Spectroscopic Investigation of the Effect of Microstructure and Energetic Offset on the Nature of Interfacial Charge Transfer States in Polymer: Fullerene Blends.

Despite performance improvements of organic photovoltaics, the mechanism of photoinduced electron-hole separation at organic donor-acceptor interfaces remains poorly understood. Inconclusive experimental and theoretical results have produced contradictory models for electron-hole separation in which the role of interfacial charge-transfer (CT) states is unclear, with one model identifying them as limiting separation and another as readily dissociating. Here, polymer-fullerene blends with contrasting photocurrent properties and enthalpic offsets driving separation were studied. By modifying composition, film structures were varied from consisting of molecularly mixed polymer-fullerene domains to consisting of both molecularly mixed and fullerene domains. Transient absorption spectroscopy revealed that CT state dissociation generating separated electron-hole pairs is only efficient in the high energy offset blend with fullerene domains. In all other blends (with low offset or predominantly molecularly mixed domains), nanosecond geminate electron-hole recombination is observed revealing the importance of spatially localized electron-hole pairs (bound CT states) in the electron-hole dynamics. A two-dimensional lattice exciton model was used to simulate the excited state spectrum of a model system as a function of microstructure and energy offset. The results could reproduce the main features of experimental electroluminescence spectra indicating that electron-hole pairs become less bound and more spatially separated upon increasing energy offset and fullerene domain density. Differences between electroluminescence and photoluminescence spectra could be explained by CT photoluminescence being dominated by more-bound states, reflecting geminate recombination processes, while CT electroluminescence preferentially probes less-bound CT states that escape geminate recombination. These results suggest that apparently contradictory studies on electron-hole separation can be explained by the presence of both bound and unbound CT states in the same film, as a result of a range of interface structures.

Relating free energy and open-circuit voltage to disorder in organic photovoltaic systems.

Efficient exciton dissociation into mobile charge carries a crucial factor underscoring the performance of organic polymer-based bulk-heterojunction photovoltaic devices. In this paper, we compute the energies of charge-transfer (CT) states of the model donor-acceptor lattice system with varying degrees of structural disorder to investigate how fluctuations in the material properties affect electron-hole separation. We also demonstrate how proper statistical treatment of the CT energies recovers the experimentally observed "hot" and "cold" exciton dissociation pathways. Using a quantum mechanical model for a model heterojunction interface, we recover experimental values for the open-circuit voltage at 50 and 100 meV of site-energy disorder. We find that energetic and conformational disorder generally facilitates charge transfer; however, due to excess energy supplied by photoexcitation, highly energetic electron-hole pairs can dissociate in unfavorable directions, potentially never contributing to the photocurrent while "cold" excitons follow the free energy curve defined at the operating temperature of the device.

Introduction of guidelines to facilitate enteral nutrition in a surgical intensive care unit is associated with earlier enteral feeding.

PURPOSE: Patients treated postoperatively in surgical intensive care units often receive delayed enteral nutrition. We hypothesized that the introduction of guidelines promoting early enteral nutrition is associated with earlier enteral feeding. METHODS: Enteral nutrition guidelines were created by the consensus of a multidisciplinary team consisting of intensivists, nurses, nutritionists, and surgeons. The guidelines were implemented through repeated staff education. We prospectively compared data on nutritional support in the surgical intensive care unit of a tertiary care center before (pre-intervention period, from January 27 to April 30, 2008) and after (post-intervention period, from May 1st to August 15th, 2008) implementation of the guidelines. The primary outcome was time to enteral feeding (oral or tube feeding). RESULTS: 146 patients were evaluated during the pre-period and 141 patients during the post-period. Patients during the two time periods had similar demographics and clinical characteristics. None of the patients were without nutrition for longer than 7 days. Oral or feeding tube nutrition was started earlier in the post-period (median 1 vs. 2 days, p < 0.001). There was no difference in the percentages of patients receiving parenteral nutrition (7.4 vs. 10%, p = 0.360). There was no increase in aspiration events in the post-period (8 vs. 9.4%, p = 0.606). CONCLUSIONS: Introduction of guidelines to facilitate enteral nutrition in a surgical intensive care unit was associated with earlier enteral feeding.

