. The polymer dispersions showed a predominantly viscous behavior (G″>G′) and the absence of plasticizers lead to building of stronger structures, while the occurrence of Maltese crosses in the retrograded dispersions indicates the occurrence of a crystalline organization. Analyses of the films included mechanical properties, thickness, superficial and cross sectional morphology, water vapor permeability, liquid uptake ability, X-ray diffractometry, in vitro dissolution and enzymatic digestion. The high resistant starch content (65.8–96.8%) assured the resistance of materials against enzymatic digestion by pancreatin. Changes in the X-ray diffraction patterns indicated a more organized and crystalline structure of free films in relation to isolated polymers. Increasing of pectin proportion and pH values favored the dissolution and liquid uptake of films. Films prepared with lower polymer concentration presented better barrier function (WVP and mechanical properties).

Modifications in selected soil attributes as influenced by long-term continuous cropping in a calcareous semiarid environment

Intensified agriculture and irrigation practices over a long-term are an important factor in soil change phenomena that can appear some unwanted effects on soil attributes. To examine this hypothesis, physicochemical properties and clay mineralogy of four major soil types (Typic Haploxerepts, Typic Xerorthents, Typic Calcixerepts, and Fluventic Haploxerepts) under sunflower cultivation over five decades and adjoining virgin lands were investigated in order to monitor changes caused by long-term cropping. The comparison of cultivated soils and virgin lands indicated that cultivation resulted in an increase in clay (3–28 %) and silt (3–25 %) content, along with a decrease in sand content (2–17 %), resulting of the cultivation practices. For most of the examined soils, soil pH and calcium carbonate equivalent were marginally increased as 0.1–0.23 unit and 4–26 mg kg−1, respectively, following intensive cropping. A relative depletion was manifested in mean value of soil organic carbon (4–18 %), soluble K (47–197 %), exchangeable K (21–34 %), available K (20–34 %), potassium absorption ratio (43–45 %), and exchangeable potassium percentage (26–54 %) due to continuous sunflower cropping. Comparing with the virgin lands, the cultivated soils showed a considerable rise in electrical conductivity (18–122 %), sodium absorption ratio (18–122 %), exchangeable Na (4–48 %), and exchangeable sodium percentage (10–47 %) likely due to the chemistry of the irrigation water used, as well as the chemical interaction between the irrigation water and its receiving soils. Over the five decades of cultivation, some changes in the X-ray diffraction pattern of illite and smectite were observed mainly as result of cropping and K depletion as well as alternating wet–dry periods induced by irrigation practices.

Reflective ghost diffraction for objects with rough surfaces

Reflective ghost diffraction (GD) for objects with rough surfaces is investigated theoretically and numerically. Using a speckle model to describe the reflectivity of the object with variable rough surfaces, the incident and reflective angle-dependent diffraction condition is obtained, and the analytical expression of the reflective GD is derived. Numerical simulations are given to show how the height variance and correlation length of the object and the reflective angle in the experimental scheme can affect the quality of the reflective GD. Specifically, we find that the changes of diffraction patterns of both the simple objects and the complicated objects are sensitive to parameters such as the reflective angle and the surface fluctuation. Additionally, comparative studies on both reflective GD and ghost imaging (GI) have also been performed. We find that reflective GI is more robust against system parameters than reflective GD. These results may be useful for future experimental works.

Rational Design of Mechano‐Responsive Optical Materials by Fine Tuning the Evolution of Strain‐Dependent Wrinkling Patterns

Rational design strategies for mechano‐responsive optical material systems are created by introducing a simple experimental system that can continuously vary the state of bi‐axial stress to induce various wrinkling patterns, including stripes, labyrinths, herringbones, and rarely observed checkerboards, that can dynamically tune the optical properties. In particular, a switching of two orthogonally oriented stripe wrinkle patterns from oxidized polydimethylsiloxane around the critical strain value is reported, as well as the coexistence of these wrinkles forming elusive checkerboard patterns, which are predicted only in previous simulations. These strain‐induced wrinkle patterns give rise to dynamic changes in optical transmittance and diffraction patterns. A theoretical description of the observed pattern formation is presented which accounts for the residual stress in the membrane and allows for the fine‐tuning of the window of switching of the orthogonal wrinkles. Applications of wrinkle‐induced changes in optical properties are demonstrated, including a mechanically responsive instantaneous privacy screen and a transparent sheet that reversibly reveals a message or graphic and dynamically switches the transmittance when stretched and released.

