To send content items to your account,
please confirm that you agree to abide by our usage policies.
If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your account.
Find out more about sending content to .
To send content items to your Kindle, first ensure firstname.lastname@example.org
is added to your Approved Personal Document E-mail List under your Personal Document Settings
on the Manage Your Content and Devices page of your Amazon account. Then enter the ‘name’ part
of your Kindle email address below.
Find out more about sending to your Kindle.
Note you can select to send to either the @free.kindle.com or @kindle.com variations.
‘@free.kindle.com’ emails are free but can only be sent to your device when it is connected to wi-fi.
‘@kindle.com’ emails can be delivered even when you are not connected to wi-fi, but note that service fees apply.
To assess the influence of mild behavioral impairment (MBI) on the cognitive performance of older adults who are cognitively healthy or have mild cognitive impairment (MCI).
Secondary data analysis of a sample (n = 497) of older adults from the Florida Alzheimer’s Disease Research Center who were either cognitively healthy (n = 285) or diagnosed with MCI (n = 212). Over half of the sample (n = 255) met the operationalized diagnostic criteria for MBI. Cognitive domains of executive function, attention, short-term memory, and episodic memory were assessed using a battery of neuropsychological tests.
Older adults with MBI performed worse on tasks of executive function, attention, and episodic memory compared to those without MBI. A significant interaction revealed that persons with MBI and MCI performed worse on tasks of episodic memory compared to individuals with only MCI, but no significant differences were found in performance in cognitively healthy older adults with or without MBI on this cognitive domain. As expected, cognitively healthy older adults performed better than individuals with MCI on every domain of cognition.
The present study found evidence that independent of cognitive status, individuals with MBI performed worse on tests of executive function, attention, and episodic memory than individuals without MBI. Additionally, those with MCI and MBI perform significantly worse on episodic memory tasks than individuals with only MCI. These results provide support for a unique cognitive phenotype associated with MBI and highlight the necessity for assessing both cognitive and behavioral symptoms.
The biraderi (brotherhood) is a long-established, widely prevalent dimension of social stratification in Pakistani communities worldwide. Alongside consanguinity, it offers a route for cementing social solidarities and so has strong socio-biological significance. A detailed breakdown of biraderi affiliation among participants in an ongoing birth cohort study in the northern English city of Bradford is presented. There is historical resilience of intra-biraderi marriage, but with a secular decline in prevalence across all biraderi and considerable reductions in some. While a majority of marriages in all biraderi are consanguineous the prevalence varies, ranging from over 80% to under 60%. In consanguineous unions, first cousin marriages account for more than 50% in five of the fifteen biraderi and >40% in six others. Within-biraderi marriage and consanguinity enhance genetic stratification, thereby increasing rates of genomic homozygosity and the increased expression of recessive genetic disorders. The trends reported constitute putative signals of generational change in the marital choices in this community.
Bulk silicon-germanium (SiGe) alloys and two SiGe thick films (4 and 5 μm) on Si wafers were tested with the electron probe microanalyzer (EPMA) using wavelength dispersive spectrometers (WDS) for heterogeneity and composition for use as reference materials needed by the microelectronics industry. One alloy with a nominal composition of Si0.86Ge0.14 and the two thick films with nominal compositions of Si0.90Ge0.10 and Si0.75Ge0.25 on Si, evaluated for micro- and macroheterogeneity, will make good microanalysis reference materials with an overall expanded heterogeneity uncertainty of 1.1% relative or less for Ge. The bulk Ge composition in the Si0.86Ge0.14 alloy was determined to be 30.228% mass fraction Ge with an expanded uncertainty of the mean of 0.195% mass fraction. The thick films were quantified with WDS-EPMA using both the Si0.86Ge0.14 alloy and element wafers as reference materials. The Ge concentration was determined to be 22.80% mass fraction with an expanded uncertainty of the mean of 0.12% mass fraction for the Si0.90Ge0.10 wafer and 43.66% mass fraction for the Si0.75Ge0.25 wafer with an expanded uncertainty of the mean of 0.25% mass fraction. The two thick SiGe films will be issued as National Institute of Standards and Technology Reference Materials (RM 8905).
Microcalorimeter X-ray detectors using a transition edge sensor depend for their linearity and energy scale on the stability of the operating point on the transition curve. We report on some sources of energy scale drift in microcalorimeter X-ray detectors and the manner in which they have been addressed. Previously observed drifts of >10 eV∕h have been reduced to 1–2 eV∕h. This improved stability has resulted in the observation of X-ray fluorescence linewidths of ⩽12 eV over 6 h of counting time.
A silicon multi-cathode detector (SMCD) has been developed for microanalysis and x-ray mapping applications. The SMCD has a large active area (∼0.5 cm2), excellent energy resolution, and high count rate capability. The detector utilizes novel structures that have produced very low dark current, high electric field, uniform charge collection, low noise and high sensitivity to low energy x-rays. The detector's spectral response was evaluated using a 55Fe radioisotope source, as well as by fluorescing materials with an x-ray generator. Figure 1 shows a 55Fe spectrum with an energy resolution of 125 eV FWHM at 5.9 keV collected at 12 μs peaking time. This energy resolution has been repeatably measured on many different detectors. To evaluate the high count rate x-ray performance, which is very important for fast x-ray mapping, a Cu sample was fluoresced using a Rh-anode x-ray tube.