Postoperative residual curarization from intermediate-acting neuromuscular blocking agents delays recovery room discharge.

BACKGROUND: Postoperative residual curarization (PORC) [train-of-four ratio (T4/T1) <0.9] is associated with increased morbidity and may delay postoperative recovery room (PACU) discharge. We tested the hypothesis that postoperative T4/T1 <0.9 increases PACU length of stay. METHODS: At admission to the PACU, neuromuscular transmission was assessed by acceleromyography (stimulation current: 30 mA) in 246 consecutive patients. The potential consequences of PORC-induced increases in PACU length of stay on PACU throughput were estimated by application of a validated queuing model taking into account the rate of PACU admissions and mean length of stay in the joint system of the PACU plus patients recovering in operation theatre waiting for PACU beds. RESULTS: PACU length of stay was significantly longer in patients with T4/T1 <0.9 (323 min), compared with patients with adequate recovery of neuromuscular transmission (243 min). Age (P=0.021) and diagnosis of T4/T1 <0.9 (P=0.027), but not the type of neuromuscular blocking agent, were independently associated with PACU length of stay. The incidence of T4/T1 <0.9 was higher in patients receiving vecuronium. Delayed discharge significantly increases the chances of patients having to wait to enter the PACU. The presence of PORC is estimated to be associated with significant delays in recovery room admission. CONCLUSIONS: PORC is associated with a delayed PACU discharge. The magnitude of the effect is clinically significant. In our system, PORC increases the chances of patients having to wait to enter the PACU.

Wigner surmise for Hermitian and non-Hermitian chiral random matrices.

We use the idea of a Wigner surmise to compute approximate distributions of the first eigenvalue in chiral random matrix theory, for both real and complex eigenvalues. Testing against known results for zero and maximal non-Hermiticity in the microscopic large- N limit, we find an excellent agreement valid for a small number of exact zero eigenvalues. Compact expressions are derived for real eigenvalues in the orthogonal and symplectic classes and at intermediate non-Hermiticity for the unitary and symplectic classes. Such individual Dirac eigenvalue distributions are a useful tool in lattice gauge theory, and we illustrate this by showing that our results can describe data from two-color quantum chromodynamics simulations with chemical potential in the symplectic class.

Monte Carlo study of the droplet formation-dissolution transition on different two-dimensional lattices.

In 2003 Biskup [Commun. Math. Phys. 242, 137 (2003)] gave a rigorous proof for the behavior of equilibrium droplets in the two-dimensional (2D) spin-1/2 Ising model (or, equivalently, a lattice gas of particles) on a finite square lattice of volume V with a given excess delta M identical with M-M 0 of magnetization compared to the spontaneous magnetization M 0=m0V . By identifying a dimensionless parameter Delta(delta M) and a universal constant Delta c , they showed in the limit of large system sizes that for DeltaDelta c a droplet of the minority phase occurs ("condensed" system). By minimizing the free energy of the system, they derived an explicit formula for the fraction lambda(Delta) of excess magnetization forming the droplet. To check the applicability of the asymptotic analytical results to much smaller, practically accessible, system sizes, we performed several Monte Carlo simulations of the 2D Ising model with nearest-neighbor couplings on a square lattice at fixed magnetization M . Thereby, we measured the largest minority droplet, corresponding to the condensed phase in the lattice-gas interpretation, at various system sizes (L=40,80,...,640) . With analytical values for the spontaneous magnetization density m 0 , the susceptibility chi , and the Wulff interfacial free energy density tau W for the infinite system, we were able to determine lambda numerically in very good agreement with the theoretical prediction. Furthermore, we did simulations for the spin-1/2 Ising model on a triangular lattice and with next-nearest-neighbor couplings on a square lattice. Again finding a very good agreement with the analytic formula, we demonstrate the universal aspects of the theory with respect to the underlying lattice and type of interaction. For the case of the next-nearest-neighbor model, where tau W is unknown analytically, we present different methods to obtain it numerically by fitting to the distribution of the magnetization density P(m) .

