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The Centre for Health Protection of the Department of Health has convened the Advisory Group on Antibiotic Stewardship Programme in Primary Care (the Advisory Group) to formulate guidance notes and strategies for optimising judicious use of antibiotics and enhancing the Antibiotic Stewardship Programme in Primary Care. Acute pharyngitis is one of the most common conditions among out-patients in primary care in Hong Kong. Practical recommendations on the diagnosis and antibiotic treatment of acute streptococcal pharyngitis are made by the Advisory Group based on the best available clinical evidence, local prevalence of pathogens and associated antibiotic susceptibility profiles, and common local practice.

Introduction There is a pressing need to identify diagnostic testing for Cushing's syndrome that can be achieved with ease and at low cost. This study aimed to explore the usefulness of late-night and post-overnight 1-mg dexamethasone suppression salivary cortisone, as measured by liquid chromatography-tandem mass spectrometry, for investigation of hypercortisolism. Methods Salivary cortisone data of subjects were investigated according to a pre-specified protocol. Subjects were classified as having 'hypercortisolism' or 'eucortisolism' on the basis of histological or biochemical criteria. Receiver operating characteristic curves were drawn to identify the cut-off values and study their performance characteristics. We measured 24-hour urinary free cortisol; late-night salivary cortisol and cortisone; and post-overnight 1-mg dexamethasone suppression serum cortisol, and salivary cortisol and cortisone. Saliva and urine samples were assayed by liquid chromatography-tandem mass spectrometry. Results In this study, 21 subjects were classified as having hypercortisolism and 78 as having eucortisolism. A late-night salivary cortisone cut-off of 13.50 nmol/L had a sensitivity of 94.7% and a specificity of 87.2%. After taking 1-mg dexamethasone the night before, a salivary cortisol cut-off of 0.85 nmol/L had a sensitivity of 76.2% and a specificity of 96.2%; a salivary cortisone cut-off of 7.45 nmol/L had a sensitivity of 85.7% and a specificity of 94.9%, while a salivary cortisone cut-off of 3.25 nmol/L had a sensitivity of 95.2% and a specificity of 79.5%. Many salivary cortisol samples were below the detection limit of liquid chromatography-tandem mass spectrometry. In comparison with salivary cortisol, salivary cortisone had a better correlation with total serum cortisol and better diagnostic performance following dexamethasone suppression. Conclusions Both late-night and post-overnight dexamethasone suppression salivary cortisone levels are of diagnostic value in the investigation of hypercortisolism.

We studied the use of the INNO-LIA syphilis score assay in the resolution of discordant positive screening results of the Murex ICE Syphilis enzyme immunoassay (EIA) with the confirmatory results of both the Serodia Treponema pallidum particle agglutination (TPPA) and the fluorescent treponemal antibody-absorption (FTA-Abs) assays, for the serological diagnosis of syphilis. This was an observational study on the serum samples received by the Syphilis Laboratory, Hong Kong, during the period from January 2006 to December 2012. A total of 801 serum samples with discordant positive screening EIA results were used. Consensus results of such serum samples were derived from results of the EIA, TPPA and FTA-abs assays. The age range of the individuals was 14 to 104 years (median of 52). There were 369 males and 432 females. Of 378 serum samples, 139 showed agreement among positive results, 23 of 310 showed agreement among indeterminate results and 277 of 465 showed agreement among negative results. The proportions of agreement among positive, indeterminate and negative results were 0.37 (95% CI 0.32–0.42), 0.07 (95% CI 0.05–0.11) and 0.60 (95% CI 0.55–0.64), respectively; kappa 0.55 (95% CI 0.49–0.60). There were 60 serum samples with positive consensus results but negative INNO-LIA syphilis score results and 10 with negative consensus results but positive INNO-LIA syphilis score results. Although the INNO-LIA syphilis score assay can be considered a valid alternative confirmatory test for the serological diagnosis of syphilis, the present study showed that its use in the resolution of discordant positive screening EIA results was moderate. A more extensive characterization of serum samples with discordant reactive screening treponemal test results is necessary.

