Mechanical strains and electric fields applied to topologically imprinted elastomers

We analyze and predict the behavior of a chirally imprinted elastomer under a mechanical strain and an electric field, applied along the helical axis. As the strain and/or field increases, the system is deformed from a conical or transverse imprinted state towards an ultimately nematic one. At a critical strain and/or field there is a first-order transition to a low imprinting efficiency state. This transition is accompanied by a discontinuous global rotation of the director toward the axis of the imprinted helix, measured by the cone angle, theta . We show that the threshold electric field required for switching this transition can be conveniently low, provided an appropriate prestrain is imposed. We suggest that these properties may give rise to a "chiral pump."

The ICD-10 injury mortality diagnosis matrix

OBJECTIVE

To standardize the presentation of the more than 1200 ICD-10 "S" and "T" codes from Chapter XIX by cross classifying the body region of injury by the nature of injury using the ICD-10 injury mortality diagnosis matrix. This paper explains the rationale for decisions made when developing the matrix and presents mortality data using the matrix.

DESIGN

ICD-10 codes are organized by diagnosis groups and body regions of injury for the purpose of standardizing presentation. The categories can be collapsed to facilitate analysis at varying levels of detail. Findings from the United States 2002 injury mortality data are used as an example.

MAIN OUTCOME MEASURES

All injury diagnoses mentioned in deaths with an underlying cause of injury.

RESULTS

There were a total of 247,195 injury diagnoses mentioned in the 161,269 deaths with an underlying cause of injury in 2002 in the United States. The matrix can be used to show that 30% of all injury diagnoses mentioned were to the head and neck region; 28% were system wide injuries, 17% were to the torso. Open wounds accounted for 17% of all injury diagnoses mentioned, and close to half of all open wounds were traumatic brain injuries. Twenty eight percent of injury diagnoses mentioned were unspecified as to their nature and 9.5% had no body region specified.

CONCLUSIONS

Multiple cause of death data are a rich but underused source of injury data often due to the complexity of the data and of the ICD classification system. Analytic techniques will need to be refined to accommodate deaths with multiple contributing injury diagnoses. The injury mortality diagnosis matrix will facilitate analysis as it is a useful tool for summarizing diagnosis data associated with injury deaths.

Haemophilia and ageing

Men with haemophilia have not only the challenges of living with HIV and/or HCV infection and premature arthritis as complications of their disorder, but they also confront the other ails of ageing. These include genitourinary problems such as prostatic hypertrophy, prostatic cancer and renal stone disease, and arterial disease for which haemophilia is not protective. Progressive arthritis and declining fitness may lead to loss of independence which causes great concern. Associated with the physical aspects of ageing, many patients also suffer from psychological symptoms which may be precipitated by changes in work such as early retirement and altered family dynamics. Many older men with haemophilia may never have consulted primary care physicians because of the rarity and complexity of their disorder. Haemophilia centre staff often assume responsibility for the identification and management of all health problems of their patients. Even when other clinicians are involved, patients require their centre's involvement in the investigation and support of many procedures such as coronary artery surgery and urological surgery. This paper addresses falls in the older man with haemophilia, their causes and consequences and cardiovascular problems in particular. Very little literature has been published about these common problems. We need to be aware of the ageing issues in haemophilia and develop 'wellness' programs which are directed to the early identification of disease as well as preventative strategies to reduce the physical and psychological impacts of ageing.

Nonlinear photoresponse of disordered elastomers

We model the polarization-dependent photocontractions of polydomain nematic elastomers. Contraction initially arises by light-induced director rotation. At higher light intensity, strain recovers because the local order parameter diminishes. Thus we predict photostrains to be nonmonotonic with light intensity and predict the induction of a negative global order parameter for the system of polydomains. Nonmonotonic strains would give curvature reversal in thick samples. Our model also predicts an elongational strain response to nonpolarized light.

Antimicrobial susceptibility and molecular analysis of Enterococcus faecalis originating from endodontic infections in Finland and Lithuania

BACKGROUND/AIMS

Enterococcus faecalis strains with multiple antibiotic resistances can cause infections that are difficult to treat. The microbial flora in treatment-resistant apical periodontitis is dominated by E. faecalis, and is a potential source of infections at other sites.