[Life expectancy, potential years of life lost (PYLL), and avoidable mortality in an East/West comparison]. / Lebenserwartung, vorzeitig verlorene Lebensjahre und vermeidbare Sterblichkeit im Ost-West-Vergleich.

The dynamics of convergence between East and West Germany in the life-prolonging process continued undiminished from 1990 until 2001. The regional differences in premature and avoidable mortality were clearly reduced, both between East and West and between the individual federal states. In the East and in the West there was an increase in life expectancy in all age groups and for both sexes, whereby the increase in life expectancy was considerably greater in East Germany and in all of the East German federal states. Also, the standardized potential years of life lost before the age of 65 decreased more intensively in East Germany. The women in East Germany achieved a lower premature mortality due to illness in the year 2001 than those in West Germany. In the initial year of 1990, the years of life lost were 27.2% greater. Unnatural premature mortality (especially due to accidents) was also relatively high in East Germany in the year 2001, but it is clearly being reduced. The avoidable mortality has been more than cut in half in all East German federal states since 1990. An almost complete alignment between East and West in regard to avoidable mortality was achieved in the year 2001. The phase of economic stagnation that can be observed in East Germany since 1997 has up to now not led to a worsening in the constitutive health references presented above.

[Not Available]. / Vorausberechnungen des Herzinfarktgeschehens in Deutschland Zur Entwicklung von Inzidenz und Prävalenz bis zum Jahre 2050 : Zur Entwicklung von Inzidenz und Prävalenz bis zum Jahre 2050.

Based on the Federal Health Survey from 1998, the Augsburg heart attack registry, and the ninth coordinated population prediction, we have estimated the occurrence of heart attacks in Germany up to the year 2050. From the mere demographic perspective - regardless of medical and social influences - we can expect that the need for cardiac care will increase considerably. If we assume that the risk or the frequency of having a heart attack will remain the same, then the number of heart attacks in people aged 25 to over 90 and 35 to under 90 will increase, although the population size of these age groups will decline. The population over 75 years of age will with certainty determine the course of the incidence and prevalence of heart attacks. In addition to standardised incidence and/or prevalence rates, estimations of the absolute number of incidents and/or prevalent cases of the respective target illness have to be included in morbidity predictions in order to avoid misinterpretations.

The cis-trans isomerization of 1,2,5,6-tetrasilacycloocta-3,7-dienes: analysis by mechanistic probes and density functional theory.

A series of alkyl- and aryl-substituted derivatives of cis,cis-1,2,5,6-tetrasilacycloocta-3,7-diene were prepared. Isomerization of these compounds to the corresponding trans,trans-1,2,5,6-tetrasilacycloocta-3,7-dienes by exposure to Ru and Zr hydride complexes was explored. Experimental probes of the isomerization were consistent with a stepwise mechanism involving metal hydride addition/elimination rather than one involving radical intermediates. Analysis of the low energy conformers of the various cis and trans isomers of 1,1,2,2,5,5,6,6-octamethyl-1,2,5,6-tetrasilacycloocta-3,7-diene using density functional theory suggested the following trend in stability: trans,trans > cis,trans > cis,cis. The calculated trend in stability was consistent with the experimentally observed unidirectional isomerization of the carbon-carbon double bonds from all cis to all trans and supports a cis,trans isomer as a tenable intermediate.

Daytime variations in central nervous system activation measured by a pupillographic sleepiness test.

