Investigation of slider out-of-plane and in-plane vibrations during the track-seeking process

This paper employs the coupled air bearing model and modal order reduction (MOR) model of head stack assembly (HSA) to investigate the track-seeking process of a femto slider. Simulations indicate that the flying height and the pitch angle may increase or decrease significantly, depending on the track-seeking directions. For the slider studied in this paper, it is safer for sweeping from OD to ID, than sweeping from ID to OD. The most serious vibration is the off-track vibration, and it is highly related to the sweeping acceleration profile. A smooth acceleration profile is crucial to reduce all the vibrations of slider, especially the off-track vibration.     

Exploring the Bioactive Potentials of C60-AgNPs Nano-Composites against Malignancies and Microbial Infections

At present, the potential role of the AgNPs/endo-fullerene molecule metal nano-composite has been evaluated over the biosystems in-vitro. The intra-atomic configuration of the fullerene molecule (C₆₀) has been studied in-vitro for the anti-proliferative activity of human breast adenocarcinoma (MDA-MB-231) cell lines and antimicrobial activity against a few human pathogens that have been augmented with the pristine surface plasmonic electrons and antibiotic activity of AgNPs. Furthermore, FTIR revealed the basic vibrational signatures at ~3300 cm⁻¹, 1023 cm⁻¹, 1400 cm⁻¹ for O-H, C-O, and C-H groups, respectively, for the carbon and oxygen atoms of the C₆₀ molecule. NMR studies exhibited the different footprints and magnetic moments at ~7.285 ppm, explaining the unique underlying electrochemical attributes of the fullerene molecule. Such unique electronic and physico-chemical properties of the caged carbon structure raise hope for applications into the drug delivery domain. The in-vitro dose-dependent application of C₆₀ elicits a toxic response against both the breast adenocarcinoma cell lines and pathogenic microbes. That enables the use of AgNPs decorated C₆₀ endo fullerene molecules to design an effective anti-cancerous drug delivery and antimicrobial agent in the future, bringing a revolutionary change in the perspective of a treatment regime.     

Modeling laser heated thin film media for heat assisted magnetic recording

In the present study, we concern laser induced heat generation and its effect on lubricant depletion on the multilayer disk structure. A mathematical model is applied to explore the local laser heating from the point of view of the interaction between the disk media and the electromagnetic wave. The absorption rate of optical energy in each layer of disk structure is derived from the Maxwell equations, which is incorporated into the energy equation by a source term. We simulate the unsteady heat transfer and lubricant depletion processes on a multilayer disk structure. The effect of multi-cycle heating on the lubricant depletion is investigated. Comparison between the present results and those obtained by applying a heat flux boundary condition is also made. The present simulations provide useful information on the media structure design of hard disk drives in heat assisted magnetic recording.     

Polarization-based compensation of astigmatism

One approach to aberration compensation of an imaging system is to introduce a suitable phase mask at the aperture plane of an imaging system. We utilize this principle for the compensation of astigmatism. A suitable polarization mask used on the aperture plane together with a polarizer-retarder combination at the input of the imaging system provides the compensating polarization-induced phase steps at different quadrants of the apertures masked by different polarizers. The aberrant phase can be considerably compensated by the proper choice of a polarization mask and suitable selection of the polarization parameters involved. The results presented here bear out our theoretical expectation.     

Back heating effect of media hot spot at nanoscale head–disk interface

Microsystem Technologies - Heat-assisted magnetic recording (HAMR) is one of prospective high density recording technologies in current hard disk industry due to its theoretical potential. In this...     

