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A Nangia

Publications and source records attributed to A Nangia.

At least 19 recordsLinked to original sources
PubMed2001

N-(4-Biphenylyl)urea.

In the crystal structure of the title compound, C13H12N2O, N-H(anti)...O hydrogen bonds produce the so-called urea alpha-network and the N-H(syn) donor forms an unconventional N-H...pi hydrogen bond.

Journal Article↗
PubMed2001

Hydrogen bonding in two tetracyclic indole alkaloids.

3-Acetyl-1,6,7,12b-tetrahydroindolo[2,3-a]quinolizin-2(12H)-one, C17H16N2O2, consists of two symmetry-independent molecules and each forms a layered structure stabilized by N-H...O and C-H...O hydrogen bonds. In 3-acetyl-6,7-dihydroindolo[2,3-a]quinolizin-4(12H)-one monohydrate, C17H14)N2O2.H2O, the structure is stabilized by O-H...O, N-H...O and C-H...O hydrogen bonds, with the ordered water molecule playing a crucial role in the self-assembly. Contribution from the weak interactions to the strong hydrogen-bonded network is a common feature in both structures.

Crystallography, X-Ray↗
PubMed2001

Finishing occlusion in Class II or Class III molar relation: therapeutic Class II and III.

The most frequent extraction regime consists of the removal of upper and lower premolars. Depending on anchorage requirements, camouflage treatment options, surgical intervention, or the absence of teeth in only one arch, it may become necessary to finalize the occlusion with a one-dental-unit discrepancy between the upper and lower dental arches. Guidelines are presented for finishing occlusions in Class II or Class III molar relation.

Anodontia↗
PubMed2000

[Tris(4-tolyl)methyl]benzene.

The crystal structure of the title compound, C(28)H(26), in the monoclinic space group C2/c has a columnar packing arrangement with a 7.20 A axis, a feature common to several tetraphenylmethanes.

Journal Article↗
PubMed2000

Pyrazine-2,3-dicarboxamide

In the crystal structure of the title diamide, C(6)H(6)N(4)O(2), linear tapes of carboxamide N-H.O and pyrazine C-H.N hydrogen-bond dimers are connected by N-H.O bonds to form a staircase-like pattern.

Journal Article↗
PubMed2000

Crystal engineering in the gem-alkynol family; synthon repetitivity and topological similarity in diphenylethynylmethanols: structures that lack O-H.O hydrogen bonds

The structures of four para-substituted derivatives of diphenylethynylmethanol have been determined [ditolylethynylmethanol, di(4-chlorophenyl)ethynylmethanol, di(4-bromophenyl)ethynylmethanol and bis(4,4'-biphenylyl)ethynylmethanol]. The dimethyl, dichloro, dibromo and diphenyl compounds have been analysed using X-ray diffraction at 150 K, and the dichloro compound has also been studied using neutron diffraction at 150 K. In common with the parent diphenylethynylmethanol [Garcia, Ramos, Rodriguez & Fronczek (1995). Acta Cryst. C51, 2674-2676], all four derivatives fail to form the expected strong O-H.O hydrogen bonds due to steric hindrance. Instead, the supramolecular structural organization in this family of gem-alkynols is mediated by a variety of weaker interactions. The two most acidic protons, O-H and C[triple-bond]C-H, participate in weak hydrogen bonds to pi-acceptors, forming synthons that stabilize all five structures. These primary interactions are reinforced by a variety of other weak hydrogen bonds involving C-H donors and the hydroxy-O as an acceptor, and by halogen.halogen interactions in the dichloro and dibromo compounds.

Journal Article↗
PubMed2000

Halogen trimer synthons in crystal engineering: low-temperature X-ray and neutron diffraction study of the 1:1 complex of 2,4, 6-tris(4-chlorophenoxy)-1,3,5-triazine with tribromobenzene

The title complex has been studied using low-temperature X-ray (150 K) and neutron (100 K) diffraction. Molecules of the triazine host form a two-dimensional hexagonal network mediated by trigonally symmetric Cl(3) synthons having Cl.Cl interactions of 3.441 (3) A, a C-Cl.Cl angle of 165 degrees and a Cl.Cl-C angle of 105 degrees, close to the ideal values of 180 and 90 degrees, respectively. The guest molecules are of an appropriate size to fit the hexagonal networks and interact with the host via C-H.pi (phenyl) and C-Br.pi (phenyl) interactions which stabilize the overall structure. Both C-donor bond vectors are directed more closely towards the mid-point (X) of an individual aromatic bond, rather than the ring centroid, with H.X 2.817 (9) A and C-H.X 174.0 (9) degrees, and Br.X 3.353 (4) A and C-Br.X 158.1 (2) degrees.

Journal Article↗
PubMed2000

Crystal chemistry of some synthetic 2-oxa-steroids: conformation, packing motifs and isostructurality.

