Mechanical excitation and marginal triggering during avalanches in sheared amorphous solids.

We study plastic strain during individual avalanches in overdamped particle-scale molecular dynamics (MD) and mesoscale elastoplastic models (EPM) for amorphous solids sheared in the athermal quasistatic limit. We show that the spatial correlations in plastic activity exhibit a short length scale that grows as t^{3/4} in MD and ballistically in EPM, which is generated by mechanical excitation of nearby sites not necessarily close to their stability thresholds, and a longer lengthscale that grows diffusively for both models and is associated with remote marginally stable sites. These similarities in spatial correlations explain why simple EPMs accurately capture the size distribution of avalanches observed in MD, though the temporal profiles and dynamical critical exponents are quite different.

Mapping out the glassy landscape of a mesoscopic elastoplastic model.

We develop a mesoscopic model to study the plastic behavior of an amorphous material under cyclic loading. The model is depinning-like and driven by a disordered thresholds dynamics that is coupled by long-range elastic interactions. We propose a simple protocol of "glass preparation" that allows us to mimic thermalization at high temperatures as well as aging at vanishing temperature. Various levels of glass stabilities (from brittle to ductile) can be achieved by tuning the aging duration. The aged glasses are then immersed into a quenched disorder landscape and serve as initial configurations for various protocols of mechanical loading by shearing. The dependence of the plastic behavior upon monotonous loading is recovered. The behavior under cyclic loading is studied for different ages and system sizes. The size and age dependence of the irreversibility transition is discussed. A thorough characterization of the disorder-landscape is achieved through the analysis of the transition graphs, which describe the plastic deformation pathways under athermal quasi-static shear. In particular, the analysis of the stability ranges of the strongly connected components of the transition graphs reveals the emergence of a phase-separation like process associated with the aging of the glass. Increasing the age and, hence, the stability of the initial glass results in a gradual break-up of the landscape of dynamically accessible stable states into three distinct regions: one region centered around the initially prepared glass phase and two additional regions characterized by well-separated ranges of positive and negative plastic strains, each of which is accessible only from the initial glass phase by passing through the stress peak in the forward and backward, respectively, shearing directions.

A review of fundamental principles for animal models of DOHaD research: an Australian perspective.

Epidemiology formed the basis of 'the Barker hypothesis', the concept of 'developmental programming' and today's discipline of the Developmental Origins of Health and Disease (DOHaD). Animal experimentation provided proof of the underlying concepts, and continues to generate knowledge of underlying mechanisms. Interventions in humans, based on DOHaD principles, will be informed by experiments in animals. As knowledge in this discipline has accumulated, from studies of humans and other animals, the complexity of interactions between genome, environment and epigenetics, has been revealed. The vast nature of programming stimuli and breadth of effects is becoming known. As a result of our accumulating knowledge we now appreciate the impact of many variables that contribute to programmed outcomes. To guide further animal research in this field, the Australia and New Zealand DOHaD society (ANZ DOHaD) Animals Models of DOHaD Research Working Group convened at the 2nd Annual ANZ DOHaD Congress in Melbourne, Australia in April 2015. This review summarizes the contributions of animal research to the understanding of DOHaD, and makes recommendations for the design and conduct of animal experiments to maximize relevance, reproducibility and translation of knowledge into improving health and well-being.

Inferring elastic properties of an fcc crystal from displacement correlations: subspace projection and statistical artifacts.