A new class of silicon multi-cathode detector (SMCD) has been developed for microanaiysis spectrometry applications. The detector has excellent energy resolution (< 150 eV FWHM) and high count rate capability (>1 Mcps). An energy resolution of 143 eV FWHM at 5.9 keV was measured with the SMCD at 6 μs peaking time.
The production and characterization of NBS K-411 glass microspheres in the 2–40 μm range for certification as NIST Standard Reference Material® 2066 (SRM®) are described. Quantitative analysis and heterogeneity testing of the microspheres were done with an electron probe microanalyzer-X-ray energy dispersive spectrometry (EPMA-EDS) automated particle analysis procedure. Results for the trimmed and normalized data produced mean compositions for the elements Mg, Si, Ca, Fe, and O (calculated from stoichiometry) that are in good agreement with the certified values for the K-411 bulk glass (NBS SRM 470 Glasses for Mineral Analysis), but with uncertainties about twice as large as those for the bulk material. Differences from the bulk are attributable to microsphere geometry as well as mass and size effects.
Multivariate statistical analysis (MSA) is a powerful tool for the analysis of series of spectra. This paper explores an application of MSA to a series of energy dispersive X-ray (EDX) spectra acquired in the scanning electron microscope (SEM) from a series of particles. The raw data were series of spectra previously acquired to test analytical procedures for trace element detection. This paper explores the possibility of performing the trace element detection with MSA components that have been extracted from the raw data without any a priori assumptions about the information content of the particle spectra. Particles were prepared from two analytical glasses, dispersed onto carbon substrates and coated with carbon. The compositions of the two glasses are substantially similar, except that one glass (K-3106) contains 0.7 wt.% Fe, whereas the other glass (K-3069) does not contain Fe at a detectable level.
One of the main goals of automated scanning electron microscopy analysis (ASEM) of particles is to provide macroscopic phase and compositional information on particle populations based on the energy dispersive x-ray spectrometry, EDS, analysis of several hundred to several thousand individual particles from the sample. The selection and identification of the various elemental groupings is often accomplished by applying techniques for grouping data, such as multivariate or cluster analysis methods, to characteristic x-ray intensities or normalized elemental concentrations. Particle groupings are often based on major and minor elements with concentrations greater than about 1-2 wt. percent. At these concentration levels, the peak-to-background ratios for the characteristic x-ray peaks are sufficiently large that in the absence of severe peak overlaps the elements can be easily identified even in spectra with poor counting statistics. Additional refinement in particle groupings may be possible if reliable information can be obtained on the trace elements present in particles at less than about 1-2 wt.%.
Under acidic sol-gel polymerization conditions, 1,3-bis(triethoxysilyl)-propane 1 and 1,4-bis(triethoxysilyl)butane 2 were shown to preferentially form cyclic disilsesquioxanes 3 and 4 rather than the expected 1,3-propylene- and 1,4-butylene-bridged polysilsesquioxane gels. Formation of 3 and 4 is driven by a combination of an intramolecular cyclization to six and seven membered rings, and a pronounced reduction in reactivity under acidic conditions as a function of increasing degree of condensation. The ease with which these relatively unreactive cyclic monomers and dimers are formed (under acidic conditions) helps to explain the difficulties in forming gels from 1 and 2. The stability of cyclic disilsesquioxanes was confirmed with the synthesis of 3 and 4 in gram quantities; the cyclic disilsesquioxanes react slowly to give tricyclic dimers containing a thermodynamically stable eight membered siloxane ring. Continued reactions were shown to perserve the cyclic structure, opening up the possiblity of utilizing cyclic disilsesquioxanes as sol-gel monomers. Preliminary polymerization studies with these new, carbohydrate-like monomers revealed the formation of network poly(cyclic disilsesquioxanes) under acidic conditions and polymerization with ring-opening under basic conditions.
It is well known that the resistance to electromigration of aluminum-based interconnects is enhanced by alloying with copper. The mechanism is thought to involve the segregation of copper to the grain boundaries. The copper concentration at grain boundaries has been measured in well annealed alloys, with the compositions A1-0.5wt% Cu and AI-2wt%Cu using a VG HB5 STEM. The grain structure was stabilized by an anneal at 673K for one hour and the grain boundaries were loaded with copper by an anneal for 90 hours at 503K. It was found that the copper concentration varied from boundary to boundary. With the assumption that the copper was concentrated in a single layer the saturation concentration of copper was found to be in the range 0.025 to 0.25. This corresponds to an enhancement of the copper concentration relative to that in the grain interiors by a factor in the range between 3 and 30. The higher value approaches the copper concentration which would correspond to a monolayer of theta phase. Extensive surface segregation, amounting to a monolayer equivalent was also detected.
In this paper we address possible causes for inconsistencies in bulge test results and describe methods by which the bulge test technique can be made to produce accurate and reliable results. Experiments have been conducted on a variety of materials: polyimide (PIQ13) and polycarbonate (Lexan), silver and silver-palladium multilayers, and silicon nitride. All the materials tested yield biaxial moduli that are in the range of expected values for the bulk material. In addition, the tests show that the technique can be used to differentiate between the elastic properties of materials throughout the range of elastic stiffnesses, with even crystallo-graphic texture having a notable impact on the measured modulus. These results will be presented along with the methods used for preparing bulge test samples.