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1.  Making waves round a structured cloak: lattices, negative refraction and fringes 
Using the framework of transformation optics, this paper presents a detailed analysis of a non-singular square cloak for acoustic, out-of-plane shear elastic and electromagnetic waves. Analysis of wave propagation through the cloak is presented and accompanied by numerical illustrations. The efficacy of the regularized cloak is demonstrated and an objective numerical measure of the quality of the cloaking effect is provided. It is demonstrated that the cloaking effect persists over a wide range of frequencies. As a demonstration of the effectiveness of the regularized cloak, a Young's double slit experiment is presented. The stability of the interference pattern is examined when a cloaked and uncloaked obstacle are successively placed in front of one of the apertures. This novel link with a well-known quantum mechanical experiment provides an additional method through which the quality of cloaks may be examined. In the second half of the paper, it is shown that an approximate cloak may be constructed using a discrete lattice structure. The efficiency of the approximate lattice cloak is analysed and a series of illustrative simulations presented. It is demonstrated that effective cloaking may be obtained by using a relatively simple lattice structure, particularly, in the low-frequency regime.
PMCID: PMC3780812  PMID: 24062625
cloaking; Helmholtz equation; metamaterial lattice; Young's double slit experiment
2.  Validity, reliability, and responsiveness of a new shortVisual Simplified Respiratory Questionnaire (VSRQ©) for health-related quality of life assessment in chronic obstructive pulmonary disease 
The Visual Simplified Respiratory Questionnaire (VSRQ) was designed to assess health-related quality of life (HRQoL) in patients with chronic obstructive pulmonary disease (COPD). It contains eight items: dyspnea, anxiety, depressed mood, sleep, energy, daily activities, social activities and sexual life. Psychometric properties were assessed during a clinical trial that evaluated the impact of tiotropium on HRQoL of COPD patients. These included the determination of structure, internal consistency reliability, concurrent validity with the St George’s Respiratory Questionnaire (SGRQ), test – retest reliability, clinical validity and responsiveness to change over two weeks. Minimal important difference (MID) was calculated; cumulative response curves (CRC) were based on the dyspnea item. Psychometric analyses showed that VSRQ structure was unidimensional. The questionnaire demonstrated good internal consistency reliability (Cronbach’s alpha = 0.84), good concurrent validity with SGRQ (Spearman = −0.70) and clinical validity, good test-retest reproducibility (ICC = 0.77), and satisfactory responsiveness (standardized response mean = 0.57; Guyatt’s statistic = 0.63). MID was 3.4; CRC median value of the ‘minimally improved’ patients was 3.5. In conclusion, VSRQ brevity and satisfactory psychometric properties make it a good candidate for large studies to assess HRQoL in COPD patients. Further validation is needed to extend its use in clinical practice.
PMCID: PMC2672786  PMID: 19436682
chronic obstructive pulmonary disease; VSRQ; SGRQ; health-related quality of life; minimal important difference
3.  Effect of tiotropium on health-related quality of life as a primary efficacy endpoint in COPD 
Clinical manifestations of chronic obstructive pulmonary disease (COPD), including airflow limitation, dyspnea, and activity limitation, ultimately lead to impaired health-related quality of life (HRQoL). This 9-month, randomized, double-blind, multicenter study compared the effect of once-daily tiotropium 18 μg and placebo on HRQoL, spirometric parameters, and exacerbations in 554 patients with moderate-to-severe COPD. HRQoL was assessed using the St. George’s Respiratory Questionnaire (SGRQ) and the new 8-item Visual Simplified Respiratory Questionnaire (VSRQ), which is currently being validated. The primary efficacy endpoint was the proportion of patients achieving a reduction of at least 4 units in the SGRQ total score at study end (Month 9). Mean ± SD baseline SGRQ total score was 47.4 ± 18.1. Significantly more tiotropium-treated patients achieved a reduction of at least 4 units in the SGRQ score vs placebo at study end (59.1% vs 48.2%, respectively; p = 0.029). Tiotropium significantly improved spirometric parameters (forced expiratory volume in 1 second [FEV1]: 0.11 ± 0.02 L vs 0.01 ± 0.02 L; between-group difference: 0.10 ± 0.03 L, p = 0.0001) and reduced exacerbations vs placebo. Maintenance treatment with tiotropium provided significant and clinically relevant improvements in HRQoL, as measured by the SGRQ.
PMCID: PMC2629970  PMID: 18686739
chronic obstructive pulmonary disease; long-acting anticholinergic; health-related quality of life; tiotropium
4.  Identification of Salmonella somatic and flagellar antigens by modified serological methods. 
This report describes two modified methods for the identification of Salmonella somatic (O) and flagellar (H) antigens. Over a period of 2 years, both modified methods were found to be approximately three times less labor intensive than the standard methods while requiring no more technical skill. The modified methods were as accurate as the standard methods in identifying the O and H antigens of 350 Salmonella isolates. Furthermore, 43 O antisera reacted exclusively with organisms possessing homologous O antigens when the modified and two standard methods were used. At the antiserum dilutions used for H antigen identification, H antisera did not react with O antigens or heterologous H antigens by either the modified or the standard method. Compared with the standard method for H antigen identification, the modified method was approximately 20 times more economical with respect to antisera and usually generated a 1.5- to 4-fold higher titer. Since the antisera stored for use in the modified method for H antigen identification were usually 100-fold more dilute than the antisera stored for the standard method, an antibody-stabilizing buffer was incorporated in the diluted antisera, allowing these reagents to be used for at least 9 to 16 months.
PMCID: PMC183245  PMID: 1689983

Results 1-4 (4)