We compute the effective dispersion and vibrational density of states (DOS) of two-dimensional subregions of three-dimensional face-centered-cubic crystals using both a direct projection-inversion technique and a Monte Carlo simulation based on a common underlying Hamiltonian. We study both a (111) and (100) plane. We show that for any given direction of wave vector, both (111) and (100) show an anomalous ω(2)∼q regime at low q where ω(2) is the energy associated with the given mode and q is its wave number. The ω(2)∼q scaling should be expected to give rise to an anomalous DOS, D(ω), at low ω: D(ω)∼ω(3) rather than the conventional Debye result: D(ω)∼ω(2). The DOS for (100) looks to be consistent with D(ω)∼ω(3), while (111) shows something closer to the conventional Debye result at the smallest frequencies. In addition to the direct projection-inversion calculation, we perform Monte Carlo simulations to study the effects of finite sampling statistics. We show that finite sampling artifacts act as an effective disorder and bias D(ω), giving a behavior closer to D(ω)∼ω(2) than D(ω)∼ω(3). These results should have an important impact on the interpretation of recent studies of colloidal solids where the two-point displacement correlations can be obtained directly in real-space via microscopy.

Density invariant vibrational modes in disordered colloidal crystals.

We experimentally measure the density of states (DOS) and dynamical structure factor (DSF) arising from the thermal fluctuations in a colloidal crystal composed of thermally sensitive micron-sized hydrogel particles at several different particle volume fractions, ϕ's. Particle positions are tracked over long times using optical microscopy and particle tracking algorithms in a single two-dimensional (2D) [111] plane of a 3D face-centered-cubic single crystal. The dynamical fluctuations are spatially heterogeneous while the lattice itself is highly ordered. At all ϕ's, the DOS exhibits an excess of low frequency modes, a so-called boson peak (BP), and the DSF exhibits a cross-over from propagating to nonpropagating behavior, a so-called Ioffe-Regel crossover, at a frequency somewhat below the BP for both longitudinal and transverse modes. As we tune ϕ from 0.64 to 0.56, the Lindemann parameter grows from ~3% to ~8%; however, the shape of the DOS and DSF remain largely unchanged when rescaled by the Debye level. This invariance indicates that the effective degree of disorder remains essentially constant even in the vicinity of melting.

Local anisotropy in globally isotropic granular packings.

We report on two-dimensional computer simulations of frictionless granular packings at various area fractions φ above the jamming point φ(c). We measure the anisotropy in coarse-grained stress ε(s) and shear modulus ε(m) as functions of coarse-graining scale, R. ε(s) can be collapsed onto a master curve after rescaling R by a characteristic length scale ξ and ε(s) by an anisotropy magnitude A. Both A and ξ accelerate as φ→φ(c) from above, consistent with a divergence at φ(c). ε(m) shows no characteristic length scale and has a nontrivial power-law form, ε(m)~R(-0.62), over almost the entire range of R at all φ. These results suggest that the force chains present in the spatial structure of the quenched stress may be governed by different physics than the anomalous elastic response near jamming.

Normal modes and density of states of disordered colloidal solids.

The normal modes and the density of states (DOS) of any material provide a basis for understanding its thermal and mechanical transport properties. In perfect crystals, normal modes are plane waves, but they can be complex in disordered systems. We have experimentally measured normal modes and the DOS in a disordered colloidal crystal. The DOS shows Debye-like behavior at low energies and an excess of modes, or Boson peak, at higher energies. The normal modes take the form of plane waves hybridized with localized short wavelength features in the Debye regime but lose both longitudinal and transverse plane-wave character at a common energy near the Boson peak.

Anisotropic power law strain correlations in sheared amorphous 2D solids.

The local deformation of steadily sheared two-dimensional Lennard-Jones glasses is studied via computer simulations at zero temperature. In the quasistatic limit, spatial correlations in the incremental strain field are highly anisotropic. The data show power law behavior with a strong angular dependence of the scaling exponent, and the strongest correlations along the directions of maximal shear stress. These results support the notion that the jamming transition at the onset of flow is critical, but suggest unusual critical behavior. The predicted behavior is testable through experiments on sheared amorphous materials such as bubble rafts, foams, emulsions, granular packings, and other systems where particle displacements can be tracked.

Correlations in the elastic response of dense random packings.