Pupil size is regulated exclusively by the autonomic nervous system, and in darkness is proportional to the level of central sympathetic tone. Spontaneous pupillary movements, while at rest in darkness and quiet, were recorded for a period of 11 min, using infrared video pupillography. Thirteen young adults took part in a 30-h experiment lasting from 08.00 h to 14.00 h on the following day. Pupillographic testing and completion of a self-rated scale for the estimate of sleepiness were repeated every two hours. Pupillary unrest index (PUI), as a measure of pupil size instability associated with daytime sleepiness, showed the lowest values at 09.00 h, when pupil size was found to be maximal, and 23.00 h. During the course of the day, amplitude spectrum < or = 0.8 Hz and PUI showed increasing values during the afternoon hours, followed by a decrease during the evening. Daytime variations in the pupillary unrest index in healthy normal subjects were found to be positively correlated with the level of alertness. These findings are similar to the daytime variations found by the MSLT (multiple sleep latency test) in young adults.

Guanylyl cyclase C messenger RNA is a biomarker for recurrent stage II colorectal cancer.

BACKGROUND: Patients with stage II colorectal cancer and no histologic evidence of lymph node invasion develop recurrent disease, presumably because of undetected micrometastases. Guanylyl cyclase C is expressed by intestinal and colorectal cancer cells but not by extraintestinal tissues or tumors. OBJECTIVE: To examine the expression of guanylyl cyclase C messenger RNA (mRNA) in lymph nodes of patients with node-negative colorectal cancer who did and did not have recurrent disease. DESIGN: Case-control study. SETTING: Tertiary care academic medical center. PATIENTS: Paraffin-embedded lymph nodes were obtained from 21 patients with histologically confirmed node-negative colorectal cancer who had undergone resection. Controls included 11 patients without disease recurrence 6 or more years after resection, and case-patients included 10 patients whose disease recurred up to 3 years after resection. MEASUREMENTS: Sections of paraffin-embedded lymph nodes were obtained from each patient and were pooled, and their RNA was analyzed by reverse transcriptase polymerase chain reaction (RT-PCR). RESULTS: Guanylyl cyclase C mRNA was expressed in lymph nodes from all patients with recurrent disease but not in those from patients without recurrent disease (P = 0.004). Nested RT-PCR that used primers for carcinoembryonic antigen, a marker for colorectal cancer, identified carcinoembryonic antigen mRNA in lymph nodes from only 1 of 10 patients with recurrent disease and those from 0 of 11 patients without recurrent disease. The odds ratio for death associated with expression of guanylyl cyclase C mRNA in regional lymph nodes was 15.0 (95% CI, 1.1 to 756.7). CONCLUSIONS: Expression of guanylyl cyclase C mRNA in lymph nodes is associated with recurrence of colorectal cancer in patients with stage II disease. Analysis of guanylyl cyclase mRNA expression by RT-PCR may be useful for colorectal cancer staging.

[Incidence of myocardial infarct in Germany: prevalence, incidence trends, East-West comparison]. / Zum Herzinfarktgeschehen in der Bundesrepublik Deutschland: Prävalenz, Inzidenz, Trend, Ost-West-Vergleich.

The German National Health Interview and Examination Survey, as a descriptive cross-sectional study, allows the recording of post-myocardial infarct cases, e.g. the number (prevalence) of survivors after an infarct has occurred (non-lethal myocardial infarcts). The 18 to 79 year old residential population in Germany had a lifetime prevalence of 2.45% for conditions after a heart attack. The age-specific lifetime prevalence values increase with increasing age for both men and women. Between the ages of 30 and 59 there are more than 4 male heart attack victims for every woman; between the ages of 60 and 79 this relation is only 1 to 1.5. The 30-< 80 year old population in Germany has around 1,450,000 post-myocardial infarct cases (heart attack victims). There are about 100,000 male post-myocardial infarct cases among relatively young adults between 30 and 49 years of age. There were hardly any cases in the female population in this age group. In regard to post-myocardial infarcts there were no significant morbidity differences between the eastern and western German states in 1997/98. A comparison of the lifetime prevalence rates between 1997/98 and 1990/92 shows the following trend: the number of post-myocardial infarcts in the German population 25-< 70 years old decreased; in Western Germany the lifetime prevalence rates also declined, in Eastern Germany the prevalence rates among both men and women increased in this period of time. In the period 1997/98 there were around 190,000 non-lethal myocardial infarcts in the 18 to 79 year old German population in a full 12 month period (incidence cases of survivors after the occurrence of an acute first and/or acute reinfarcts).

