Internal rotation and chlorine nuclear quadrupole coupling in 2-chloro-4-fluorotoluene explored by microwave spectroscopy and quantum chemistry.

2-Chloro-4-fluorotoluene was investigated using a combination of molecular jet Fourier transform microwave spectroscopy in the frequency range from 5 to 21 GHz and quantum chemistry. The molecule experiences an internal rotation of the methyl group, which causes fine splittings of all rotational transitions into doublets with separation on the order of a few tens of kHz. In addition, hyperfine effects originating from the chlorine nuclear quadrupole moment coupling its nuclear spin to the end-over-end rotation of the molecule are observed. The torsional barrier was derived using both the rho and the combined-axis-method, giving a value of 462.5(41) cm-1. Accurate rotational constants and quadrupole coupling constants were determined for the 35Cl and 37Cl isotopologues and compared with Bailey's semi-experimental quantum chemical predictions. The gas phase molecular structure was deduced from the experimental rotational constants supplemented with those calculated by quantum chemistry at various levels of theory. The values of the methyl torsional barrier and chlorine nuclear quadrupole coupling constants were compared with the theoretical predictions and with those of other chlorotoluene derivatives.

The structure and low-barrier methyl torsion of 3-fluorotoluene.

The rotational spectra of 3-fluorotoluene and its seven 13C isotopic species have been recorded at natural abundance in the frequency range from 4 to 26 GHz using a pulsed molecular jet Fourier transform microwave spectrometer. The molecular structure comprising bond lengths and angles as well as parameters describing the methyl torsion were determined with high accuracy. Due to the very low torsional barrier of 17 cm-1, the lowest torsional states of the vibrational ground state exhibited large splittings in the spectrum, which were modeled satisfactorily with a modified version of the program XIAM and the program aixPAM, both developed to treat the methyl internal rotation effects. They were also applied to refit the microwave data of 3,4-difluorotoluene to standard deviations close to measurement accuracy.

Reactivity and rotational spectra: the old concept of substitution effects.

The internal rotation of methyl groups and nuclear quadrupole moments of the halogens Cl, Br, I in o-halotoluenes cause complex spectral fine and hyperfine structures in rotational spectra arising from angular momentum coupling. Building on the existing data regarding o-fluorotoluene and o-chlorotoluene, the investigations of o-bromotoluene and o-iodotoluene allow for a complete analysis of the homologous series of o-halogenated toluenes. The trend in the methyl barriers to internal rotation rising with the size of the halogen can be rationalised by repulsion effects as predicted by MP2 calculations. Furthermore, the analysis of the observed quadrupole coupling serves as a quantitative intra-molecular probe, e.g. for the explanation of the relative reaction yields in the nitration of halotoluenes, related to the different π-bond character of the C-X bond depending on the position of substitution.

The puzzling hyper-fine structure and an accurate equilibrium geometry of succinic anhydride.

An accurate semiexperimental equilibrium structure of succinic anhydride has been determined from a combination of experiment and theory. The cm-wave and mm-wave rotational spectra of succinic anhydride, 3,4-dihydrofuran-2,5-dione, were recorded in a pulsed supersonic jet using Fourier-transform microwave spectroscopy and in a free-jet using mm-wave absorption spectroscopy. Many lines in the cm-wave spectrum show fine structure and after eliminating all other possibilities the origin of this fine structure is determined to be from spin-spin interaction. Accurate rotational and quartic centrifugal distortion constants are determined. Assignments of 13C and 18O singly substituted isotopologues in natural abundance were used to obtain a substitution geometry for the heavy atoms of succinic anhydride. Theoretical approaches permitted the calculation of a Born-Oppenheimer ab initio structure and the determination of a semiexperimental equilibrium structure in which computed rovibrational corrections were utilized to convert vibrational ground state rotational constants into equilibrium constants. The agreement between the semiexperimental structure and the Born-Oppenheimer ab initio structure is excellent. Succinic anhydride has been shown to have a planar heavy atom equilibrium structure with the effects of a large amplitude vibration apparent in the resultant rotational constants.

Inter-leg Distance Measurement as a Tool for Accurate Step Counting in Patients with Multiple Sclerosis.