MATERIAL AND METHODS

Sensitivities to a range of antibiotics were determined for 59 endodontic E. faecalis isolates from Finland and Lithuania. The DNA sequence of the gene responsible for the species' intrinsic quinupristin-dalfopristin resistance, lsa, was determined from two isolates with diminished resistance. Four pairs of isolates from the same root canal were typed by pulsed-field gel electrophoresis.

RESULTS

A high prevalence of resistance to rifampicin was found, whereas all isolates were susceptible or showed intermediate susceptibility to penicillin and ampicillin and four isolates were unusually susceptible to cefotaxime. No vancomycin or high-level gentamicin resistance was detected. Nine of 59 isolates were susceptible to quinupristin-dalfopristin. A fully quinupristin-dalfopristin-susceptible isolate also susceptible to clindamycin produced a truncated Lsa polypeptide, and an isolate with borderline quinupristin-dalfopristin-susceptibility had mutations proximal to the predicted ribosomal binding site. Pulsed-field gel electrophoresis showed that the same root canal could harbor two different strains of E. faecalis during the course of the same infection.

CONCLUSION

Despite the differing antibiotic usage in Finland and Lithuania, E. faecalis from endodontic infections in these countries showed similar susceptibility patterns with levels of resistance considered typical for the species, and decreased resistance to clindamycin and quinupristin-dalfopristin as well as lesions in the lsa gene which were similar to those described in other clinical isolates.

Comparison of four methods for detection of teicoplanin resistance in methicillin-resistant Staphylococcus aureus

OBJECTIVES

To determine which method of determining the MIC of teicoplanin produces a result closely related to outcome in the critically ill patient.

METHODS

Four methods of teicoplanin susceptibility testing-disc diffusion, Etest, VITEK (Legacy and VITEK 2) and agar incorporation-were compared for 47 methicillin-resistant Staphylococcus aureus (MRSA) isolates from invasive intensive care unit (ICU) infections and 83 isolates from ICU patients colonized with the organism. Clinical outcome was recorded prospectively for all the patients. Another 13 reference laboratory strains of MRSA with reduced susceptibility to teicoplanin were tested.

RESULTS

Both VITEK systems failed to demonstrate resistance in the three isolates identified as resistant by Etest or agar incorporation, and disc testing detected only one resistant isolate. A higher MIC, as found by Etest or agar incorporation, was associated with lower survival (n = 130, 95% CI -0.082 to -0.006, P = 0.023, Etest; n = 130, 95% CI -0.156 to -0.020, P = 0.011, agar). The findings for the 13 reference strains were similar, with a > or = 4-fold reduction in MIC between agar incorporation or Etest and VITEK2 for six isolates.

CONCLUSIONS

Neither disc diffusion nor the VITEK systems are reliable for detection of teicoplanin resistance in MRSA. Etest and agar incorporation remain the methods of choice.

The effects of recall on reporting injury and poisoning episodes in the National Health Interview Survey

OBJECTIVE

To examine effects of length of time between injury or poisoning and interview on the number of reported injury and poisoning episodes in the National Health Interview Survey (NHIS). (Hereinafter, both injuries and poisonings will be referred to as "injuries".)

DESIGN

The NHIS collects data continuously on medically attended injuries occurring to family members during the three months before interview. Time between injury and interview was established by subtracting the reported injury date from the interview date. Values were multiply imputed for the 25% of the episodes for which dates were only partially reported.

MAIN OUTCOME MEASURES

An analysis of mean square error (MSE) was used to quantify the extent of errors in estimated annual numbers of injuries and to compare the contributions of bias and variance to these errors.

RESULTS

The lowest estimated MSEs for annualized estimates for all injuries and for less severe injuries were attained when the annualized estimates were based on 3--6 elapsed cumulative weeks between injury and interview. The average weighted number of injuries reported per week per year was 8% lower in later weeks (weeks 6--13) than in earlier weeks (weeks 1--5) for all episodes, and 24% lower in later weeks than in earlier weeks for contusions/superficial injuries, with both differences being statistically significant. For fractures, however, the averages in the two periods were statistically similar.

CONCLUSIONS

The error associated with the estimated annual number of injuries was large with a three month reference period for all injuries and for less severe injuries. Limiting analysis to episodes with up to five weeks between injury and interview has statistical, intuitive, and analytic appeal for all injuries and for less severe injuries.