MOF stability and gas adsorption as a function of exposure to water, humid air, SO2, and NO2

Gas adsorption and stability to liquid water, humid air, and acid gasses on metal organic frameworks have been studied using a high-throughput adsorption measurement system. Among the seven MOFs studied, Cu-HF, Zn-NDC, and Ni-NIC showed higher CO2/N2 sorption selectivities, (8–12), than the other MOFs (∼4), mainly due to high CO2 adsorption. Long term (5days) NO2 exposure, as well as exposure to liquid water, resulted in partial decomposition of the original structure of Zn-NDC with a corresponding 26–30% decrease in CO2 adsorption capacity. No noticeable changes in X-ray diffraction (XRD) patterns were observed for the other MOFs with small variations in adsorption capacities, indicating structural robustness to acid gas and liquid water. Short-term exposure to humid air (3d) and acid gasses (2d) caused a decrease in CO2 and N2 adsorption capacity for Cu-HF and an increase in adsorption capacity for Ni-NIC. Measurements indicate that pore flexibility in Cu-HF, Zn-NDC, Ni-NIC and Cu-NH2 is modulated by temperature: large SF6 molecules are rejected from the pores at room temperature (as expected based on kinetic diameter), but N2, which does adsorb internally at room temperature, is rejected from the pores at 77K.

Understanding the Evolution of CdTe Buffer Layer Surfaces on ZnTe/Si(211) and GaAs(211)B During Cyclic Annealing

We present the results of a detailed study of the changes that occur on CdTe buffer layer surfaces grown on ZnTe/Si(211) and GaAs(211)B during the routine thermal cyclic annealing (TCA) process. Observations indicate that CdTe buffer layer surfaces are Te saturated when the TCA is performed under Te overpressure. In the absence of Te flux during the TCA step, the CdTe surface loses CdTe congruently and the typical CdTe nanowires show the presence of nodules on their surfaces. The observed changes in reflection high-energy electron diffraction patterns during TCA are explained in terms of surface chemistry and topography observations. Overall, the Te overpressure is necessary to maintain a smoother and pristine surface to continue the molecular beam epitaxy (MBE) growth.

Ultrafast electron crystallography of monolayer adsorbates on clean surfaces: Structural dynamics

By combining the surface sensitivity and ultrafast temporal resolution of ultrafast electron crystallography (UEC) with in situ surface preparation, adsorbate deposition and surface characterization, we extend the capability of UEC to monitor structural dynamics of monolayer adsorbates. Here, we report investigation of the Ni(100)–c(2×2)–S, Ni(100)–p(2×2)–O, and Ni(100)–c(2×2)–CO systems. Their structural dynamics are quantified by comparing the temporal change of the experimental electron diffraction patterns to the theoretically-obtained multi-scattering simulations. This Letter paves the way to future exploration of monolayer reactivity under controlled conditions of ultrahigh vacuum and with spatiotemporal resolutions at the atomic scale.

Vapochromic and Mechanochromic Phosphorescence Materials Based on a Platinum(II) Complex with 4-Trifluoromethylphenylacetylide

Planar platinum(II) complex Pt(Me(3)SiC≡CbpyC≡CSiMe(3))(C≡CC(6)H(4)CF(3)-4)(2) (6) with 5,5'-bis(trimethylsilylethynyl)-2,2'-bipyridine and 4-trifluoromethylphenylacetylide exhibits remarkable luminescence vapochromic and mechanochromic properties and a thermo-triggered luminescence change. Solid-state 6 is selectively sensitive to vapors of oxygen-containing volatile compounds such as tetrahydrofuran (THF), dioxane, and tetrahydropyrane (THP) with phosphorescence vapochromic response red shifts from 561 and 608 nm to 698 nm (THF), 689 nm (dioxane), and 715 nm (THP), respectively. Upon being mechanically ground, desolvated 6, 6·CH(2)Cl(2), and 6·(1)/(2)CH(2)ClCH(2)Cl exhibit significant mechanoluminescence red shifts from 561 and 608 nm to 730 nm, while vapochromic crystalline species 6·THF, 6·dioxane, or 6·THP affords a mechanoluminescence blue shift from 698 nm (THF), 689 nm (dioxane), or 715 nm (THP) to 645 nm, respectively. When the compounds are heated, a thermo-triggered luminescence change occurs, in which bright yellow luminescence at 561 and 608 nm turns to red luminescence at 667 nm with a drastic red shift. The multi-stimulus-responsive luminescence switches have been monitored by the changes in emission spectra and X-ray diffraction patterns. Both X-ray crystallographic and density functional theory studies suggest that the variation in the intermolecular Pt-Pt interaction is the key factor in inducing an intriguing luminescence switch.