Step detection is commonly performed using wearable inertial devices. However, methods based on the extraction of signals features may deteriorate their accuracy when applied to very slow walkers with abnormal gait patterns. The aim of this study is to test and validate an innovative step counter method (DiSC) based on the direct measurement of inter-leg distance. Data were recorded using an innovative wearable system which integrates a magneto-inertial unit and multiple distance sensors (DSs) attached to the shank. The method allowed for the detection of both left and right steps using a single device and was validated on thirteen people affected by multiple sclerosis (0 <; EDSS <; 6.5) while performing a six-minute walking test. Two different measurement ranges for the distance sensor were tested (DS200: 0-200 mm; DS400: 0-400 mm). Accuracy was evaluated by comparing the estimates of the DiSC method against video recordings used as gold standard. Preliminary results showed a good accuracy in detecting steps with half the errors in detecting the step of the instrumented side compared to the non-instrumented (mean absolute percentage error 2.4% vs 4.8% for DS200; mean absolute percentage error 2% vs 5.4% for DS400). When averaging errors across patients, over and under estimation errors were compensated, and very high accuracy was achieved (E%<; 1.2% for DS200; E%<; 0.7% for DS400). DS400 is the suggested configuration for patients walking with a large base of support.

Free-living and laboratory gait characteristics in patients with multiple sclerosis.

BACKGROUND: Wearable sensors offer the potential to bring new knowledge to inform interventions in patients affected by multiple sclerosis (MS) by thoroughly quantifying gait characteristics and gait deficits from prolonged daily living measurements. The aim of this study was to characterise gait in both laboratory and daily life conditions for a group of patients with moderate to severe ambulatory impairment due to MS. To this purpose, algorithms to detect and characterise gait from wearable inertial sensors data were also validated. METHODS: Fourteen patients with MS were divided into two groups according to their disability level (EDSS 6.5-6.0 and EDSS 5.5-5.0, respectively). They performed both intermittent and continuous walking bouts (WBs) in a gait laboratory wearing waist and shank mounted inertial sensors. An algorithm (W-CWT) to estimate gait events and temporal parameters (mean and variability values) using data recorded from the waist mounted sensor (Dynaport, Mc Roberts) was tested against a reference algorithm (S-REF) based on the shank-worn sensors (OPAL, APDM). Subsequently, the accuracy of another algorithm (W-PAM) to detect and classify WBs was also tested. The validated algorithms were then used to quantify gait characteristics during short (sWB, 5-50 steps), intermediate (iWB, 51-100 steps) and long (lWB, >100 steps) daily living WBs and laboratory walking. Group means were compared using a two-way ANOVA. RESULTS: W-CWT compared to S-REF showed good gait event accuracy (0.05-0.10 s absolute error) and was not influenced by disability level. It slightly overestimated stride time in intermittent walking (0.012 s) and overestimated highly variability of temporal parameters in both intermittent (17.5%-58.2%) and continuous walking (11.2%-76.7%). The accuracy of W-PAM was speed-dependent and decreased with increasing disability. The ANOVA analysis showed that patients walked at a slower pace in daily living than in the laboratory. In daily living gait, all mean temporal parameters decreased as the WB duration increased. In the sWB, the patients with a lower disability score showed, on average, lower values of the temporal parameters. Variability decreased as the WB duration increased. CONCLUSIONS: This study validated a method to quantify walking in real life in people with MS and showed how gait characteristics estimated from short walking bouts during daily living may be the most informative to quantify level of disability and effects of interventions in patients moderately affected by MS. The study provides a robust approach for the quantification of recognised clinically relevant outcomes and an innovative perspective in the study of real life walking.

Six-fold-symmetry internal rotation in toluenes: the low barrier challenge of 2,6- and 3,5-difluorotoluene.

Pure six-fold symmetry (V6) internal rotation poses significant challenges to experimental and theoretical determination, as the very low torsional barriers result in huge tunneling splittings difficult to identify and to model. Here we resolved the methyl group internal rotation dynamics of 2,6- and 3,5-difluorotoluene using a newly developed computer code especially adapted to V6 problems. The jet-cooled rotational spectra of the title molecules in the 5-25 GHz region revealed internal rotation tunneling doublings of up to 3.6 GHz, which translated in methyl group potential barriers of V6 = 0.14872(24) and 0.0856(10) kJ mol(-1), respectively, in the vibrational ground-state. Additional information on Stark effects and carbon isotopic species in natural abundance provided structural data and the electric dipole moments for both molecules. Ab initio calculations at the MP2 level do not reproduce the tiny torsional barriers, calling for experiments on other systems and additional theoretical models.

