The world of two-dimensional carbides and nitrides (MXenes)

A decade after the first report, the family of two-dimensional (2D) carbides and nitrides (MXenes) includes structures with three, five, seven, or nine layers of atoms in an ordered or solid solution form. Dozens of MXene compositions have been produced, resulting in MXenes with mixed surface terminations. MXenes have shown useful and tunable electronic, optical, mechanical, and electrochemical properties, leading to applications ranging from optoelectronics, electromagnetic interference shielding, and wireless antennas to energy storage, catalysis, sensing, and medicine. Here we present a forward-looking review of the field of MXenes. We discuss the challenges to be addressed and outline research directions that will deepen the fundamental understanding of the properties of MXenes and enable their hybridization with other 2D materials in various emerging technologies.

Depression, intellectual impairment, and Parkinson disease

To determine the prevalence of depression in Parkinson disease (PD) we evaluated 55 consecutive patients without dementia and 31 of their spouses. All subjects completed the Beck depression inventory and a quantitative mini-mental state examination. Using the Beck criteria, 47% of the patients and 12% of the spouses rated themselves as significantly depressed. Mental state scores were significantly lower in the patients. There was a correlation between the severity of depression and cognitive impairment, particularly for calculation, digit span, and visuomotor skills. The severity of parkinsonism, particularly bradykinesia, also paralleled cognition. There was a slight but significant relationship between parkinsonism and depression. These results confirm the high incidence of depression in PD, and suggest that depression in Parkinson patients may be accompanied by mild intellectual impairment and inattention which is independent of the severity of the illness.

Spacing of palindromic half sites as a determinant of selective STAT (signal transducers and activators of transcription) DNA binding and transcriptional activity

Signal transducers and activators of transcription (STAT proteins) bind to palindromic sequence elements related to interferon gamma (IFN-gamma) activation sites, which were first identified in the promoters of IFN-gamma-inducible genes. Although the sequences of the natural palindromic STAT-binding elements vary considerably, they conform to the general structure TT(N)5AA. We have systematically examined the effects of the spacing between the TT and AA core half sites on the binding of the STAT complexes activated by IFN-gamma, interleukin (IL) 6, granulocyte-macrophage colony-stimulating factor, and IL-4. We show that (i) as suggested earlier, a core palindromic TT--AA motif with a 5-bp spacing displays general STAT binding, (ii) a palindromic motif with a spacing of 4 bp selectively binds to complexes containing Stat3, and (iii) a motif with a 6-bp spacing selectively binds the STAT complexes activated by IL-4. We have examined natural elements in the promoters of cytokine-responsive genes that differ in half-site spacing and found that they display binding properties predicted from the synthetic binding sites. Furthermore, the observed differential selective binding characteristics for the most part correlate with the ability to mediate transcriptional activation of transfected test genes in response to the cytokines tested. Our results thus demonstrate that the specificity of STAT-directed transcription in response to particular cytokines or cytokine families depends in part on the spacing of half sites within the conserved response element sequence.

Force controlled and teleoperated endoscopic grasper for minimally invasive surgery--experimental performance evaluation

Minimally invasive surgery generates new user interfaces which create visual and haptic distortion when compared to traditional surgery. In order to regain the tactile and kinesthetic information that is lost, a computerized force feedback endoscopic surgical grasper (FREG) was developed with computer control and a haptic user interface. The system uses standard unmodified grasper shafts and tips. The FREG can control grasping forces either by surgeon teleoperation control, or under software control. The FREG performance was evaluated using an automated palpation function (programmed series of compressions) in which the grasper measures mechanical properties of the grasped materials. The material parameters obtained from measurements showed the ability of the FREG to discriminate between different types of normal soft tissues (small bowel, lung, spleen, liver, colon, and stomach) and different kinds of artificial soft tissue replication materials (latex/silicone) for simulation purposes. In addition, subjective tests of ranking stiffness of silicone materials using the FREG teleoperation mode showed significant improvement in the performance compared to the standard endoscopic grasper. Moreover, the FREG performance was closer to the performance of the human hand than the standard endoscopic grasper. The FREG as a tool incorporating the force feedback teleoperation technology may provide the basis for application in telesurgery, clinical endoscopic surgery, surgical training, and research.

