Filter feeders are key to small microplastic residence times in stratified lakes: A virtual experiment.

Microplastic (MP) is potentially harmful to lake ecosystems, with its uptake into the food web largely controlled by its residence time in the lake water column. Here we combine laboratory and virtual experiments to quantify residence times of small MP (<15 µm) in two contrasting model lakes; Lake Constance (large lake) and Esthwaite Water (a small lake). We compare MP residence times in a purely physical system with MP transport controlled by sinking and mixing to a model where, in addition to physical processes, zooplankton package MP into faecal pellets that are then egested into the water column. The laboratory experiments showed that MP settling velocities increased from ~5 × 10-6-10-3 mm s-1 for pristine MP to ~1 mm s-1 for MP embedded faeces. Modeled lake residence times for the 0.5 and 5 µm particles were >15 years in the abiotic models, while in the biotic simulations they were reduced to ~1 year. There was little difference between abiotic and biotic simulations for the 15 µm particles. The ratio of the MP zooplankton uptake velocity to the sinking velocity (v_up/vs_epi) was used to classify biological vs. physical transport pathways. For the 0.5 and 5 µm particles v_up/vs_epi was ≫1 in all cases for both lakes, while for the 15 µm MP there was a transition between biological and physical processes dominating residence times depending on zooplankton numbers. Our results suggest that packaging of small MP in faecal pellets by zooplankton will control its residence time in lakes. Moreover, the majority of small MP will cycle through organisms before reaching the sediment, increasing the likelihood of negative ecological effects and transfer in the food web.

Equipping soldiers to benefit from goal-focused leadership: The moderating effects of non-discriminatory leader behaviors and workgroup cohesion.

We apply the Job Demands-Resources model to explicate how two contextual factors (nondiscriminatory leadership behavior and cohesion) may equip subordinates to benefit from the leadership style of goal-focused leadership (GFL), a predominant leadership style in the military context. We predict that only when GFL is delivered in conjunction with nondiscriminatory leadership behaviors in a cohesive workgroup (which, we theorize, combine to create a resource-rich environment), subordinates may experience the lowest levels of exhaustion. We tested our hypothesis in two independent samples of uniformed United States Department of Defense personnel deployed in non-combat zones, and results are fully supportive. We add to recent efforts to expand the nomological network of GFL, pinpointing situational factors that may equip subordinates to experience lower (rather than higher) exhaustion when working with a goal-focused leader. In doing so, we also contribute to theory on diversity and stress, and we suggest practical applications for leadership across a range of hierarchical contexts, including the military and other large organizations. In all, our work may help inform the proper balance of leadership and workgroup factors, which determine the optimal context in which individuals can be equipped to benefit from GFL.

Conservation of writhe helicity under anti-parallel reconnection.

Reconnection is a fundamental event in many areas of science, from the interaction of vortices in classical and quantum fluids, and magnetic flux tubes in magnetohydrodynamics and plasma physics, to the recombination in polymer physics and DNA biology. By using fundamental results in topological fluid mechanics, the helicity of a flux tube can be calculated in terms of writhe and twist contributions. Here we show that the writhe is conserved under anti-parallel reconnection. Hence, for a pair of interacting flux tubes of equal flux, if the twist of the reconnected tube is the sum of the original twists of the interacting tubes, then helicity is conserved during reconnection. Thus, any deviation from helicity conservation is entirely due to the intrinsic twist inserted or deleted locally at the reconnection site. This result has important implications for helicity and energy considerations in various physical contexts.

Bullied no more: when and how DNA shoves proteins around.

The predominant protein-centric perspective in protein-DNA-binding studies assumes that the protein drives the interaction. Research focuses on protein structural motifs, electrostatic surfaces and contact potentials, while DNA is often ignored as a passive polymer to be manipulated. Recent studies of DNA topology, the supercoiling, knotting, and linking of the helices, have shown that DNA has the capability to be an active participant in its transactions. DNA topology-induced structural and geometric changes can drive, or at least strongly influence, the interactions between protein and DNA. Deformations of the B-form structure arise from both the considerable elastic energy arising from supercoiling and from the electrostatic energy. Here, we discuss how these energies are harnessed for topology-driven, sequence-specific deformations that can allow DNA to direct its own metabolism.

General job performance of first-line supervisors: the role of conscientiousness in determining its effects on subordinate exhaustion.

