Laser ion mobility spectrometry in the detection of ultra-low quantities of explosives.

The paper presents the results of research and development of ion mobility spectrometer with laser ion sources for detecting ultra-low quantities of explosives in air. Particular attention is paid to the mechanisms of the formation of negative ions. It is shown that laser ionization with respect to ion mobility spectrometry provides an increase of sensitivity and selectivity of detection. The ion mobility spectra of the most common nitro explosives are investigated. The detection threshold for laser ion mobility spectrometer was reached at the level of 10-14 g/cm3 (for trinitrotoluene).

[The cross-plastic correction of the soft tissue defect on the neck with the use of a pectoral flap harvested from the opposite side]. / Perekrestnaya plastika defekta myagkikh tkanei shei pektoral'nym loskutom s protivopolozhnoi storony.

The authors describe a patient presenting with initially multiple metachronous cancer spreading over the right-handed side of the mouth floor and the right-handed part of the lower jaw. The patient who underwent cross-plastic surgery for the correction of the extensive soft tissue defect on the neck with the use of the musculocutaneous pectoral flap with the axial blood supply is described. The observation during the 14 year follow-up period confirmed the good functional outcome of the treatment.

[Prognostic value of renal resistance index in estimating the progression of chronic kidney disease].

AIM: To study a relationship between main renal and intraparenchymal renal arterial resistance indices (RIs) measured by Doppler ultrasonography and clinical and laboratory parameters and to determine their prognostic value in estimating the progression of chronic kidney disease (CKD). SUBJECTS AND METHODS: The investigation enrolled 53 CKD patients divided into groups: glomerular and interstitial diseases. Glomerular filtration rate (GFR) calculated using the CKD-EPI formula, proteinuria (PU) severity, kidney sizes, renal parenchyma thickness, parenchyma/collecting index, and main and intrarenal vessel RIs were determined at the first hospitalization. The mean follow-up was 14 ± 2.64 months. The rate of GFR decline was estimated at the rehospitalization. RESULTS: Main renal and intrarenal vessel RIs depend on patient age and pulse pressure. The RIs are associated with GFR and PU in the group of glomerular diseases and with kidney sizes and structure in that of interstitial diseases. The interlobar arterial RI is the most sensitive predictor for worsening renal function with a threshold of 0.65, which is comparable to the prognostic value of PU. CONCLUSION: The main renal and intrarenal vessel RIs may be considered as a predictor for worsening renal function.

Optoelectronic Properties of Semiconductor Quantum Dot Solids for Photovoltaic Applications.

Quantum dot (QD) solids represent a new type of condensed matter drawing high fundamental and applied interest. Quantum confinement in individual QDs, combined with macroscopic scale whole materials, leads to novel exciton and charge transfer features that are particularly relevant to optoelectronic applications. This Perspective discusses the structure of semiconductor QD solids, optical and spectral properties, charge carrier transport, and photovoltaic applications. The distance between adjacent nanoparticles and surface ligands influences greatly electrostatic interactions between QDs and, hence, charge and energy transfer. It is almost inevitable that QD solids exhibit energetic disorder that bears many similarities to disordered organic semiconductors, with charge and exciton transport described by the multiple trapping model. QD solids are synthesized at low cost from colloidal solutions by casting, spraying, and printing. A judicious selection of a layer sequence involving QDs with different size, composition, and ligands can be used to harvest sunlight over a wide spectral range, leading to inexpensive and efficient photovoltaic devices.

'Virtual lesion' in pain research; a study on magnetic stimulation of the primary motor cortex.

BACKGROUND: 'Virtual lesion' ('VL') is a transient disruption of cortical activity during task performance. It can be induced by single pulses or short trains of transcranial magnetic stimulation (TMS) directed to functionally relevant brain areas. We applied 'VL' methodology of a short train of TMS given on top of experimental tonic pain, expecting to see changes in pain scores. METHODS: Thirty young healthy subjects (15 women) were assessed with active ('VL') or 'sham' TMS in different sessions, randomly. In each session, 30 sec-long contact heat (47.5 °C, right forearm) was applied stand-alone ('baseline') and with 5 sec-long 10 Hz-TMS over left primary motor cortex (M1) starting at 17 sec of the heat stimulation. RESULTS: Pain scores decreased after 'VL' or 'sham' (p < 0.001). Independently of the type of TMS, pain reduction was stronger in women (p = 0.012). A triple Sex x Stimulation type ('VL' or 'sham') x Condition ('baseline' heat pain vs. heat pain with TMS) interaction (p = 0.027) indicated stronger pain reduction by 'VL' in women (p = 0.008) and not in men (p = 0.78) as compared to 'baseline'. Pain catastrophizing and perceived stress ratings affected the model (p = 0.010 and p < 0.001, respectively), but without sex differences. CONCLUSIONS: This study indicates that interactions between cortical excitability of the motor cortex and nociceptive processing may be gender-related.