Delayed crystallization of ultrathin Gd2O3 layers on Si(111) observed by in situ X-ray diffraction

We studied the early stages of Gd2O3 epitaxy on Si(111) in real time by synchrotron-based, high-resolution X-ray diffraction and by reflection high-energy electron diffraction. A comparison between model calculations and the measured X-ray scattering, and the change of reflection high-energy electron diffraction patterns both indicate that the growth begins without forming a three-dimensional crystalline film. The cubic bixbyite structure of Gd2O3 appears only after a few monolayers of deposition.

Identification of Breast Cancer-Associated Lipids in Scalp Hair

A correlation between the presence of breast cancer and a change in the synchrotron-generated X-ray diffraction (XRD) pattern of hair has been reported in several publications by different groups, and on average XRD-based assays detect around 75% of breast cancer patients in blinded studies. To date, the molecular mechanisms leading to this alteration are largely unknown. We have determined that the alteration is likely to be due to the presence of one or more breast cancer-associated phospholipids. Further characterization of these lipids could be used to develop a novel, sensitive and specific screening test for breast cancer, based on hair initially, and potentially extendable to other biological samples.

Direct growth of carbon nanotubes on hydroxyapatite using MPECVD

For the first time carbon nanotubes (CNTs) have been successfully grown directly on hydroxyapatite (HA) by using microwave plasma enhanced chemical vapor deposition (MPECVD). Such integration has potential to capitalize on the merits of both HA and CNTs. This type of coating could be useful to improve the interface between bone and the implant. Scanning electron microscope SEM investigations show that; the surface of the CNTs is relatively clean and free of amorphous carbon. The CNTs diameters lie in the range 30–70 nm. In addition HA encapsulation by carbon was observed at a growth temperature 750 °C. Raman spectroscopy indicates that the CNTs are of high quality and the I G/ I D ratio lies between 1.243 and 1.774. The changes in the X-ray diffraction (XRD) patterns give an indication that during the plasma deposition the HA-substrate surface is subjected to a temperature sufficient for partial conversion to the β-tricalcium phosphate via dehydroxylation.

Development of an x-ray diffraction camera used in magnetic fields up to 10 T

A high-field x-ray diffraction (HF-XRD) camera was developed to observe structural changes of magnetic materials in magnetic fields up to 10 T. The instrument mainly consists of a Debye-Scherrer-type camera with a diameter of 80.1 mm, a 10-T cryocooled superconducting magnet with a 100-mm room-temperature bore, an x-ray source, a power supply, and a chiller for the x-ray source. An x-ray detector (image plate) in the HF-XRD camera can be taken out and inserted into the magnet without changing the sample position. The performance of the instrument was tested by measuring the HF-XRD for silicon and ferromagnetic MnBi powders. A change of x-ray diffraction pattern was observed due to the magnetic orientation of MnBi, showing that the instrument is useful for studying field-induced orientation processes and structural properties of field-controlled materials.

Pressure-induced phase transition of Bi2Te3to a bcc structure

The pressure-induced phase transition of bismuth telluride, Bi2Te3, has been studied by synchrotron x-ray diffraction measurements at room temperature using a diamond-anvil cell (DAC) with loading pressures up to 29.8 GPa. We found a high-pressure body-centered cubic (bcc) phase in Bi2Te3 at 25.2 GPa, which is denoted as phase IV, and this phase apperars above 14.5 GPa. Upon releasing the pressure from 29.8 GPa, the diffraction pattern changes with pressure hysteresis. The original rhombohedral phase is recovered at 2.43 GPa. The bcc structure can explain the phase IV peaks. We assumed that the structural model of phase IV is analogous to a substitutional binary alloy; the Bi and Te atoms are distributed in the bcc-lattice sites with space group Im-3m. The results of Rietveld analysis based on this model agree well with both the experimental data and calculated results. Therefore, the structure of phase IV in Bi2Te3 can be explained by a solid solution with a bcc lattice in the Bi-Te (60 atomic% tellurium) binary system.