Markov modeling of minimally invasive surgery based on tool/tissue interaction and force/torque signatures for evaluating surgical skills

The best method of training for laparoscopic surgical skills is controversial. Some advocate observation in the operating room, while others promote animal and simulated models or a combination of surgery-related tasks. A crucial process in surgical education is to evaluate the level of surgical skills. For laparoscopic surgery, skill evaluation is traditionally performed subjectively by experts grading a video of a procedure performed by a student. By its nature, this process uses fuzzy criteria. The objective of the current study was to develop and assess a skill scale using Markov models (MMs). Ten surgeons [five novice surgeons (NS); five expert surgeons (ES)] performed a cholecystectomy and Nissen fundoplication in a porcine model. An instrumented laparoscopic grasper equipped with a three-axis force/torque (F/T) sensor was used to measure the forces/torques at the hand/tool interface synchronized with a video of the tool operative maneuvers. A synthesis of frame-by-frame video analysis and a vector quantization algorithm, allowed to define F/T signatures associated with 14 different types of tool/tissue interactions. The magnitude of F/T applied by NS and ES were significantly different (p < 0.05) and varied based on the task being performed. High F/T magnitudes were applied by NS compared with ES while performing tissue manipulation and vise versa in tasks involved tissue dissection. From each step of the surgical procedures, two MMs were developed representing the performance of three surgeons out of the five in the ES and NS groups. The data obtained by the remaining two surgeons in each group were used for evaluating the performance scale. The final result was a surgical performance index which represented a ratio of statistical similarity between the examined surgeon's MM and the MM of NS and ES. The difference between the performance index value, for a surgeon under study, and the NS/ES boundary, indicated the level of expertise in the surgeon's own group. Using this index, 87.5% of the surgical procedures were correctly classified into the NS and ES groups. The 12.5% of the procedures that were misclassified were performed by the ES and classified as NS. However in these cases the performance index values were very close to the NS/ES boundary. Preliminary data suggest that a performance index based on MM and F/T signatures provides an objective means of distinguishing NS from ES. In addition, this methodology can be further applied to evaluate haptic virtual reality surgical simulators for improving realism in surgical education.

Neuropathologic and neurochemical correlates of psychosis in primary dementia

Neuropathologic and neurochemical correlates of psychosis were determined using brain tissue from 27 autopsy-confirmed cases of Alzheimer's disease. The densities of senile plaques and neurofibrillary tangles were determined in the middle frontal and superior temporal cortex, the prosubiculum, and the entorhinal cortex of the hippocampus. The concentrations of norepinephrine, dopamine, and serotonin, the metabolites of these biogenic amines, and the specific activity of choline acetyltransferase were also determined in these four cortical regions as well as in the substantia nigra, thalamus, amygdala, and caudate nucleus. Psychosis was associated with significantly increased densities of senile plaques and neurofibrillary tangles in the prosubiculum and middle frontal cortex, respectively, with trends toward increased densities of these lesions in the other areas examined. This finding is consistent with the increased rate of cognitive decline that accompanies this behavioral disorder. Psychosis was also associated with the relative preservation of norepinephrine in the substantia nigra, with trends in this direction for five of the remaining seven brain regions examined, and a significant reduction of serotonin in the prosubiculum that was accompanied by trends toward reduced levels of serotonin and 5 hydroxyindoleacetic acid in the remaining regions. The profile of neuropathologic and neurochemical changes associated with psychosis is distinct from that previously reported for major depression in the context of primary dementia.