Conformational steering in dicarboxy acids: the native structure of succinic acid.

Succinic acid, a dicarboxylic acid molecule, has been investigated spectroscopically with computational support to elucidate the complex aspects of its conformational composition. Due to the torsional freedom of the carbon backbone and hydroxy groups, a large number of potentially plausible conformers can be generated with an indication that the gauche conformer is favored over the trans form. The microwave and millimeter wave spectra have been analyzed and accurate spectroscopic constants have been derived that correlate best with those of the lowest energy gauche conformer. For an unambiguous conformational identification measurements were extended to the monosubstituted isotopologues, precisely determining the structural properties. Besides bond distances and angles, particularly the dihedral angle has been determined to be 67.76(11)°, confirming the anomalous tendency of the methylene units to favor gauche conformers when a short aliphatic segment is placed between two carbonyl groups.

Subarachnoid haemorrhage: an unusual complication of implantation of an intrathecal baclofen pump.

STUDY DESIGN: Single case-report. OBJECTIVES: To describe subarachnoid haemorrhage; an unusual complication following implantation of an intrathecal baclofen pump in an adult with spinal cord injury. SETTING: Princess Royal Spinal Injuries Unit, Sheffield, UK. METHODS: Review of the medical notes and literature. RESULTS: A 77-year-old man with an incomplete ASIA-C spinal cord injury at C5 level sustained 2 years previously, developed subarachnoid haemorrhage following implantation of an intrathecal baclofen pump for the management of spasticity that was unresponsive to treatment with oral antispasticity agents. CONCLUSION: Subarachnoid haemorrhage can occur as a rare complication of insertion of Intrathecal baclofen pump. This need to be considered while evaluating patients who present with headache, confusion and seizures in the post operative period. SPONSORSHIP: Not applicable.

Superimposed myasthenia gravis in chronic spinal cord injury: a case report.

STUDY DESIGN: Case report. BACKGROUND/OBJECTIVE: Myasthenia gravis (MG) complicating spinal cord injury (SCI) is extremely rare. We report a patient with SCI developing MG leading to death. There are no similar articles at present on literature search. CASE REPORT: A 54-year-old man, paralysed at the T12 level (ASIA A) for 40 years, was admitted for surgical repair of his grade IV sacral pressure sore. During the admission he developed diplopia, fluctuating dysphagia and slurred speech. Elevated anti-acetylcholine receptor antibodies and single fibre electromyography confirmed the diagnosis of MG and pyridostigmine was commenced. His admission was complicated by intermittent episodes of unexplained tachycardia and tachypnoea. He succumbed following cardio respiratory within 6 weeks of admission. Post mortem examination was inconclusive of a definite cause of death. In the presence of SCI, it can be challenging to diagnose MG or its complications like myasthenic and cholinergic crisis. CONCLUSION: The case highlights the difficulty in diagnosis and management of MG in persons with SCI.

Lower urinary tract dysfunction in acute disseminated encephalomyelitis.

BACKGROUND: Lower urinary tract dysfunction (LUTD) in multiple sclerosis has been well documented. However, its occurrence and outcome in acute disseminated encephalomyelitis (ADEM) has only been variably reported. OBJECTIVE: To evaluate LUTD in ADEM, correlation with other neurological deficits, and outcome. METHODS: Patients with ADEM having significant LUTD were evaluated. LUTD was evaluated by symptom analysis, ultrasonography, and urodynamics. Storage symptoms were managed using antimuscarinics and significant voiding dysfunction by catheterization. RESULTS: Of 61 patients, 20 (33%) had LUTD. Voiding dysfunction was more common and 16 patients were in urinary retention. Cystometry demonstrated detrusor overactivity in four patients and underactivity in four patients. Incontinence was reported more often in patients with frontoparietal white matter changes in MR imaging. LUTD was found to be associated with occurrence of paraparesis or tetraparesis, though did not predict functional outcome at discharge. At 3 months follow up, five patients continued to have LUTD and urgency and hesitancy were commonest symptoms. CONCLUSION: LUTD is common in ADEM, especially in patients with lower limb pyramidal involvement and its causes multifactorial. Presence of LUTD does not influence the functional outcome of patients with ADEM. Recovery may be incomplete and symptoms may persist even after recovery of other neurological deficits.