Surface morphology and transport properties of Cr nanoparticles in single electron tunneling regime

We have carried out an investigation of surface structures of Cr nanoparticles grown on a MgO layer for studying single electron tunneling (SET). Reflection high-energy electron diffraction pattern changes from spotty to streak with decreasing Cr nominal thickness, while Cr forms nano size particles with the size of around 3.5 nm in diameter for all the samples. The double tunnel junctions for the Cr nominal thickness of 0.1 nm show clear Coulomb blockade with the threshold voltage of 50 mV, indicating that this Cr nanoparticle satisfies the condition for the appearance of SET. The relatively large volume of the Cr nanoparticles may be related with the fact that tunnel magnetoresistance due to spin accumulation in Cr nanoparticles is small.

Extremely Early Diagnostic Test for Prostate Cancer.

PURPOSE: This article reports the results of a blinded fibre diffraction study of skin samples taken from TRAMP mice and age-matched controls to determine whether changes noted in fibre diffraction studies of human skin were present in these TRAMP mice studies. These mice are bred to progress to Gleeson Type 3 to Type 5 prostate cancer. METHODS: Small strips, 1mm×5mm, cut from the mouse skin samples were loaded into cells in the same way as human samples and slightly stretched to remove the crimp. They remained completely hydrated throughout exposure to the synchrotron beam. RESULTS: The added change that was reported for prostate cancer in 2009 was obtained for all TRAMP mice samples, indicating that this change can be read as High Grade Cancer in human diagnostic tests. DISCUSSION: These changes were evident for all 3 and 7 week old TRAMP mice samples but not for any of the control samples. This indicates that the changes in the fibre diffraction patterns appear much earlier than in any other available prostate cancer diagnostic test which cannot verify the presence of prostate cancer before 10 weeks of age. The fibre diffraction test is therefore the most accurate and earliest test for high grade prostate cancer.

Compressibility and Elasticity of Amphiphilic and Acidic β-Sheet Peptides at the Air−Water Interface

Grazing incidence X-ray diffraction measurements were performed on monolayer films of three amphiphilic and acidic β-sheet peptides having the general sequence Pro-Y-(Z-Y)(5)-Pro, with Y = Asp or Glu and Z = Phe or Leu denoted, P(FD)-5, P(LE)-5, P(LD)-5, and the 1:1 molar ratio mixture of P(LD)-5 and P(LE)-5. The crystalline domains of these peptides exhibited compressibility and elasticity of the crystalline unit cell indicated by changes in diffraction patterns on compression. Higher compressibility values appeared to be associated with more favorable cross-strand interactions between peptides with the larger side chains, whereas P(LD)-5, decorated by the smaller side chain amino acids, exhibited the lowest crystalline compressibility. Diffraction patterns provided evidence for a new subunit cell generated by the pleated β-strand motif in an apparently favorable mode of cross-strand intermolecular packing in β-sheets. The study contributes to the understanding of β-sheet flexibility at interfaces with relevance to natural proteins and designed biomaterials composed of β-sheet peptides.

Dissociation characteristic of the inclusion complex of cyclomaltohexaose (α-cyclodextrin) with 1-methylcyclopropene in response to stepwise rising relative humidity

The dissociation of a crystalline complex of cyclomaltohexaose (α-cyclodextrin) and 1-methylcyclopropene has been studied in response to stepwise rising relative humidity at 50 °C using a dynamic vapor sorption instrument. The dissociation of the inclusion complex was monitored with a proton transfer reaction mass spectrometer. The increase in relative humidity generally triggered the complex dissociation. However, the dissociation was greatly retarded at 80% relative humidity, presumably owing to collapse of the crystalline structure. Abrupt dissociation was observed at 90% relative humidity which corresponded to complex dissolution. The changes in powder X-ray diffraction pattern of the inclusion complex during the storage period were also investigated.