Cover Image,Volume 98, Issue 1

The cover image, by Livnat Goldenberg et al., is based on the Review Mandarin fruit quality: a review, DOI: 10.1002/jsfa.8495 .

     

Automatic detection of obstructive sleep apnea using speech signals

Obstructive sleep apnea (OSA) is a common disorder associated with anatomical abnormalities of the upper airways that affects 5% of the population. Acoustic parameters may be influenced by the vocal tract structure and soft tissue properties. We hypothesize that speech signal properties of OSA patients will be different than those of control subjects not having OSA. Using speech signal processing techniques, we explored acoustic speech features of 93 subjects who were recorded using a text-dependent speech protocol and a digital audio recorder immediately prior to polysomnography study. Following analysis of the study, subjects were divided into OSA (n=67) and non-OSA (n=26) groups. A Gaussian mixture model-based system was developed to model and classify between the groups; discriminative features such as vocal tract length and linear prediction coefficients were selected using feature selection technique. Specificity and sensitivity of 83% and 79% were achieved for the male OSA and 86% and 84% for the female OSA patients, respectively. We conclude that acoustic features from speech signals during wakefulness can detect OSA patients with good specificity and sensitivity. Such a system can be used as a basis for future development of a tool for OSA screening.     

An electrical equivalent for barrier anodic films on aluminium

A duplex-film model for barrier anodic films on aluminium is suggested, the lower layer being homogeneous and amorphous and the upper consisting of a dispersion of a crystalline phase in an amorphous matrix. From impedance measurements over a range of frequencies, the dielectric constants of the layers are estimated as 12 and 9 respectively.     

Stress-activated protein kinases are negatively regulated by cell density

Stimulation by UV irradiation, TNFalpha, as well as PDGF or EGF activates the JNK/SAPK signalling pathway in mouse fibroblasts. This results in the phosphorylation of the N-terminal domain of c-Jun, increasing its transactivation potency. Using an antibody that specifically recognizes c-Jun phosphorylated at Ser63, we show that culture confluency drastically inhibited c-Jun N-terminal phosphorylation due to the inhibition of the JNK/SAPK pathway. Transfection experiments demonstrate that the inhibition occurs at the same level as, or upstream of, the small G-proteins cdc42 and Rac1. In contrast, the classical MAPK pathway was insensitive to confluency. The inhibition of JNK/SAPK activation depended on the integrity of the actin microfilament network. These results were confirmed and extended in monolayer wounding experiments. After PDGF, EGF or UV stimulation, c-Jun was predominantly phosphorylated in cells bordering the wound, which are the cells that move to occupy the wounded area. Thus, modulation of the stress-dependent signal cascade by confluency will restrict c-Jun N-terminal phosphorylation in response to mitogenic or chemotactic agents to cells that border a wounded area.     

Mechanical Alloying and Spark Plasma Sintering of Higher Manganese Silicides for Thermoelectric Applications

The present challenges in the energy crisis require finding new ways to reduce consumption of fossil fuels. Thermoelectrics can help reduce fuel consumption by producing electricity from waste heat. The higher manganese silicides (HMS) have shown promise in this field as inexpensive, nontoxic, and highly stable p-type thermoelectric materials. One of the production techniques for HMS is mechanical alloying by ball milling. In this research the effect of the ball-milling duration and speed on the phases produced was studied. Mn and Si powders were milled at speeds of 200 RPM to 800 RPM for 1 h to 7 h. X-ray diffraction (XRD) results of the samples prepared using mechanical alloying show deterioration into the MnSi phase. The sample that underwent 5 h of milling at 800 RPM showed the greatest amount of HMS phase and was subsequently spark plasma sintered. The sample showed insufficient thermoelectric properties (ZT ≈ 0.1 at 450°C), compared with either solid-state reaction samples showing ZT ≈ 0.4 or cast samples showing ZT ≈ 0.63 at 450°C. The reduced ZT values of the mechanically alloyed and spark-plasma-sintered samples were attributed to the high relative amount of MnSi phase. The correlation between the relative amount of MnSi and the transport properties is described in detail.     

Creep and Creep Recovery Response of Load Cells Tested According to U.S. and International Evaluation Procedures

The 60 min creep data from National Type Evaluation Procedure (NTEP) tests performed at the National Institute of Standards and Technology (NIST) on 65 load cells have been analyzed in order to compare their creep and creep recovery responses, and to compare the 60 min creep with creep over shorter time periods. To facilitate this comparison the data were fitted to a multiple-term exponential equation, which adequately describes the creep and creep recovery responses of load cells. The use of such a curve fit reduces the effect of the random error in the indicator readings on the calculated values of the load cell creep. Examination of the fitted curves show that the creep recovery responses, after inversion by a change in sign, are generally similar in shape to the creep response, but smaller in magnitude. The average ratio of the absolute value of the maximum creep recovery to the maximum creep is 0.86; however, no reliable correlation between creep and creep recovery can be drawn from the data. The fitted curves were also used to compare the 60 min creep of the NTEP analysis with the 30 min creep and other parameters calculated according to the Organization Internationale de Métrologie Légale (OIML) R 60 analysis. The average ratio of the 30 min creep value to the 60 min value is 0.84. The OIML class C creep tolerance is less than 0.5 of the NTEP tolerance for classes III and III L.     

Novel stationary-sample atomic force microscope with beam-tracking lens

An atomic force microscope with a stationary sample and a scanning cantilever using an optical lever method is demonstrated for the first time. The cantilever tip is translated to measure surface profiles while a simple lens attached to the cantilever holder guides a focused beam from a fixed collimated diode laser. The imaging capability is demonstrated up to 100*100 mu m/sup 2/.<>