Quality of life in Wilson's disease.

BACKGROUND: Assessment of Quality of life (QoL) is fast assuming significance as the measure of health in many disorders. AIM: To correlate clinical severity and QoL in patients with Wilson's disease (WD). MATERIALS AND METHODS: We evaluated patients of WD on regular follow up for at least two years and aged over 18 years using Neurological Symptom Score (NSS) for clinical severity and WHO-BREF for QoL at a university teaching hospital. Patients with inability to respond to the questionnaire due to behavioral problems, low IQ or other disease related factors were excluded. These 30 patients (M:F:: 23:7) had a mean age of 27.97 +/- 11.16 years at evaluation and the mean duration of treatment of 9.2 +/- 6.4 years. RESULTS: All four domains of WHO-QoL-BREF viz., Physical, Psychological, Social and Environmental correlated well with each other (p < 0.01). The NSS correlated inversely with the physical domain (p < 0.02), while the duration of treatment had a positive correlation with the physical domain (p < 0.01). None of the other features of QoL showed any significant correlation with age, NSS or duration of treatment. CONCLUSION: QoL is complementary to formal neurological assessment and should be routinely incorporated in the evaluation of outcome of patients with WD and other chronic neurological disorders.

Brachial plexus injuries: outcome following neurotization with intercostal nerve.

OBJECT: Brachial plexus root avulsion injuries, which are devastating, usually result from high-speed accidents. Nerve transfer provides hope for successful treatment of this difficult set of injuries. Nevertheless, the controversies regarding indications, techniques, and outcome of the various available surgical procedures continue. METHODS: A retrospective analysis was performed in 51 patients (43 male and eight female patients) with brachial plexus injuries who underwent neurotization at the authors' institute between 1997 and 2003. Clinical, electrophysiological, and imaging data were used to identify the type and pattern of involvement of the various elements of the plexus. The mean duration of denervation was 6.4 months (range 2-24 months). Outcome was computed in terms of the overall improvement in power of the target muscle as well as the functional usefulness of such recovery. RESULTS: There were 50 supraclavicular injuries (25 preganglionic, eight postganglionic, and 17 mixed). One patient had an infraclavicular (posterior spinal cord) injury. Pan-brachial plexus injury with a flail upper limb was the most common pattern. Overall, 55 nerves were neurotized-33 musculocutaneous, 18 axillary, and two each for ulnar and radial nerves (47 single and four double neurotizations-by using intercostal nerve donors in the majority of cases. Adequate follow-up data were available in 36 patients (38 nerves) and these were used for the analysis of outcome. Overall, 58.3% of patients had improvement, and of these 62% achieved useful recovery. This accounted for 36% of overall useful recovery. Multiple logistic regression analysis revealed that regardless of age, sex, mode and pattern of injury, and recipient nerve, the duration of denervation showed a trend toward significance that correlated with overall (but not useful) improvement. The critical duration of denervation was 5.5 months. CONCLUSIONS: Neurotization for brachial plexus root avulsion injuries is a viable option. Early detection and intervention (within 5.5 months) leads to a better overall recovery.

Urinary disturbances following traumatic brain injury: clinical and urodynamic evaluation.

AIM: To detect presence of urodynamic abnormalities in patients with traumatic brain injuries. MATERIALS AND METHODS: A prospective study was conducted recruiting patients sustaining moderate or severe head injuries. Clinical and radiological evaluation was done. Neurocognitive and functional outcomes were assessed. Patients then underwent standardized urodynamic studies. The urodynamic findings were correlated with outcome and statistically analyzed. RESULTS: 11 of 20 patients recruited had urodynamic abnormalities, in spite of only two being symptomatic. An overactive detrussor was detected in 8 (one with sphincter dyssynergia) and reduced detrussor compliance was found in 3. Only presence of motor deficits correlated statistically with the occurrence of these abnormalities. CONCLUSIONS: Asymptomatic urodynamic abnormalities may be common in patients with moderate/severe traumatic brain injury. Presence of motor deficits may predict the occurrence of such abnormalities.

Vibrational overtone spectra of o-fluorophenol and the "anomalous" order of intramolecular hydrogen bonding strengths.