Presence of maternal antibodies to human immunodeficiency virus 1 envelope glycoprotein gp120 epitopes correlates with the uninfected status of children born to seropositive mothers

The present study demonstrates that maternal antibodies to certain epitopes of human immunodeficiency virus 1 (HIV-1) proteins are associated with a defined outcome for at-risk pregnancies of HIV-infected women. An initial retrospective analysis of antibodies to synthetic peptides and recombinant proteins representing env, pol, and gag regions of HIV-1 was carried out. Sera studied were from 33 children who were born to HIV-infected mothers and whose clinical outcome was known at the time of analysis. Sera, collected within the first 6 months of life, of uninfected at-risk children were found to selectively contain maternal antibodies to certain peptides containing epitopes of the HIV envelope glycoprotein gp120. To confirm the predictive role of maternal antibodies to defined HIV-1 epitopes, a prospective analysis was then performed on sera from 21 HIV-seropositive mothers and their infants, whose clinical and immunological status was then followed up for a period of at least 15 months. As expected, antibodies to the same envelope protein peptides were detected almost exclusively in sera from mothers of uninfected children. Our data suggest that antibodies against select epitopes of HIV envelope protein gp120 might play an important role in preventing mother-to-child transmission of HIV-1 infection. Accordingly, site-directed serology might be used to predict the outcome of an at-risk pregnancy of an HIV-infected woman.

Nitric acid trihydrate (NAT) in polar stratospheric clouds

A comprehensive investigation of polar stratospheric clouds was performed on 25 January 2000 with instruments onboard a balloon gondola flown from Kiruna, Sweden. Cloud layers were repeatedly encountered at altitudes between 20 and 24 kilometers over a wide range of atmospheric temperatures (185 to 197 kelvin). Particle composition analysis showed that a large fraction of the cloud layers was composed of nitric acid trihydrate (NAT) particles, containing water and nitric acid at a molar ratio of 3:1; this confirmed that these long-sought solid crystals exist well above ice formation temperatures. The presence of NAT particles enhances the potential for chlorine activation with subsequent ozone destruction in polar regions, particularly in early and late winter.

Interictal memory and language impairment in temporal lobe epilepsy

Memory and language were evaluated in patients with temporal lobe epilepsy and generalized epilepsy. Subjects were matched for age, duration of illness, and seizure frequency, and grouped according to the electroencephalographic results and seizure type into right temporal, left temporal, and generalized. In formal tests of intelligence, auditory and visual memory, and language, a significant difference was noted only on a confrontation naming test. The mean score on this test was considerably lower in the left temporal group; right temporal and generalized groups scored in the normal range. This correlated with impairment on many verbal subtests of intelligence and memory. These results suggest that the interictal memory impairment of temporal lobe epilepsy may be an anomia and that the anomia may contribute to impairment of verbal learning and memory; both circumlocution and circumstantiality may compensate for anomia.

Perceptual motor dysfunction in Parkinson's disease: a deficit in sequential and predictive voluntary movement

We studied the ability of Parkinsonian patients and controls to generate voluntary movements on a tracing task. Subjects were videotaped while tracing designs of increasing complexity, presented on a vertical, transparent screen. Some designs were presented in a degraded form and subjects filled in their missing sections. Subjects also received a constructional task and a test of general intellectual ability. The quality of errors on the tracing task differed in the Parkinsonian and control groups. Parkinsonian patients made two distinct types of errors. One probably related to the motor disorders of the disease, but another seemed to be related to a higher level of control over sequential and predictive movements. The latter correlated with performance on the constructional and general intellectual tasks. These results suggest that Parkinson's disease may affect basal ganglia structures that are necessary for voluntary movements which require sequencing or planning. Clinically this may be observed in perceptual motor tasks since they require both voluntary movement and sequential organisation of behaviour.

A small, nonpeptidyl mimic of granulocyte-colony-stimulating factor [see commetns]

A nonpeptidyl small molecule SB 247464, capable of activating granulocyte-colony-stimulating factor (G-CSF) signal transduction pathways, was identified in a high-throughput assay in cultured cells. Like G-CSF, SB 247464 induced tyrosine phosphorylation of multiple signaling proteins and stimulated primary murine bone marrow cells to form granulocytic colonies in vitro. It also elevated peripheral blood neutrophil counts in mice. The extracellular domain of the murine G-CSF receptor was required for the activity of SB 247464, suggesting that the compound acts by oligomerizing receptor chains. The results indicate that a small molecule can activate a receptor that normally binds a relatively large protein ligand.

