Analysis of anaerobic digester mixing: comparison of long shafted paddle mixing vs gas mixing.

The anaerobic digestion (AD) process is influenced by a variety of operation parameters, such as sludge rheology, mixing, temperature, solid retention time (SRT), hydraulic retention time (HRT) and solids concentration. The optimum in the mixing lies somewhere between no-mixing and continuous mixing, as the lack or excessive mixing can lead to poor AD performance instead. A three-dimensional computational fluid dynamics steady/unsteady model, incorporating the rheological properties of the sludge, was developed and applied to quantify mixing in a full-scale anaerobic digester. Mechanical and gas mixing solutions were taken into account, keeping constant the daily energy consumption. Results, consisting of velocity magnitude and patterns, dead zone formation and turbulence levels were discussed. Compared to the mechanical mixing, gas mixing had lower percentage of dead zones (about 5% against 50%), larger maximum velocity (about 3 m/s against 1 m/s) as well as larger turbulent kinetic energy levels (0.24 m2/s2 against 0.001 m2/s2).

Modeling Water Quality in Watersheds: From Here to the Next Generation.

In this synthesis, we assess present research and anticipate future development needs in modeling water quality in watersheds. We first discuss areas of potential improvement in the representation of freshwater systems pertaining to water quality, including representation of environmental interfaces, in-stream water quality and process interactions, soil health and land management, and (peri-)urban areas. In addition, we provide insights into the contemporary challenges in the practices of watershed water quality modeling, including quality control of monitoring data, model parameterization and calibration, uncertainty management, scale mismatches, and provisioning of modeling tools. Finally, we make three recommendations to provide a path forward for improving watershed water quality modeling science, infrastructure, and practices. These include building stronger collaborations between experimentalists and modelers, bridging gaps between modelers and stakeholders, and cultivating and applying procedural knowledge to better govern and support water quality modeling processes within organizations.

Instantaneous transport of a passive scalar in a turbulent separated flow.

The results of large-eddy simulations of flow and transient solute transport over a backward facing step and through a 180° bend are presented. The simulations are validated successfully in terms of hydrodynamics and tracer transport with experimental velocity data and measured residence time distribution curves confirming the accuracy of the method. The hydrodynamics are characterised by flow separation and subsequent recirculation in vertical and horizontal directions and the solute dispersion process is a direct response to the significant unsteadiness and turbulence in the flow. The turbulence in the system is analysed and quantified in terms of power density spectra and covariance of velocity fluctuations. The injection of an instantaneous passive tracer and its dispersion through the system is simulated. Large-eddy simulations enable the resolution of the instantaneous flow field and it is demonstrated that the instabilities of intermittent large-scale structures play a distinguished role in the solute transport. The advection and diffusion of the scalar is governed by the severe unsteadiness of the flow and this is visualised and quantified. The analysis of the scalar mass transport budget quantifies the mechanisms controlling the turbulent mixing and reveals that the mass flux is dominated by advection.

Cardiovascular biomarkers and carotid IMT scores as predictors of cognitive function.

OBJECTIVE: Multiple cardiovascular risk factors are associated with early cognitive decline. Measures of complex information processing provide one of the earliest signs of cognitive decline and appear related to arterial plaque growth. The purpose of this study was to determine how cardiovascular risk factors and carotid intima-media thickness (IMT) scores are associated with cognitive function and complex information processing scores. METHODS: This study used a retrospective, cross-sectional analysis of 536 men and women attending an executive evaluation program. Measurements were made of body composition, cardiovascular status, fitness and diet, and laboratory measures, including carotid IMT. Each subject was tested with a computerized neurocognitive test battery. RESULTS: Complex information processing (CIP), also called executive function, is independently related to carotid IMT scores (p < 0.01), as are other cardiovascular biomarkers, including aerobic capacity fiber, B12, and long-chain n-3 fatty acid intake (p < 0.01 for each). However, after controlling for carotid IMT, only IMT showed a significant relationship with CIP scores. CONCLUSIONS: Carotid IMT scores are the strongest independent cardiovascular biomarker for cognitive function, especially complex information processing. Greater intake of fiber, long-chain n-3 fatty acids (N3FAs), and vitamin B12, as well as measures of aerobic fitness, is associated with enhanced cognitive function, yet controlling for IMT scores diminished their association. Because decreasing CIP scores are linearly associated with cognitive decline, future randomized clinical trials that yield improvements in carotid IMT scores should also assess for changes in cognitive function.

Heritability in cognitive performance: evidence using computer-based testing.

