The Pfaffian solution of a dimer-monomer problem: Single monomer on the boundary

We consider the dimer-monomer problem for the rectangular lattice. By mapping the problem into one of close-packed dimers on an extended lattice, we rederive the Tzeng-Wu solution for a single monomer on the boundary by evaluating a Pfaffian. We also clarify the mathematical content of the Tzeng-Wu solution by identifying it as the product of the nonzero eigenvalues of the Kasteleyn matrix.Comment: 4 Pages to appear in the Physical Review E (2006

Lasing from single, stationary, dye-doped glycerol/water microdroplets located on a superhydrophobic surface

We report laser emission from single, stationary, Rhodamine B-doped glycerol/water microdroplets located on a superhydrophobic surface. In the experiments, a pulsed, frequency-doubled Nd:YAG laser operating at 532 nm was used as the excitation source. The microdroplets ranged in diameter from a few to 20 um. Lasing was achieved in the red-shifted portion of the dye emission spectrum with threshold fluences as low as 750 J/cm2. Photobleaching was observed when the microdroplets were pumped above threshold. In certain cases, multimode lasing was also observed and attributed to the simultaneous lasing of two modes belonging to different sets of whispering gallery modes.Comment: to appear in Optics Communication

The contribution of staff call light response time to fall and injurious fall rates: an exploratory study in four US hospitals using archived hospital data

Abstract Background Fall prevention programs for hospitalized patients have had limited success, and the effect of programs on decreasing total falls and fall-related injuries is still inconclusive. This exploratory multi-hospital study examined the unique contribution of call light response time to predicting total fall rates and injurious fall rates in inpatient acute care settings. The conceptual model was based on Donabedian's framework of structure, process, and health-care outcomes. The covariates included the hospital, unit type, total nursing hours per patient-day (HPPDs), percentage of the total nursing HPPDs supplied by registered nurses, percentage of patients aged 65 years or older, average case mix index, percentage of patients with altered mental status, percentage of patients with hearing problems, and call light use rate per patient-day. Methods We analyzed data from 28 units from 4 Michigan hospitals, using archived data and chart reviews from January 2004 to May 2009. The patient care unit-month, defined as data aggregated by month for each patient care unit, was the unit of analysis (N = 1063). Hierarchical multiple regression analyses were used. Results Faster call light response time was associated with lower total fall and injurious fall rates. Units with a higher call light use rate had lower total fall and injurious fall rates. A higher percentage of productive nursing hours provided by registered nurses was associated with lower total fall and injurious fall rates. A higher percentage of patients with altered mental status was associated with a higher total fall rate but not a higher injurious fall rate. Units with a higher percentage of patients aged 65 years or older had lower injurious fall rates. Conclusions Faster call light response time appeared to contribute to lower total fall and injurious fall rates, after controlling for the covariates. For practical relevance, hospital and nursing executives should consider strategizing fall and injurious fall prevention efforts by aiming for a decrease in staff response time to call lights. Monitoring call light response time on a regular basis is recommended and could be incorporated into evidence-based practice guidelines for fall prevention.http://deepblue.lib.umich.edu/bitstream/2027.42/112579/1/12913_2011_Article_2004.pd

Dye lasing in optically manipulated liquid aerosols

We report lasing in airborne, rhodamine B-doped glycerol-water droplets with diameters ranging between 7.7 and 11.0 mu m, which were localized using optical tweezers. While being trapped near the focal point of an infrared laser, the droplets were pumped with a Q-switched green laser. Our experiments revealed nonlinear dependence of the intensity of the droplet whispering gallery modes (WGMs) on the pump laser fluence, indicating dye lasing. The average wavelength of the lasing WGMs could be tuned between 600 and 630 nm by changing the droplet size. These results may lead to new ways of probing airborne particles, exploiting the high sensitivity of stimulated emission to small perturbations in the droplet laser cavity and the gain medium