A brain imaging (single photon emission computerized tomography) study of semantic and affective processing in psychopaths

Psychopaths have been described as human predators who use charm, intimidation, and violence to control others and to satisfy their own needs. Underlying their propensity to violate social norms and expectations is a profound lack of empathy, guilt, or remorse, affective processes that have long resisted scientific investigation. Using brain imaging technology we found that psychopaths differed from nonpsychopaths in the pattern of relative cerebral blood flow during processing of emotional words. The results were consistent with the hypothesis that there are anomalies in the way psychopaths process semantic and affective information.

"Tip-of-the-tongue" phenomenon in Parkinson disease

Articulatory disturbances are frequently described in Parkinson disease, but language disorders are not. We have occasionally encountered parkinsonian patients with word-finding difficulty unrelated to memory loss, intellectual impairment, or dysarthria. To examine this, 22 medically stable parkinsonian patients were given the vocabulary subtest of the WAIS, the Boston Naming Test, measures of verbal fluency, and sentence repetition. Signs and symptoms of parkinsonism were rated. WAIS vocabulary subtest scores were above the mean for normal aged subjects, but confrontation naming was one standard deviation below norms for age and education. Naming was facilitated by cues in most patients. Only sentence repetition correlated with dysarthria. Category naming was impaired and correlated significantly with the severity of parkinsonism, especially bradykinesia. This suggests that a type of anomia may occur in Parkinson disease. it shares the clinical characteristics of the "tip-of-the-tongue" phenomenon and "word production anomia" seen in some aphasics.

Emergence of psychosis and depression in the longitudinal evaluation of Alzheimer's disease

Prospective psychiatric evaluations were performed as part of a longitudinal study of 32 demented patients who met criteria for the histopathological diagnosis of Alzheimer's disease at the time of death. Psychosis and major depressive disorder emerged in 15 (47%) and 7 (22%) patients, respectively, none of whom had a history of either behavioral disorder prior to the onset of dementia. The prevalence of psychosis increased with increasing dementia severity, was associated with more rapid cognitive decline, and once present was often persistent. In this regard, the emergence of psychosis in the context of Alzheimer's disease appears to be a poor prognostic sign. In contrast to its relationship to cognitive impairment, psychosis was not associated with an increased mortality rate.

Skills evaluation in minimally invasive surgery using force/torque signatures

BACKGROUND

One of the more difficult tasks in surgical education is to teach the optimal application of instrument forces and torques necessary to facilitate the conduct of an operation. For laparoscopic surgery, this type of training has traditionally taken place in the operating room, reducing operating room efficiency and potentially affecting the safe conduct of the operation. The objective of the current study was to measure and compare forces and torques (F/T) applied at the tool/hand interface generated during laparoscopic surgery by novice (NS) and experienced (ES) surgeons using an instrumented laparoscopic grasper and to use this data for evaluating the skill level.

METHODS

Ten surgeons (five-NS, five-ES) performed a cholecystectomy and Nissen fundoplication in a porcine model. An instrumented laparoscopic grasper with interchangeable standard surgical tips equipped with a three-axis F/T sensor located at the proximal end of the grasper tube was used to measure the F/T at the hand/tool interface. In addition, one axis force sensor located at the grasper's handle was used to measure the grasping force. F/T data synchronized with visual view of the tool operative maneuvers were collected simultaneously via a novel graphic user interface incorporated picture-in-picture video technology. Subsequent frame-by-frame video analysis of the operation allowed a definition of states associated with different tool/tissue interactions within each step of the operation. F/T measured within each state were further analyzed using vector quantization (VQ). The VQ analysis defines characteristic sets of F/T in the database that were defined as F/T signature.

RESULTS

The magnitude of F/T applied by NS and ES were significantly different (p < 0.05) and varied based on the task being performed. Higher F/T magnitudes were applied by NS than by ES when performing tissue manipulation, whereas lower F/T magnitudes were applied by NS than by ES during tissue dissection. Furthermore, the time to complete the surgical procedure was longer for NS by a factor of 1.5-4.8 when compared to the time for ES. State analysis suggests that most of this time is consumed in an [idle] state, in which movements of the surgeon make no tissue contact.