There is overwhelming evidence of genetic influence on cognition. The effect is seen in general cognitive ability, as well as in specific cognitive domains. A conventional assessment approach using face-to-face paper and pencil testing is difficult for large-scale studies. Computerized neurocognitive testing is a suitable alternative. A total of 267 parent-child dyads were selected from a larger database of computerized neurocognitive test results. Correlations were determined between parent-child dyads, as well as matched parent-child dyads. Univariate regression analyses were estimated to determine the extent to which children's performance could be accounted for by that of their parents, compared with matched control parents. Multiple significant positive correlations in neurocognitive test performance were found in parent-child dyads. Parent performance accounted for a greater proportion of variability in every case. These findings indicated that a computerized neurocognitive battery is an effective tool for studying heritability in cognitive performance in a large sample.

Does familiarity with computers affect computerized neuropsychological test performance?

The purpose of this study was to determine whether self-reported computer familiarity is related to performance on computerized neurocognitive testing. Participants were 130 healthy adults who self-reported whether their computer use was "some" (n = 65) or "frequent" (n = 65). The two groups were individually matched on age, education, sex, and race. All completed the CNS Vital Signs (Gualtieri & Johnson, 2006b) computerized neurocognitive battery. There were significant differences on 6 of the 23 scores, including scores derived from the Symbol-Digit Coding Test, Stroop Test, and the Shifting Attention Test. The two groups were also significantly different on the Psychomotor Speed (Cohen's d = 0.37), Reaction Time (d = 0.68), Complex Attention (d = 0.40), and Cognitive Flexibility (d = 0.64) domain scores. People with "frequent" computer use performed better than people with "some" computer use on some tests requiring rapid visual scanning and keyboard work.

Assessment of fibromyalgia & chronic fatigue syndrome: a new protocol designed to determine work capability--chronic pain abilities determination (CPAD).

The objective was to design a protocol to assess work ability in people suffering ill-defined painful and disabling disorders, the outstanding prototype of which is fibromyalgia/chronic fatigue syndrome (FM/CSF).Following an extensive literature search, the mos appropriate components of current methods of assessment of physical and cognitive abilities were incorporated into the protocol, occasionally with appropriate modification to suit the specific requirements of the individual. The initial part of the assessment consists of a standard history taking, principally focusing on the patient's self-reported physical and cognitive abilities and disabilities, as well as the completion of established pain and fatigue scales, and relevant disability questionnaires. Following this, physical and cognitive abilities are objectively assessed on two separate occasions, utilizing computerized hand-held dynamometers, inclinometers, algometers, and force dynamometers. Specific work simulation tests using the industrial standards Methods-Time-Measurement testing are availed of, as is aerobic testing using the Canadian Aerobic Fitness Test (CAFT). Objective computerised neuro-cognitive testing are also utilised as an integral component of the assessment. All results are then subject to specific computerized analysis and compared to normative and standardised work-based databases. The designed system produces reliable, consistent and reproducible results. It also proves capable of detecting any inconsistencies in patient input and results, in addition to being independent of any possible assessor bias. A new protocol has been designed to determine the working capability of individuals who suffer from various chronic disabling conditions, and represents a significant step forward in a difficult but rapidly expanding area of medical practice.

The frequency of cognitive impairment in patients with anxiety, depression, and bipolar disorder: an unaccounted source of variance in clinical trials.

BACKGROUND: Patients with anxiety, depression, and bipolar disorder are known to be impaired relative to healthy controls on neurocognitive tests, but the degree of impairment may be obscured if the data are analyzed in terms of group means. METHOD: Patients and controls were administered a comprehensive neurocognitive assessment that measured performance in 5 domains: memory, psychomotor speed, reaction time, attention, and cognitive flexibility. Clinic patients diagnosed per DSM-IV-TR criteria with generalized anxiety disorder (N = 63), major depressive disorder (N = 285), and bipolar I or II disorder (N = 96) were compared with 907 controls. Subjects' age range was 18 to 65 years. Patients had no comorbid psychiatric disorders and no medical, neurologic, or developmental conditions that might affect cognition (e.g., attention-deficit/hyperactivity disorder, brain injury, mild cognitive impairment, chronic pain). Data on patients and controls (collected from March 2003 through February 2007) were taken from a clinical database that also contained neurocognitive test scores. RESULTS: There were small differences between patients and controls, between different patient groups, and between treated and untreated patients when neurocognitive results in terms of group means were compared. Comparisons of results in terms of the frequency with which patients and controls fell below certain cutoff scores amplified the importance of these differences. Only 4% of controls fell below a standard score of 70 (2 standard deviations below the mean) on 2 or more cognitive domains, but 19% of anxiety patients, 21% of depressed patients, and 30% of bipolar patients fell below the standard score. CONCLUSIONS: Substantial numbers of patients with anxiety, depression, and bipolar disorder are cognitively impaired. A score that is 2 standard deviations below the mean is usually clinically important, and 2 domain scores in that range is cause for serious concern. The importance of this finding is discussed, with respect to clinical trials, in terms of establishing a homogeneous trial population and minimizing the placebo response rate.