Therapeutic efficacy of right prefrontal slow repetitive transcranial magnetic stimulation in major depression: a double-blind controlled study.

BACKGROUND: Transcranial magnetic stimulation (TMS), a noninvasive technique for stimulation of the brain, has recently been suggested to be effective for the treatment of major depression. We conducted a double-blind, placebo-controlled study to assess the efficacy of slow repetitive TMS (rTMS) in patients with major depression. METHODS: Seventy patients with major depression (53 women, 17 men; mean age, 58.7 years; SD, 17.2 years) were randomly assigned to receive rTMS or sham rTMS in a double-blind design. Treatment was administered in 10 daily sessions during a 2-week period. Severity of depression was blindly assessed before, during, and after completion of the treatment protocol. RESULTS: All patients completed the first week of treatment and 67 completed the entire protocol. Patients who received rTMS had a significantly greater improvement in depression scores compared with those who received sham treatment. At the end of 2 weeks, 17 of 35 patients in the rTMS group, but only 8 of 32 in the sham-treated group, had an improvement of greater than 50% in their depression ratings. CONCLUSIONS: This controlled study provides evidence for the short-term efficacy of slow rTMS in patients with recurrent major depression. Additional studies will be necessary to assess the efficacy of rTMS as compared with electroconvulsive therapy as well as the long-term outcome of this treatment in major depression and possibly other psychiatric disorders.

Right prefrontal slow repetitive transcranial magnetic stimulation in schizophrenia: a double-blind sham-controlled pilot study.

BACKGROUND: The aim of this study was to extend our previous work on the therapeutic efficacy of repetitive transcranial magnetic stimulation (rTMS) in major depression to patients with schizophrenia. METHODS: Thirty-five inpatients with schizophrenia were randomly assigned to either right prefrontal rTMS or sham treatment and were rated before and after treatment for positive, negative, and depressive symptoms. RESULTS: Thirty-one subjects (rTMS = 16, sham = 15) completed a 2-week treatment protocol. No serious adverse effects were reported; however, rTMS was not superior to sham treatment on any of the clinical ratings. CONCLUSIONS: In contrast to our previous positive findings in major depression, right prefrontal slow rTMS does not appear to have a beneficial effect for actively psychotic patients with schizophrenia.

Dissociation of somatosensory and motor evoked potentials in non-comatose patients after head injury.

OBJECTIVES: This study was performed to evaluate the clinical value of combined use of somatosensory evoked potentials (SEPs) and motor evoked potentials (MEPs) in patients with different brain lesions after head trauma. METHODS: A total of 64 patients with minor and moderate head injury were investigated by means of SEPs recorded over the parietal and frontal areas and MEPs following single-pulse transcranial magnetic stimulation (sTMS) and slow-rate repetitive transcranial magnetic stimulation (rTMS). RESULTS: In almost 50% of the patients, a dissociated impairment of somatosensory and motor evoked potentials was found. This dissociation was related to different distribution of SEP and MEP abnormalities in head injury subgroups. The higher threshold to sTMS and increased variability of the MEP amplitude during slow-rate rTMS were the most prominent features in patients with focal brain contusions, suggesting impairment of the cortical excitability. SEP abnormalities, as well as central conduction impairments, were more noticeable in patients with diffuse brain injury. CONCLUSIONS: A combined analysis of SEPs and MEPs may improve the assessment of cortical dysfunctions and central conduction abnormalities in non-comatose patients with head injury. A slow-rate rTMS may be considered as a complementary technique to the evaluation of the threshold in assessment of the excitability of the motor cortex in minor and moderate head injury.

Simulation of geometrical and electronic structure of quasi-two-dimensional layer consisting of fullerenes D6h-C36.