Results are presented for the autocorrelation function of the vortexlike nonaffine piece of the linear elastic displacement field in dense random bidisperse packings of harmonically repulsive disks in 2D. The autocorrelation function is shown to scale precisely with the length of the simulation cell in systems ranging from 20 to 100 particles across. It is shown that, to first order, the displacement fields can be thought to arise from the action of uncorrelated local random forcing of a homogeneous elastic sheet, and a theory is presented which gives excellent quantitative agreement with the form of the correlation functions. These results suggest measurements to be made in many types of densely packed, random materials where the elastic displacement fields are accessible experimentally such as granular materials, dense emulsions, colloidal suspensions, etc.

Reconstruction of the spinal accessory nerve with autograft or neurotube? Two case reports.

Injury to the spinal accessory nerve is most commonly iatrogenic, but can be related to cervical trauma or resection of tumor. Of the two most recent publications related to injury of the spinal accessory nerve, one describes transfer of the levator scapulae muscle to restore shoulder function, while the other reports on the results of six surgical repairs, three of which used a sural nerve graft to reconstruct a short neural defect. The present report describes the results obtained in two patients when an iatrogenic injury to the XIth nerve was reconstructed at 3 months after the loss of shoulder function. Denervation of the XIth nerve was confirmed by a first EMG at 6 weeks, and a second one at 12 weeks. At surgery, each XIth nerve was found to have an in-continuity neuroma, most probably related to electrocoagulation. Intraoperative electrical stimulation did not pass the region of nerve injury. In the first patient, the XIth nerve was reconstructed with an autograft from the greater auricular nerve. In the second patient, the XIth nerve was reconstructed with a bioabsorbable conduit, the Neurotube. The patient with the Neurotube reconstruction reached M5 trapezius function by 3 months after surgery, and had no nerve graft donor-site morbidity, while the patient with the autograft reached M4 function by 6 months after reconstruction, and has persistent numbness of the ear lobe. This is the first reported case of a cranial motor nerve being reconstructed with a bioabsorbable conduit.

Effects of rancidity and free fatty acids in choice white grease on growth performance and nutrient digestibility in weanling pigs.

Two experiments were conducted to determine the effects of rancidity and FFA in choice white grease (CWG) on growth performance and nutrient digestibility in nursery pigs. In Exp. 1,150 crossbred pigs (average initial BW of 6.8 kg and average initial age of 21 d) were used. Treatments (as-fed basis) were a corn-soybean meal-based control with no added fat, 6% CWG, and 6% CWG heated at 80 degrees C, with oxygen gas bubbled through it at 849 mL/min for 5, 7, 9, or 11 d. Peroxide value for the CWG increased as oxidative exposure was increased from 0 to 7 d (i.e., peroxide values of 1, 40, and 105 mEq/kg for d 0, 5, and 7, respectively), but decreased to 1 mEq/kg as the hydroperoxides decomposed after 9 and 11 d of oxidation. Pigs fed the control diet (no added fat) had the same (P = 0.91) overall ADG (d 0 to 35) but lower G:F (P < 0.04) than pigs fed diets with added fat. As for the effects of fat quality, ADG (linear effect, P < 0.01) and ADFI (linear effect, P < 0.001) decreased as the fat was made more rancid. However, there were no changes in digestibility of fatty acids as the rancidity of the fat was increased (P = 0.16), suggesting that the negative effects of rancidity were from decreased food intake and not decreased nutrient utilization. In Exp. 2, 125 crossbred pigs (average initial BW of 6.2 kg and average initial age of 21 d) were used to determine the effects of FFA in CWG on the growth performance and nutrient digestibility in nursery pigs. Treatments (as-fed basis) were a corn-soybean meal-based control with no added fat, 6% CWG, and 6% CWG that had been treated with 872, 1,752 or 2,248 lipase units/g of fat. The FFA concentrations in the CWG were increased from 2% with no lipase added to 18, 35, and 53% as lipase additions were increased. Pigs fed the control diet (no added fat) had the same (P = 0.30) overall ADG (d 0 to 33) but lower G:F (P < 0.01) than pigs fed diets with added fat. There were no effects of FFA concentration on ADG (P = 0.18), and ADFI increased (linear effect, P < 0.04) as FFA concentration in the CWG increased. Fatty acid digestibility was not affected (P = 0.17) by FFA in the diet. In conclusion, our data suggest that as fat is oxidized (especially to peroxide values greater than 40 mEq/kg), ADG and ADFI in nursery pigs will decrease; however, FFA concentrations of at least 53% do not adversely affect utilization of CWG in nursery pigs.