A computerized test battery sensitive to mild and severe brain injury.

OBJECTIVE: Computerized neurocognitive testing (CNT) appears to be suited to measure relatively mild degrees of neurocognitive impairment in circumstances where speed, efficiency, and low cost are important. Computerized tests are used in the evaluation and management of patients who have had mild brain injuries; the objective is to determine if computerized testing is equally reliable and valid in the evaluation of patients who have had more severe brain injuries. DESIGN: A cross-sectional, naturalistic study of brain injury patients compared with normal controls. SETTING: An outpatient neuropsychiatry clinic. PARTICIPANTS: 141 patients, aged 18-65 years, who had sustained traumatic brain injuries (TBIs): 13 patients with postconcussion syndrome; 15 who had recovered from mild brain injuries; 85 patients who had had severe brain injuries, but who had recovered, and were living independently; and 28 severe brain injury patients who were unable to live without assistance; compared with 145 normal controls. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: The CNS Vital Signs (CNS VS) battery is a PC-based system that includes tests of verbal and visual memory, psychomotor speed, complex attention, reaction time, and cognitive flexibility. RESULTS: Performance on the CNS VS battery was related to severity of brain injury and degree of recovery. Tests of psychomotor speed and cognitive flexibility were the most relevant to TBI status. Patients who had recovered from mild brain injuries scored almost as well as normal controls. The Neurocognition Index (NCI), a summary score based on performance on all the tests in the battery, was 100 for normal controls and 98 for recovered mild brain injury patients. Postconcussive patients scored 82 on the MCI, and severe brain injury patients scored 66 on the NCI if they were living independently and 47 if they were not. CONCLUSIONS: Computerized tests like CNS VS allow clinicians the advantage of precise neurocognitive measurement in the service of diagnosis and appropriate treatment. CNTs are never going to replace the flexibility or comprehensiveness of conventional neuropsychological testing, but they have a role to play in circumstances where a full test battery is not feasible, such as screening and serial assessment.

Age-related cognitive decline in patients with mood disorders.

BACKGROUND: The relationship between depression and dementia is complex and appreciation of its true nature is evolving. Depression is an early symptom of dementia. Recent research suggests that mood disorders, in general, may be risk factors for the development of dementia. METHOD: This was a cross-sectional study of the effect of aging on cognition in patients with mood disorders compared to normal controls. Patients and controls were tested with a comprehensive neurocognitive test battery, CNS Vital Signs. The question at issue was the rate of aging-related cognitive decline the same or different in mood disorder patients compared to normal controls. SUBJECTS: 455 patients with mood disorders, 336 with major depression and 119 with bipolar affective disorder, age 18-86, and 1003 normal controls, age 35-90. Normal controls were age 18 or older in the CNS Vital Signs normative database. The normal subjects were healthy, on no centrally-active medication, and free of psychiatric and neurological disorders. RESULTS: Cognitive performance in the two groups run in parallel from age 18 to 45; they begin to diverge during the next decade; after age 65, mood disorder patients, as a group, decline more sharply than normal controls. The differential rate of decline was seen in the domains of memory, attention, processing speed and executive function. CONCLUSIONS: There seems to be an acceleration in age-related cognitive decline in patients with depression in particular, and mood disorders in general, compared to age-matched normal controls. It is likely, then, that as people age, the ones who develop depression, or who fail to recover from early episodes of depression, include a substantial number of patients at risk for developing dementia. This is consistent with the fact that late-life depression may be an early manifestation of dementia. The data are also consistent with the idea that mood disorders are a risk factor, albeit a weak one, for the development of dementia. From a slightly different perspective, one might imagine that some pathophysiological event is shared by the mood disorders and dementing conditions.

Medications do not necessarily normalize cognition in ADHD patients.

