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Characterization of gene expression is a central tenet of the synthetic biology design cycle. Sometimes it requires high-throughput approaches that allow quantification of the gene expression of di...

Polyethylene has been used as a bearing surface in numerous applications for in excess of four decades. The semi-crystalline structure of this material has been proposed to have fundamental influence over its wear characteristics; however, reports considering its crystalline phase are sparse. Nanotribological measurements on supported polyethylene single crystals (PESCs) were conducted using lateral force microscopy (LFM). It was observed that the amorphous thin layer on the surface of PESC made a significant contribution to their tribological behaviour. At modest contact stresses, repeated scans on the surface of a single crystal induced changes in sliding friction due to modification of the PESC's structure but in the absence of wear. At high contact stress, material removal and nano-particle production was observed. The results are indicative of the role of both the crystalline lamellae and amorphous domains within the PESC in the wear and nano-particle debris production of the bulk semi-crystalline polyethylene.

Crosslinking is known to increase the wear resistance of ultra-high molecular weight polyethylene (UHMWPE) used as an acetabular cup in total hip replacement. The same wear benefit is not afforded when UHMWPE is used as a tibial component. A programmable multi-directional motion and dynamic load tribometer has been used to investigate ultra-structural development in both unirradiated (−PE) and highly crosslinked (100 kGy) UHMWPE (+PE). To investigate surface anisotropy in UHMWPE, both linear-reciprocating and elliptical wear paths were applied. Following three million elliptical cycles, crosslinking reduced wear by up to 92%. Under reciprocating motion, mean steady state wear of −PE and +PE groups was not significantly different ( p =0.652). Raman spectra indicated a de-crystallisation zone on the near surface of −PE and +PE reciprocating pins. This was attributed to large strain development in conjunction with slow lamellar removal and renewal of new surface material in the lower wearing specimens. SEM images of fragmented lamellae supported this observation.

Arsenic is a serious problem in groundwater in Bangladesh, West Bengal, and other regions, with up to 100 million people worldwide estimated to be at risk. Long term consumption leads to arsenicosis, skin lesions and cancers. There is a clear need for cheap, simple, non-toxic field test kits for routine monitoring of arsenic levels in drinking water. Whole-cell biosensors may provide a solution, but current systems require expensive reagents or laboratory equipment. Here we present two new approaches: firstly, a biosensor in which detection of arsenic is signalled as an easily detectable drop in pH; secondly, a chromogenic system using endospores, which can be stored and distributed in dried form without requiring freeze-drying or refrigeration. Further development of these concepts may lead to a cheap practical device which can be used in the field by workers with minimal training.

Biomaterial wear particles are known to provoke a foreign-body reaction when released from total joint prostheses. Considerable effort is being invested in the search for materials which, by wearing less, will release fewer particles. In this research the role of joint wear simulators is paramount. The wear debris from 26 simulator tests of hip prostheses was extracted from the bovine serum lubricant and sized using a laser diffraction technique. The influence on particle size of a broad range of parameters was examined. The parameters considered included the bedding-in phenomenon, the femoral head material and roughness and physiological versus simplified load cycles and wear paths. The physiological wear simulators produced a similar size distribution of wear particles to that produced by implanted joints. Head material had no effect on this observation. Simplifying the loading cycle or wear path independently made no impact on this finding. This remained the case when simplified load and wear path were combined in one test. The effect of head roughness was pronounced with an increase in minimum particle size with increasing roughness. Joint simulators remain the optimal method for assessing new joint materials and designs. However, their use to characterise joints in terms of wear rate solely should be guarded against. Instead focus should be concentrated on a combination of the size and amount of the wear debris created. In this way the “loosening hazard” of a joint can be distilled.

The limitation of wear is fundamental to the optimization of total hip arthroplasty longevity. The maintenance of the supersmooth femoral head surface is considered to be paramount in maximizing prosthesis life expectancy. Ex vivo studies have failed to substantiate a relationship between roughness and the clinical wear factor, however. A hip simulator wear study was undertaken to investigate this contradiction. Three explanted femoral heads were articulated for 5 million cycles against new acetabular liners. The simulator wear rate was 5 times the ex vivo value. This difference can be explained only if the explant head roughness was not that which existed for most of the joint's life. The relationship between surface roughness and wear deduced for simulator testing is substantially different from that of unidirectional wear screening methods. The multiphasic nature of wear in cementless joints has been illustrated: a wear-in period, followed by a steady-state phase, until a head-roughening event causes a rapid wear period.

Corticotropin releasing hormone (CRH, sometimes known as CRF) is an endogenous 41 amino acid peptide that has been implicated in the onset of pregnancy, the ‘fight or flight’ response, in addition to a large number of physiological disorders. Recently, medicinal chemists have developed a number of potent and selective compounds that show promise in a vast array of therapeutic uses. Herein we review the current status of research.

Forty-seven explanted Porous Coated Anatomic (PCA, Howmedica, Rutherford, NJ) cementless acetabular components were acquired at revision surgery. All the components articulated against CoCrMo femoral heads of 32-mm diameter. The penetration depth and angle were measured using the shadowgraph technique. The wear volume was then calculated using Kabo's formula. Using weighted linear regression analysis, the mean penetration rate and mean volumetric wear rate were calculated to be 0.23 (SE, 0.03) mm 3 /y and 96 (SE, 13) mm 3 /y, respectively. The creep component was not found to be significantly different from zero. The clinical wear factor, k clinical , for this cohort was also calculated using linear regression analysis but with the assumption that creep was zero. The value found, k clinical = 1.93 (SE, 0.29) × 10 −6 mm 3 /N-m, was similar to those in previous studies involving cemented joints with a 22-mm femoral head diameter. The similar k clinical values of these substantially different joint types suggest that the high volumetric wear rate for the PCA joint can be attributed entirely to its larger head size and the younger, more active, patient profile. Fixation technique and metal backing seem not to influence the rate of wear.

The design of a stereoplotter requires careful consideration of the technology available in many fields and the possible application of recent developments to the design concept. Rapid technological change means that components which are unsuitable one day may be ideal the next. Therefore, it is important to consider exactly the function of each component and design accordingly. Traditional ways of overcoming design problems may no longer be valid.