The crystal structures of six synthetic 2-oxa-steroids (A-ring lactone steroids) have been determined by single-crystal X-ray diffraction. The conformation and hydrogen bonding in these oxa-steroids is compared with packing motifs in the natural steroids and the anabolic agent, Anavar. O-H...O hydrogen bonding with lactone carbonyl O is the preferred arrangement in molecules with a C-OH group. The donor H atoms of A, B and D rings participate in C-H...O interactions with lactone carbonyl O and D-ring hydroxyl/ketone O acceptor atoms. The conformation of the lactone ring in these analogues is different from the natural androgens because replacement of the C2-methylene group by an O atom changes the geometry of the A ring. Two structurally related lactone steroids provide the first example of O-H...O/C-H...O interaction mimicry and furthermore the two components form a binary solid solution. The O-H...O and C-H...O hydrogen bonds in 2-oxa-steroid crystal structures are analysed and the observed preferences discussed in terms of geometric and chemical factors.

Crystallography, X-Ray↗
PubMed2000

Leiomyosarcoma of the mesocolon--a case report.

Retroperitoneal leiomyosarcomas including those arising from the mesentery are rare. These account for 5.8% of all soft tissue sarcomas. Most of these tumors present in late life with female preponderance. Diagnosing these tumors at an early stage is difficult due to their location. Hence, most of them attain large sizes with metastases to distant sites at the time of diagnosis. We report a case of leiomyosarcoma arising from the sigmoid mesocolon due to it's rarity and unusual clinical presentation.

Adult↗
PubMed1999

A comparative study of the crystal structures of tetrahalogenated hydroquinones and gamma-hydroquinone.

gamma-Hydroquinone (1) and its tetrafluoro, tetrachloro and tetrabromo derivatives (2), (3) and (4) adopt crystal structures that have an almost invariant system of O-H.O hydrogen bonds. However, within this O-H.O framework, the four structures display variations that are characteristic of the C-H, C-F, C-Cl and C-Br groups. In the parent compound (1) aromatic rings are packed with a herringbone geometry, whilst in the halogenated derivatives (3) and (4), polarization-type halogen.halogen contacts are optimized. The fluoro derivative (2) is exceptional in that neither of the above possibilities is adopted, even though the O-H.O scaffolding does not per se prohibit either of them geometrically.

Journal Article↗
PubMed1999

Malignant histiocytosis in childhood: A case report.

A case of malignant histiocytosis (MH) in a 12-year-old male child is described. Fever and wasting were the most prominent symptoms. Bilateral cervical and axillary lymphadenopathy was present along with hepatosplenomegaly. The haematological, cytological and histopathological features are described. The diagnostic dilemma presented during the diagnosis of this case is also discussed. Diagn. Cytopathol. 1999;21:359-361.

Biopsy, Needle↗
PubMed1999

Advantages and risks of ileovesicostomy for the management of neuropathic bladder.

OBJECTIVES: To evaluate the efficacy and complications of ileovesicostomy in patients with neurogenic bladder dysfunction. METHODS: Fifteen consecutive neurologically impaired patients (8 from multiple sclerosis, 4 from spinal cord injury, 3 from other causes) with complications of previous bladder management underwent ileovesicostomy. There were 10 women and 5 men. All patients were either poor candidates for or refused continent urinary diversion or bladder augmentation cystoplasty. RESULTS: At a mean follow-up of 23.2 months, 14 of 15 patients had low-pressure urine drainage through their ileovesicostomy. Four women with documented preoperative detrusor hyperreflexia had postoperative intermittent mild urge incontinence per native urethra. They did not require any further treatment, except for oral anticholinergic drugs (oxybutynin and tolterodine). Because of persistent severe urge incontinence, 1 woman required conversion of her ileovesicostomy to an ileal conduit with concurrent cystectomy. The ileovesicostomy of another myelodysplastic man who had four failed artificial urinary sphincters in the past was also converted to an ileal conduit because of persistent urethroperineal fistula despite perineal urethral closure. Renal function was preserved in all patients. Long-term complications were stomal stenosis in 2 patients, bladder and kidney stone formation in 5, and symptomatic urinary tract infections in 3. CONCLUSIONS: Ileovesicostomy can be safely performed in neurologically impaired women and men. Severe preoperative detrusor hyperreflexia with urge incontinence appears to be a risk factor for persistent urge incontinence postoperatively in women. Continued routine urologic surveillance for infection and stones is mandatory. Ileovesicostomy is a versatile procedure for neurologically impaired patients, because it can be converted to a conventional ileal conduit if necessary. In addition, in cases of neural recovery, the ileal "chimney" can be excised and the patient's original lower urinary tract would be preserved.

Adult↗
PubMed1999

Idiopathic priapism.

Idiopathic priapism is rarely seen in children. Two children with idiopathic priapism are presented, followed by a detailed discussion of priapism. Particular attention is paid to idiopathic priapism. Additionally, an algorithm for diagnosing and managing children presenting with priapism is presented.

Adolescent↗
PubMed1998

Use of NMR imaging in the optimization of a compression-coated regulated release system.

Nuclear magnetic resonance (NMR) imaging is routinely used to detect the protons of mobile water molecules within samples. In this investigation, this non-destructive, non-invasive technique was used to determine the cause for faster than predicted drug release from a dissolution-based regulated-release tablet. The NMR images of tablets, from two different formulations, taken at various intervals of time while immersed in static USP dissolution medium showed that the tablet with faster than predicted drug release had a porous coating. The porous coat exposed more of the core surface area to the dissolution medium than desired and this caused an increase in the rate of dissolution of the core. The data presented in this paper demonstrate the usefulness of NMR imaging in solid dosage form development.

Cellulose↗