1. The aim of this study was to determine the epithelial changes of the conjunctiva and cornea up to 7 days after corneal debridement and the changes highlighted included (1) proliferation, (2) production of growth factor, (3) changes in calcium binding protein marker, (4) production of cytokine, and (5) maturity of the regeneration corneal epithelium.

Let ${\cal T}_n$ be the collection of trees on $n$ vertices. Let ${\cal T}_n(b;p,q),$ ${\cal T}_n(m;k)$, and ${\cal T}_n(d;k)$ be subsets of ${\cal T}_n$ comprising trees, each whose vertex set has bipartition (p,q), trees whose maximum matching has size $k$, and trees of diameter k, respectively. Brualdi and Goldwasser Discrete Math., 48 (1984), pp. 1--21] obtained lower bounds on the permanent of the Laplacian matrix of a tree from each of these subsets. They characterized the tree in each of these subsets whose Laplacian matrix has the smallest permanent as the "double star" in ${\cal T}_n(b;p,q)$, the "spur" in ${\cal T}_n(m;k)$, and the "broom" in ${\cal T}_n(d;k).$ In this work, the concept of vertex orientations and a new interpretation of the matching numbers in a tree allow us to formulate a unified approach to extending these results to all other immanant functions besides the permanent. It turns out that the ``double star'' and the "spur" remain the tree in ${\cal T}_n(b;p,q)$ and the tree in ${\cal T}_n(m;k)$, respectively, whose Laplacian matrix has the smallest immanant value for all immanants. For ${\cal T}_n(d;k)$ the tree that has the smallest immanant value varies with the immanant function, but it belongs to a small family of "caterpillars" whose legs are all concentrated on a single vertex.

Let d ¯ k denote the normalized hook immanant corresponding to the partition (k, ln-k) of n. P. Heyfron proved the family of immanantal inequalities det A = d ¯ 1 ( A ) ⩽ d ¯ 2 ( A ) ⩽ ⋯ ⩽ d ¯ n ( A ) = per A ( 1 ) for all positive semidefinite Hermitian matrices A. Motivated by a conjecture of R. Merris, it was shown by the authors that (1) may be improved to d ¯ k − 1 ( L ( T ) ) ⩽ k − 2 k − 1 d ¯ k ( L ( T ) ) ( 2 ) for all 2 ⩽ k ⩽ n whenever L(T) is the Laplacian matrix of a tree T. The proof of (2) relied on rather involved recursive relations for weighted matchings in the tree T as well as identities of hook characters. In this work, we circumvent this tedium with a new proof using the notion of vertex orientations. This approach makes (2) immediately apparent and more importantly provides an insight into why it holds, namely the absence of certain vertex orientations for all trees. As a by-product we obtain an improved bound, 0 ⩽ 1 k − 1 [ d ¯ k ( L ( T )) − d ¯ k ( L ( S ( n ) ) ) ] ⩽ k − 2 k − 1 d ¯ k ( L ( T ) ) − d ¯ k − 1 ( L ( T ) ) , where S(n) is the star with n vertices. The ease with which the inequality in (2) and its improvement are derived points to the value of the concept of vertex orientation in the study of immanantal inequalities on graphs.

A relation has been recently established between the Wiener number W and an immanant of the Laplacian matrix of the molecular graph [Chan, O.; Lam, T. K.; Merris, R. J. Chem. Inf. Comput. Sci. 1997, 37, 762−765]. On the basis of this result we now show that there exist algebraic connections between W and certain molecular-graph-based structure descriptors which, until now, were believed not to be related to W, namely the Hosoya index and quantities derived from it and the simple topological index of Narumi.