Spontaneous shears in smectic elastomers

We model the spontaneous elastic shear deformations of smectic elastomers as they make the thermal transition between the A and C phases. Tilt of the director is accompanied by shear. Unlike nematic elastomers where spontaneous elongation is associated with changes in the magnitude of order, spontaneous distortion in smectics is instead shear and is associated with rotation of the director of the underlying nematic order. The effect of the multistage cross-linking associated with creating monodomain elastomers is taken into account. The angle of molecular tilt and the angle associated with spontaneous shear deformation are not simply related.

Can activated recombinant factor VII be used to postpone the exposure of infants to factor VIII until after 2 years of age?

Two retrospective studies have suggested that exposure to factor VIII (FVIII) in early infancy is associated with an increased risk of FVIII inhibitor development. We prospectively studied 11 infants who needed replacement therapy for bleeding episodes before the age of 2 years. They received activated recombinant factor VII (rFVIIa) concentrate on demand, with the intention of postponing their first exposure to FVIII after 2 years of age. Thirty-three bleeding episodes were treated with 154 doses of rFVIIa with no evidence of adverse effect. Bleeding was controlled in 27 of 33 episodes. Mouth bleeds were most difficult to treat. The use of rFVIIa allowed postponement of the use of FVIII for a mean of 5.5 months (median 4, range 0-12) but in only three of 11 children could be the first exposure to factor postponed after the age of 2 years. With this modest effect of rFVIIa in postponing the first exposure to FVIII, more convincing evidence for the benefit of such a postponement will have to be demonstrated before rFVIIa could be recommended for this indication.

Effect of medium type, age and aeration on the MICs of tigecycline and classical tetracyclines

BACKGROUND

Tigecycline is a minocycline derivative, belonging to a chemical class prone to oxidation and to medium-related effects on susceptibility. We therefore studied the effect of medium type and age on the tigecycline MICs found in broth and on agar by the Clinical Laboratory Standards Institute and British Society for Applied Chemotherapy methods.

METHODS

MICs of tigecycline, minocycline and tetracycline were determined for 96 non-fastidious bacteria and 20 streptococci using Mueller-Hinton broth (MHB), Mueller-Hinton agar (MHA), Iso-Sensitest broth (ISB) and Iso-Sensitest agar (ISA) as: (i) freshly-prepared media; (ii) fresh media but with the antibiotic added 1 day before inoculation and (iii) media stored for 7 days before antibiotic addition and use.

RESULTS

MICs of tigecycline in fresh MHB were up to two doubling dilutions higher than on or in MHA, ISA or ISB. Media with tigecycline or classical tetracyclines added a day before use gave raised MICs, though rarely by more than one dilution. MICs of tigecycline (less so classical tetracyclines) were increased in 7-day-old MHB or ISB, even though the antibiotic was freshly added. This latter effect was greatest for the most susceptible strains and was absent or much reduced for organisms with MICs > or = 8 mg/L; it did not occur in the corresponding agar dilution tests. Addition of blood to MHB largely abrogated the effect, as did steaming the broth before adding the antibiotic.

CONCLUSIONS

The raised MICs of tigecycline in aged broth probably reflect inactivation by dissolved oxygen. This accords with the lack of any MIC increase in newly-steamed (i.e. degassed) MHB or on aged agar (which is melted at 100 degrees C before use). Blood, which also abrogated the effect, may increase reducing capacity, protecting the tigecycline. At a practical level, broth MIC determinations for tigecycline should always employ fresh media.

Getting the measure of spasticity in multiple sclerosis: the Multiple Sclerosis Spasticity Scale (MSSS-88)