CONCLUSIONS

Preliminary data suggest that F/T magnitudes associated with the tool/tissue interactions provide an objective means of distinguishing novices from skilled surgeons. Clinical F/T analysis using the proposed technology and methodology may be helpful in training, developing surgical simulators, and measuring technical proficiency during laparoscopic surgery.

Guidelines To Validate Control of Cross-Contamination during Washing of Fresh-Cut Leafy Vegetables

The U.S. Food and Drug Administration requires food processors to implement and validate processes that will result in significantly minimizing or preventing the occurrence of hazards that are reasonably foreseeable in food production. During production of fresh-cut leafy vegetables, microbial contamination that may be present on the product can spread throughout the production batch when the product is washed, thus increasing the risk of illnesses. The use of antimicrobials in the wash water is a critical step in preventing such water-mediated cross-contamination; however, many factors can affect antimicrobial efficacy in the production of fresh-cut leafy vegetables, and the procedures for validating this key preventive control have not been articulated. Producers may consider three options for validating antimicrobial washing as a preventive control for cross-contamination. Option 1 involves the use of a surrogate for the microbial hazard and the demonstration that cross-contamination is prevented by the antimicrobial wash. Option 2 involves the use of antimicrobial sensors and the demonstration that a critical antimicrobial level is maintained during worst-case operating conditions. Option 3 validates the placement of the sensors in the processing equipment with the demonstration that a critical antimicrobial level is maintained at all locations, regardless of operating conditions. These validation options developed for fresh-cut leafy vegetables may serve as examples for validating processes that prevent cross-contamination during washing of other fresh produce commodities.

Impulsivity

Disorders characterized by impulsivity include disorders of impulse control (intermittent explosive disorder, pyromania, kleptomania, pathological gambling and trichotillomania), paraphilias, sexual impulsions and sexual addictions and impulsive aggression personality disorders (borderline, antisocial, histrionic and narcissistic personality disorders). Impulsivity has a substantial impact on both individuals and society. Impulse control disorders may be conceptualized as a subset of the obsessive-compulsive spectrum. In this article, we examine the genetic and neurobiological aetiology of these disorders and possible treatment options. The link between serotonergic dysfunction and the pathophysiology of impulsivity is discussed, and studies that examine the efficacy of various selective serotonin reuptake inhibitors and other alternatives in the treatment of impulsive disorders such as pathological gambling, sexual addictions and borderline personality disorder are presented.

Is "subcortical dementia" a recognizable clinical entity?

The concept of "subcortical dementia" is controversial, lacking clinical validation and having only a questionable pathological basis. Over 100 patients with Alzheimer's, Parkinson's or Huntington's disease, subdivided into three functional disability stages, were given a brief quantitative neuropsychological assessment. Patients with Huntington's or Parkinson's disease were less intellectually impaired than those with Alzheimer's disease at each functional stage. Criteria for dementia were present in all of the Alzheimer's patients but in only half of the Huntington's and Parkinson's disease groups. Patients with similar overall intellectual function scores had no distinct pattern of neuropsychological test performance. Depression, absent in patients with Alzheimer's disease, was present in half the patients with Huntington's and Parkinson's disease and was correlated with intellectual decline. The concept of subcortical dementia is misleading. The pattern of neuropsychological impairment is not distinct, and the neuropathological basis of dementia in these diseases may result from a combination of cortical and subcortical degeneration.

Mo2Ga2C: a new ternary nanolaminated carbide

We report the discovery of a new hexagonal Mo₂Ga₂C phase, wherein two Ga layers – instead of one – are stacked in a simple hexagonal arrangement in between Mo₂C layers.

Hydrazinonaphthalene and azonaphthalene thrombopoietin mimics are nonpeptidyl promoters of megakaryocytopoiesis

High-throughput screening for the induction of a luciferase reporter gene in a thrombopoietin (TPO)-responsive cell line resulted in the identification of 4-diazo-3-hydroxy-1-naphthalenesulfonic acids as TPO mimics. Modification of the core structure and adjustment of unwanted functionality resulted in the development of (5-oxo-1,5-dihydropyrazol-4-ylidene)hydrazines which exhibited efficacies equivalent to those of TPO in several cell-based assays designed to measure thrombopoietic activity. Furthermore, these compounds elicited biochemical responses in TPO-receptor-expressing cells similar to those in TPO itself, including kinase activation and protein phosphorylation. Potencies for the best compounds were high for such low molecular weight compounds (MW < 500) with EC(50) values in the region of 1-20 nM.