A review of the readmissions of patients with tetraplegia to the Regional Spinal Injuries Centre, Southport, United Kingdom, between January 1994 and December 1995

Patients with chronic tetraplegia are prone to develop unique clinical problems which require readmission to specialised centres where the health professionals are trained specifically to diagnose, and treat the diseases afflicting this group of patients. An appraisal of the readmission pattern of tetraplegic patients will provide the necessary data for planning allocation of beds for treatment of chronic tetraplegic patients. Hospital records of patients with tetraplegia readmitted to the Regional Spinal Injuries Centre, Southport, UK between 1 January 1994 and 31 December 1995 were analyzed to find out the number of tetraplegic patients who required readmission, reasons for readmission, duration of hospital stay, and mortality among patients readmitted. During the 2-year period, 155 tetraplegic patients were readmitted and 44 of them (28.4%) required more than one readmission (total readmission episodes: 221); these patients occupied 4.5 beds which is equivalent to 11.5% of the total bed capacity of the spinal unit. Among the reasons for the readmissions, evaluation and care of urinary tract disorders topped the list with 96 readmission episodes (43.43%) involving 70 patients; the median hospital stay was 3 days, and 18 patients (26%) required more than one readmission during this period. One hospital bed was occupied by the tetraplegic patients requiring treatment/evaluation of urinary tract disorders. Assessment and treatment of cardio-respiratory diseases was the second most common reason for readmission with 51 readmission episodes pertaining to 27 patients having a median hospital stay of 6 days; 13 patients (48%) were readmitted more than once within this 2-year period. Treatment of cardio-respiratory diseases in chronic tetraplegic patients required 1.2 hospital beds yearly. Only five tetraplegic patients were readmitted for treatment of pressure sore(s); however they had a prolonged hospital stay (median duration: 101 days). Social reasons accounted for 13 readmission episodes concerning nine patients who stayed in the hospital for varying periods (median: 6.5 days; mean: 35 days). Four tetraplegic patients readmitted with acute chest infection expired. An 81 year-old tetraplegic died of myocardial infarction. Urinary sepsis, renal insufficiency, respiratory failure and intra-cerebral haemorrhage accounted for the demise of a 41 year-old tetraplegic patient following surgical removal of a large, impacted stone at the pelviureteric junction. A tetraplegic patient who was admitted with haematuria subsequently underwent cystectomy for squamous cell carcinoma of the urinary bladder; he developed secondaries and expired 5 months later. As more patients with high cervical spinal cord injury survive the initial period of trauma, and as the life expectancy of tetraplegic patients increases, it is likely that greater numbers of tetraplegic patients will be requiring readmission to spinal injuries centre. Although it may be possible to prevent some of the complications of spinal cord injury and hence the need for a readmission, progress in medicine and rehabilitation technology will create additional demands for readmissions of chronic tetraplegic patients in order to implement the newer therapeutic strategies. Thus a change in the pattern of readmission of chronic tetraplegic patients is likely to be the future trend and this should be taken into account while making plans for providing the optimum care to chronic tetraplegic patients.     

Recurrent bilateral renal calculi in a tetraplegic patient

An 18-year-old male developed C-5 complete tetraplegia following a motor-cycle accident in May 1975. The neuropathic bladder was managed by an indwelling urethral catheter. He developed recurrent episodes of urinary infection with Proteus species. In September 1975, an X-ray of the abdomen revealed small calculi in both the kidneys. In July 1976, he underwent transurethral resection of the bladder neck and division of the external urethral sphincter; subsequently, he was put on a penile sheath drainage. He continued to suffer from repeated episodes of urinary tract infection with Proteus, Providencia, and Pseudomonas species, and he was treated with antibiotics. In 1980, intravenous urography (IVU) showed two large stones in the left kidney with marked caliectasis. The IVU performed in 1984 showed an increase in the size of the calculi in the left kidney which was grossly hydronephrotic. There were clusters of small calculi in the right kidney. The left renal calculi were treated by percutaneous lithotripsy in two sessions. In 1988, an X-ray of the abdomen revealed staghorn calculus in the right kidney and recurrence of stones in the left kidney. The staghorn calculus in the right kidney was treated by percutaneous nephrostolithotomy in two sessions. In 1991, he was admitted with acute urinary infection. IVU showed a stone in the pelviureteric junction with no excretion of contrast in the left kidney. Percutaneous nephrostomy drainage was established followed by left percutaneous nephrostolithotomy. In 1992, he was found to retain large amount of urine in the bladder; subsequently, his mother was taught to perform regular intermittent catheterisations. In 1995, he was admitted with acute urine infection. Abdominal X-ray revealed recurrence of large stones in both kidneys. With multiple sessions of Extracorporeal Shockwave Lithotripsy (ESWL), about 80% clearance was achieved on the left side. Right staghorn renal stone awaits treatment. This case shows that recurrent urinary infection in spinal cord injury patients is a predisposing factor for renal lithiasis. These patients require annual urological evaluation. Urinary tract calculi, if detected, should be dealt with promptly to prevent renal damage due to urinary obstruction and urosepsis. Renal calculi can be treated effectively and safely by ESWL in spinal cord injury patients, thus avoiding the need for an invasive procedure. It is essential to achieve low-pressure, adequate emptying of the urinary bladder in patients with spinal cord injury in order to prevent recurrent urinary infection and its sequelae. Social issues involved in the care of a tetraplegic patient play a vital role in the implementation of ideal medical treatment and need to be addressed promptly to avoid any compromise in the quality of medical care.     