OBJECTIVE: Although ADHD medications are effective for the behavioral components of the disorder, little information exists concerning their effects on cognition, especially in community samples. METHOD: A cross-sectional study of ADHD patients treated with three different ADHD drugs was conducted. Patients' performance on a computerized neurocognitive screening battery was compared to untreated ADHD patients and normal controls (NML). A total of 177 ADHD patients aged 10 to 18, achieved a favorable response to one of the following medications: Adderall XR (AMP), atomoxetine (ATMX), and Concerta (MPH-OROS) compared to 95 untreated ADHD patients and 101 NML. RESULTS: Significant differences were detected between normals and untreated ADHD patients. Treated patients performed better than untreated patients but remained significantly impaired compared to normal subjects. CONCLUSION: Even with optimal treatment, based on parents' and teachers' opinions, subtle and not-so-subtle neurocognitive impairments persisted in the ADHD patients. Some ADHD patients may require additional educational assistance, even in the face of successful medication treatment.

An Internet-based symptom questionnaire that is reliable, valid, and available to psychiatrists, neurologists, and psychologists.

The Neuropsych Questionnaire (NPQ) addresses 2 important clinical issues: how to screen patients for a wide range of neuropsychiatric disorders quickly and efficiently, and how to acquire independent verification of a patient's complaints. The NPQ is available over the Internet in adult and pediatric versions. The adult version of the NPQ consists of 207 simple questions about common symptoms of neuropsychiatric disorders. The NPQ scores patient and/or observer responses in terms of 20 symptom clusters: inattention, hyperactivity-impulsivity, learning problems, memory, anxiety, panic, agoraphobia, obsessions and compulsions, social anxiety, depression, mood instability, mania, aggression, psychosis, somatization, fatigue, sleep, suicide, pain, and substance abuse. The NPQ is reliable (patients tested twice, patient-observer pairs, 2 observers) and discriminates patients with different diagnoses. Scores generated by the NPQ correlate reasonably well with commonly used rating scales, and the test is sensitive to the effects of treatment. The NPQ is suitable for initial patient evaluations, and a short form is appropriate for follow-up assessment. The availability of a comprehensive computerized symptom checklist can help to make the day-to-day practice of psychiatry, neurology, and neuropsychology more objective.

Reliability and validity of a computerized neurocognitive test battery, CNS Vital Signs.

CNS Vital Signs (CNSVS) is a computerized neurocognitive test battery that was developed as a routine clinical screening instrument. It is comprised of seven tests: verbal and visual memory, finger tapping, symbol digit coding, the Stroop Test, a test of shifting attention and the continuous performance test. Because CNSVS is a battery of well-known neuropsychological tests, one should expect its psychometric properties to resemble those of the conventional tests upon which it is based. 1069 subjects age 7-90 participated in the normative database for CNSVS. Test-retest reliability (TRT) was evaluated in 99 Ss who took the battery on two separate occasions, separated, on the average, by 62 days; the results were comparable to those achieved by equivalent conventional and computerized tests. Concurrent validity studies in 180 subjects, normals and neuropsychiatric patients, indicate correlations that are comparable to the concurrent validity of similar tests. Discriminant validity is supported by studies of patients with mild cognitive impairment and dementia, post-concussion syndrome and severe traumatic brain injury, ADHD (treated and untreated) and depression (treated and untreated). The tests in CNSVS are also sensitive to malingerers and patients with conversion disorders. The psychometric characteristics of the tests in the CNSVS battery are very similar to the characteristics of the conventional neuropsychological tests upon which they are based. CNSVS is suitable for use as a screening instrument, or as a serial assessment measure. But it is not a substitute for formal neuropsychological testing, it is not diagnostic, and it will have only a limited role in the medical setting, absent the active participation of consulting neuropsychologists.

Neurocognition in depression: patients on and off medication versus healthy comparison subjects.

Patients with depression have neuropsychological deficits in attention, memory, psychomotor speed, processing speed, and executive function. It is not clear, however, whether neurocognition in depression is impaired in a global or nonspecific way or if specific cognitive domains are selectively impaired. This naturalistic cross-sectional study employed a computerized neurocognitive screening battery to evaluate 38 depressed, drug-free patients, compared to 31 patients who responded to antidepressant monotherapy and to 69 healthy comparison subjects. There was evidence for global neuropsychological impairment in untreated depressed patients. In patients who had been successfully treated, performance was improved but not normalized. There was also evidence for specific depression-related deficits in executive function and processing speed but not in memory, psychomotor speed, or reaction time. Although depressed patients have global neurocognitive impairments, deficits in certain cognitive domains are more important than in others. In particular, impairments are noted in tests of executive control and in tests that demand effortful attention. Information processing speed is also impaired but not reaction time. Computerized testing in the clinic setting demonstrates a range of neurocognitive problems in patients with depression. These problems may have a bearing on treatment and outcome.