Spasticity is most commonly defined as an inappropriate, velocity dependent, increase in muscle tonic stretch reflexes, due to the amplified reactivity of motor segments to sensory input. It forms one component of the upper motor neuron syndrome and often leads to muscle stiffness and disability. Spasticity can, therefore, be measured through electrophysiological, biomechanical and clinical evaluation, the last most commonly using the Ashworth scale. None of these techniques incorporate the patient experience of spasticity, nor how it affects people's daily lives. Consequently, we set out to construct a rating scale to quantify the perspectives of the impact of spasticity on people with multiple sclerosis. Qualitative methods (in-depth patient interviews and focus groups, expert opinion and literature review) were used to develop a conceptual framework of spasticity impact, and to generate a pool of items with the potential to convert this framework into a rating scale with multiple dimensions. This item pool was administered, in the form of a questionnaire, to a sample of people with multiple sclerosis and spasticity. Guided by Rasch analysis, we constructed and validated a rating scale for each component of the conceptual framework. Decisions regarding item selection were based on the integration and assimilation of seven specific analyses including clinical meaning, ordering of thresholds, fit statistics and differential item functioning. The qualitative phase (17 patient interviews, 3 focus groups) generated 144 potential scale items and a conceptual model with eight components addressing symptoms (muscle stiffness, pain and discomfort and muscle spasms,), physical impact (activities of daily living, walking and body movements) and psychosocial impact (emotional health, social functioning). The first postal survey was sent to 272 people with multiple sclerosis and had a response rate of 88%. Findings supported the development of scales for each component but demonstrated that five item response options were too many. The 144-item questionnaire, reformatted with four-item response options, was administered with four validating instruments to an independent sample of 259 people with multiple sclerosis (response rate 78%). From the responses, an 88-item instrument with eight subscales was developed that satisfied criteria for reliable and valid measurement. Correlations with other measures were consistent with predictions. The 88-item Multiple Sclerosis Spasticity Scale (MSSS-88) is a reliable and valid, patient-based, interval-level measure of the impact of spasticity in multiple sclerosis. It has the potential to advance outcomes measurement in clinical trials and clinical practice, and provides a new perspective in the clinical evaluation of spasticity.

Chiral-mechanical transitions in topologically imprinted elastomers

We extend a previous model for chirally imprinted monodomain nematic elastomers to allow a director rotation (by an angle pi/2-theta) towards the pitch axes of the imprinted helices. We find that provided the rubber matrix is allowed to spontaneously deform, the director array will make use of this additional degree of freedom, relaxing into a conical state in both the low and high imprinting efficiency regimes. Consequently, the transition between the regimes of differing imprinting efficiency is coupled to angle theta. This interdependence is nontrivial and involves discontinuous director rotation at the transitions.

Soft elasticity in smectic elastomers

We investigate the soft elastic modes of smectic elastomers, that is shape change without energy cost. We use a microscopic model for their nonlinear elasticity, similar to those used for nematic elastomers. We consider two different phases of smectic elastomer; the biaxial smectic A for a simple illustration, and smectic C phases which are of great practical significance. We show that only one nontrivial trajectory of the director gives soft deformations. We give a geometrical interpretation of this soft elastic mode and give an explicit example.

Elasticity of smectic-A elastomers

We present a fully nonlinear model of the elasticity smectic-A elastomers, and compare our results with a wide range of experimental observations: extreme Poisson ratios, the in-plane modulus, the modulus before and after threshold to layer rotation in response to stretches along the layer normal, the threshold strain, the characteristic, and singular rotation of layers after the threshold. We calculate the x-ray scattering from rotating layers and compare with available data. The model is derived in two ways: from geometrical constraints imposed by layers on a nematic elastomer, and from application of statistical mechanics to a microscopic model of the effect of crosslink points confined in a corrugated potential.

Hairpin rubber elasticity

We model the elastic properties of main chain liquid crystalline elastomers, formed by cross linking chains in a strongly nematic state, when they have hairpin defects. We study the response of the elastomer to imposed uniaxial extension along the nematic direction, and employ a microscopic model of how the deformation is distributed non-affinely amongst the hairpin and straight chain populations. The rubber shows a plateau in the stress as a function of the elongation imposed along the director. It is a consequence of the depletion of the actively stretching population of hairpin chains and should not be confused with soft elasticity effects associated with director rotation.

A prevalent, multiresistant clone of Acinetobacter baumannii in Southeast England

A multiresistant clone of Acinetobacter baumannii was identified in 24 hospitals in the UK, predominantly in the London area, over a period of three years. Isolates were characterized by distinctive ApaI macrorestriction profiles, as resolved by pulsed-field gel electrophoresis (PFGE), which all clustered within 80% similarity using a 1% band position tolerance setting. The first isolates identified were received by the reference laboratories in April 2000, and by June 2003, a total of 375 isolates with similar PFGE profiles from 310 patients from 24 hospitals had been received. The isolates originated mainly from sputum and wound specimens, with the majority from patients in intensive care units. Amplified fragment length polymorphism analysis of a subset of isolates showed that they clustered closely, supporting the PFGE results. All the isolates tested were highly resistant to ampicillin, piperacillin, piperacillin/tazobactam, ceftazidime, cefotaxime, gentamicin and ciprofloxacin, and most isolates were carbapenem resistant. Amikacin sensitivity varied from susceptible [minimum inhibitory concentration (MIC) <or= 4 mg/L] to highly resistant (MIC >256 mg/L).