Effects of dietary electrolyte balance on the chemistry of blood and urine in lactating sows and sow litter performance.

One hundred fifty-three sows (average parity of 2.2) were used to determine the effects of dietary electrolyte balance (calculated as mEq/kg of diet for Na + K - Cl) on sows and their litters during lactation. The sows were fed corn-soybean meal-based diets (1.0% lysine, 1.0% valine, 0.95% Ca, and 0.80% P; as-fed basis) starting on d 109 of gestation and throughout the 21-d lactation experiment. Dietary electrolyte balance (dEB) was 0, 100, 200, 350, and 500 mEq/kg (as-fed basis), well above and below the dEB of 185 mEq/kg found in a simple corn-soybean meal-based lactation diet. To achieve the desired dEB, diets had the following: 1) 1.8% HCl (6 N) and 1.06% CaCl2, 2) 1.0% CaCl2, 3) 0.04% NaHCO3, 4) 1.29% NaHCO3, and 5) 2.54% NaHCO3 (as-fed basis). Increasing dEB increased blood pH (linear and quadratic effects, P < 0.001), partial pressure of carbon dioxide (linear effect, P < 0.001), HCO3- concentration (linear and quadratic effects, P < 0.001), and blood base excess (linear and quadratic effects, P < 0.001). However, increased dEB resulted in lower blood concentrations of K (linear and quadratic effects, P < 0.04), Cl (linear and quadratic effects, P < 0.001), and ionized Ca (linear and quadratic effects, P < 0.001). Changing dEB did not affect ADFI; water usage, litter weight gain; sow weight change; sow backfat change; percentages of CP, lactose, and fat in the milk; percentage of sows returning to estrus; days to estrus; and number of pigs born alive in the subsequent litter (P = 0.06). However, piglet survivability to d 10 and overall was greatest with the lower dEB treatments (linear effect, P < 0.05). The pH (linear and quadratic effects, P < 0.001) and colony forming units of total bacteria (linear effect, P < 0.03) in the urine increased as dEB of the diet was increased. In conclusion, dEB had pronounced effects on the physiological status of sows and decreasing dEB below that in a simple corn-soybean meal-based diet decreased bacterial counts in the urine and increased piglet survivability. However, milk composition, sow and litter weights at weaning, and subsequent rebreeding performance of the sows were not affected by dEB.

Haemophilus segnis: a rare cause of endocarditis.

This report presents a case of endocarditis due to Haemophilus segnis, which represents a speciation difficulty for the routine laboratory. In this study, a molecular approach provided speciation, which was confirmed phenotypically by a reference laboratory. The use of molecular genotypic analysis is an additional strategy in the investigation of endocarditis. It has applications not only in isolate identification but also in primary detection of infection, particularly in patients whose blood is culture negative by conventional methodologies.

Pulmonary function testing in spinal cord injury: effects of abdominal muscle stimulation.

The purpose of this study was to assess the effects of applying transcutaneous electrical stimulation to paralyzed abdominal muscles during pulmonary function testing (PFT) of individuals with spinal cord injury (SCI). Ten male subjects with anatomical level of SCI between C5-T7 were studied. Subjects performed PFTs with and without electrical stimulation delivered to the abdominal muscles. Subjects with the lowest percentage of predicted expiratory volumes and flows demonstrated the greatest improvement when electrical stimulation was delivered during forced expiration. The overall increases seen in percent of predicted for the study sample were 23 percent for forced vital capacity (FVC), 16 percent for forced expiratory flow in 1 s (FEV1), and 22 percent for peak expiratory flow rate (PEF). Contractions of paralyzed expiratory muscles in response to electrical stimulation during the performance of PFT maneuvers can significantly improve FVC, FEV1, and PEF in some individuals with SCI.