This article describes a computer simulation of the geometrical and electronic structure of a quasi-two-dimensional carbon layer with a trigonal lattice consisting of fullerenes C36 (1) with topological symmetry D6h. Every polyhedral cluster 1 of this polymeric layer (2) is surrounded by six similar fullerenes and connected with every such a fullerene by two covalent bonds. Atomic coordinates of the repeating unit are estimated on the basis of MNDO/PM3 calculations of hydrocarbon molecule (D6h)-C132H48 (3). The carbon skeleton of 3 coincides with a sufficiently large fragment of the polymeric layer 2. The electronic spectrum of the quasi-two-dimensional layer 2 is calculated by the crystalline orbital method in the EHT approximation. The band gap in the electronic spectrum of 2 was found to be equal to 1.5 eV. The geometric and electronic structure of some oligomers of cluster C36, quasi-linear macromolecule [C36]n, and "hypergraphite" layer is also discussed.

Motor and somatosensory conduction in cervical myelopathy and radiculopathy.

STUDY DESIGN: Motor and sensory conduction times were measured in patients with cervical myelopathy and radiculopathy. The results were compared with those of control subjects. OBJECTIVE: To evaluate the clinical value of the combined use of motor-evoked potentials with F wave recording and somatosensory-evoked potentials in cervical myelopathy and radiculopathy. SUMMARY OF BACKGROUND DATA: Electromyography and somatosensory-evoked potentials provide only indirect information on the motor pathways. The development of magnetic transcranial stimulation has provided a direct and reliable physiologic insight into the motor system. METHODS: Magnetic stimulation of the motor cortex and nerve roots with F wave recording was used to assess central and peripheral motor conduction times. Somatosensory conduction was evaluated by somatosensory-evoked potentials. RESULTS: Significant prolongation of the central sensory and motor conduction times was found in the group with myelopathy. These findings were much more pronounced in patients who had multiple level spondylotic stenosis of the spinal canal than in those harboring a single disc herniation compressing the spinal cord. In contrast to somatosensory-evoked potentials, motor-evoked potentials combined with F wave recording showed marked impairment of peripheral conduction in patients with radiculopathy. CONCLUSION: Motor-evoked potentials associated with F wave recording was suitable for the evaluation of patients with radiculopathy. The severity of conduction impairment in patients with myelopathy can be assessed by combined motor-evoked potentials and somatosensory-evoked potentials.

Classification of brain-stem trigeminal evoked potentials in multiple sclerosis, minor head injuries and post-concussion syndrome pathologies by similarity measurements.

In this study measurements obtained from brain-stem trigeminal evoked potentials (BTEP) are applied to the problem of diagnosing Multiple Sclerosis (MS) and Post-concussion syndrome (PCS). We present a simplistic model that depicts the BTEP waveform as the linear combination of a set of filters excited by a short stimulus. The relation between the BTEP latencies and the 1st to 4th harmonic components is shown. The performance of a fuzzy similarity measure based classifier is compared with that of human experts. The efficiency of the proposed classifier in conjunction with delay time and amplitude features is examined. Using this novel approach, a classification rate of 93.55% and 84.1% for MS and PCS pathologies, respectively, was achieved. This performance compares favorably to the classification rates of 84.28% for MS and 70.47% for PCS pathologies achieved by human experts.

Results of otovestibular tests in mild head injuries.

The neurotological workup of patients with minor head trauma was carried out prospectively. The preliminary results of the ongoing study were derived from 38 subjects (12 female, 26 male) at an average age of 33.5 years. All had been hospitalized after having suffered minimum head trauma followed by a temporary loss of consciousness, by amnesia, or by vomitting. The 38 subjects underwent the examination within 72 hours of the event and were summoned for a follow-up visit 3 months later. The anamnestic data show that the most frequent complaint was dizziness (81%). Tinnitus was noted in fewer than one-half of the patients, with a variety of descriptions. Twenty-six percent complained of hearing loss. The correlation between reported hearing loss and the finding on subsequent behavioral audiometry (within 72 hours after the event) was studied. The sensitivity of hearing loss (as complaint) was found to be only 40%, but its specificity was much higher at 83%. The overall equilibrium reflected in the composite score of the sensory testing in computed dynamic posturography actually worsened between tests. A good correlation was found between posturography results and symptomatology. We concluded that, after minor head trauma, most patients suffer from dizziness, and more than one-half complain of tinnitus or hearing loss. The unsteadiness does not subside within 3 months after concussion. A more protracted follow-up is required to summarize the outcome of head injury from a neurootological point of view. A clear correlation is found between complaints and posturography results. After minor head trauma, pure vestibular injuries are much less frequent than are central lesions. Motor dysfunction is less frequent than are the sensory abnormalities.