To the Editor: Community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) is an emerging infectious disease worldwide and is increasingly reported in Asia (1). We describe a community case of invasive MRSA infection, which appeared as bacteremia and pneumonia; CA-MRSA was initially suspected, and eventually the patient was treated successfully with ampicillin/sulbactam. A 52-year-old man with chronic eczema was admitted to the Prince of Wales Hospital, Hong Kong, with fever and chills. Before admission, he had been treated for infected eczematous lesions for several weeks with oral ampicillin, cloxacillin, and cefazolin. He had no history of hospitalization in the past 10 years, and none of his family members were healthcare workers. Examination showed an oral temperature of 40°C, blood pressure 95/55 mm Hg, and no audible murmur. Cellulitis in the left leg complicated his eczematous skin lesions. Chest radiograph showed right-middle-zone pneumonia. Neutrophilia (leukocytes 15.5 × 109/L, neutrophils 86%), thrombocytopenia (platelets 55 × 109/L), prolonged activated partial thromboplastin time (43.6 s), and elevated bilirubin level (31 μmol/L) were observed. Two initial blood cultures grew gram-positive cocci in clusters, identified as S. aureus by positive results for catalase and slide/tube coagulase and a negative result for ornithine decarboxylase. Intravenous cloxacillin (2 g every 6 h) was given on days 2–5. Antimicrobial drug susceptibility testing was performed by the disk-diffusion method (1 μg oxacillin/disk, Mueller-Hinton agar, 2% NaCl), followed by MIC determination with the agar dilution method in accordance with NCCLS (former National Committee for Clinical Laboratory Standards, now Clinical and Laboratory Standards Institute) recommendations (2). One blood isolate was identified as methicillin-resistant S. aureus (MRSA), with an oxacillin MIC 4 μg/mL. The other isolate was identified as methicillin-sensitive S. aureus (MSSA), with an oxacillin MIC of 0.5 μg/mL. In view of a possible CA-MRSA infection (which could have been β-lactam–resistant), cloxacillin was substituted with intravenous vancomycin plus rifampin on day 5. However, the patient's condition progressively deteriorated from day 2 to day 10 with persistent fever, chills, hypotension, and hemoptysis. A repeated chest radiograph showed small lung cavities with fluid, and a thoracic computed tomographic scan confirmed multiple lung abscesses. Results of an initial transthoracic echocardiograph were normal, but a subsequent transesophageal echocardiograph demonstrated tricuspid valve vegetation. The MRSA isolate was susceptible to gentamicin, cotrimoxazole, erythromycin, ciprofloxacin, clindamycin, fusidic acid, tetracycline, chloramphenicol, vancomycin, and rifampin; a different pattern of multidrug-resistant MRSA isolates from that usually found in our facility (2,3). The isolate was also susceptible to ampicillin/sulbactam, with an equivalent breakpoint MIC 4–8 μg/mL) are associated with community-acquired, serious infections (e.g., blood isolates) and are not multidrug resistant, one can consider mecA (or PBP2a) testing to delineate the resistance mechanism (Table). If mecA is present, further testing for PVL gene locus with or without staphylococcal chromosomal cassette mec (SCCmec) type IV can be performed to diagnose CA-MRSA; if mecA is not detected, further testing for BORSA may be indicated, and β-lactam therapy should be evaluated individually. If these pathogens are not differentiated and all are treated as CA-MRSA, a non–β-lactam antimicrobial drug, such as vancomycin, will be used (1,4,7,8). However, for serious and deep-seated S. aureus infections (e.g., bacteremia, endocarditis), vancomycin is inferior to β-lactam antimicrobial drugs, even when in vitro testing indicates susceptibility. Treatment failures have been encountered (4). Linezolid is a good alternative but limited by availability and cost, and clindamycin therapy can be associated with inducible resistance. For BORSA-associated infections, β-lactam antimicrobial drugs, including high-dose penicillinase-resistant penicillins (PRPs) (e.g., cloxacillin) or β-lactam/β-lactamase–inhibitor combinations (e.g., ampicillin/sulbactam) are regarded as treatments of choice (4,6,9). Table Comparison between methicillin-sensitive and methicillin-resistant strains of Staphylococcus aureus BORSA initially described nonheteroresistant strains of S. aureus with oxacillin MIC