Use of the internal mammary artery graft and in-hospital mortality and other adverse outcomes associated with coronary artery bypass surgery.

BACKGROUND: There is clear evidence that patients having coronary artery bypass graft surgeries with an internal mammary artery (IMA) have better long-term survival. Some studies have suggested a short-term protective effect as well but, because older and sicker patients are less likely to receive an IMA graft, there has been concern that the apparent protective effect of the IMA on short-term mortality has been confounded by other risk factors. This study was intended to examine the independent effect of IMA grafts on in-hospital mortality while adjusting for patient and disease factors. METHODS AND RESULTS: We studied the use of the left IMA (LIMA) in 21 873 consecutive, isolated, first-time coronary artery bypass graft procedures from 1992 through 1999. A total of 87% of the patients received a LIMA graft. LIMA graft use was associated with a significantly decreased risk of mortality. The crude odds ratio for death (LIMA versus no LIMA) was 0.26 (95% confidence intervals, 0.22, 0.31; P:<0.001). LIMA grafts were protective across all major patient and disease subgroups. The odds ratios by subgroup ranged from 0.13 to 0.48. After adjustment for all major risk factors, the odds ratio for death was 0.40 (95% confidence intervals, 0.33, 0.48; P:<0.001). Rates of cerebrovascular accident, return to cardiopulmonary bypass, return to the operating room for bleeding, and mediastinitis or sternal dehiscence requiring surgery were also less in the LIMA group, although not significantly so. CONCLUSIONS: These data suggest that in addition to its well-documented patency and long-term beneficial effect, LIMA grafting has a strong protective effect on perioperative mortality.

Implementation of a nursing home urinary incontinence management program with and without tolterodine.

OBJECTIVE: To evaluate the implementation of a nursing home urinary incontinence management program. DESIGN: A prospective field trial of the program incorporating practice guidelines and principles of continuous quality improvement. SETTING: Five nursing homes in New York, Virginia, and Georgia PARTICIPANTS: One hundred fifty-one residents identified as being incontinent of urine and who met inclusion criteria for ongoing participation in the program. INTERVENTION: Key multidisciplinary staff from the five nursing homes were trained in the program and assumed responsibility for implementing it in their facilities. The program consisted of a clinical assessment, toileting protocols, and the addition of the antimuscarinic drug tolterodine in selected residents who did not respond well to toileting alone. Data on dryness rates during the 60-day toileting protocols, collected by nursing home staff, were analyzed on a weekly basis by an overall project coordinator who sent data back to the nursing homes in an easy-to-read graphical format. MEASURES: (1) The dryness rate, defined as the number of times the resident was dry divided by the number of times the resident was checked (every 2 hours from 7 a.m. to 7 p.m.); and (2) adverse events (eg, dry mouth, increased confusion, need for dosage reduction). RESULTS: Of 645 residents in the 5 nursing homes, 377 (58%) were identified as incontinent of urine, of whom 151 (40%) were placed on an ongoing toileting program. Of these 151 residents, 48 (32%) were prescribed tolterodine, and 117 (78%) completed the 60-day trial. The initial dryness rate was 57%, and for the group as a whole remained essentially unchanged (increase in dryness 1%, P = 0.50). Among 50 clinically stable residents on a toileting program alone, the increase in the dryness rate was 16% (P = 0.001), and for 31 clinically stable residents prescribed tolterodine, the increase in the dryness rate was 29% (P = 0.012). Two residents had their dosage of tolterodine reduced because of dry mouth and nausea,one resident was taken off the drug because of increased pain in the back and legs and increased confusion. CONCLUSIONS: Overall, this program resulted in significant increases in dryness rates for clinically stable incontinent nursing home residents. These residents represented 22% of the total number of residents identified as incontinent in the five participating nursing homes. Tolterodine was prescribed for approximately one-third of incontinent residents as a supplement to a toileting program, and was well tolerated. Nursing homes should be encouraged to implement similar urinary incontinence programs, target toileting protocols to the most responsive residents, and maintain the program using principles of continuous quality improvement.