Theory of impedance networks: The two-point impedance and LC resonances

We present a formulation of the determination of the impedance between any two nodes in an impedance network. An impedance network is described by its Laplacian matrix L which has generally complex matrix elements. We show that by solving the equation L u_a = lambda_a u_a^* with orthonormal vectors u_a, the effective impedance between nodes p and q of the network is Z = Sum_a [u_{a,p} - u_{a,q}]^2/lambda_a where the summation is over all lambda_a not identically equal to zero and u_{a,p} is the p-th component of u_a. For networks consisting of inductances (L) and capacitances (C), the formulation leads to the occurrence of resonances at frequencies associated with the vanishing of lambda_a. This curious result suggests the possibility of practical applications to resonant circuits. Our formulation is illustrated by explicit examples.Comment: 21 pages, 3 figures; v4: typesetting corrected; v5: Eq. (63) correcte

Alteplase administration for acute ischemic stroke (AIS) in ER - a 5-year review

ER visits for AIS grown in last 10 years by 25% Ongoing effort by AHA/ASA to improve access to care with early stroke recognition and awareness Time is brain; rate of thrombolysis with alteplase (ALT) should increase with better EMS systems, awareness, and educatio

Distinct predictors of pre‐ versus post‐discharge venous thromboembolism after hepatectomy: analysis of 7621 NSQIP patients

AbstractObjectivesHepatectomy patients are known to be at significant risk for venous thromboembolism (VTE), but previous studies have not differentiated pre‐ versus post‐discharge events. This study was designed to evaluate the timing, rate and predictors of pre‐ (‘early’) versus post‐discharge (‘late’) VTE.MethodsAll patients undergoing elective hepatectomy during 2005–2010 and recorded in the American College of Surgeons National Surgical Quality Improvement Program participant use file were identified. Perioperative factors associated with 30‐day rates of early and late VTE were analysed.ResultsA total of 7621 patients underwent 4553 (59.7%) partial, 802 (10.5%) left, 1494 (19.6%) right and 772 (10.1%) extended hepatectomies. Event rates were 1.9% for deep venous thrombosis, 1.2% for pulmonary embolus and 2.8% for VTE. Of instances of VTE, 28.6% occurred post‐discharge. The median time of presentation of late VTE was postoperative day 14. Multivariate analysis determined that early VTE was associated with age ≥75 years [odds ratio (OR) 1.92, P = 0.007], male gender (OR 1.87, P = 0.002), intraoperative transfusion (OR 2.49, P < 0.001), operative time of >240 min (OR 2.28, P < 0.001), organ space infection (OSI) (OR 2.60, P < 0.001), and return to operating room (ROR) (OR 3.25, P < 0.001). Late VTE was associated with operative time of >240 min (OR 2.35, P = 0.008), OSI (OR 3.78, P < 0.001) and ROR (OR 2.84, P = 0.011).ConclusionsLate VTE events occur in patients with clearly identifiable intraoperative and postoperative risk factors. This provides a rationale for the selective use of post‐discharge VTE chemoprophylaxis in high‐risk patients

Control of Myoblast Fusion by a Guanine Nucleotide Exchange Factor, Loner, and Its Effector ARF6

AbstractMyoblast fusion is essential for the formation and regeneration of skeletal muscle. In a genetic screen for regulators of muscle development in Drosophila, we discovered a gene encoding a guanine nucleotide exchange factor, called loner, which is required for myoblast fusion. Loner localizes to subcellular sites of fusion and acts downstream of cell surface fusion receptors by recruiting the small GTPase ARF6 and stimulating guanine nucleotide exchange. Accordingly, a dominant-negative ARF6 disrupts myoblast fusion in Drosophila embryos and in mammalian myoblasts in culture, mimicking the fusion defects caused by loss of Loner. Loner and ARF6, which also control the proper membrane localization of another small GTPase, Rac, are key components of a cellular apparatus required for myoblast fusion and muscle development. In muscle cells, this fusigenic mechanism is coupled to fusion receptors; in other fusion-competent cell types it may be triggered by different upstream signals