Activity of daptomycin against multi-resistant Gram-positive bacteria including enterococci and Staphylococcus aureus resistant to linezolid

The activity of daptomycin was assessed against 545 isolates of Gram-positive bacteria including enterococci, coagulase-positive and -negative staphylococci, beta-haemolytic streptococci, viridans streptococci and coryneforms. The panel of isolates was biased towards those with resistance to first-line antimicrobial agents and included linezolid-resistant enterococci and Staphylococcus aureus. MICs of daptomycin were < or =1mg/l for all the staphylococci, streptococci, and coryneforms, except for two isolates of Corynebacterium aquaticum, for which MICs were 8 mg/l. Daptomycin MICs were < or =2 and < or =4 mg/l for Enterococcus faecalis and Enterococcus faecium, respectively.

Community and hospital spread of Escherichia coli producing CTX-M extended-spectrum β-lactamases in the UK

OBJECTIVES

During 2003, the Health Protection Agency's Antibiotic Resistance Monitoring and Reference Laboratory began to receive isolates of Escherichia coli for confirmation of extended-spectrum beta-lactamase production with a phenotype implying a CTX-M-type beta-lactamase, i.e. MICs of cefotaxime > or = 8-fold higher than MICs of ceftazidime. Many were referred as being from community patients. We examined 291 CTX-M-producing isolates from the UK and investigated the genetic basis of their phenotype.

METHODS

PCR was used to detect alleles encoding CTX-M enzymes and to assign these to their blaCTX-M phylogenetic groups. Selected alleles were sequenced. Producers were compared by analysis of banding patterns generated by pulsed-field gel electrophoresis of XbaI-digested genomic DNA. MICs were determined by an agar dilution method or by Etest.

RESULTS

Of 291 CTX-M-producing E. coli isolates studied from 42 UK centres, 70 (24%) were reportedly from community patients, many of whom had only limited recent hospital contact. Community isolates were referred by 12 centres. Two hundred and seventy-nine (95.9%) producers contained genes encoding group 1 CTX-M enzymes and 12 contained blaCTX-M-9-like alleles. An epidemic CTX-M-15-producing strain was identified, with 110 community and inpatient isolates referred from six centres. Representatives of four other major strains also produced CTX-M-15, as did several sporadic isolates examined. Most producers were multi-resistant to fluoroquinolones, trimethoprim, tetracycline and aminoglycosides as well as to non-carbapenem beta-lactams.

CONCLUSIONS

CTX-M-producing E. coli are a rapidly developing problem in the UK, with CTX-M-15 particularly common. The diversity of producers and geographical scatter of referring laboratories indicates wide dissemination of blaCTX-M genes. Because of the public health implications, including for the treatment of community-acquired urinary tract infections, the spread of these strains--and CTX-M-15 beta-lactamase in particular--merits close monitoring.

Uterine leiomyoma and menstrual cycle characteristics in a population-based cohort study

BACKGROUND

We examined the association of uterine leiomyoma with menstrual cycle characteristics in a population of non-care-seeking women.

METHODS

This cross-sectional study uses data from the Seveso Women's Health Study (SWHS), a population-based cohort in Italy. Participants included 341 premenopausal women, 30-60 years old, who had an intact uterus and were not pregnant, lactating, or using oral contraception or intra-uterine devices. We examined the presence of any ultrasound-detected uterine leiomyoma in relation to self-reported menstrual cycle length, flow length and heaviness of flow. The association of leiomyoma number, volume, tissue layer location and axial position with menstrual cycle characteristics was also examined.

RESULTS

Uterine leiomyomata were detected in 73 women (21.4%). After adjustment for covariates, the presence of a leiomyoma was not significantly related to menstrual cycle length, flow length or heaviness of flow [odds ratio (OR) for scanty flow =1.9, 95% confidence interval (CI) 0.8-4.3; OR for heavy flow =1.3, 95% CI 0.7-2.5; relative to moderate flow]. Number, volume, tissue layer location (subserosal or intramural) and axial position (anterior or posterior) of the leiomyoma were also not related to menstrual cycle characteristics.

CONCLUSION

In this Italian population of women not seeking gynaecological care, menstrual characteristics are not related to leiomyoma.