[Motor potentials evoked by magnetic stimulation--a tool for objective assessment of motor conduction along the spinal cord and its roots].

Magnetic stimulation of the motor cortex and nerve roots in conjunction with F-wave recording was used for assessment of central and peripheral motor conduction times in 98 patients suffering from myelopathy and cervical or lumbo-sacral radiculopathy. Significant prolongation of the central motor conduction times was found in the myelopathy group. The Motor Evoked Potential was of low amplitude and distorted shape. The amplitude of the F-wave was markedly increased. The main feature of the radiculopathy group was prolonged motor root conduction time as evident by delayed F-wave. Motor evoked potentials proved to be a reliable objective tool in the functional evaluation of conduction along the spinal cord and its roots.

[Exhaustion of motor cortex after head injury--revealed by transcranial magnetic stimulation].

We evaluated the pattern of motor evoked potentials elicited by single-pulse and slow-rate (1 Hz) repetitive, transcranial, magnetic stimulation (RTMS) in minor head injuries. The motor response to a single magnetic stimulus in patients with minor head injury was characterized by a significantly higher threshold than in healthy subjects. However, central and peripheral motor conduction was normal in all patients. A stable pattern of MEP throughout the RTMS session was the most prominent feature in the control group. A progressive decrease in MEP amplitude and irregular alternation of large and very small MEPs over the course of RTMS was observed in minor head injury. The higher threshold of the motor response and the abnormal patterns of MEP behavior revealed by RTMS may reflect impaired excitability and enhanced exhaustion of the motor cortex in patients with minor head injuries, which improve with time.

Asymmetry in the dorsolateral prefrontal cortex and aggressive behavior: a continuous theta-burst magnetic stimulation study.

Aggressive behavior is aimed at causing damage or pain to another individual. Aggression has been associated with structural and functional deficits in numerous brain areas, including the dorsolateral region of the prefrontal cortex (DLPFC), typically related to inhibition and impulse control. In this study, we used inhibitory continuous theta-burst magnetic stimulation (cTBS) to explore the role of the right and left DLPFC in aggression. Sixteen healthy right-handed volunteers underwent two sessions involving random, real and sham, right and left DLPFC stimulations. These sessions were followed by the Social Orientation Paradigm (SOP), a monetary task that was specially designed to assess participants' aggressive tendencies by measuring the patterns of their reactive aggression (a response to a perceived provocation) and proactive aggression (an aggressive act with goal-oriented purposes). Results indicate that using cTBS to target the left DLPFC was associated with a greater increase in aggressive responses than right DLPFC stimulation. This pattern of results was found for both reactive and proactive types of aggressive reactions. It is concluded that DLPFC asymmetry is involved in modulating reactive and proactive aggression. Our results are in line with recent studies suggesting that the left DLPFC plays a major role in aggressive behavior.

Comparison of moderate hyperventilation and mannitol for control of intracranial pressure control in patients with severe traumatic brain injury--a study of cerebral blood flow and metabolism.

OBJECTIVE: To compare the respective effects of established measures used for management of traumatic brain injury (TBI) patients on cerebral blood flow (CBF) and cerebral metabolic rates of oxygen (CMRO2), glucose (CMRGlc) and lactate (CMRLct). METHODS: Thirty-six patients suffering from severe traumatic brain injury (TBI) were prospectively evaluated. In all patients baseline assessments were compared with that following moderate hyperventilation (reducing PaCO2 from 36 +/- 4 to 32 +/- 4 mmHg) and with that produced by administration of 0.5 gr/kg mannitol 20% intravenously. Intracranial and cerebral perfusion pressure (ICP, CPP), CBF and arterial jugular differences in oxygen, glucose and lactate contents were measured for calculation of CMRO2, CMRGlc and CMRLct. RESULTS: Following hyperventilation, CBF was significantly reduced (P < 0.0001). CBF remained most often above the ischemic range although values less than 30 ml x 100 gr(-1) x min(-1) were found in 27.8% of patients. CBF reduction was associated with concurrent decrease in CMRO2, anaerobic hyperglycolysis and subsequent lactate production. In contrast, mannitol resulted in significant albeit moderate improvement of cerebral perfusion. However, administration of mannitol had no ostensible effect either on oxidative or glucose metabolism and lactate balance remained mostly unaffected. CONCLUSIONS: Moderate hyperventilation may exacerbate pre-existing impairment of cerebral blood flow and metabolism in TBI patients and should be therefore carefully used under appropriate monitoring. Our findings rather support the use of mannitol for ICP control.