In an integrated test of the job demands-resources model and trait activation theory, we predicted that the general job performance of employees who also hold supervisory roles may act as a demand to subordinates, depending on levels of subordinate conscientiousness. In a sample of 313 customer service call centre employees, we found that high-conscientiousness individuals were more likely to experience emotional exhaustion, and low-conscientiousness individuals were less likely as the general job performance of their supervisor improved. The results were curvilinear, such that high-conscientiousness individuals' exhaustion levelled off with very high supervisor performance (two standard deviations above the mean), and low-conscientiousness individuals' exhaustion levelled off as supervisor performance improved from moderate to high. These findings suggest high-conscientiousness employees may efficiently handle demands presented by a low-performing coworker who is their boss, but when performance expectations are high (i.e. high-performing boss), these achievement-oriented employees may direct their resources (i.e. energy and time) towards performance-related efforts at the expense of their well-being. Conversely, low-conscientiousness employees suffer when paired with a low-performing boss, but benefit from a supervisor who demonstrates at least moderate job performance.

Service employees give as they get: internal service as a moderator of the service climate-service outcomes link.

We lend theoretical insight to the service climate literature by exploring the joint effects of branch service climate and the internal service provided to the branch (the service received from corporate units to support external service delivery) on customer-rated service quality. We hypothesized that service climate is related to service quality most strongly when the internal service quality received is high, providing front-line employees with the capability to deliver what the service climate motivates them to do. We studied 619 employees and 1,973 customers in 36 retail branches of a bank. We aggregated employee perceptions of the internal service quality received from corporate units and the local service climate and external customer perceptions of service quality to the branch level of analysis. Findings were consistent with the hypothesis that high-quality internal service is necessary for branch service climate to yield superior external customer service quality.

Safety of glucose-containing solutions during accidental hyperinfusion in piglets.

BACKGROUND: Errors in fluid management can lead to significant morbidity in children. We conducted an experimental animal study to determine the margin of safety in accidental hyperinfusion of different glucose and electrolyte containing solutions. METHODS: Fifteen piglets [bodyweight 12.1 (sd 2.0) kg] were randomly assigned to receive either 100 ml kg⁻¹ of balanced electrolyte solution with glucose 1% (BS-G1), hypotonic electrolyte solution with glucose 5% (HE-G5), or glucose 40% solution (G40) over 1 h. Blood electrolytes, glucose, and osmolality and intracranial pressure (ICP) were measured before, during, and after fluid administration. RESULTS: Hyperinfusion of BS-G1 led to moderate hyperglycaemia [baseline 3.4 (sd 1.3) mmol litre⁻¹, study end 12.6 (1.8) mmol litre⁻¹], but no other relevant pathophysiological alterations. Hyperinfusion of HE-G5 produced marked hyperglycaemia [baseline 3.9 (1.2) mmol litre⁻¹, study end 48.6 (4.3) mmol litre⁻¹, P < 0.05] and hyponatraemia [baseline 136.4 (1.3) mmol litre(-1), study end 119.6 (2.1) mmol litre⁻¹, P < 0.05], whereas osmolality remained stable during the course of the study. Hyperinfusion of G40 induced acute hyperglycaemic/hyperosmolar decompensation with an extreme decrease in serum electrolytes [e.g. sodium baseline 138 (1.1) mmol litre⁻¹, 30 min 87.8 (6.4) mmol litre⁻¹, P < 0.01], leading to cardiac arrest after infusion of 50-75 ml kg⁻¹. ICP remained within a physiological range in all groups. CONCLUSIONS: In an animal model of accidental hyperinfusion, BS-G1 showed the widest margin of safety and can therefore be expected to enhance patient safety in perioperative fluid management in children; HE-G5 proved significantly less safe; and G40 was found to be outright hazardous.

The downside of goal-focused leadership: the role of personality in subordinate exhaustion.

Exhaustion has a significant impact on employees and organizations, and leader behavior may affect it. We applied conservation of resources theory to test propositions regarding the joint effects of goal-focused leadership (GFL) and personality on employee exhaustion. We proposed that the relationship between GFL and exhaustion depends on employees' standing on both conscientiousness and emotional stability. Specifically, we expected that high-conscientiousness subordinates experience greater compatibility with a goal-focused leader because of their predisposition to direct resources toward achievement and goal setting, resulting in lower exhaustion under such a leader than among low-conscientiousness employees. Furthermore, high emotional stability may compensate for GFL incompatibility among low-conscientiousness employees by providing additional resources to manage GFL. In contrast, employees low on both traits likely experience greater exhaustion under a goal-focused leader compared with other employees. Results revealed a 3-way interaction in 2 independent samples and were generally supportive of our predictions. GFL was associated with heightened exhaustion among individuals in the low-emotional-stability, low-conscientiousness group but not among workers having any other trait combination.

The role of goal-focused leadership in enabling the expression of conscientiousness.