Effect of local conjugated estrogens on vaginal pH in elderly women.

OBJECTIVE: The decline in estrogens during and after menopause is associated with an increase in vaginal pH and an increased susceptibility to urinary tract infections (UTIs). Decreased vaginal pH following short-term treatment with topical estrogens may reduce the incidence of such infections. This study was undertaken to evaluate the effect of low-dose, topical conjugated estrogens vaginal cream (CEVC) on vaginal pH in older, postmenopausal women. DESIGN: We conducted a retrospective analysis of initial and follow-up evaluations of older, postmenopausal women residing in 19 long-term care facilities who were referred to Seton Health System's Incontinence Treatment Center between January 2, 1997, and June 13, 1998. Patients were untreated or were administered conjugated estrogens intravaginally (0.5 g/d, 3 days per week). SETTING: Incontinence Treatment Center, Seton Health System. PARTICIPANTS: Two hundred fifty-eight postmenopausal women (mean age 83 years), residents of skilled nursing facilities, who were diagnosed with urinary incontinence, were included in the study. MEASUREMENTS: Measurements included age, CEVC treatment, vaginal pH, and history of UTIs or hysterectomy. RESULTS: In the CEVC-treated women, vaginal pH was reduced from a mean of 7.41 +/- 0.71 to 6.80 +/- 0.70 after 6 weeks (n = 213; P = 0.0001). No differences in vaginal pH were observed in untreated women (n = 45). Continuation of CEVC treatment for an additional 6 weeks (n = 93) resulted in further decreases in vaginal pH (P = 0.017). Women who discontinued treatment after 6 weeks maintained a lower vaginal pH for 6 weeks (P = 0.0004), and there was no significant difference between groups at Week 12. CONCLUSIONS: Low-dose CEVC for 6 and 12 weeks reduces vaginal pH in older women residing in long-term care facilities. The decreased vaginal pH following short-term treatment with topical estrogens may reduce the incidence of recurrent UTIs.

Breathing pattern retraining and exercise in persons with chronic obstructive pulmonary disease.

Breathing pattern retaining, in the form of pursed-lip breathing, has been used as one method in pulmonary rehabilitation to help alleviate the symptoms of dyspnea endured by people who suffer from airflow obstruction secondary to chronic obstructive pulmonary disease (COPD). Other techniques such as biofeedback also have been successfully used. This article describes the altered breathing patterns used by patients with COPD at rest and during physical activity. The literature is reviewed regarding techniques of breathing pattern retraining that have been developed to improve the capacity of persons with COPD to perform activities of daily living, a primarily rehabilitative outcome.

Induction of cyclooxygenase-2 by human monocytes exposed to group B streptococci.

Group B streptococcal (GBS) infections are associated with high morbidity and mortality. The molecular pathways mediating the pathophysiological events in GBS infection are not fully delineated. Cyclooxygenases (COX) are the enzymes that convert arachidonate to active eicosanoids. To identify the effects of GBS on eicosanoid metabolism and regulatory mechanisms, we exposed human monocytes to GBS and found that they secreted prostaglandin E2, prostacyclin, and thromboxane A2. Exposure to GBS caused monocytes to express COX-2 mRNA and protein in both a time- and concentration-dependent manner that correlated with eicosanoid production. COX-1 protein was unchanged. Addition of the anti-inflammatory cytokines interleukin (IL)-4 or IL-10 markedly attenuated GBS-induced COX-2 protein accumulation after GBS exposure, as did inhibition of p38 MAPK. Our experiments are the first to show that exposure of monocytes to a gram-positive bacterium (GBS) results in induction of functional COX-2, suggesting that eicosanoids may play important roles in the pathogenesis of GBS infections.