For an irreducible character Xλ of the symmetric group Sn, indexed by the partition λ, the immanant function dλ, acting on an n × n matrix A = (aij), is defined as dλ(A) = Σσ ∈ Sn Xλ(σ)Πni = 1 aiσ(i). The associated normalized immanant d λ is defined as d λ = d λ X λ (identity) where identity is the identity permutation. P. Heyfron has shown that for the partitions (k, 1n−k), the normalized immanant d k satisfies det A = d 1 ( A ) ⩽ d 2 ( A ) ⩽ ⋯ ⩽ d n ( A ) = per A (1) for all positive semidefinite Hermitian matrices A. When A is restricted to the Laplacian matrices of graphs, improvements on the inequalities above may be expected. Indeed, in a recent survey paper, R. Merris conjectured that d n −1 ( A ) ⩽ n − 2 n − 1 d n ( A ) (2) wherever A is the Laplacian matrix of a tree. In this note, we establish a refinement for the family of inequalities in (1) when A is the Laplacian matrix of a tree, that includes (2) as a special case. These inequalities are sharp and equality holds if and only if A is the Laplacian matrix of the star. This is proved via the inequalities d k (A) − d k − 1 (A) ⩽ d k + 1 (A) − d k (A) for k = 2, 3, …, n − 1, where A is the Laplacian matrix of a tree.

In this work, we show that the Wiener number of an acyclic molecule may be expressed as a linear function of a hook immanant of the Laplacian matrix associated with the molecule. This relation leads to a new interpretation of the Wiener number as a weighted sum of matchings in the molecular graph of acyclic compounds. The connection between the Wiener number and immanants may pave the way for more use of algebraic tools in the study of the Wiener number.

(2005). Myiasis by Chrysomya bezziana in surgical pathology. Pathology: Vol. 37, No. 1, pp. 80-82.

As evidence accumulates on the use of genomic tests and other health-related applications of genomic technologies, decision makers may increasingly seek support in identifying which applications have sufficiently robust evidence to suggest they might be considered for action. As an interim working process to provide such support, we developed a horizon-scanning method that assigns genomic applications to tiers defined by availability of synthesized evidence. We illustrate an application of the method to pharmacogenomics tests.

The human facial nucleus can be sub-divided into five structurally discrete regions. Immunohistochemistry was used to locate various neurotransmitters and neuropeptides in the neurons and nerve fibres of the human facial nucleus at 14 and 27 weeks of gestation and in the neonate. Whilst choline acetyltransferase-positive neurons were observed in the facial nucleus at all stages of development, dopamine beta-hydroxylase-positive neurons were only found in the neonate. In addition, afferent nerve fibres positive for choline acetyl-transferase, enkephalin and substance P were observed at all stages of development. In the younger specimens these fibres were evenly distributed; however, in the neonates the fibres were asymmetrically distributed as the different types became concentrated in the various structurally distinct regions of the facial nucleus.

We evaluated the performance of two immunoblot assays: the INNO-LIA Syphilis Score (LIA) and the MarDx T. pallidum IgG Marblot Test (TWB), as compared with that of the Murex ICE Syphilis enzyme immunoassay (EIA), the Serodia Treponema pallidum particle agglutination (TPPA) assay and the fluorescent treponemal antibody-absorption (FTA-abs) assay, for the serological diagnosis of syphilis using serum samples of 135 attendees of the social hygiene clinics of the Department of Health in Hong Kong newly diagnosed with syphilis and provided with clinical stages (39 in primary, 20 in secondary, 18 in early latent and 58 in latent of unknown duration) and of 43 normal healthy subjects between October and December 2004. The differences in the overall sensitivities of the LIA assay and the EIA/TPPA/FTA-abs assays were not statistically significant ( P > 0.05) whereas the overall sensitivity of the TWB assay was significantly lower ( P < 0.05) than the overall sensitivities of the EIA, the TPPA and the FTA-abs assays. The LIA assay had an overall sensitivity of 94.1% (95% CI 88.7–97.0%) whereas the TWB assay 65.2% (95% CI 56.8–72.7%). Both the LIA and the TWB assays have a specificity of 100%. When consensus results were derived from the most predominant results of the EIA, the TPPA and the FTA-abs assays, the LIA assay had a positive agreement with the consensus results of 98.5% (95% CI 94.5–99.6%) whereas the TWB assay 68.2% (95% CI 59.8–75.6%). Therefore, the LIA assay performed significantly better ( P < 0.05) than the TWB assay. The LIA assay can be considered to be a valid alternative confirmatory test for the serological diagnosis of syphilis.