The near infrared vibrational overtone absorption spectrum of liquid phase o-fluorophenol is examined in the region deltav=2, 3 and 4. The OH frequencies are compared with that of o-chlorophenol and phenol. Considering the relative electronegativities of all halogens, one might expect the order of intramolecular hydrogen bond strength for o-fluorophenol to be the greatest among all halogenophenols. It is evident that o-fluorophenol forms a weaker intramolecular hydrogen bond (an anomalous trend) contrary to that expected from relative electronegativities of halogens. The local mode mechanical frequency values and anharmonicity values obtained from fitting the overtones are analysed. Our observation is in agreement with the previous experimental as well as the recent theoretical vibrational analysis of halogenophenols using density functional theory (B3LYP). The overtone spectra of o-fluorophenol in carbon tetrachloride in different concentrations are also examined. It is noted that the OH-red shift which arises due to the intermolecular bond formation between the cis and trans conformers of o-fluorophenol (dimerization) increases with concentration.

Near IR overtone spectral investigations of liquid phase imidazole and the blue-shifting hydrogen bonds.

The near infrared vibrational overtone absorption spectrum of imidazole dissolved in carbon tetrachloride is examined in the region Delta v = 2, 3 and 4. Instead of the standard hydrogen bonding, unusual blue-shifted hydrogen bonds are observed in NH positions. This observation is in agreement with the recent conclusions drawn from theoretical studies of the coupling character between the Imidazole-Imidazolium complex, which is strongly hydrogen bonded. The NH local mode mechanical frequency values and anharmonicity values obtained from fitting the overtones are analysed. The anharmonicity of blue-shifted hydrogen bonded NH stretching bands is greater compared to those of the free NH stretching bands. It is contrary to the decrease in anharmonicity due to the standard red shifting of NH bonds.

Near IR overtone spectral investigations of cyclohexanol using local mode model--evidence for variation of anharmonicity with concentration due to hydrogen bonding.

The near infrared vibrational overtone absorption spectrum of liquid phase cyclohexanol in carbon tetrachloride in different concentrations are examined in the region Deltav=2, 3 and 4. The free and bonded OH local mode mechanical frequency values and anharmonicity values obtained from fitting the overtones are analysed. The observation supports the conclusions drawn from earlier experimental studies on anharmonicity variation of OH-stretching vibrations of alcohols due to intermolecular hydrogen bonding. Our observation is also in agreement with the ab initio calculations on water dimer and trimer. Mechanical anharmonicity of bonded OH-stretching bands tends to increase as a consequence of strong hydrogen bonding at higher concentrations.

Role of clinical neurophysiological tests in evaluation of erectile dysfunction in people with spinal cord disorders.

BACKGROUND: While erectile dysfunction is frequent among people with disorders of the spinal cord, the role of various clinical neurophysiological tests in assessment is not clear. AIMS: To study the role of clinical neurophysiological investigations in assessing erectile dysfunction among men with spinal cord disorders. SETTING: National Institute of Mental Health and Neurosciences, India. DESIGN: Survey. MATERIALS AND METHODS: Subjects with a score of 21 or less on the International Index of Erectile Function-5 were classified as with erectile dysfunction and with a score of more than 21 as without erectile dysfunction. Clinical neurophysiological studies done were Sympathetic Skin Response from limbs, posterior tibial sensory evoked potential, pudendal sensory potential and bulbocavernous reflex. STATISTICAL ANALYSES: Chi-square test. RESULTS: Among 40 subjects 26 had erectile dysfunction. The frequency of abnormalities in clinical neurophysiological studies were: pudendal sensory evoked potentials--16, posterior tibial sensory evoked potentials--26, bulbocavernous reflex--5, sympathetic skin response from sole--24 and, sympathetic skin response from palm--18. Significant associations were noted between erectile dysfunction and abnormal pudendal sensory evoked potentials (P=0.0479), and absent sympathetic skin response from palm (P=0.0279) and sole (P< 0.001). There was no correlation between erectile dysfunction and posterior tibial sensory evoked potentials (P=0.133) or bulbocavernous reflex (P=0.418). Sympathetic skin response from sole was most sensitive (80.8%) and had best positive (87.5%) and negative predictive (68.8%) values. The specificity of these three tests was 78.6%. CONCLUSIONS: Sympathetic skin response from the sole of the foot was the most sensitive and specific clinical neurophysiological test for erectile dysfunction in spinal cord disorders.