Nondestructive testing of railroad wheels and rails by ultrasonics

Quality control of wheels and rails can be improved by using ultrasonic technique developed for measuring stresses in metallic materials. In addition, parts already in use can be tested and replaced if they are found to be unsafe. Test equipment includes two transducers

A Photometrically and Morphologically Variable Infrared Nebula in L483

We present narrow and broad K-band observations of the Class 0/I source IRAS 18148-0440 that span 17 years. The infrared nebula associated with this protostar in the L483 dark cloud is both morphologically and photometrically variable on a time scale of only a few months. This nebula appears to be an infrared analogue to other well-known optically visible variable nebulae associated with young stars, such as Hubble's Variable Nebula. Along with Cepheus A, this is one of the first large variable nebulae to be found that is only visible in the infrared. The variability of this nebula is most likely due to changing illumination of the cloud rather than any motion of the structure in the nebula. Both morphological and photometric changes are observed on a time scale only a few times longer than the light crossing time of the nebula, suggesting very rapid intrinsic changes in the illumination of the nebula. Our narrow-band observations also found that H_2 knots are found nearly twice as far to the east of the source as to its west, and that H_2 emission extends farther east of the source than the previously known CO outflow.Comment: 19 pages, 6 figures, 1 tabl

Label-Free C-Reactive Protein Si Nanowire FET Sensor Arrays With Super-Nernstian Back-Gate Operation

We present a CMOS-compatible double gate and label-free C-reactive protein (CRP) sensor, based on silicon on insulator (SOI) silicon nanowires arrays. We exploit a reference subtracted detection method and a super-Nernstian internal amplification given by the double gate structure. We overcome the Debye screening of charged CRP proteins in solutions using antibodies fragments as capturing probes, reducing the overall thickness of the capture layer. We demonstrate the internal amplification through the pH response of the sensor, in static and real-time working modes. While operated in back-gate configuration, the sensor shows excellent stability (<20 pA/min in the worst case), low hysteresis (<300 mV), and a great sensitivity up to 1.2 nA/dec toward CRP proteins in the linear response range. The reported system is an excellent candidate for the continuous monitoring of inflammation biomarkers in serum or interstitial fluid

DNA transport by a micromachined Brownian ratchet device

We have micromachined a silicon-chip device that transports DNA with a Brownian ratchet that rectifies the Brownian motion of microscopic particles. Transport properties for a DNA 50mer agree with theoretical predictions, and the DNA diffusion constant agrees with previous experiments. This type of micromachine could provide a generic pump or separation component for DNA or other charged species as part of a microscale lab-on-a-chip. A device with reduced feature size could produce a size-based separation of DNA molecules, with applications including the detection of single nucleotide polymorphisms.Comment: Latex: 8 pages, 4 figure

Reversible and irreversible processes during cyclic voltammetry of an electrodeposited manganese oxide as catalyst for the oxygen evolution reaction

Manganese oxides have received much attention over the years among the wide range of electrocatalysts for the oxygen evolution reaction OER due to their low toxicity, high abundance and rich redox chemistry. While many previous studies focused on the activity of these materials, a better understanding of the material transformations relating to activation or degradation is highly desirable, both from a scientific perspective and for applications. We electrodeposited Na containing MnOx without long range order from an alkaline solution to investigate these aspects by cyclic voltammetry CV , scanning electron microscopy SEM and X ray absorption spectroscopy XAS at the Mn K and Mn L edges. The pristine film was assigned to a layered edge sharing Mn3 4 oxide with Mn O bond lengths of mainly 1.87 and some at 2.30 as well as Mn Mn bond lengths of 2.87 based on fits to the extended X ray fine structure EXAFS . The decrease of the currents at voltages before the onset of the OER followed power laws with three different exponents depending on the number of cycles and the Tafel slope decreases from 186 48 to 114 18 mV dec 1 after 100 cycles, which we interpret in the context of surface coverage with unreacted intermediates. Post mortem microscopy and bulk spectroscopy at the Mn K edge showed no change of the microstructure, bulk local structure or bulk Mn valence. Yet, the surface region of MnOx oxidized toward Mn4 , which explains the reduction of the currents in agreement with literature. Surprisingly, we find that MnOx reactivates after 30 minutes at open circuit OC , where the currents and also the Tafel slope increase. Reactivation processes during OC are crucial because OC is unavoidable when coupling the electrocatalysts to intermittent power sources such as solar energy for sustainable energy productio

Estimation of speciated and total mercury dry deposition at monitoring locations in eastern and central North America

Dry deposition of speciated mercury, i.e., gaseous oxidized mercury (GOM), particulate-bound mercury (PBM), and gaseous elemental mercury (GEM), was estimated for the year 2008–2009 at 19 monitoring locations in eastern and central North America. Dry deposition estimates were obtained by combining monitored two- to four-hourly speciated ambient concentrations with modeled hourly dry deposition velocities (&lt;i&gt;V&lt;/i&gt;&lt;sub&gt;d&lt;/sub&gt;) calculated using forecasted meteorology. Annual dry deposition of GOM+PBM was estimated to be in the range of 0.4 to 8.1 μg m&lt;sup&gt;−2&lt;/sup&gt; at these locations with GOM deposition being mostly five to ten times higher than PBM deposition, due to their different modeled &lt;i&gt;V&lt;/i&gt;&lt;sub&gt;d&lt;/sub&gt; values. Net annual GEM dry deposition was estimated to be in the range of 5 to 26 μg m&lt;sup&gt;−2&lt;/sup&gt; at 18 sites and 33 μg m&lt;sup&gt;−2&lt;/sup&gt; at one site. The estimated dry deposition agrees very well with limited surrogate-surface dry deposition measurements of GOM and PBM, and also agrees with litterfall mercury measurements conducted at multiple locations in eastern and central North America. This study suggests that GEM contributes much more than GOM+PBM to the total dry deposition at the majority of the sites considered here; the only exception is at locations close to significant point sources where GEM and GOM+PBM contribute equally to the total dry deposition. The relative magnitude of the speciated dry deposition and their good comparisons with litterfall deposition suggest that mercury in litterfall originates primarily from GEM, which is consistent with the limited number of previous field studies. The study also supports previous analyses suggesting that total dry deposition of mercury is equal to, if not more important than, wet deposition of mercury on a regional scale in eastern North America

Ecosystem coupling:A unifying framework to understand the functioning and recovery of ecosystems

Global change frequently disrupts the connections among species, as well as among species and their environment, before the most obvious impacts can be detected. Therefore, we need to develop a unified conceptual framework that allows us to predict early ecological impacts under changing environments. The concept of coupling, defined as the multiple ways in which the biotic and abiotic components of ecosystems are orderly connected across space and/or time, may provide such a framework. Here, we operationally define the coupling of ecosystems based on a combination of correlational matrices and a null modeling approach. Compared with null models, ecosystems can be (1) coupled; (2) decoupled; and (3) anticoupled. Given that more tightly coupled ecosystems displaying higher levels of internal order may be characterized by a more efficient capture, transfer, and storage of energy and matter (i.e., of functioning), understanding the links between coupling and functioning may help us to accelerate the transition to planetary-scale sustainability. This may be achieved by promoting self-organized order