Immunoassays using either viral lysate (Western blot) or recombinant/synthetic antigen (immunoblot) for anti-HIV capture are still the preferred method to confirm HIV infection. Two cases of HIV-1-infected patients presented with acquired immunodeficiency syndrome (AIDS)-defining illnesses. Laboratory tests were performed using multiple commercial HIV test kits on multiple sera from both patients over several weeks. Both patients were strongly positive on the anti-HIV/p24 antigen combined screening assay. Yet, HIV-1 infection could not be confirmed using a popular commercial immunoassay. Eventually, HIV infection was confirmed using an alternative commercial Western blot assay as well as an HIV quantitative PCR test. In laboratories without nucleic acid testing (NAT) for HIV, indeterminate results may delay confirmation of HIV infection, if commercial line immunoassays alone are available. Some end-stage HIV/AIDS patients may not produce antibodies to specific HIV antigens and may therefore give indeterminant or negative results on some immunoassays, depending on the type of antigen used. This report highlights the utility of having NAT available when diagnosing difficult cases of HIV infection, especially in light of the recent Centers for Disease Control and Prevention move towards more universal, routine, HIV testing.

Human melanoma cells express high-affinity glucocorticoid receptors, and adrenalectomy has been shown to have antimelanoma effects in animal models. Long-term regression of distant metastatic melanoma was observed in one patient after bilateral adrenalectomy, prompting a review of adrenalectomy for melanoma metastases performed at this center. A retrospective study in which all patients treated at the Sydney Melanoma Unit and recorded as having adrenal gland metastases between January 1987 and January 2004 were identified and their survival analyzed. One hundred eighty-six patients with adrenal gland metastases were identified. Adrenalectomy was performed in 23 patients; the other 163 patients were treated nonsurgically. The adrenal glands were the sole site of disease in five patients. All symptomatic patients were free of pain after recovery from the surgical procedure. Thirteen patients were rendered clinically and radiologically disease-free by their surgery. There was no postoperative mortality within 30 days. Median overall survival after adrenalectomy was 16 months (2-year survival, 39%), compared with 5 months for patients with documented adrenal metastases treated nonsurgically (P

1. Neuropeptide Y is found throughout the central nervous system where it appears to play a wide range of often poorly understood functions. In this study, the distribution of neuropeptide Y immunoreactive (NPY-ir) neurons in the brainstem, cerebellum, and cerebral cortex of human fetuses ranging in age from 11 gestational weeks to term was investigated by immunohistochemistry. 2. The NPY-ir cells were detected in the dorsal and ventral rostral midbrain and the interpeduncular nucleus by 21 weeks and 32 weeks of gestation, respectively. Although no positive cells were found in the pons, the NPY-ir fibers were detected there at 32 gestational weeks. 3. The vagal, hypoglossal, and olivary nuclei of the medulla oblongata contained immunoreactive cells by week 21 and the medullary reticular formation by week 25 of gestation. In most of these locations, both the number and size of neuropeptide Y positive cells were greater at birth and reached maximal values of 100-400 cells per 1 mm2 and 2-5 microm in diameter, respectively. 4. In the cerebellum, numerous NPY-ir horizontal and granule cells, as well as the cells within the dentate nucleus were observed as early as 21 weeks of gestation. 5. The NPY-ir cells were also detected in the developing cerebral cortex, with the earliest activity observed within the temporal cortex at 14 weeks of gestation. By week 21, positive cells appeared in the visual, frontal, sensory, and motor cortices. Most of these cells were bipolar or multipolar in morphology but their numbers at birth were relatively low. 6. Our results show a wide distribution of the NPY-ir cells in the developing human brain and offer supporting evidence for the important modulatory role of NPY in both the fetus and adult.