Preliminary evidence for a beneficial effect of low-frequency, repetitive transcranial magnetic stimulation in patients with major depression and schizophrenia.

OBJECTIVE: This study was designed to evaluate the potential efficacy of repetitive transcranial magnetic stimulation (rTMS) at low-frequency in patients with major depression and schizophrenia. EXPERIMENTAL DESIGN: We investigated the therapeutic effect of a course of 10 rTMS sessions in 14 subjects with major depression (MD) and 10 with schizophrenia. PRINCIPAL OBSERVATIONS: Seven of the depressed patients reported significant improvement in depressive symptomatology, and seven of the schizophrenic subjects reported amelioration of anxiety and restlessness. CONCLUSIONS: These preliminary results suggest that low-frequency rTMS may be beneficial mainly in MD and to some extent in schizophrenia, and support the need for controlled studies to further validate its therapeutic potential.

A comparison of neural network and Bayes recognition approaches in the evaluation of the brainstem trigeminal evoked potentials in multiple sclerosis.

This article describes the application of Multi-Layer Perceptron (MLP), Probabilistic Neural Network and Kohonen's Learning Vector Quantization to the problem of diagnosing Multiple Sclerosis. The classification information is obtained from brainstem trigeminal evoked potential. The performance of the neural networks based classifiers is compared with that of the human experts and the Bayes classifier. The ability of the MLP classifier to generalize is far better than that of the Bayes classifier. The efficiency of the neural network based classifiers in conjunction with several types of well-known evoked potential features, such as Fourier transform space, latency and temporal wave, is examined. Although a large clinical data base would be necessary, before this approach can be fully validated, the initial results are promising.

Trigeminal and auditory evoked responses in minor head injuries and post-concussion syndrome.

Forty patients who sustained minor head trauma were investigated by brainstem trigeminal and auditory evoked potentials (BTEP, BAEP) and middle-latency auditory evoked potentials (MLAEP). The patients were evaluated within the first 48 h following their admission and at 3 months after the injury. Outcome was scored at the follow-up examination according to six complaints: failure to resume previous professional activity, headache, memory disorders, dizziness and vertigo, behavioural and emotional disturbances, and other symptoms of a neurological nature. Post-concussion syndrome (PCS) was defined by the presence of four or more of the listed features. All three evoked potential modalities showed significantly increased latencies at the initial assessment, disclosing disseminated axonal damage. Unlike the BTEPs and the BAEPs, the MLAEPs proved to correlate to outcome at 3 months, especially in its psychocognitive aspects. These findings suggest that organic diencephalic-paraventricular primary damage may account for the occurrence of PCS.

Neuropsychological effects of prefrontal slow rTMS in normal volunteers: a double-blind sham-controlled study.

Recent reports have suggested that repetitive transcranial magnetic stimulation (rTMS) is effective in major depression. Unlike ECT, rTMS does not involve a seizure and is associated with minimal side-effects, including cognitive difficulties. However, the effect of rTMS on cognitive functioning has not been systematically evaluated. This study was designed to examine the neuropsychological effects of slow rTMS in normal volunteers. Forty-six normal volunteers were randomly assigned to receive one session of right (N = 16) or left prefrontal (N = 15), or sham (N = 15) rTMS at 1 HZ. Patients were assessed before and after stimulation by a computerized neurospychological battery. All three groups showed significant improvement over time in processing speed (reaction time) and efficiency (correct responses per unit of time). However, no time by group interaction was found for any of the neuropsychological tests. These findings suggest that a single session of slow rTMS does not interfere with neurospychological functioning in normal volunteers, supporting clinical reports of no adverse cognitive effects.