Antidepressant side effects in children and adolescents.

The association between antidepressant treatment and suicidality in children and adolescents has been the subject of a great deal of recent discussion and controversy. Appropriate warnings have been attached to these drugs by governing bodies in the United Kingdom and the United States. However, the data upon which these deliberations have been based derive almost exclusively from clinical trials supported by the manufacturers of the respective drugs; data that are rigorous, in some respects, but which may not capture the clinical realities of antidepressant treatment in real-world settings. Data are presented from a neuropsychiatry clinic where 128 children and adolescents were treated with modern antidepressants over the past 14 months. Behavioral side effects, including suicidal ideation and self-injurious behavior, were not an uncommon accompaniment of antidepressant treatment. The problems, however, were mild and decidedly nonlethal and easily managed in the clinic setting. Ironically, 34 of 36 patients who had developed behavioral side effects to antidepressants were subsequently managed, without further incident, either on an alternative antidepressant or on lower doses of the offending agent.

Efficient allocation of attentional resources in patients with ADHD: maturational changes from age 10 to 29.

BACKGROUND: It has been proposed that ADHD is an executive control disorder. Little is known however about the maturation of executive control in ADHD. METHOD: A cross-sectional study of ADHD patients compared to normal controls tested on a computerized neurocognitive test battery. PARTICIPANTS: 175 patients with ADHD, age 10 to 29, compared to 175 age-matched normal controls. RESULTS: In every age group, ADHD patients were impaired in measures of psychomotor speed, reaction time, cognitive flexibility, and attention. Participants in both groups improved with age. In tests of executive control, normals improved their performance with shorter reaction times. ADHD patients improved their performance but by adopting a less efficient strategy: Their reaction times increased with age. CONCLUSIONS: These data support executive control as a "core deficit" in ADHD. In the Stroop and the shifting attention tests, ADHD patients proved to be inefficient in allocating their attentional resources.

Comparative neurocognitive effects of 5 psychotropic anticonvulsants and lithium.

CONTEXT: Many of the new antiepileptic drugs have psychiatric indications, and most are prescribed by psychiatrists for patients with mood disorders, even when a specific indication is absent. Epileptic drugs as a whole, even the newer ones, are known to affect cognition, sometimes in untoward ways. Research on the neurocognitive effects of antiepileptic drugs, however, has been done exclusively in normal volunteers and in patients with seizure disorders. METHOD: A naturalistic, cross-sectional study was conducted on patients who were taking 1 of 5 different antiepileptic drugs or lithium (LIT). Cognitive status was measured by a computerized neurocognitive screening battery, CNS Vital Signs (CNSVS). SUBJECTS: One hundred fifty-nine patients with bipolar disorder, aged 18-70 years, were treated with carbamazepine (CBZ) (N = 16), lamotrigine (LMTG) (N = 38), oxcarbazepine (OCBZ) (N = 19), topiramate (TPM) (N = 19), and valproic acid (VPA) (N = 37); 30 bipolar patients were treated with LIT. RESULTS: Significant group differences were detected in tests of memory, psychomotor speed, processing speed, reaction time, cognitive flexibility, and attention. Rank-order analysis indicated superiority for LMTG (1.8) followed by OCBZ (2.1), LIT(3.3), TPM (4.3), VPA (4.5), and CBZ (5.0). CONCLUSION: The relative neurocognitive effects of the various psychotropic antiepileptic drugs in patients with bipolar disorder were concordant with those described in the seminal literature in normal volunteers and patients with epilepsy. LMTG and OCBZ had the least neurotoxicity, and TPM, VPA, and CBZ had the most. LIT effects on neurocognition were intermediate. Choosing a mood-stabilizing drug with minimal neurocognitive effects may enhance patient compliance over the long term.

ADHD: Is Objective Diagnosis Possible?

Although attention deficit/hyperactivity disorder (ADHD) is one of the most common cognitive disorders, the usual diagnostic procedures pursued by psychiatrists, neurologists, pediatricians, and family practitioners are based largely, if not exclusively, on subjective assessments of perceived behavior. The recommended approaches to ADHD diagnosis are reviewed, first from the perspective of the various expert panels, and then from the research literature upon which those recommendations are based. The authors agree that ADHD is a clinical diagnosis, and that the assessment of subjective reports can be systematic. But they propose that objective data should also contribute to the clinical diagnosis of ADHD; and that new computerized assessment technology can generate objective cognitive data in an efficient and cost-effective way. Computerized tests can also improve the assessment of treatment response over time.