The Chinese population is the biggest ethnic group in the world. However, there are few reports on the treatment outcome of childhood acute lymphoblastic leukaemia (ALL) among the Chinese population.Sixty-five children with ALL were treated with a modified protocol of the Medical Research Council United Kingdom Acute Lymphoblastic Leukaemia protocol X(MRC UKALL X) at the Prince of Wales Hospital, Hong Kong. Most patients were ethnic Chinese. They were divided into groups A and B, depending on whether their presenting leucocyte count being was less or greater than 50 x 10(9)/l, respectively. Group A patients of received induction, early intensification (week 5), cranial irradiation, and maintenance for 3 years. Group B patients received an additional late intensification (week 20).The median follow-up duration was 6.8 years(range: 3.4-10.1 years). The event-free and overall survival rates of all patients at 7 years were 66% (confidence interval [CI] 53-76) and 75% (CI 63-84), respectively. The event-free survival rates of groups A and B at 7 years were 67% (CI 52-79) and 60% (CI 32-80), respectively (P= 0.39). The overall survival rates of groups A and B at 7 years were 80% (CI 66-89) and 60% (CI 32-80), respectively (P = 0.07). With this treatment protocol, the factors which adversely affected the outcome were age (2 years and10 years) and T-cell subtype. Sex, white blood count at diagnosis, and FAB subtypes were not statistically significant prognostic factors.The treatment outcomes were comparable with those reported from the MRC UKALL X trials.

Enkephalin (ENK) positive sites in the developing human cerebellum (gestation ages 18 weeks to 30 weeks) were studied by immunohistochemistry (ABC method). Positive reactions were registered as early as 20 weeks of gestation and initially in the deep cerebellar nuclei. By 23 weeks some mossy fibers exhibited positivity and by 27 weeks some climbing fibers as well as a few Purkinje basket, golgi and granule cells were also positive. This result indicated that the human cerebellum possesses ENK positive fibers and neurons before birth.

Ferritin, the major intracellular iron storage protein of eucaryotic cells, is regulated during inflammation and malignancy. We previously reported that transcription of the H subunit of ferritin (ferritin H) is negatively regulated by the adenovirus E1A oncogene in mouse NIH 3T3 fibroblasts (Y. Tsuji, E. Kwak, T. Saika, S. V. Torti, and F. M. Torti, J. Biol. Chem. 268:7270-7275, 1993). To elucidate the mechanism of transcriptional repression of the ferritin H gene by E1A, a series of deletions in the 5' flanking region of the mouse ferritin H gene were constructed, fused to the chloramphenicol acetyltransferase (CAT) gene, and transiently cotransfected into NIH 3T3 cells with an E1A expression plasmid. The results indicate that the E1A-responsive region is located approximately 4.1 kb 5' to the transcription initiation site of the ferritin H gene. Further analyses revealed that a 37-bp region, termed FER-1, is the target of E1A-mediated repression. This region also serves as an enhancer, augmenting ferritin H transcription independently of position and orientation. FER-1 was dissected into two component elements, i.e., a 22-bp dyad symmetry element and a 7-bp AP1-like sequence. Insertion of these DNA sequences into a ferritin H-CAT chimeric gene lacking an E1A-responsive region indicated that (i) the 22-bp dyad symmetry sequence by itself has no enhancer activity, (ii) the AP1-like sequence has moderate enhancer activity which is repressed by E1A, and (iii) the combination of the dyad symmetry element and the AP1-like sequence is required for maximal enhancer activity and repression by E1A. Gel retardation assays and cotransfection experiments with c-fos and c-jun expression vectors suggested that members of the Fos and Jun families bind to the AP1-like element of FER-1 and contribute to its regulation. In addition, gel retardation assays showed that E1A reduces the ability of nuclear proteins to bind to the AP1-like sequence without affecting the levels of nuclear factors that recognize the 22-bp dyad symmetry element. Taken together, these results demonstrate that FER-1 serves as both an enhancer of ferritin H transcription and a target for E1A-mediated repression.