[Stroke: prevalence, incidence, trends, East-West comparison. Initial results of the 1998 Federal Health Survey]. / Schlaganfall: Prävalenz, Inzidenz, Trend, Ost-West-Vergleich. Erste Ergebnisse aus dem Bundes-Gesundheitssurvey 1998.

The prevalence of survival after a stroke is dependent on the incidence and the fatality rate, whereby the incidence and the fatality rate are influenced by different factors. A survey can only include the minor cases of post-stroke conditions. The prevalence figures thus only reflect the less serious or rehabilitated strokes. Despite this underrepresentation of strokes in the survey we can observe an underestimation of the stroke problem in Germany. Whereas we previously assumed 440,000 to 500,000 strokes in Germany, the projection from the data of the German National Health Interview and Examination Survey amounted to around 945,000 cases (only strokes with "minor" motor, sensory and cognitive losses and restrictions which allow a participation in the survey). The lifetime prevalence rate of the 18-< 80 year old female population is somewhat higher than the male population of the same age (n.s.). The 50 to < 60 year old men have a relatively high prevalence rate. The corresponding age specific prevalence rates increase with increasing age. There are no significant differences in morbidity between the former East and West German states, the prevalence rates of men are somewhat higher in the East and those of women in the West. We can see the following trends in a comparison of the lifetime prevalence rates between 1997/98 and 1990/92: the number of post-stroke conditions among German men 25-< 70 years old declined significantly, among women they increased slightly (n.s.); the prevalence as a whole also declined significantly among men in western Germany, among women they increased slightly (n.s.) in contrast to former West Germany the prevalence rates among men in eastern Germany increased slightly, among women they were almost cut in half. 32.8% of the population with "minor" post-stroke conditions is characterized by sensory disruptions, 32.1% by impairments when walking, 31.3% by paralyses, 20.5% by speech impairments, 17.1% by cognitive disorders and 3.1% by disturbances of consciousness.

Changes in oxygenation and compliance as related to body position in acute lung injury.

Body positioning during mechanical ventilation for acute lung injury has not been studied in a detailed manner. We evaluated the relationship between oxygenation, compliance, and body position during mechanical ventilation of patients with acute lung injury (ALI). Sixteen patients on mechanical ventilation with a diagnosis of ALI (partial pressure of oxygen/fraction of inspired oxygen <300 and no clinical evidence of congestive heart failure) were prospectively studied. Each patient was placed in a supine position followed by a 30 degrees head elevation and a 45 degrees head elevation. Data obtained in each position (after a 45-60 minute equilibration time) included static pulmonary compliance and partial pressure of oxygen from arterial blood gas sampling. Oxygenation is not improved and compliance is adversely affected by upright body positioning as compared to the supine position in patients receiving mechanical ventilation for ALI.

The effect of granulocyte colony stimulating factor in patients with leukopenia due to sepsis.

The use of granulocyte stimulating factor (G-CSF) (Neupogen, Amgen Inc., Thousand Oaks, Calif.) has become acceptable for treating both primary and acquired leukopenia. Leukopenia associated with infection is an ominous sign of overwhelming sepsis. In this article, we present two cases of infection that were related to leukopenia which were successfully treated with G-CSF.

Psychology and optometry. Interaction and collaboration.

Health care professionals have long recognized the value of interdisciplinary collaboration, although it is sometimes difficult to effect such collaborations. One unique possibility for interdisciplinary exchange involves the professions of clinical psychology and optometry. A number of vision conditions have psychological components and some psychological conditions may be complicated by vision difficulties; thus, there are a number of ways in which psychologists and optometrists could inform each others' practices. Better organized health care delivery is likely to result from interdisciplinary training and cooperation, as clients are likely to receive more efficient diagnosis, treatment, and management of health problems.