The authors tested the hypothesis that goal-focused leadership enables conscientious workers to perform effectively by helping them to accurately understand organizational goal priorities. Data collected from 162 workers in a private sector document processing organization supported the hypotheses that goal-focused leadership moderates the relationship between conscientiousness and job performance and that person-organization goal congruence mediates this moderated relationship. Specifically, conscientiousness was more strongly positively related to performance among workers who perceived that their supervisors effectively set goals and defined roles, responsibilities, and priorities than among workers who did not perceive this type of goal-focused leadership.

Equal effects of gelatin and hydroxyethyl starch (6% HES 130/0.42) on modified thrombelastography in children.

BACKGROUND: Artificial colloids are frequently used to prevent or treat circulatory failure due to hypovolaemia. Whereas gelatin has been shown not to affect coagulation besides its haemodilutional effect, hydroxyethyl starches (HES) have additional negative effects on haemostasis. The third-generation HES solutions have been developed to minimise these effects. We therefore conducted a prospective, randomised study, to verify the hypothesis that a 6% HES 130/0.42/6 : 1 and a 4% gelatin infusion influences modified thrombelastography (TEM) parameters in children in the same manner and to the same extent. METHODS: A total of 50 paediatric patients aged 0-12 years scheduled for surgery were assigned to receive either 10 ml/kg HES 130/0.42 or gelatin. Blood gas analysis, haemodynamic parameters and TEM measurements were performed before and after colloid administration. RESULTS: Patient characteristics, indications/surgical procedures and the main results obtained from blood gas analysis were comparable between the two groups. After administration of either gelatin or HES, all TEM parameters, except for clotting time, indicated impaired coagulation whereas the mean values of all TEM parameters remained within the normal ranges. Comparing the gelatin and HES 130/0.42/6 : 1 groups, none of the measured TEM parameters was found to show between-group differences at baseline or after colloid infusion. CONCLUSION: In conclusion, we could demonstrate that the investigational product, HES 130/0.42/6 : 1 solution, administered at a dosage of 10 ml/kg to children, had comparable effects on coagulation monitored with TEM as a gelatin solution. Perioperative administration of HES 130/0.42/6 : 1 does not alter coagulation to an extent above and beyond the effect of haemodilution.

Hin-mediated DNA knotting and recombining promote replicon dysfunction and mutation.

BACKGROUND: The genetic code imposes a dilemma for cells. The DNA must be long enough to encode for the complexity of an organism, yet thin and flexible enough to fit within the cell. The combination of these properties greatly favors DNA collisions, which can knot and drive recombination of the DNA. Despite the well-accepted propensity of cellular DNA to collide and react with itself, it has not been established what the physiological consequences are. RESULTS: Here we analyze the effects of recombined and knotted plasmids in E. coli using the Hin site-specific recombination system. We show that Hin-mediated DNA knotting and recombination (i) promote replicon loss by blocking DNA replication; (ii) block gene transcription; and (iii) cause genetic rearrangements at a rate three to four orders of magnitude higher than the rate for an unknotted, unrecombined plasmid. CONCLUSION: These results show that DNA reactivity leading to recombined and knotted DNA is potentially toxic and may help drive genetic evolution.

The work-family interface and job performance: moderating effects of conscientiousness and perceived organizational support.

Based on conservation of resources (COR) theory, the authors hypothesized that two aspects of the work-family interface--family-to-work conflict (FWC) and family-to-work enrichment (FWE)--are related to job performance. The authors also hypothesized that two variables moderate those relationships--individual differences in conscientiousness and aspects of the work environment in terms of perceived organizational support (POS). Data collected from a matched set of 136 private sector workers and their respective supervisors revealed that high FWC was more strongly related to lower job performance: (1) among high- than low-conscientiousness workers and (2) among workers reporting low rather than high levels of organizational support. However, FWE was unrelated to job performance.

The interaction of social skill and organizational support on job performance.

The present study examined the moderating effect of perceived organizational support (POS) on the relationship between social skill and supervisor-rated job performance. On the basis of regulatory and activation models of behavior, the authors argue that low-POS environments activate social skill because they reflect situations in which interpersonal acuity is required to demonstrate effective job performance. Accordingly, the authors hypothesize that social skill is more strongly related to performance among workers reporting low rather than high levels of organizational support. Results of hierarchical moderated multiple regression analyses on data gathered from 2 samples support the hypothesis. These results suggest that the relevance of social skill to job performance may be dependent on contextual cues. Implications for substantive research, strengths and limitations, and directions for future research are offered.

The role of age in the perceptions of politics--job performance relationship: a three-study constructive replication.

This research examined the interaction of organizational politics perceptions and employee age on job performance in 3 studies. On the basis of conservation of resources theory, the authors predicted that perceptions of politics would demonstrate their most detrimental effects on job performance for older workers. Results across the 3 studies provided strong support for the hypothesis that increases in politics perceptions are associated with decreases in job performance for older employees and that perceptions of politics do not affect younger employees' performance. Implications of these results, strengths and limitations, and directions for future research are discussed.