Anaplastic large cell Ki-1 lymphoma is an uncommon type of non-Hodgkin's lymphoma that rarely presents primarily in the bone. Three such cases are reported. All patients were young and had bone pain; one had paraparesis as a complication of collapse of the thoracic vertebral body. The involvement was either monostotic or polyostotic. Radiologically, the lesions were lytic and had ill-defined borders. Histologically, the large neoplastic cells had pleomorphic bizarre nuclei, prominent nucleoli, abundant deeply amphophilic cytoplasm, and paranuclear pale hof. They were admixed with variable numbers of inflammatory cells. One case each was of T-cell, B-cell, and non-T non-B lineage. All three cases showed excellent responses to chemotherapy with or without radiation therapy. Recognizing the lymphomatous nature of this highly pleomorphic tumor is important because of its potential curability with appropriate chemotherapy.

We report a case of transient myeloproliferative disorder (TMD) involving the megakaryocytic lineage in a cytogenetically normal newborn infant. Prominent megakaryocytic phagocytosis in the bone marrow was observed. This finding might suggest that TMD was due to a self-limiting malignant clone in myelopoiesis.

Nitride-based p-i-n photodetectors (PDs) with a p-AlGaN blocking layer were proposed, fabricated, and characterized. It was found that peak responsivities of the PDs with and without a p-AlGaN blocking layer both occurred at 355 nm and with the same value of about 0.076 A/W at zero bias. It was also found that reverse leakage current increased by 7 orders of magnitude after - 1000 V electrostatic discharge (ESD) stressing for a conventional homostructure p-i-n PD. In contrast, the heterostructure PD with a 300 nm thick p-Al 0.10 Ga 0.9 N blocking layer can endure an extremely large -8000 V ESD surge.

In a 1947 paper [6], M. Kac derived the eigenvalues and eigenvectors of the probability transition matrix associated with the Ehrenfest urn model with $n$ balls, in which a ball is selected at random and moved to the other urn. The connection (see, for instance, [1, p. 19]) between the Markov chain defined by the Ehrenfest model and the nearest-neighbour uniform random walk on the abelian group $\Z^n_2$ prompted M. Kac to ask when a Markov chain may be lifted to a random walk on a group. More specifically, given a Markov chain $\{X_m\}_{m \geq 0}$ with state space $S = \{1, 2, \ldots, n \}$ and probability transition matrix ${\mbox{\bf $P$}} = [p_{ij}] (\mbox{here } p_{ij}:= P(X_{r + 1} = j | X_r = i) \mbox{ for all } r \geq 0)$, we say that the Markov chain $\{X_m\}_{m \geq 0}$ or equivalently ${\mbox{\bf $P$}}$ lifts to a random walk on a finite group $G$ if there exists a probability measure $\mu$ on $G$ and a surjective map $L:G \rightarrow S$ such that, for all $i, j \in S$, and for each $g \in L^{-1}(i)$, $$ p_{ij} = \sum_{h \in L^{-1}(j)} \!\! \mu (g^{-1}h).$$

Microwave irradiation of EAT cells caused an increase in length and number of surface microvilli. The tumor cells tend to form large aggregates by means of extensive interdigitation of surface microvilli. On the other hand, heat hyperthermia caused a decrease of surface microvilli but an increase of surface blebs. Hence the surface morphology of EAT cells after in vitro exposure to microwave irradiation differs markedly from that after heat hyperthermia.

We recently observed a 4-year-old Chinese boy with multifocal leiomyosarcoma of the small intestine with evidence of dissemination. Complete surgical excision was not possible and the response to postoperative chemotherapy was poor. The patient died 3 months after diagnosis. The prognosis for disseminated intestinal leiomyosarcoma in childhood appears to be poor.