Alzheimer's disease with delusions and hallucinations: neuropsychological and electroencephalographic correlates

We longitudinally evaluated the neuropsychological functions, rate of progression, and waking EEG findings in 17 patients with probable Alzheimer's disease (AD) with delusions and hallucinations, and compared them with those of matched AD patients without delusions and hallucinations. AD patients with delusions and hallucinations had a more rapid rate of decline, as measured by the Mini-Mental State Examination, a specific defect in receptive language, and a greater frequency of aggression and hostility. Visual EEG analysis showed that these patients had a significantly greater proportion of moderately abnormal EEGs, and spectral analysis confirmed the increased amount of delta and theta activity. These data demonstrate that AD patients with delusions and hallucinations have a greater degree of cerebral dysfunction and a relatively focal neuropsychological defect, which may indicate a localized pathologic abnormality.

Genes and sites involved in replication and incompatibility of an R100 plasmid derivative based on nucleotide sequence analysis

The nucleotide sequence of the entire region required for autonomous replication and incompatibility of an R100 plasmid derivative, pSM1, has been determined. This region includes the replication region and all plasmid encoded information required for replication. Numerous reading frames for possible proteins can be found in this region. The existence of one of these proteins called RepA1 (285 amino acids; 33,000 daltons) which is encoded within the region known by cloning analysis to be required for replication is supported by several lines of evidence. These include an examination of the characteristic sequences on the proximal and distal ends of the coding region, a comparison of the sequence of the replication regions of pSM1 and the highly related R1 plasmid derivative Rsc13 as well as other biochemical and genetic evidence. The existence of two other proteins, RepA3 (64 amino acis; 7000 daltons) and RepA2 (103 amino acids; 11,400 daltons) is also consistent with most of the criteria mentioned above. However, the region encoding RepA3, which by cloning analysis is within the region responsible for both replication and incompatibility, has never been demonstrated to produce a 7,000 dalton polypeptide. Since a large secondary structure can be constructed in this region, it is possible that the region contains structure or other information that is responsible for incompatibility. RepA2, encoded entirely within the region identified by cloning analysis to be responsible for incompatibility but not for replication can be visualized in vivo and in vitro. However, the nucleotide sequence of the region encoding RepA2 is completely different in mutually incompatible plasmid derivatives of R1 and R100. It is therefore unlikely that RepA2 plays a major role in incompatibility. Thus, we predict that RepA2 is required to initiate DNA synthesis at the replication origin and that the region proximal to RepA2 either encodes a gene product or structure information that is responsible for incompatibility.

Performances of hill-type and neural network muscle models-toward a myosignal-based exoskeleton

Muscle models are the essential components of any musculoskeletal simulation. In addition, muscle models which are incorporated in neural-based prosthetic and orthotic devices may significantly improve their performance. The aim of the study was to compare the performances of two types of muscle models in terms of predicting the moments developed at the human elbow joint complex based on joint kinematics and neuromuscular activity. The performance evaluation of the muscle models was required to implement them in a powered myosignal-driven exoskeleton (orthotic device). The experimental setup included a passive exoskeleton capable of measuring the joint kinematics and dynamics in addition to the muscle myosignal activity (EMG). Two types of models were developed and analyzed: (i) a Hill-based model and (ii) a neural network. The task, which was selected for evaluating the muscle models performance, was the flexion-extension movement of the forearm with a hand-held weight. For this task the muscle model inputs were the normalized neural activation levels of the four main flexor-extensor muscles of the elbow joint, and the elbow joint angle and angular velocity. Using this inputs, the muscle model predicted the moment applied on the elbow joint during the movement. Results indicated a good performance of the Hill model, although the neural network predictions appeared to be superior. Relative advantages and shortcomings of both approaches were presented and discussed.