Effect of process parameters on residual stress distribution in poly(ethylene terephthalate) fibers and films as revealed by chemical etching

Poly(ethylene terephthalate) fibers and films produced by varying process parameters, such as production speed and medium, temperature and rate of drawing, were annealed at temperatures between 100 and 250°C in the free-to-shrink and constant-length conditions. The as-spun, as-drawn, and drawn and annealed samples were etched in 40% aqueous methylamine at room temperature for 4 h. The etch patterns were examined on a scanning electron microscope and were found to be related mainly to residual stress and its distribution in the samples and thereby to sample morphology. The studies clearly bring about the important role played by the processing history. © 1995 John Wiley & Sons, Inc.     

Reactivity of Hydroxamate Ions in Cationic Vesicular Media for the Cleavage of Carboxylate Esters

The hydrolysis of carboxylate esters viz. p‐nitrophenyl acetate (PNPA), p‐nitrophenyl butyrate (PNPB) and p‐nitrophenyl octanoate (PNPO) in the presence of cationic vesicles of the surfactant dioctadecyldimethylammonium bromide (DODAC) by different hydroxamate ions i.e. acetohydroxamate (AHA^?), benzohydroxamate (BHA^?) and salicylhydroxamate (SHA^?) were studied. The kinetic data was supported by spectrophotometric measurements. The effects of vesicular size on the reaction have been discussed. The differential reactivity under endo‐ and exovesicular conditions has also been evaluated. Critical vesicle concentrations (CVC) of cationic vesicular surfactants were determined from conductometric and fluorimetric measurements at 300 K. Fluorescence probe pyrene and pyrene‐1‐carboxaldehyde have been used for determination of CVC. Further, thermodynamic parameters viz. Standard Gibb's energy (?G°), enthalpy (?H°), and entropy (?S°) of vesicles has also been evaluated within a temperature range of 303.15–328.15 K.     

Micellar and Surface Properties of Some Monomeric Surfactants and a Gemini Cationic Surfactant

The physicochemical and interfacial properties of the monomeric surfactants cetyltrimethyl ammonium bromide (CTAB), cetyltriphenyl phosphonium bromide (CTPB), tetradecyl triphenyl phosphonium bromide (TTPB), cetyldiethylethanol ammonium bromide (CDEEAB), cetyltrimethyl ammonium chloride (CTACl), tetradecyltrimethyl ammonium bromide (TTAB), and a gemini surfactant (C₁₆-3-C_16, 2Br⁻) at different pH (3.1, 7.0, and 7.75) have been investigated by conductivity and surface tension measurements at 300 K. The critical micellar concentration (CMC), degree of micellar ionization (α), surface excess concentration (Г_max), minimum surface area per molecule of surfactant (A _min), Gibbs free energy of micellization (∆G _m⁰), surface pressure at the CMC (π _CMC), and the Gibbs energy of adsorption (∆G _ads⁰) of the monomeric surfactants have also been determined. The CMC, α and Г_max, increase with increasing pH whereas A _min decreases.