Interactive effects of personality and perceptions of the work situation on workplace deviance.

Previous research on workplace deviance has examined the relationship of either personality or employees' situational perceptions with deviant behavior. In this study, the authors focused on the joint relationship of personality and perceptions of the work situation with deviant behavior. Using 4 samples of employees and multiple operationalizations of the core constructs, the authors found support for the hypothesis that positive perceptions of the work situation are negatively related to workplace deviance. In addition, consistent with hypotheses, the personality traits of conscientiousness, emotional stability, and agreeableness moderated this relationship. Specifically, the relationship between perceptions of the developmental environment and organizational deviance was stronger for employees low in conscientiousness or emotional stability, and the relationship between perceived organizational support and interpersonal deviance was stronger for employees low in agreeableness.

Blood-feeding of Tunga penetrans males.

The jigger Tunga penetrans (Linnaeus, 1758: type-species of the family Tungidae) is the smallest known species of flea (Siphonaptera), causing serious ectoparasitosis of humans and domestic animals. The adult female Tunga lodges in the epidermis of the mammalian host, grows by neosomy, becomes gravid and expels eggs. Relatively little is known about the free-living male Tunga adults. Among impoverished communities of Fortaleza in north-east Brazil, we observed T. penetrans males as well as females penetrating the skin of human hosts. After penetrating the epidermis for a few hours, evidently for capillary feeding from the dermis, males withdrew their mouthparts and crawled away, whereas the females remained completely embedded, hypertrophying to become gravid, eventually dying in situ after oviposition. Caged rats were placed on the sandy soil and examined periodically for Tunga infestation. On five rats we obtained 140 females embedded and we detected 75 males biting, with rat erythrocytes observed in the proventriculus and midgut of all five males dissected and examined microscopically. This confirms that T. penetrans males are hamatophagous ectoparasites of mammals.

Social skill as moderator of the conscientiousness-performance relationship: convergent results across four studies.

The authors conducted 4 studies to test the hypothesis that the relationship between Conscientiousness and job performance reflecting interpersonal effectiveness is more strongly positive among workers who are higher rather than lower in social skill. Results of hierarchical moderated regression analyses supported the hypothesis in all 4 studies. Among workers high in social skill. Conscientiousness was positively related to performance. Among workers low in social skill, the relationship between Conscientiousness and performance was essentially irrelevant in Study 2 but was negative in the other 3 studies. Potential implications of these results are discussed as are directions for future research.

The interactive effect of leader-member exchange and communication frequency on performance ratings.

The authors tested the hypothesis that communication frequency moderates the relationship between leader-member exchange (LMX) and job-performance ratings. In a study of 188 private sector workers, they found that LMX was more strongly related to job-performance ratings among individuals reporting frequent communication with the supervisor than among those reporting infrequent communication. At high levels of LMX, workers reporting frequent communication with the supervisor received more favorable job-performance ratings than did workers reporting infrequent communication. In contrast, at low levels of LMX, workers reporting frequent communication with the supervisor received less favorable job-performance ratings than workers reporting infrequent communication. The authors conducted a 2nd study of 153 public sector workers to provide a constructive replication and found similar results.

Spontaneous intracranial internal carotid artery dissection: report of 10 patients.

BACKGROUND: Spontaneous intracranial internal carotid artery (ICA) dissection is an uncommon cause of cerebral infarction, particularly when compared with the dissection of the ICA's cervical portion. Most reports describe extensive strokes with very high mortality rates. OBJECTIVE: To report the clinical and radiological findings of 10 patients with spontaneous intracranial ICA dissection. METHODS: Ten patients (5 women) were included with ages ranging from 15 to 59 years (mean age, 28 years). RESULTS: Nine patients had a stroke (1 had an associated subarachnoid hemorrhage), whereas 1 patient had only transient ischemic attacks. Severe retro-orbital or temporal headache followed by contralateral hemiparesis was the most common initial clinical symptom. No patient had vascular risk factors or a history of neck or head trauma. Stenosis of the supraclinoid portion of the ICA occurred in 8 patients, with extension to the middle cerebral artery or anterior cerebral artery in 2 patients each. Aneurysm formation in the ipsilateral anterior cerebral artery was seen in 1 patient. Two patients had a total occlusion of the supraclinoid portion of the ICA. All patients did well, with no (n = 3), mild (n = 4), or moderate (n = 3) disability on the Modified Rankin Scale during a 3-month follow-up period. CONCLUSIONS: Spontaneous intracranial ICA dissection can cause ischemic stroke with or without subarachnoid hemorrhage and should be considered in the differential diagnosis of intracranial ICA stenosis or occlusion, especially in young patients. Some patients survive with few or moderate deficits.